Honda-SOHC

SOHC.co.uk Forums => CB350/400 => Topic started by: Alexrayz on January 09, 2022, 07:24:43 PM

Title: The elusive surge
Post by: Alexrayz on January 09, 2022, 07:24:43 PM
Hey all, hope you're doing good!

I have made significant progress with my bike the last few weeks I'd like to especially thank Alankelly1 for his most precious help and Nurse Julie for the O-rings and the mounting advice that made the job of replacing the old ones so much easier!.

So: I have stripped the carbs, cleaned and blown every jet screws and passages possible. I have swapped the idle jets I had from an overhaul kit with nice keihin originals, thanks Alan!
The floats have been set to 21mm and checked for holes. The carbs have been bench synced. O rings were replaced and put in place with red rubber grease to avoid shearing. The slides snap back nicely. The mixture screws have been set to 1 1/2 turns out.
After installing the carbs back I have fiddled with the idle stop screw to get to 1200rpm when warm and off the choke. I then set the fast idle screw to 0.2mm clearance.
I get a respectably stable idle at 1200 rpm when warm. Startup isnt too rough.
The problem I have is jsut that the damn thing surges, it can be when operating the throttle or just when left alone for a while. In which case only fiddling with the idle stop screw will make it come down. I then have to fiddle again to bring it back to 1200rpm.
I have removed the throttle cables to make sure they were not messing with anything and indeed no change in behavior. |

Overall it seems like a lean condition problem. But when I turn the mixture screws by a 1/4 turn in to enrich the mix it stutters. My guess would turn to an air leak but doing the "squirt brake cleaner on suspect spots"method to no avail. I tried the inlet boots, fore and aft; the top of the carbs on the gaskets, the depression ports on the boots and the spark plugs just in case and nothing.

Do you guys have any leads or ideas what might cause this?

So close!

Take care
Title: Re: The elusive surge
Post by: Nurse Julie on January 09, 2022, 09:00:16 PM
What spark plugs have you fitted Alex?
Title: Re: The elusive surge
Post by: daz-j on January 10, 2022, 12:04:45 PM
Hi Alex, apologies for butting in with an extra question but you beat me to it, I was going to ask advice for very similar issues - in my case the engine starts easily but isn't stable when idling - the revs can randomly increase up to ~3-4000, or decrease to the point of stalling, without any throttle input.  Hopefully we can learn together and crack the problems!

I've taken the carbs off a few times now (the joys!) to clean and recheck things - all appears to be ok to the best of my knowledge.  When refitting I've rechecked valve clearances, timing, pilot air screws, vacuum leaks, carb balance - again all seem ok but the issue persists.

So the carbs are off again - I'm slightly suspicious of seals I fitted previously so have just ordered a kit from Julie to replace them.  General advice welcome, but my main question for the forum at this point is what are the worthwhile checks for me to do whilst the carbs are stripped and on the bench please?
Title: Re: The elusive surge
Post by: McCabe-Thiele (Ted) on January 10, 2022, 12:56:14 PM
FWIW - this a long shot as I do not know at what point the advance & retard mechanism trips in. I would check the mechanism is nice and free plus check the timing dynamically rather than statically.
Likewise as NJ has noted are you on the right plugs & caps &  leads.
Title: Re: The elusive surge
Post by: K2-K6 on January 10, 2022, 12:57:49 PM
Small observation, have you bench synced the carbs as detailed in "tricks and tips" section of forum ?

There's simple but very influential information in there that sets the carb slides in relation to the throttle lift mechanism to allow correct balanced movement to work without the relationship being compromised.

It's easy to miss this potential conflict if the carbs have been dismantled and rebuilt.
Title: Re: The elusive surge
Post by: Alexrayz on January 10, 2022, 04:39:07 PM
Hey Julie, finally got time to search for it, I knew it was buried somewhere in my mailbox.

The plugs are NGK D8EA and the caps fitted on it are XD05F and VD05F. The leads are originals, same as the coils.

Ted: I did do that, I have a daytona electronic ignition trigger, there is an LED that turns on to show when the sparks will happen and I'd say it is right on the dot. It was a static test though.
You'd recommend getting a stroboscopic light?

K2-K6 I have bench synced them yup. Some lad at work advised me to do a running sync to make sure everything is tip top on that front. Even with a bench sync you can get inbalances that throw off the whole thing.

Daz-J did you check float heights?

Thanks for your help guys, means a lot!

Take care,

Alex
Title: The elusive surge
Post by: allankelly1 on January 10, 2022, 05:01:23 PM
Question for the group rather than Alex but may help

With the original coils there are two HT leads but can you lose one HT output but the other HT output be OK?

I.e 1 coil does cylinders 1 and 4 and the other does 2 and 3 so can 1 coil intermittently feed a spark to say cylinder 1 but the spark to cylinder 4 is consistent as on the wiring diagram it look like all plugs “go to earth” unlike my RD where both HT leads make up 1 circuit so if you disconnect 1 cylinder you lose everything as you have broken the single complete HT circuit

Hope that makes sense

Just that an inconsistent spark on 1 cylinder will imitate this surge as when all 4 are running the revs will be X but if you lose a cylinder the revs will drop to Y as the other 3 cylinders have to carry the “dead” cylinder and then when it decides to run again the revs will rise

Just a question for the experts as had this issue on a old 125T where a dodgy CDi was dropping in and out so it would run on two then drop to one cylinder for a short period of time with a big drop in revs to where it would die if at tick over and then it would decide to work again with again the rise in revs back to correct idle


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Title: Re: The elusive surge
Post by: Alexrayz on January 10, 2022, 05:43:45 PM
Hey Alan,

I guess that could be possible with old cables. As it gets old with many manipulations and service the copper wires can fray and cut which could lead to intermittent connections.

I have never encountered the case in motorcycles or cars or else but I have in houses and offices with old electric installations.

Soo maybe?
Title: The elusive surge
Post by: allankelly1 on January 10, 2022, 05:52:18 PM
Hey Alan,

I guess that could be possible with old cables. As it gets old with many manipulations and service the copper wires can fray and cut which could lead to intermittent connections.

I have never encountered the case in motorcycles or cars or else but I have in houses and offices with old electric installations.

Soo maybe?
Hi Alex

Yes that why I asked the question

When I did my Boyer system I bit the bullet as replaced the complete ignition system (As in theory the whole system was over 40 years old) So that as well as the magnet pick up system that replaced the points system, it also does away with the mechanical advance and replaces it with a “mapped” CDI (so you have an advance curve programmed in) and two new coils etc

But on the old Honda system I am not sure if both HT cable make up the HT circuit(Like my RD). Or as I suspect on the Honda,one end of the HT winding goes to earth but the other end is split to two HT leads, and then goes to earth via both spark plugs, hence one lead could be good and the other bad / damaged giving a intermittent spray to that cylinder.

Let’s see what the experts say

Best wishes Al


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Title: Re: The elusive surge
Post by: 400 Cafe Racer on January 10, 2022, 06:22:27 PM
Hey Alan,

I guess that could be possible with old cables. As it gets old with many manipulations and service the copper wires can fray and cut which could lead to intermittent connections.

I have never encountered the case in motorcycles or cars or else but I have in houses and offices with old electric installations.

Soo maybe?

Hi Allan and Alex,

To the best of my knowledge the spark performance on each coil provides for simultaneous sparking on both cylinders served by the coil - ie  1 + 4 for one coil and 2 + 3 for the other coil. This means in fact that the cyinder that is not on compresion stroke has the spark "wasted".

Unless there is a specific problem with one HT lead or cap, the spark performance should be the same.

My comments below assume that there are no carb or inlet manifold air leaks.

Having looked  at the issue you have got Alex, I encounted a similar situation during tuning my carbs after doing only a bench sync. I found that spending time afterwards with close attention on the vacuum guage balancing and mixture sync method, this unevenness and surge disappeared.  It only needs one of the cylinders not contributing equally to the tick over, and a little off with the mixture to cause this. When the off cylinder decides to clear a little and then "comes in and contributes", this causes a rise in engine revs for no apparent reason. You will be supprised when making adjustment with the vacuum guage, even - say 5 degrees - rotation of the balance screw for 1 cylinder will make a big difference to all the other cylinders.  Just keep repeating the sequence until they are all the same.

Hope this helps. ;) :)

Dennis

PS  Just thought I would add a small note to explain that for example in the same period (1970 - 1980 )that with a 6 cylinder car engine with 2 or 3 Carbs, to overcome a tendency for imbalance on idling the manufacturer would tend to put a small balance pipe connected across the manifolds so that all cylinders could suck Air/Fuel mixture, even though the individual Carbs may not be set spot-on.

In the case of the 400F all manifols are individual and have NO interconnecting balance pipe, so this makes the correct balancing and mixture for each Carb and Cylinder hyper critical to get best running and performance.
Title: Re: The elusive surge
Post by: Alexrayz on January 10, 2022, 09:46:47 PM
Hey Dennis, thanks for all that sweet sweet info, I think I will do the vacuum gauge sync next time working on the bike. Seems like it will clear up more questions and hopefully solve my issues.

I was actually wondering if there is a proper methodology for the mixture screw settings. I know that the look of the plugs is a telltale sign but I was wondering how precise it gets without requiring an IR exhaust gas probe.

Cheers!
Title: Re: The elusive surge
Post by: K2-K6 on January 10, 2022, 10:26:40 PM
Certainly it's interesting to gain the contributing views already expressed, and hopefully add to the picture.

Generally these engine don't "surge" as such with a std setup but would more indicate something amiss that has not been quantified.

The reference to bench setup in the tips section is to very particularly include the routine contained in establishing the correct offset between carb slide position and overall idle speed control mechanism. I'd encourage anyone to fully apply that in rebuilding these carburettor to prevent effectively unseen errors while using.
Without that,  you can build in a mechanical conflict that becomes apparent as you try to set the idle rpm speed with the adjuster as it's possible to force a shift in balance between the 4 carbs by doing this. It shouldn't be there, obviously,  but completing that routine will remove that potential.

Carb balance is not in reality set for idle speed. That may seem contradictory, but it's primarily to set parity of slide height for wider open settings with idle speed smoothness a side effect resulting from this adjustment. 

Honda gave in their manuals at the time a routine to then fine tune each individual cylinder's speed at idle to trim that point of running,  once the parity of slide has been established, which is micro adjustment of the airscrew individually.

I'd,  at this point in how it's running, argue not to set the sync using gauges. If you've a problem on one cylinder that's not fully identified, then setting by using vac guages can put a compensating error into your carburettor balance that's not needed. Yes it may sound better at that point, but it's wrong with other mechanical errors needing attention first.
Pre requisites for vac synchronisation are that all other parameters are within adjustment before that is employed.

Bench synchronisation avoids the above as it's independent of engine condition and running problems residing elsewhere, also perfectly good enough to run the engine accurately.  Guages don't hold the upper hand here and it may help to diagnose faults by leaving accurately "bench" set as detailed.

Listing order of work, bench sync as tips post on here, then assess what you've got without further changes. It may influence the condition, but you can only check that one way.
Then look at idle air setup in manual and complete that to assess effects.
Title: Re: The elusive surge
Post by: K2-K6 on January 10, 2022, 10:34:15 PM
"Dennis

PS  Just thought I would add a small note to explain that for example in the same period (1970 - 1980 )that with a 6 cylinder car engine with 2 or 3 Carbs, to overcome a tendency for imbalance on idling the manufacturer would tend to put a small balance pipe connected across the manifolds so that all cylinders could suck Air/Fuel mixture, even though the individual Carbs may not be set spot-on."

That's generally used on SU, Solex type constant velocity carburettor and not essentially to promote mixture sharing but to give vacuum parity across the different intake tracts as it's the vacuum variation that would cause the fuel air metering slide to run at different heights in spite of each throttle butterfly being equal in position. 

These engine having a fixed relationship from one slide to another don't  manifest that variance, and so don't need it.
Title: Re: The elusive surge
Post by: McCabe-Thiele (Ted) on January 11, 2022, 01:07:44 AM
Hey Julie, finally got time to search for it, I knew it was buried somewhere in my mailbox.

The plugs are NGK D8EA and the caps fitted on it are XD05F and VD05F. The leads are originals, same as the coils.

Ted: I did do that, I have a daytona electronic ignition trigger, there is an LED that turns on to show when the sparks will happen and I'd say it is right on the dot. It was a static test though.
You'd recommend getting a stroboscopic light?

K2-K6 I have bench synced them yup. Some lad at work advised me to do a running sync to make sure everything is tip top on that front. Even with a bench sync you can get inbalances that throw off the whole thing.

Daz-J did you check float heights?

Thanks for your help guys, means a lot!

Take care,

Alex


The bonus of a strobe check is you will see the timing fluctuating - that said it would not get you any further forward as a carb inbalance causing a surge would probably bring in the advance/retard mechanism thus showing timing fluctuation. Someone here will know at what r.p.m the advance trips in.
Sounds like you have it right statically with your method.

I did my timing statically initially and then dynamically - there was a very slight difference between the pairs of cylinders,  after adjusting 2 & 3 it made no obvious difference though I was not able to ride it on the road to check for what it felt like in use.





Title: Re: The elusive surge
Post by: Bryanj on January 11, 2022, 01:37:41 AM
Should be on full advance by 2500 rpm
Title: Re: The elusive surge
Post by: 400 Cafe Racer on January 11, 2022, 03:35:07 PM
Hey Dennis, thanks for all that sweet sweet info, I think I will do the vacuum gauge sync next time working on the bike. Seems like it will clear up more questions and hopefully solve my issues.

I was actually wondering if there is a proper methodology for the mixture screw settings. I know that the look of the plugs is a telltale sign but I was wondering how precise it gets without requiring an IR exhaust gas probe.

Cheers!

Hi  thanks Alex, you are welcome,

I would say that the if your bike is standard spec regarding air intake, air filter design and exhaust system, that the standard procedures and guides documented for carb settings are the best to use. The plug colour can be a useful guide for normal settings.

In any event the matching of equal slide heights from idle to full throttle is desireable to ensure equal fuel/air volume to all cylinders and in theory deliver equal power from each cylinder. There inevitably could be small variations on position of the idle mixture screw position between individual cylinders for final setting, due to small variations in manufacture. This is fundamental to all tuning.

On my 400F the air filters and exhaust are non standard and I have an Innovate Air / Fuel Ratio guage already fitted which was very useful during re-jetting and setting up under actual running conditions on the road. The settings I have used are to deliver best power, torque and engine temperature, with no specific regard to economy or plug colour.

I have assumed that all is OK with the Ignition advance unit and that if you have standard ignition, that all your contact breaker points, condensers and other factors are correct.

As Ted has hinted, its worth checking that all is OK with the static timing and centrifugal advance unit. Look for anything that could cause variation. Seized or stiff action on the spindle or weights, preload on the springs with no looseness, correct full advance as Bryan says at 2500 RPM

I am sure with patience and perseverence you will nail the problem - and keep us up to date with how you get on.  ;) :)

Dennis
Title: Re: The elusive surge
Post by: daz-j on January 11, 2022, 09:10:22 PM
Thanks Alex, yes I have checked the float heights previously but I'm thinking maybe under-estimated how accurate they need to be, so will be revisiting that when I reassemble the carbs with the new O rings that arrived today (thanks Julie).

Really interesting to read the viewpoints on carb balancing thank you.  I've bench sync'd previously before refitting, pretty confident that I did it correctly but will go through it carefully again and report back. 
Title: Re: The elusive surge
Post by: philward on January 11, 2022, 09:17:38 PM

On my 400F the air filters and exhaust are non standard and I have an Innovate Air / Fuel Ratio guage already fitted which was very useful during re-jetting and setting up under actual running conditions on the road. The settings I have used are to deliver best power, torque and engine temperature, with no specific regard to economy or plug colour.

[/quote]

Dennis, I'd be interested to hear how the Air/Fuel physically fits on a 4 cylinder 4 carb bike?
Title: Re: The elusive surge
Post by: Lobo on January 11, 2022, 09:58:54 PM
… the easiest way to rule out an issue wrt fluctuations in the timing would be to ‘jam’ the advance mechanism to fully regarded and run the bike at idle.
Title: Re: The elusive surge
Post by: 400 Cafe Racer on January 12, 2022, 02:32:49 PM

On my 400F the air filters and exhaust are non standard and I have an Innovate Air / Fuel Ratio guage already fitted which was very useful during re-jetting and setting up under actual running conditions on the road. The settings I have used are to deliver best power, torque and engine temperature, with no specific regard to economy or plug colour.


Dennis, I'd be interested to hear how the Air/Fuel physically fits on a 4 cylinder 4 carb bike?
[/quote]


Hi Phil,

To avoid distraction from Alexs' post I have put a link to my post showng recent guage additions. I have just added a final one to show where the sensor is fitted in the intermediate pipe.

Dennis
http://www.sohc.co.uk/index.php/topic,26987.0.html
Title: Re: The elusive surge
Post by: philward on January 12, 2022, 05:35:12 PM

On my 400F the air filters and exhaust are non standard and I have an Innovate Air / Fuel Ratio guage already fitted which was very useful during re-jetting and setting up under actual running conditions on the road. The settings I have used are to deliver best power, torque and engine temperature, with no specific regard to economy or plug colour.


Dennis, I'd be interested to hear how the Air/Fuel physically fits on a 4 cylinder 4 carb bike?


Hi Phil,

To avoid distraction from Alexs' post I have put a link to my post showng recent guage additions. I have just added a final one to show where the sensor is fitted in the intermediate pipe.

Dennis
http://www.sohc.co.uk/index.php/topic,26987.0.html
[/quote]
Thanks Dennis - seems its not pracrical for me - My 500/750 have standard exhausts and my CR750  has 4 into 4 race exhaust. (all of which I'm not prepared to weld bits on obvious reasons) - thanks anyway
Title: Re: The elusive surge
Post by: daz-j on January 15, 2022, 07:44:58 PM
Just to report back I seem to have cured the problem  ;D - I took the carb bodies to work and gave them a good blast with compressed air, fitted the new seals, and reset the float heights.  So one (or a combination?) of these made the difference - my gut feeling is the float heights were the culprit.

Thanks Alex and everyone, hopefully I won't need to take those carbs off again anytime soon!
Title: Re: The elusive surge
Post by: Nurse Julie on January 15, 2022, 08:37:14 PM
Just to report back I seem to have cured the problem  ;D - I took the carb bodies to work and gave them a good blast with compressed air, fitted the new seals, and reset the float heights.  So one (or a combination?) of these made the difference - my gut feeling is the float heights were the culprit.

Thanks Alex and everyone, hopefully I won't need to take those carbs off again anytime soon!
I'm pleased you have them sorted Darren, well done.
Title: Re: The elusive surge
Post by: 400 Cafe Racer on January 16, 2022, 04:09:02 PM
Just to report back I seem to have cured the problem  ;D - I took the carb bodies to work and gave them a good blast with compressed air, fitted the new seals, and reset the float heights.  So one (or a combination?) of these made the difference - my gut feeling is the float heights were the culprit.

Thanks Alex and everyone, hopefully I won't need to take those carbs off again anytime soon!

Hi Alex,

Pleased it was straight forward to find and that you got it fixed . :)

All the best

Dennis
Title: Re: The elusive surge
Post by: Alexrayz on January 17, 2022, 11:28:19 AM
Hey everyone,

Just giving an update on the situation: Still not working atm.

The last actions taken were as follows: Did a vacuum sync which gave good results, smoother idle and no surges (or at least none happened while I was testing in in the shop). I still had revs hanging after giving the slides a quick lift. Actuating the slides the other way helped bringing it down. New issue though: Even without the idle screw acting on the slides the tick over is 2500RPM. No good.

My guess while vacuum syncing I lifted the slides too much. So I decided to get the carbs off again and redo the bench sync.

Did just that, also reajusted the choke's butterflies as they were not even. Put the carbs on again and it ran like crap again. Surges crazily and when it doesnt it can barely hold tick over at 1000rpm. Acting on the idle screw results in instant surges to 2500/3500 rpm. Still managed to sort of sync it at 2500rpm but without improvement.

Tried to lift the slides with the cable grip and it killed the engine immediately. I gave up after that.

I am starting to consider seeing a mechanic as I feel this is beyond my capabilities and knowledge.

I really struggle to see a consistency in the behavior and the right actions to take.
Title: Re: The elusive surge
Post by: K2-K6 on January 17, 2022, 12:12:58 PM
Its this proceedure referred to above http://www.sohc.co.uk/index.php/topic,17769.0.html have you worked in this sequence as it deals with exactly the problem you describe ?

Effectively, it resets the initial relationship between the slide position in the carb venturi and where the main idle speed adjust screw interacts with the throttle lift system components.

If the two conflict, then you'll never get it to run consistently.
Title: Re: The elusive surge
Post by: Alexrayz on January 17, 2022, 02:50:36 PM
I did indeed! Even found an actuall drill bit that is 0.15mm (1/8")
Title: Re: The elusive surge
Post by: Bryanj on January 17, 2022, 02:59:14 PM
1/8 inch is 3mm not  0.15mm
Title: Re: The elusive surge
Post by: Alexrayz on January 17, 2022, 03:08:28 PM
1/8 inch is 3mm not  0.15mm

Right. 1/16" then. Still not accustomed to imperial measurements, but it was 0.15mm thick measured on the engine side.
Title: Re: The elusive surge
Post by: K2-K6 on January 17, 2022, 05:49:28 PM
I did indeed! Even found an actuall drill bit that is 0.15mm (1/8")

Apologies for labouring this point, but it's fundamental to identifying why you are having difficulty.  If you complete this successfully you should be able to wind the "idle" screw down far enough for there to be no real gap under the slides when you look through the carburettor, this is correct and should be able to effectively almost stall the engine when it's running.

It's then important that you leave them alone (don't now synchronise with guages) to further assess the problem. This effectively separates different causes to let you find the real problem. 

Then start the engine when reassembled for 20 seconds and switch off. Now check to see if all cylinders have hot exhaust which would indicate they all fire straight away. Any cold pipes and you'll need to find why that cylinder is not firing. All ok ? Move to next check.

Then, with it running, complete a spray test on inlet tracts to see if the engine speed alters (spray wd40 or similar around carb to head rubbers) this should not change the engine speed,  but if it does it will confirm there's a leak somewhere that is allowing air to enter the engine after the throttle slides which are supposed to be the only control.

Title: Re: The elusive surge
Post by: Alexrayz on January 19, 2022, 08:46:37 AM
Hey K2 (is that your droid name?)

Nah man by all means labour away! Having taken some time off and re read Bryanj's post, I did not in fact follow that procedure to the letter. I will take it back from the top.

Two things I have forgotten to mention: I do not have the spring retainer for the air filter and I haven't got either the air filter cover. I have used duct tape as a makeshift cover but no garantee it is air tight. Do you think these missing elements might leanen the mixture? I say this knowing that at the moment the mixture is rich ( sooty plugs) but if it does leanen the mix it wouldn't  help getting a reliable setup right?
Lastly on that front: The airbox is the original and because of its age, it has warped a bit, the front end is a tad concave. Consequently connecting properly the air intakes for carb 2 and 3 is not feasable. I can get them in and even tighten the collars but not get the connectors all the way in. I guess that doesn't help either? Could not find a lot of info on those issues.

All the best
Title: Re: The elusive surge
Post by: Bryanj on January 19, 2022, 10:51:19 AM
If you have covered the top with tape no air can get in! Use half a clothes peg to pushthe filter forward and leave the top open totest
Title: Re: The elusive surge
Post by: McCabe-Thiele (Ted) on January 19, 2022, 11:05:23 AM
When I ran my engine for the first time after 12 years prior to the current rebuild I had great difficulty with fitting the four air box connections - it's such a tight space and difficult to connect them.

When rebuilding the bike I found that with no rear mudguard, wheel, or filter housing  the whole lot can be fitted much easier and you can get the pipes to fit fully & clamp them in place. That said it's a lot of work to just get the darn pipes fitting into the carb intakes - just mentioned it out of interest.

Trying to think outside the box:-

Just a thought are all your compressions good & even could this variation be due to changes in compressions as the engine starts to warm up?


Title: Re: The elusive surge
Post by: taysidedragon on January 19, 2022, 11:48:59 AM
Alex, the best way to get the airbox rubbers to fit onto the centre carbs is to remove the air filter element from the   air filter box, remove the connector tube and rubber to give you as much access room as possible.
Then use a screwdriver handle or a piece of wood with a rounded end to push the airbox rubbers forward onto the carb stubs from inside. Your hand has to manoeuvre down into the air filter box and partly through the large opening in the front.

It's difficult,  frustrating and even painful at times, but it's possible.
Title: Re: The elusive surge
Post by: allankelly1 on January 19, 2022, 11:54:02 AM
Hey K2 (is that your droid name?)

Nah man by all means labour away! Having taken some time off and re read Bryanj's post, I did not in fact follow that procedure to the letter. I will take it back from the top.

Two things I have forgotten to mention: I do not have the spring retainer for the air filter and I haven't got either the air filter cover. I have used duct tape as a makeshift cover but no garantee it is air tight. Do you think these missing elements might leanen the mixture? I say this knowing that at the moment the mixture is rich ( sooty plugs) but if it does leanen the mix it wouldn't  help getting a reliable setup right?
Lastly on that front: The airbox is the original and because of its age, it has warped a bit, the front end is a tad concave. Consequently connecting properly the air intakes for carb 2 and 3 is not feasable. I can get them in and even tighten the collars but not get the connectors all the way in. I guess that doesn't help either? Could not find a lot of info on those issues.

All the best
Hi Alex

Here is the picture of the filter retaining

(https://uploads.tapatalk-cdn.com/20220119/0a88b226be3bd2abca8cfe786195658e.jpg)

You can get this from David Silvers

Also if you have no filter lid I could 3d print one based on my original

(https://uploads.tapatalk-cdn.com/20220119/a3af548c20eb97a355ffc7e6a35aec7f.jpg)

Just let me know

Best wishes Al


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Title: Re: The elusive surge
Post by: Alexrayz on January 19, 2022, 12:05:18 PM
Hey Alan,

That would be great indeed, I'll see that with you by PM! I was thinking of making a sudo retainer with a wire coathanger, just something to hold the filter snug.
Title: Re: The elusive surge
Post by: allankelly1 on January 19, 2022, 12:19:58 PM
Hey Alan,

That would be great indeed, I'll see that with you by PM! I was thinking of making a sudo retainer with a wire coathanger, just something to hold the filter snug.
Yes coat hanger would work

Also modelled your air box lid now

(https://uploads.tapatalk-cdn.com/20220119/545e2b096d4a6ea8240f1fac9e1ef8fe.jpg)


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Title: Re: The elusive surge
Post by: Alexrayz on January 19, 2022, 12:53:47 PM
Thanks Alan!
Title: Re: The elusive surge
Post by: allankelly1 on January 19, 2022, 01:11:57 PM
If you have covered the top with tape no air can get in! Use half a clothes peg to pushthe filter forward and leave the top open totest
Solid lid or duct tape is ok as there snorkel at the back of the filter housing

(https://uploads.tapatalk-cdn.com/20220119/4b1ba6707a3c53d08525e372127ee2ea.jpg)


Sent from my iPhone using Tapatalk
Title: Re: The elusive surge
Post by: Alexrayz on January 19, 2022, 01:31:36 PM
Alex, the best way to get the airbox rubbers to fit onto the centre carbs is to remove the air filter element from the   air filter box, remove the connector tube and rubber to give you as much access room as possible.
Then use a screwdriver handle or a piece of wood with a rounded end to push the airbox rubbers forward onto the carb stubs from inside. Your hand has to manoeuvre down into the air filter box and partly through the large opening in the front.

It's difficult,  frustrating and even painful at times, but it's possible.

I shall suffer then. Sucks to have big hands in those cases. Thanks for the tips!

Gotta say this thread is starting to co;pile quite a bit of info, good for everyone.
Title: Re: The elusive surge
Post by: allankelly1 on January 20, 2022, 09:16:49 AM
Well that a new air box lid for Alex sorted

(https://uploads.tapatalk-cdn.com/20220120/668907bce11006c7a8f9fd97448c9abb.jpg)


(https://uploads.tapatalk-cdn.com/20220120/8ac8c65932d1b7edec20d546f3971dea.jpg)
(https://uploads.tapatalk-cdn.com/20220120/554b39c50ab7822223969f31a79c87b1.jpg)


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Title: Re: The elusive surge
Post by: taysidedragon on January 20, 2022, 03:49:28 PM
Very nice. 👍 You might get a few requests for more of those. 😁
Title: Re: The elusive surge
Post by: K2-K6 on January 20, 2022, 04:36:15 PM
Very nice work there Alan.
Title: Re: The elusive surge
Post by: allankelly1 on January 20, 2022, 04:37:16 PM
Very nice work there Alan.
Thank you


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Title: Re: The elusive surge
Post by: Dave on January 20, 2022, 05:01:24 PM
Excellent work!
Title: Re: The elusive surge
Post by: Nurse Julie on January 20, 2022, 05:34:22 PM
It's a shame I don't need one, due to not having Hettie anymore and she had a lid anyway but, thats just great.
Title: Re: The elusive surge
Post by: K2-K6 on January 21, 2022, 09:41:00 AM
Hey K2 (is that your droid name?)

Nah man by all means labour away! Having taken some time off and re read Bryanj's post, I did not in fact follow that procedure to the letter. I will take it back from the top.

Two things I have forgotten to mention: I do not have the spring retainer for the air filter and I haven't got either the air filter cover. I have used duct tape as a makeshift cover but no garantee it is air tight. Do you think these missing elements might leanen the mixture? I say this knowing that at the moment the mixture is rich ( sooty plugs) but if it does leanen the mix it wouldn't  help getting a reliable setup right?
Lastly on that front: The airbox is the original and because of its age, it has warped a bit, the front end is a tad concave. Consequently connecting properly the air intakes for carb 2 and 3 is not feasable. I can get them in and even tighten the collars but not get the connectors all the way in. I guess that doesn't help either? Could not find a lot of info on those issues.

All the best

Nothing profound in my site name, met someone from this site at the Ace cafe that told me about this site, setting up first ever such interaction and just used previous Honda models that I'd owned. Not very inventive I'm afraid  ;D

For the surge problems, as we on here can't be present to see things it makes the process a little more laboured naturally.  The bench synchronisation and then leaving it alone is also an important element in giving continuity of conditions. It is easily good enough to run any of the four cylinder engines at correct parity and importantly vetifies that technically correct status to analyse other components and their effects.
If, gradually, you fix down each variable (the box lid another good move) then the potential problem sites will just be less in number, and possibly more visible to help you find solution.
The significant problem that may arise with gauge carb sync at this point is that if you have an air leak or similar as principle cause, then the synchronisation with guages will direct you to adjust the slides to accommodate it,  making another error included on the bike, then it just keeps you going round in circles.

Something else to check if the carbs are appart is the idle circuits as they are very small and hard to fully clean, but absolutely crucial to how the engine runs.
One way to check with the carbs installed is to try each carb on it's own (not change all four together) and turn the idle airscrew both in and out from it's accepted setting. Each one "should" give you a response in engine running as you move it. If there's no or very little response, that would indicate that one is partially or fully blocked and nor able to meter fuel consistently enough to run smoothly.
Title: Re: The elusive surge
Post by: Lobo on January 21, 2022, 11:17:33 AM
Last year I had no end of problems with a 15HP outboard that wouldn’t idle consistently. I had the carb apart a couple of times, was CONVINCED it was clean as a whistle and moved on to dismantle the whole bloody engine as thinking internal seals (2 stroke). Not fixed. Bought a whole new ignition system. Not fixed. Tearing my hair out. Carb out a third time… and on this occasion I finally discovered a blocked gallery in the idle circuit … aargh. Totally embarrassed at the time and expense it cost me 🙁.
(the gallery split into two paths - unknown to me. Finally got it clear by successive syringes of isopropyl blasting through. Happy days 🙄)

I’m no mechanic… but surely an air leak on the atmospheric side of the carb would not give the significant problems you’re seeing? Ie is it not more likely within the carb or inlet manifold area?
Title: Re: The elusive surge
Post by: Alexrayz on January 22, 2022, 02:12:45 PM
Last year I had no end of problems with a 15HP outboard that wouldn’t idle consistently. I had the carb apart a couple of times, was CONVINCED it was clean as a whistle and moved on to dismantle the whole bloody engine as thinking internal seals (2 stroke). Not fixed. Bought a whole new ignition system. Not fixed. Tearing my hair out. Carb out a third time… and on this occasion I finally discovered a blocked gallery in the idle circuit … aargh. Totally embarrassed at the time and expense it cost me 🙁.
(the gallery split into two paths - unknown to me. Finally got it clear by successive syringes of isopropyl blasting through. Happy days 🙄)

I’m no mechanic… but surely an air leak on the atmospheric side of the carb would not give the significant problems you’re seeing? Ie is it not more likely within the carb or inlet manifold area?

Haha yep I know that feeling. It sucks harder than an airplane toilet.

Makes me wonder if there are any resources like schematics showing the innards of a carb.
Title: Re: The elusive surge
Post by: Alexrayz on January 25, 2022, 10:10:08 AM
Hey everyone, I figured a small update would be in order.

I took the carbs off this week end to go over it once again. Checked all the passages I’m aware of and rechecked the floats height. The mixture air screws were set to 2 turns out as the plugs were sooty and the manual calls for 2 turns as a base setting for the 400F. I then did a bench sync, this time making sure I followed bryanj’s instructions to the letter.

With the carbs back on I made a sudo air filter cover and spring (too impatient to wait for Alan’s care package to arrive hehe). With a BTR wrench I managed to push the air box boots properly onto the carbs.
As a result the bike fired up nicely!. Haven’t done the diagnosis and touch ups while running, just wanted to hear it run. Will investigate more this week end.

Cheers
Title: Re: The elusive surge
Post by: taysidedragon on January 25, 2022, 10:12:55 AM
Hey everyone, I figured a small update would be in order.

I took the carbs off this week end to go over it once again. Checked all the passages I’m aware of and rechecked the floats height. The mixture air screws were set to 2 turns out as the plugs were sooty and the manual calls for 2 turns as a base setting for the 400F. I then did a bench sync, this time making sure I followed bryanj’s instructions to the letter.

With the carbs back on I made a sudo air filter cover and spring (too impatient to wait for Alan’s care package to arrive hehe). With a BTR wrench I managed to push the air box boots properly onto the carbs.
As a result the bike fired up nicely!. Haven’t done the diagnosis and touch ups while running, just wanted to hear it run. Will investigate more this week end.

Cheers

Sounds promising,  well done. 👍
Title: Re: The elusive surge
Post by: K2-K6 on January 26, 2022, 10:15:36 AM
Hopefully you've a decent platform to get the finer parts where you want them now.

That's a very neat routine that Bryan put up there as it covers all the elements to reassemble and provide accurate setup in one go.

Once done, they stay remarkably close during use and don't usually need constant retuning as many internet views seem to suggest.
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