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SOHC.co.uk Forums => CB500/550 => Topic started by: Erny on June 22, 2019, 11:44:07 AM

Title: 550K1 - carb questions (022A)
Post by: Erny on June 22, 2019, 11:44:07 AM
Starting new thread as it seems I will have more questions. Sorry for them, going to "play" with carb for the first time..
Appologize if this has been answered elsewhere many times already

So let's start:
- is it possible to check and change needle settings (to see which notch is used) without complete disassembly? I'm afraid answer is no, but just in case ;)
- on my carb set, after I removed main jets and turned carbs over emulsification tube dropped out just by gravity.. Just on 1st carb. Tube is very loose in rge hole.. Is that ok? No impact on carb function?
- mixture screw - I suppose it changes air flow, correct? So turning in makes mix richer? (https://uploads.tapatalk-cdn.com/20190622/6716da221441db21d510f0f3576b1d23.jpg)
Title: Re: 550K1 - carb questions (022A)
Post by: deltarider on June 23, 2019, 07:44:16 AM

- is it possible to check and change needle settings (to see which notch is used) without complete disassembly? I'm afraid answer is no, but just in case ;)

There's a vid somewhere on youtube. Anyway, you do NOT have to separate carbs from eachother.
Quote
- on my carb set, after I removed main jets and turned carbs over emulsification tube dropped out just by gravity.. Just on 1st carb. Tube is very loose in rge hole.. Is that ok? No impact on carb function?
That's not abnormal at all. On mine they either come down by gravity or when helped a little by inserting a wooden toothpick or whatever from below, cant it and then wiggle it out. That's normal, I never had to tap them out from above. 
Quote
- mixture screw - I suppose it changes air flow, correct? So turning in makes mix richer?
Correct.
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on June 23, 2019, 12:30:02 PM
Many thanks for the answers!

BTW, isnt there detailed step-by-step instructions how to dissassembly and reassembly these carbs?
I have in mind something I found for PD42A carbs here : http://forums.sohc4.net/index.php/topic,146893.0.html
Title: Re: 550K1 - carb questions (022A)
Post by: Seabeowner on June 23, 2019, 01:05:57 PM
I found this on the net:
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on June 23, 2019, 02:11:01 PM
Another 2 questions:
- what's the length of fuel hoses from carbs to cock?
- is it possible to replace hoses (installation especially) provided I use genuine Honda (got from 4into1 declared as genuine) without separating carbs from stay plate?
Title: Re: 550K1 - carb questions (022A)
Post by: Bryanj on June 23, 2019, 04:38:16 PM
You can even replace the hoses with the carbs on the engine if you have small flexible hands, hose lengths are quotef in parts book.
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on June 23, 2019, 09:43:22 PM
Thanks for all replies.

Just finished another round of carbs removal, opening, cleanup (it was clean anyway).
Carbs set are freshly rebuilt by Gerben - blasted from out and in, very clean. Jets 40/100.

Why I was doing it:
- engine don't start on choke, only without with certain trottle, after some warmup, it idles well. When using choke it dies (looks too rich when choke is engaged). Apart of that, when warm, egine idles and starts well, I feel too rich mix on low revs, from mid-high revs it pulls OK I guess (this is my first 550, so cannot compare)
- Cabs were leaking

What I did:
- removal and clenup of all what I could (without separation of the carbs and w/o taking out slides and needles. According to Gerben, needles and emulsification tubes are Keihin genuine and set on 4th groove
- I changed slow jets from 40 to 38 genuine Keihin

After assembly:
- bike still does not start on choke  >:(, so no improvement
- carbs are not leaking now  :)

I tried to remove filter element (replica from cmsnl) hoping for leaner mix, but no improvement too
Static ignition set OK, valves adjusted too.

Any advice what else can be wrong?
I reallly dont know what to do  :'( :'( :'(
Title: Re: 550K1 - carb questions (022A)
Post by: paulbaker1954 on June 24, 2019, 08:58:53 AM
I am not sure what your real problem is here, you say bike wont start on choke but you are obviously able to start it, so is the issue that it is harder to start than you would expect only from cold.

I am assuming the chokes are operating properly as Gerben has rebuilt the carbs and I am also assuming the pilot air circuits are clear and the pilot jets are clear.

Are you using the correct starting procedure, below is what the original Honda owners manual recommends

COLD ENGINE STARTING
PROCEDURE
1) Turn the fuel tank valve to the "ON" position.
2) Insert the key into the main switch and turn to the "ON" position. At this time, observe the GREEN neutral indicator lamp on the lamp cluster. The lamp will be lighted when the transmission is in the neutral position. Also at this time the RED oil pressure warning lamp should be lighted. If the lamp fails to come on, the connection should be checked for an open circuit and the bulb checked and replaced if burned out.
3) Make sure that handle grip ignition switch is in the "ON" position.
4) Position the choke lever to the full closed position.
5) Twist the throttle grip inward slightly and depress the starter button. If the engine does not start within 5 seconds, release the starter button and allow the starter motor to rest for approximately 10 seconds before pressing the starter button again. If the engine does not start readily with the electric starter, to prevent excess battery discharge, use the kick starter pedal to start the engine. If the engine fails to start after several repeated attempts, turn off the main switch and lower the choke lever to the full open position, twist the throttle grip inward fully and crank the engine using either the electric starter or the kick starter pedal. This is then followed by turning the main switch to the "ON" position and following the starting procedure out-lined in steps 1 through 5, however, at this time the use of the choke is not necessary.
6) After the engine starts, operate at approximately 2,000 rpm until the engine will properly respond to the throttle with the choke open.

You also say that when warm it runs and idles well which would seem to indicate that the idle circuits and pilot jets etc in the carbs are all OK.

My 500 was never been a brilliant starter from cold and always needed a few cranks and throttle opening to get going. This has got better since moving over to a Boyer Ignition system using the Boyer Micro Coils. This led me to believe my starting issue was more down to maybe old weak coils rather than a carburation problem.

Here is my recommendation

1) Make sure there are no air leaks at the carb to head rubber joints
2) Are you sure you dont have a restriction in the fuel lines ( I had a strange problem with my old petcock that was strangling the fuel flow). I found this because if i turned the fuel on and then left the bike for 5 minutes this gave time to fill the float bowls and starting was much easier. Have you tried just  directly connecting an external auxiliary fuel tank to eliminate any such issues
3) May be worth changing points and condensors
4) Try another set of coils if you are using the original ones
5) You said you used a 38 pilot jet but I thought the right one was 40 (that said I have 627 carbs)
6) Make sure this is not an ignition problem rather than a carb problem



Title: Re: 550K1 - carb questions (022A)
Post by: Erny on June 24, 2019, 09:48:59 AM
Hi Paul
thanks for reply!

Yesterday evening I opened (yes, for the first time  ::)) manual to my CB550K1, reading the cold start procedure. Seems I had different expectations from how starting cold engine...
but point to point answers to your post:

I am not sure what your real problem is here, you say bike wont start on choke but you are obviously able to start it, so is the issue that it is harder to start than you would expect only from cold.
Yes, I can start, but impossible without trottle opening. When I open trottle its starts well without choke, but then I need to keep trottle open till it is warm enough to keep idling itself w/o trottle. If I use choke I need to use trottle too, but it starts much harder and does not respond trottle well (too rich mix).
Normally choke should make mix richer but in my case looks too much???
Another example, after I start w/o choke, while keeping engine alive with trottle to warm it up I engage choke (even partially), RPMs goes down, engine tends to stop / runs hard (too rich symptom)

I am assuming the chokes are operating properly as Gerben has rebuilt the carbs and I am also assuming the pilot air circuits are clear and the pilot jets are clear.
Yes, I confirm chokes operates properly, all pilot circuits are clear and jets are new genuine Keihin 38

Are you using the correct starting procedure, below is what the original Honda owners manual recommends
After reading manual and your post seems not really  :)

COLD ENGINE STARTING
PROCEDURE

...

4) Position the choke lever to the full closed position. Yes
5) Twist the throttle grip inward slightly and depress the starter button. I did not do this as part of procedure, but finally was doing so as the only way to start  ;D
Honestly, I expected I should only use choke and engine will run on higher RPMs, like my CB750 K7....
6) After the engine starts, operate at approximately 2,000 rpm until the engine will properly respond to the throttle with the choke open. Does this means I need to keep trottle open for some time to make engine warmer? But this can be quite some time... strange to me, I really expected that no trottle needed to warm-up using choke. This is not really very user friendly

You also say that when warm it runs and idles well which would seem to indicate that the idle circuits and pilot jets etc in the carbs are all OK. Exactly. BUT, when riding it, I feel that when trying to accerate from lower RPMs, engine suffers from too rich mix till it reaches higher RPMs.


Here is my recommendation

1) Make sure there are no air leaks at the carb to head rubber joints Rubber joints looks good and tight, I don't know how to test better. But if they would not be tight, mix should be leaner, which is not my case
2) Are you sure you dont have a restriction in the fuel lines ( I had a strange problem with my old petcock that was strangling the fuel flow). I found this because if i turned the fuel on and then left the bike for 5 minutes this gave time to fill the float bowls and starting was much easier. Have you tried just  directly connecting an external auxiliary fuel tank to eliminate any such issues Yes, I'm sure there is nothing blocking. Petcock is new (Honda), new hoses...
3) May be worth changing points and condensors I will, but normally this does not explain my symphoms
4) Try another set of coils if you are using the original ones Don't have spare set, but again I don't think this can cause my issue
5) You said you used a 38 pilot jet but I thought the right one was 40 (that said I have 627 carbs) According to specs, 022A, model year 1975 shall have 38
6) Make sure this is not an ignition problem rather than a carb problem
[/quote] as points 3&4 above

All in all, it still looks to me choke is completely useles (maybe can help in really cold weather?)
Are there any other carbs on later 550s that are better for cold start? (550F?)
Title: Re: 550K1 - carb questions (022A)
Post by: K2-K6 on June 24, 2019, 10:14:40 AM
Unsure of choke application on this carb set,  don't think it lifts throttles as well as making richer?

K7 definitely lifts throttles with choke application,  manual allows nearly 3000rpm for running on choke so it's quite a bit of throttle applied when set. So fundamentally different from this one in discussion.

All the symptoms seem to agree with your feeling of running rich. The exhaust would smell of fuel too if that's the case.

You say that needle clips are in fourth position,  is that 4 from top of needle or 4 up from bottom position?

Suggestion if not like this,  put needle clips in fourth slot from bottom of needle (lowers needle to make leaner) then turn idle air screws out 1/2 turn from where they are.

You will need to use throttle while it warms up on this I believe.

Title: Re: 550K1 - carb questions (022A)
Post by: paulbaker1954 on June 24, 2019, 10:28:46 AM
Unsure of choke application on this carb set,  don't think it lifts throttles as well as making richer?

K7 definitely lifts throttles with choke application,  manual allows nearly 3000rpm for running on choke so it's quite a bit of throttle applied when set. So fundamentally different from this one in discussion.

All the symptoms seem to agree with your feeling of running rich. The exhaust would smell of fuel too if that's the case.

You say that needle clips are in fourth position,  is that 4 from top of needle or 4 up from bottom position?

Suggestion if not like this,  put needle clips in fourth slot from bottom of needle (lowers needle to make leaner) then turn idle air screws out 1/2 turn from where they are.

You will need to use throttle while it warms up on this I believe.

Yes on the 550 there is no throttle speed increase mechanism like you normally find on other carbs.

I normally use choke open to start and once running close chokes to about half way whilst it warms up. I do NOT need to keep the throttle open though whilst warming up so there is something not right with your setup. Moving the clip will not (I don't think) help as the needle position only starts to have effect at higher revs. That said I run mine in the middle position so you may want to change them ans see if it has any impact.
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on June 24, 2019, 10:45:19 AM
Unsure of choke application on this carb set,  don't think it lifts throttles as well as making richer?

K7 definitely lifts throttles with choke application,  manual allows nearly 3000rpm for running on choke so it's quite a bit of throttle applied when set. So fundamentally different from this one in discussion.

All the symptoms seem to agree with your feeling of running rich. The exhaust would smell of fuel too if that's the case.

You say that needle clips are in fourth position,  is that 4 from top of needle or 4 up from bottom position?

Suggestion if not like this,  put needle clips in fourth slot from bottom of needle (lowers needle to make leaner) then turn idle air screws out 1/2 turn from where they are.

You will need to use throttle while it warms up on this I believe.

That's very good point, I did not realise before that K7 lifts trottles. That would explain why I need to use trottle

And yes, exhaust smells of fuel a lot

Concerning needles - honestly, I just rely on info double-confirmed by Gerben - that needles are 4th groove from top and they are genuine Keihin together with emulsification tubes. I did not checked that personally, as was too lazy (and under time pressure) to disassembly carbs.
What I can say they all looks to be the same settings (I saw needles sat equally in each tube when I removed main jets)
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on June 24, 2019, 10:52:50 AM

Yes on the 550 there is no throttle speed increase mechanism like you normally find on other carbs.

I normally use choke open to start and once running close chokes to about half way whilst it warms up. I do NOT need to keep the throttle open though whilst warming up so there is something not right with your setup. Moving the clip will not (I don't think) help as the needle position only starts to have effect at higher revs. That said I run mine in the middle position so you may want to change them ans see if it has any impact.

"I normally use choke open to start and once running close chokes to about half way whilst it warms up" - do I understand you start engine like me, e.g. w/o choke use (= choke open) and then you use it halfway? Or wise versa, meaning you engage choke fully (= flaps are fully closed, so restricting air and making mix richer)? Sorry for such question, I'm not native english speaker  :D
Title: Re: 550K1 - carb questions (022A)
Post by: paulbaker1954 on June 24, 2019, 10:59:43 AM

Yes on the 550 there is no throttle speed increase mechanism like you normally find on other carbs.

I normally use choke open to start and once running close chokes to about half way whilst it warms up. I do NOT need to keep the throttle open though whilst warming up so there is something not right with your setup. Moving the clip will not (I don't think) help as the needle position only starts to have effect at higher revs. That said I run mine in the middle position so you may want to change them ans see if it has any impact.

"I normally use choke open to start and once running close chokes to about half way whilst it warms up" - do I understand you start engine like me, e.g. w/o choke use (= choke open) and then you use it halfway? Or wise versa, meaning you engage choke fully (= flaps are fully closed, so restricting air and making mix richer)? Sorry for such question, I'm not native english speaker  :D

I normally start with choke fully engaged (ie flaps fully closed (lever in fully up position) and then lower to around halfway once running.

As these bikes dont have a device to increase throttle with choke movement they rely on you to do that !!!
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on June 24, 2019, 11:24:14 AM
OK, now it is clear.
So I still have some issue to fix  :'(
Title: Re: 550K1 - carb questions (022A)
Post by: paulbaker1954 on June 24, 2019, 11:30:22 AM
OK, now it is clear.
So I still have some issue to fix  :'(

One thing worth adding is that in fact the original Honda manual states that you should warm the engine up before riding. See below from manual

After the engine has been warmed up, the motorcycle is ready for riding.
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on June 24, 2019, 11:36:04 AM
This is obvious  ;D
My only pb is cold start on choke and idling till engine is warmed-up
Title: Re: 550K1 - carb questions (022A)
Post by: deltarider on June 24, 2019, 01:44:38 PM
Fuelline to the T-joint of carbs 1+2 on your model (CB550K1) should have a length of 17 cm with an ideal internal ⌀ of 5,5 mm. The line to 3+4 should measure 28cm. However, if you happen to have the old model fuelcock (with the bowl), fuel lines lengths are 18 and 30 cm respectively. Outside ⌀ will be around 10 mm. With the correct dimensions there's no chance of kinking. Abstain from inline fuel filters. They'll cause irregularities on a CB500/550. The CB500/550 is very sensitive to correct fuel line routing.
Title: Re: 550K1 - carb questions (022A)
Post by: deltarider on June 24, 2019, 02:02:45 PM
As for the chokes: the CB500/550 models with chokelever at the side of the carbrack were not ment to ride with the chokes (partially) on. There's a good reason for that: having the lever not in your view, you'll forget you have them partially on. Just keep your hand on the throttle. This practice is confirmed by the Owner's Manual. I guess Honda didn't want you to unnecessarily fiddle with a lever somewhere below that you can't see. Honda wanted you to have the hands at the handlebars at all times. No need to use the big idle knob unless you plan to do things with your right hand (which I often do btw). These models do not necessarily need a stationary warm-up as they had a pretty rich idle, so just a bit of throttle as the manual suggests. With the arrival of models with the chokeknob at the handlebars, it's a different story. They had a far leaner idle and a fast cam. For convenience the knob is now positioned directly in your view, so you can see whether it is engaged or not. Ofcourse you can choose what you like best. But if you need the chokes partially on whilst riding an old model, your idle is probably set too lean. 
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on June 24, 2019, 11:14:37 PM
Small update, I'm just back from garage.

I did start the bike ususal way (w/o choke), after warm-up I was checking ingition, found stripped screw on 1-4 points  >:(, after fixing it, static settings and settings with strobe light I went for test ride. Bike generally pulls good, was able to rech pretty 90mph (reading on tacho gauge).
Mix screw set to 1 3/4 turns out (looked to me the best) on all, did not manage to make my RPM meter meauring reliably so did not played with each carb separately.

Another observation linked to carbs - after engine fully warmed-up, when idling stable for several seconds, I tried to quickly twist the trottle and engine dies! Is that normal? I manage to reproduce anytime... slower twisting is OK...

Note: after spending quite some time with points ( >:( >:( >:() where one is obviously replica, and still having strobe flashing irregularly, fire mark moving left-right, I'm strongly thinking about Dyna S. I installed it to my friend recently and it was really perfect...uncomparable with points. New points set cost ~100 USD, new Dyna S about 160..
Title: Re: 550K1 - carb questions (022A)
Post by: paulbaker1954 on June 25, 2019, 08:53:18 AM
Small update, I'm just back from garage.

I did start the bike ususal way (w/o choke), after warm-up I was checking ingition, found stripped screw on 1-4 points  >:(, after fixing it, static settings and settings with strobe light I went for test ride. Bike generally pulls good, was able to rech pretty 90mph (reading on tacho gauge).
Mix screw set to 1 3/4 turns out (looked to me the best) on all, did not manage to make my RPM meter meauring reliably so did not played with each carb separately.

Another observation linked to carbs - after engine fully warmed-up, when idling stable for several seconds, I tried to quickly twist the trottle and engine dies! Is that normal? I manage to reproduce anytime... slower twisting is OK...

Note: after spending quite some time with points ( >:( >:( >:() where one is obviously replica, and still having strobe flashing irregularly, fire mark moving left-right, I'm strongly thinking about Dyna S. I installed it to my friend recently and it was really perfect...uncomparable with points. New points set cost ~100 USD, new Dyna S about 160..

I don't have any experience with Dyna ignition but I put the full Boyer kit on mine including the Micro Coils and I would highly recommend this set up. Bike just runs better all round, starts easier  and no more points maintenance !!

 Also very easy to fit and their tech support is excellent.

http://www.boyerbransden.com/microdigitalmicropower.html (http://www.boyerbransden.com/microdigitalmicropower.html)

You need KIT00289 and when I bought was £218

ALso see my post on how I installed the Boyer coils using the standard Honda brackets (makes for a very neat installation)

http://www.sohc.co.uk/index.php/topic,14509.msg117905.html#msg117905 (http://www.sohc.co.uk/index.php/topic,14509.msg117905.html#msg117905)
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on June 25, 2019, 10:16:04 AM
This is interesting, never heard about this ingition system!

Just wonder what is its reliability, because, still you can easily fix issues in legacy ignition. Of course, Dyna S brings electronics too (in fact replacing whole points plate and cam, but keeping advancer) but coils are still legacy.

I'll contact Boyer for some details ;)
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on June 25, 2019, 12:16:50 PM
SK = Slovakia (Slovak Republic), Bratislava, Europe  8)
Title: Re: 550K1 - carb questions (022A)
Post by: paulbaker1954 on June 25, 2019, 12:43:21 PM
Where is SK? just trying to see what your location is.

Ha Ha not near Stockport then Ken :)
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on June 25, 2019, 06:07:25 PM
You would be welcome to come! Anytime!
Title: Re: 550K1 - carb questions (022A)
Post by: paulbaker1954 on June 25, 2019, 10:50:26 PM
Where is SK? just trying to see what your location is.

Ha Ha not near Stockport then Ken :)

It did cross my mind Paul, thought I could pop over and sort the carbs out for him.

Hey nice run to Bratislava
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on June 27, 2019, 09:31:31 AM
Small update after yesterday carb sync (only #2 was out of sync):
- it now idles very nice when warm (sync definitely helped)
- start is OK somehow - after discussion here I consider it this way as OK and normal :)

However - under 3k RPM, using little trottle (typical when moving within city traffic), is NOT good.. Over ~3k it improves but still not perfect smooth and over 5-6K is really good.
When I try to use choke partially (under 3k RPM) it is significantly worse.
=> I have feeling that it is caused by too rich mix on low rpms.

One additional observation, when idling for few seconds and I'm twisting trottle quickly (I do not release immediately), engine kills. Is that normal?

Note:
What else I can try? I believe that playing with needles does not help as issue is on low rpm or I'm wrong?

Title: Re: 550K1 - carb questions (022A)
Post by: K2-K6 on June 27, 2019, 05:49:35 PM
It looks to me that all of your assessment of mixture is telling you it's generally too rich, going with that feeling you'd need to experiment in the opposite direction to prove it or not.

If the needles are not in the middle clip groove then it seems logical to try them there.  As you note,  it doesn't directly affect mixture right at the bottom but it does attach it's graduation on top of the idle circuits. They have to at least be close at that changeover point to give a smooth response.

Flat spots are either mixture too rich to get it igniting cleanly,  or too lean to get the burn to start and complete entirely.  That ratio of air to fuel goes roughly from 10 to 1 (rich) and 14 to 1 (lean) at which points you'll feel it's not responding to the throttle.
These engines will generally run an average of around 12 to 1 approximately,  so if you have lean idle then rich mid range,  it will give very confusing responses.

What you are trying to do is step gently toward bringing the two parts of range together to give better average.

With needles in central setting and air screws closed a little you can assess it to see if that's the correct direction. Then further adjust the air screws from there.

What do you currently have the air screws set at?
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on June 27, 2019, 06:45:53 PM
Currently no1 and 4 are 1.5 turn, 2 is 1.75 and 3 is around 1.6. I did that based on plugs colour, where 2 was darkest, 3 was bit dark, 1 and 4 I considered ok.
Attached how plugs looked like on Mon after I had all screws 1.5 turn and before longer riding (after that I found no3 bit too dark too) and before syncing carbs. I don't jave actual view, will take pic once I'll be back at garage.
(https://uploads.tapatalk-cdn.com/20190627/0cd213ba0c753a3b4dd88885d5117c94.jpg)
Title: Re: 550K1 - carb questions (022A)
Post by: K2-K6 on June 27, 2019, 07:34:51 PM
Plug colour is usually main jetting accuracy,  and completed under load when fully up to temperature. You'd not normally trim with colour by using idle adjustments.

For plug "chop" you'd get it warm,  then ride it under full load with throttle wide open,  cut ignition,  then look at plugs.  It's setting the maximum demand mixture so that it's safely in correct range and not too lean that it will cause any damage. It's done like this to deliberately get the engine running fully on main jet and not influenced by low speed settings.

Idle air screws should be adjusted at tickover by bringing the engine speed to its highest level for each carb,  indicating that the slow speed mixture is correct. Honda manuals contain a routine for this.
If you get one carb not responding to this within a small range of the others,  then it indicates a problem with that carb.
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on June 28, 2019, 02:15:25 PM
Yes I know about prcedure to tune slow. Despite I'm now quite skeptic, I'll try to still play with air screws hoping for improvement
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on June 28, 2019, 07:22:06 PM
So, I tried to play with air screws, seems settings 1.5turn is the best... Strange.
Attached pic of plugs, no change 2nd still much darker(https://uploads.tapatalk-cdn.com/20190628/3bc317367b92bf3ea7755f28ba36157a.jpg)
Title: Re: 550K1 - carb questions (022A)
Post by: K2-K6 on June 28, 2019, 07:48:16 PM
It's worth considering if no2 carb is operating the fuel level the same as the other 3.

Although set up correctly with float height dry checking,  some examples on here have shown different fuel levels when checked with a tube to show real time fuel level when installed on the bike.
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on June 28, 2019, 07:55:16 PM
When I had carbs on the bench I did float height set to 22mm and then after closing bowls also with clear tubes, all were the same level. True is that after I did not test on engine. I hate that somehow as there is always gasoline on the engine, but will have to do.

Question is if one carb can cause behavior I'm experiencing?
Title: Re: 550K1 - carb questions (022A)
Post by: K2-K6 on June 28, 2019, 08:07:37 PM
You seem to have reasonably checked the things that affect it so it's a puzzle to see what is making that difference.

You are getting into a level that would be helpful to have more information to assist you in making decisions.  If it's running on four exhaust pipes you can get emmisions readings for each one to see how each cylinder is burning. HC level increase shows unburnt fuel (too rich)  so it would give you confirmation if you have access to test equipment.

Edit:- this thread recently looked into it like above http://www.sohc.co.uk/index.php/topic,18831.0.html

May be of interest.
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on June 28, 2019, 11:24:44 PM
Interesting!
I have original, 4 into 4 pipes.

Testing HC is definitely good idea, but I don't have access to, need to investigate...

But thinking more about it, my pipes are far from being perfect, all have small holes in lower seam and no1 and no4 (upper ones) have quite big holes on the bottom behind rubbers crossconnecting pipes at their back, see pics.

Can this cause my issue?

Pics of pipes and bike as it looks like attached
(https://uploads.tapatalk-cdn.com/20190628/1473abceebb599cd80d6fd122ad92538.jpg)(https://uploads.tapatalk-cdn.com/20190628/11a3ed5d24c8d608fdf67be367c9a411.jpg)
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on July 31, 2019, 10:05:43 AM
Update on this issue.

Since last update I did:
- replaced main jets O-rings by proper ones 3.5x1.2 (bought in local shop). O-rings I had in carbs before were smaller crossection and larger diam and main jets were quite loose in casting. I had to apply some force to push jets into castings, before they went in very easy almost zero force. I was hoping that this is main reason for my issue (leak arounf main jets O-rings). Pic showing differences between O-rings attached
- replaced O-rings under intake manifolds (OEM). Another issue with manifolds discovered see another thread http://www.sohc.co.uk/index.php/topic,19713.msg174773.html#msg174773
- replaced rubbers between manifolds and carbs by new OEM
- carbs again checked for float height, including clear tube test (see pic for levels)
- carbs sync'ed after full warm up
- idle screws left in basic settings (1.5 turn)

Result:
There is zero or little improvement compare to before... Still, under ~3k RPM, using little trottle when trying to keep stable speed (cruising in the city) or trying to accelerate from ~2k - 3k still not good, engine has "hard" run, I feel it like too rich mix or like one cyl is not working. Otherwise, on higher RPM (5k+) I think bike runs well

I did >60miles test, most of the time bike runs on higher RPMs (this is my favourite test route, curvy uphill/downhill area). After i came back I check plugs. Result the same as before no2 is fouled, see pic. it is dry black smoke, easy to clean with brakecleaner, not oily. I can definitely put plug issue out of the question, becase I swapped plug 1 & 2 before this test, so previously dark no2 became clean in no1 and previously clean no1 is now black in no2..

Was thinking if this could be caused by coil/spark issue on no2 (intermittent spark, HT cable broken etc)?
But looking at plug there is some spark for sure. I tried to swap cables 2&3 but no2 is not long enough to reach cyl3...

Can somedy advice what else I can try/test?

note: Maybe no2 dark plug issue is linked to issues on low RPMs? (e.g. engine running virtually on 3 cylinders?)


Title: Re: 550K1 - carb questions (022A)
Post by: K2-K6 on July 31, 2019, 10:51:11 AM
To answer you're question about if the exhaust pipe hole could cause this problem,  I don't think that would because it's right at the end.

Have you considered moving the idle jets from one carb to swap with another to see if the problem transfers with those parts? Swap both jet and screw together to test it.

If it moves the problem,  then obvious which part is causing it. 

If it stays there as it is now,  then more linked to that cylinder.

To get one cylinder rich is less likely to be that cylinder specifically as it just needs more fuel to go like that.  Generally a fault mechanically would move toward lean.

So more likely fault is in the carb,  see what results you get with jet swap first as it may give definitive results.
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on July 31, 2019, 11:13:46 AM
OK, I can try. This could be manageable w/o taking carbs off the bike.
I doubt this is caused by idle jets themselves as I replaced all 4 by new Keihin genuine (38). But screw is another story.

Back to my previous question - what about eventual issue with coil / HT lead? (plug caps are new, but I can swap no2 and 3 caps at least to exclude them from investigation)
Title: Re: 550K1 - carb questions (022A)
Post by: K2-K6 on July 31, 2019, 11:23:54 AM
Yes to swapping the plug cap,  but do each swap on its own to avoid confusion.
Title: Re: 550K1 - carb questions (022A)
Post by: Nurse Julie on July 31, 2019, 11:42:46 AM
You probably have but, have you checked that all the holes are clean and clear in the air screws?
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on July 31, 2019, 11:47:32 AM
Well, this I did not check honestly!
I assumed it must be clear as carbs came from Gerben completely dry, I used them first time after rebuild

But will check! Thanks!
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on August 02, 2019, 11:12:01 AM
Small update : yesterday did test swapping plug caps no2 and no3 and cleaned plugs. Result is no change, no2 still dark.

Next steps
 - I'll try to test with another coil 2-3 to eliminate coil no2 output (cable) issue
- replace intake manifold 1-2 to ensure rubber seals as it should
- recheck carb2 for dirt, especially around airscrew
Title: Re: 550K1 - carb questions (022A)
Post by: K2-K6 on August 02, 2019, 01:30:01 PM
Thinking about this Erny over a few days, did you see a previous thread on here with very similar problem (I forget which owner) and it was a problem none of the suggestions we made got the problem.

Finally turned out to be the original exhaust of one cylinder was partially blocked within the first section. It seems it was manufactured with the pipe's inner skin deformed about 200mm down into the pipe from front entry. 

If you removed the pipe from cylinder two and either put a camera down there or something to see if there's a restriction it would tell you.
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on August 02, 2019, 01:45:39 PM
hmmm, interesting idea. Will try to check that, just not sure how long cable my camera has. But in theory it could explain too.
Title: Re: 550K1 - carb questions (022A)
Post by: K2-K6 on August 02, 2019, 01:54:27 PM
I've tried searching for it but so far can't find the thread,  someone else may help remembering to give us a link.

Pictures of it posted and cut open afterwards as pipe was scrapped.
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on August 02, 2019, 01:59:59 PM
my pipes does not look bad from outside but have tiny holes at the bottom silencer rim. So shall not be normally bad
Title: Re: 550K1 - carb questions (022A)
Post by: K2-K6 on August 02, 2019, 02:10:00 PM
That problem could not be seen from the outside.

The original pipes are double skinned,  so one pipe inside the pipe you see from outside.  They did this to prevent the pipe's discolouration from heat of exhaust which is why they don't normally go blue from running.

It's just the inside pipe that was buckled from original manufacture it appears,  so was like it from being a new bike,  the problem must have been there all along.
Title: Re: 550K1 - carb questions (022A)
Post by: Trigger on August 03, 2019, 08:20:13 PM
I think people read too much in to plug colour. I have had a look at the pictures of the plugs and would run with them.
To get the so called perfect plug colour you would need a new exhaust, new carbs and a fully rebuilt top end. You can get a dark plug from a valve not seating properly .

Always better to have a slightly darker plug than one that is running too lean  ;)
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on August 05, 2019, 09:50:21 PM
Graham, thanks for your opinion, I start to feel the same now :)

I managed to have another coil (from 550F 1976) to test - result is no change, plug 2 still darker than others.

Next:
waiting for intake manifold to replace mine w/o grooves. Carbs will go off again, so time to re-check around air screw (did not checked before).
if no improvement, I'll try to look at another carb set  :-\
Title: Re: 550K1 - carb questions (022A)
Post by: deltarider on August 05, 2019, 09:55:03 PM
Without having read all the above... have you checked the plugcaps, both connections as well as resistance?
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on August 05, 2019, 10:19:42 PM
yes, they are all checked, are new NGK, I even swapped cap 2 and 3, issue remains on cyl2

Moreover, ign coil I had for test had came with caps, so I tested another coil and another cups. No change
Title: Re: 550K1 - carb questions (022A)
Post by: jon stead on August 09, 2019, 07:05:20 PM
Thinking about this Erny over a few days, did you see a previous thread on here with very similar problem (I forget which owner) and it was a problem none of the suggestions we made got the problem.

Finally turned out to be the original exhaust of one cylinder was partially blocked within the first section. It seems it was manufactured with the pipe's inner skin deformed about 200mm down into the pipe from front entry. 

If you removed the pipe from cylinder two and either put a camera down there or something to see if there's a restriction it would tell you.

Hi, yes, it was me that had the collapsed inner pipe on number 3 cylinder. However, in my case, the engine ran lovely at lower revs and struggled at higher revs, which would fit with a partially blocked exhaust.
Title: Re: 550K1 - carb questions (022A)
Post by: jon stead on August 09, 2019, 07:16:10 PM
I've tried searching for it but so far can't find the thread,  someone else may help remembering to give us a link.

Pictures of it posted and cut open afterwards as pipe was scrapped.

http://www.sohc.co.uk/index.php/topic,13971.msg119059.html#msg119059
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on September 02, 2019, 09:15:02 AM
Graham, thanks for your opinion, I start to feel the same now :)

I managed to have another coil (from 550F 1976) to test - result is no change, plug 2 still darker than others.

Next:
waiting for intake manifold to replace mine w/o grooves. Carbs will go off again, so time to re-check around air screw (did not checked before).
if no improvement, I'll try to look at another carb set  :-\
After some time update :
- intake manifold replaced (thanks Phil again!)
- carbs checked again, especially around air screw on carb 2

Result - no change, plug 2 still darker than others.

Next: will try to tune airscrew (now all 4 are still at standard settings 1.5turns out).

For this would be great to have good RPM meter, I have one digital from China, but not good for this application as it refreshes each 1s (I think) and rpms resolution seems to be +/- several tens..
Can someone recommend good sensitive  RPM meter for idle?
Title: Re: 550K1 - carb questions (022A)
Post by: K2-K6 on September 02, 2019, 09:46:29 AM
Some multi meters will give you a frequency readout that you can use,  just connect to one of the points trigger wires to read crankshaft rotations.

That's what electronic tachometer do when installed in vehicles (although some read frequency from alternator output).

As a cross check of rich running carburettor,  you should be able to swap that idle jet with another carb to see if the problem moves. It will give you a cross check of relative calibration of one jet to another.
Title: Re: 550K1 - carb questions (022A)
Post by: Erny on September 02, 2019, 10:13:51 AM
Thanks, great idea with freq meter, I should have some.
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