Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: ManicGTI on October 31, 2016, 01:59:07 PM
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So, big progress for me. After 20 odd years since it's last road tax, I have got her ('75 CB400F) started for the first time since my top end rebuild! Thanks to all that have reponded previously.
IT STARTS!
Literally on the button, first attempt, with Choke open or closed. Very happy about this! However I'm far from out of the woods.
- Appears to be running very rich (all plugs immediately / consistently blackened)
- Revs increase dramatically when I try to open the choke.
What's changed since my last attempt:
- Carbs stripped and rebuilt (again), bodies simmered in a pan for an hour or so with a dishwasher tablet, then recleaned with parts cleaner spray and went over all ports blowing and checking (concentrating on idle circuit).
- Re-Bench synced them, this time doing it in the 'closed position' rather than open. Used a 4mm drill bit as it was what I had to hand, maybe I should have gone for 3mm as closer to the 'interweb recommended' 1/8".
- Also rechecked/adjusted Tappet clearances, Points Gaps, and Static timing.
So, any thoughts on what to do next?
- Check timing with timing light now I can run the engine.
- Redo carb Static balance?
- Idle screws?
- Try the OEM Idle jets back in there now the bodies are cleaned.
- Fit Hondaman transitorised ignition box (likely unrelated, but i'll fit it anyway)
Or is this likely to be something more fundamental, ie Rebuild kit jets not correct? Carbs bodies still not clean? REv counter isn't working, so not a clue what
At the very least this has renewed my enthusiasm so i'm keen to keep the momentum up!
Dave
For info, my previous thread: http://www.sohc.co.uk/index.php/topic,9575.0.html
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glad its running,
when I assembled my carbs and bench synced them ,I used a torch to shine through the carb ,and adjusted then so they all were
almost closed,I figured I could use the main throttle stop screw to open them as needed,
are you sure you have the float heights set correctly? seems very rich ,so maybe levels to high ?
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I've got exactly the same problem! I started mine today after the rebuild. I had the carbs ultrasonically cleaned, new jets, needles and float valves. I set the carb floats using a 26mm gauge as recommended by Mr Haynes in his book and used a 3mm drill to set the slides.
When I turned the fuel on everything was fine for 5 minutes and carb no.4 flooded closely followed a couple of minutes later by no.1! When I connected the Morgan gauges only carb no.3 registered any reading, no matter how much I tried to adjust the settings on the screws and lockouts using a Honda tool nothing happened! The carbs are back on the bench and I'm scratching my head, I followed the carb rebuild instructions to the letter!
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If I remember correctly, the float heights are 21mm.
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I agree, 26mm certainly doesn't sound right. This thread on setting float heights may help (people have been here before!).
http://www.sohc.co.uk/index.php/topic,7882.0.html
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Thanks Chris.
I've given up for the day now, lesson learnt, try the carbs off the bike in future!
I'll try again on Saturday, work gets in the way for the rest of the week :(.
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The float heights I did to 21mm, is that not right for the 400? Bowls are are all filling fine, none of them are overflowing.
Sounds like I do the syncing in a slightly more closed position, but I don't see how that would help the richness? I like the idea of adjusting to almost closed then using the main screw, I was just trying to stay as close as possible to the manual method.
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Oops, should have checked the subsequent posts. Yup, 21mm.
I'm wondering if starting it in the garage doesn't help, always going to sound more 'dramatic'.
My plugs were like this:
https://goo.gl/photos/dF5kWjGSGkeJ6j3e6 (https://goo.gl/photos/dF5kWjGSGkeJ6j3e6)
Is there anything else I should be checking on top of the following?
- Bench Syncing (possibly have them too far open)
- Float levels
- Idle Jets?
- Idle screw adjustment?
I'm sticking with the idle at the mo, not touching the throttle really!
Dave
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With a bench sync it is easy to get the slides so they dont close
first back off the idle screw till it falls out, then un adjust the carb slide adjusters so all slides hit the bottom pick one(on the 550 k3 its easy as one has no adjuster) and adjust the slide adjuster till it nearly moves, refit the idle screw and adjust it till the one you picked lets your prefered drill bit fit, 3mm is too big you need 1.5 if poss, then adjust all the others to the same. Finally undo the idle screw again and make sure all slides hit the bottom.
Run engine till hot ad ajust with gaudes AFTER you haveset tappets, cam chain and ignition timing
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Thanks for the run down Bryan, I'll redo the Bench Sync as suggested.
Cam Chain I haven't touched yet.
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I had a rummage in my garage and found the tool I made when I did my float heights.
I can't remember whether I read about it on this forum or elsewhere, not that it matters - maybe it will be of help to others.
The tool was made from the lid of a tub of soft cheese (Philadelphia in this case; other brands are available).
Outer cutouts are 21mm deep (float height), inner cutout is as deep as it needs to be to clear the tube holding the main jet.
Working with the bank of carbs on end eliminates the effects of gravity - the height needs to be set with the float arm just touching the needle jet.
If the pivot pin is loose in the holes use masking tape or similar to hold it in place.
I have noticed that the text in the Haynes manual says set to 22mm. This is the 500/550 setting, 400 is 21mm according to the specifications.
I had never set float heights before but found this method worked well for me.
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All very interesting info and unavailable in the Haynes manual. I found the piece of card I used, it's 22mm, not 26mm as I stated in my earlier reply, two of the four carbs still leak though so I'm going with your idea Chris to make a proper 21mm gauge followed by the bench sync as recommended by Bryan.
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Well, I made the gauge from some ali sheet to 21mm. All floats carefully reset and checked over and over just to be sure. I set the carbs using Bryan's recommended technique and all was good. I thought I'd bench test the carbs before putting back on the bike and placed them very gently in the vice, connected the bottle of fuel and waited. Everything as great for 5 minutes and then petrol poured from 2 of the overflows and also the central overflow pipes between carbs 3&4 >:(. Am I doing something fundementaly wrong?
To cap a bad afternoon, I got that horrible feeling when one of the float bowl screws just kept turning, undoing the screw pulled out the tread with it! I need to get a 4mm helicoil kit now although opinion is timeserts are a better option (I've never used one). At least it's winter and I'm not missing out on any sunshine ::).
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Not enough meat for a timesert as they are a lot thicker in the wall, Do the float needle seats have an O ring on them? Are the float bowls very full or could the internal standpipes be cracked
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The float height would not usually alter how it shuts fuel off within reasonable range, just the mixture when running.
If the valve seats are brass you can use something like a cotton bud with brasso or T-cut to spin slowly with a drill and get them smooth / polished. Needs thorough clean afterwards.
If the needles are plastic or rubber tipped, they can be hard to get to seal properly with just the float pressure on them. I know it's a slim hope, but the heat and engine vibrations do seem to assist this process when installed and running. I can see why you'd want to reassure yourself prior to install though.
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I need to get a 4mm helicoil kit now ....
Someone else had this problem recently too, this thread should help: http://www.sohc.co.uk/index.php/topic,11339.0.html
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Thought i'd drop this simple little Carb Float explanation here for prosperity, although it's light on actual technical explanation: https://www.fix.com/blog/motorcycle-carburetor-float-height-adjustment/ (https://www.fix.com/blog/motorcycle-carburetor-float-height-adjustment/).
I've had another thought regarding my richness. At the moment I have the Fuel tank sat off to one side on top of my garage shelf's, (ie >1m higher than the bike itself), running a temp long fuel hose down to the carbs so I can work on it with the tank off. Would the additional head from this setup cause me issues?
All being well I should get a chance to pull the carbs and reBench Sync / Float Check tonight :P
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I like that one Oddjob.
Manic, you should have no effect on jetting as the mixture is influenced by the float height which sets a equal pressure into the jets because it interrupts the fuel coming into the carb. You may struggle to get the floats to shut off the fuel if you had any effect at all.
Sounds like you've got too much air to get the revs down though in order to make any sensible judgment of it.
As already posted, check to see if the slides are going fully down, the only thing lifting any throttle slide when left alone is the tickover / throttle stop screw on any system, the operating mechanism (cables twistgrip etc) should all finish their influence when you let go of it.
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Carbs are like life, you can't get enough head :) :)
;D ;D ;D ;D ;D
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Carbs are like life, you can't get enough head :) :)
Hey, it's cold and lonely out there in the garage. I'll take what I can get.
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Bryan, The float valves are from the Keyster (?) kits I bought and do not have a viton sealing rubber on the tips as the old ones did. I'll give it another go maybe over the weekend when I get the helicoil kits (thanks for the tip Chris, the kit is on order). I will test the floats to see if any are punctured.
Its only the carbs that are stopping progress and the MOT :(
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Thought i'd drop this simple little Carb Float explanation here for prosperity, although it's light on actual technical explanation: https://www.fix.com/blog/motorcycle-carburetor-float-height-adjustment/ (https://www.fix.com/blog/motorcycle-carburetor-float-height-adjustment/).
I've had another thought regarding my richness. At the moment I have the Fuel tank sat off to one side on top of my garage shelf's, (ie >1m higher than the bike itself), running a temp long fuel hose down to the carbs so I can work on it with the tank off. Would the additional head from this setup cause me issues?
All being well I should get a chance to pull the carbs and reBench Sync / Float Check tonight :P
I read in classic motorcycle mechanics magazine recently that you should not mount your tank/fuel source to high for this very reason.
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I've got an old two stroke oil tank you can use of you want Dave. You can make a list of the stuff off mine you have ;)
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With a bench sync it is easy to get the slides so they dont close
first back off the idle screw till it falls out, then un adjust the carb slide adjusters so all slides hit the bottom pick one(on the 550 k3 its easy as one has no adjuster) and adjust the slide adjuster till it nearly moves, refit the idle screw and adjust it till the one you picked lets your prefered drill bit fit, 3mm is too big you need 1.5 if poss, then adjust all the others to the same. Finally undo the idle screw again and make sure all slides hit the bottom.
Run engine till hot ad ajust with gaudes AFTER you haveset tappets, cam chain and ignition timing
Ok, I just tried it this method and hit on an isssue straight away. Essentially the idle screw bottoms out just at it touches the casting, so i'm getting nothing out of the idle screw. Hmm, an adjustment i've missed?
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I think the motorcycle mechanics need to sit down with a nice cup of tea and a biscuit to give themselves time to think about that.
It's exactly what a float chamber is for, to break the head pressure ( no sniggering at the back there, oddjob and Julie) and provide a reasonably constant fuel weight for the carb's vacuum to work on, which in turn gives you a chance of linear jetting response.
If it didn't do this then as the fuel tank volume varied then so would the jetting and the float height would be absolutely meaningless.
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I believe we are taking about the same screw, yeah the casting is to far away from the tip of the idle screw.
I had the carbs completely in pieces, only the chokes were left on. Idle screws all completely removed, so yes it does look like I may have assembly incorrectly. Bugger. I'm not sure what could even be wrong!
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Take a few photos, we may be able tp spot the problem.
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If the tickover screw when screwed all the way in still has a gap to the lever it adjustes you definately have the slides not right
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"Snigger, Snigger"
Sorry couldn't help myself. :) :) :) :)
I'll write out "I shouldn't snigger in class" 50 times as a punishment.
I will stand in the corner for 10 mins, sorry Sir ;D ;D ;D
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So, 5 minutes after posting my 10PM message last night I took a long swig from the beer bottle sat on my workbench. It was a big mouthful.
Sadly however, it turned out that the cool, refreshing (and undrunk!) Hop House 13 was in fact at the other end of the bench. The bottle I had taken a swig from contained the petrol I had drained from the carb bowls.
Yuck. Luckily I don't 'think' I actually swallowed any, but I've gone through many litres of water to dilute and flush it through. I can still taste petrol now.
At that point, my interest in continuing to work in the cold diminished rapidly. So the only picture I have is this one:
(http://i67.tinypic.com/1z2pzxv.jpg)
If the tickover screw when screwed all the way in still has a gap to the lever it adjustes you definately have the slides not right
The lever does touch the idle screw when fully screwed in, but only just. This is with the slides all bottomed out (ie the individual slide adjusters all screwed in as far as they will go), there's about 6mm gap.
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At the risk of travelling too far along the axis of smut and double meaning, you may need to wear school uniform for that.
Back to the problem in hand :) the first part of Bryan's setup of setting up on the bench is where I think you maybe going wrong. Perhaps thinking about it in reverse may get you going the right way.
Let the slides drop to bottom of carbs (closed throttle) then think how when you make slide adjustments you are trying to move the throttle mech towards the idle adjust screw. With the screw turned perhaps one turn in from nothing, keep making adjustments to slides until mech meets stop screw, at this point the operation should be within normal range and you can sync them on the bench.
It's harder to explain in writing than with them in front of you so hope this helps.
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It's exactly what a float chamber is for, to break the head pressure ( no sniggering at the back there, oddjob and Julie) and provide a reasonably constant fuel weight for the carb's vacuum to work on, which in turn gives you a chance of linear jetting response.
If it didn't do this then as the fuel tank volume varied then so would the jetting and the float height would be absolutely meaningless.
Thanks for the clarification, I have to admit I'm new to Carbs and this era of vehicles. I'm used to working on Mk1 Golfs and MX5s!
Take a few photos, we may be able to spot the problem.
Thanks, I'll try and take some clearer images of the set up as it stands as soon as I can.
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Stealing a pic from ebay for reference, i'm confident that I assembled the adjusters correctly (although I could be proven wrong!):
(http://i215.photobucket.com/albums/cc141/cooper_man2/1999_PARTS_LEFT/1999-627-2.jpg)
So if I back all the adjusters out, the throttle will be returned towards the idle adjustment screw, and the slides towards closed? I'll give it a poke tonight.
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Now you're thinking it through logically. Dont try starting the bike with Hophouse 13 (other beers are available)
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There is another factor here.
I had the same issue when I stripped/rebuilt my carbs. Following all the set up dimensions in the Haynes manual, I could not get my Idle screw to operate in the normal range. After a lot of checking and re-checking I finally worked out that I had re-assembled the throttle assembly incorrectly.
Have you done anything to the spindle that the throttles pivot on? Mine was slightly out of position and affected the whole operation of the throttle. There is a flat on the top of the spindle that a fixing bolt locates on and it's fairly critical where it's positioned in my experience. Once I worked this out, I had my carbs dialled in sweet.
Where about in London are you?
Peter.
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This was pissing me off so I made haste home on the Street and got cracking. Backing all the adjusters off did bring the throttle Mech back round to about 2mm from the idle screw. Much better! I've now synced them with a 1.5mm drill bit.
Thanks for that tip Peter, I'll take a look at the Mech position.
I was up near Dalston on the same road as Tom, but now in New Malden.
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Looks like you're getting somewhere with them at least.
Take from your title that you're talking about the Bosch fuel injected golf's. As you say a bit different from these old bikes.
I'm just the other side of the A3 from you, so if you need another pair of eyes to look at the carbs, give us a shout.
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Ah cool, thanks. Yes indeed, I've had a couple of '83 GTIs on K-Jet.
It feels like I've progressed anyway! Hopefully i'll get to refit at the weekend and try again...
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There's a mk1 lives near me, they look modern even now and very crisp design. We ran an 86yr Audi 5 cylinder some time ago a close relative in engine and fuel injection.
I don't think there's any mysteries in the bike carbs, just a bit of time and careful setup and they're not much trouble when up and running. You can't be far from getting them sorted I think.
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There's a mk1 lives near me, they look modern even now and very crisp design. We ran an 86yr Audi 5 cylinder some time ago a close relative in engine and fuel injection.
I don't think there's any mysteries in the bike carbs, just a bit of time and careful setup and they're not much trouble when up and running. You can't be far from getting them sorted I think.
Indeed, even the later engines weren't too far removed, I fitted the 2.0 16V from a mid 90s Corrado, running a mix of 16v mk2 Golf and 8v Mk1 k-jet systems.
So carbs are back on and bike is started, but appears to be running on only cylinder 1&4 now. Idle with choke on is laboured (Unsurprisingly).
Must have knocked something as all Four were firing beforehand. I have a feeling I'm going to be chasing my tale a little on this beasty before I get anywhere close to setting it up properly.
In the mean time I'm going to set up the brakes so at least I can run it up the road at some point!
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Don't ignore other possibilities. Have you got a spark on 2 & 3? Gremlins have a way of diverting your attention while you're chasing something else.
Worth checking so you know for sure that it's fuel and not ignition.
Hope you get it resolved soon.
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If it's 2 and 3 not working, its4 more likely to be ignition related than carb related.because 2 and 3 carbs get their petrol before 1 and 4.
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All 4 carbs are filling, so yeah I'm assuming I've got a dodgy connection somewhere on that coil
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You appear to be getting somewhere with your carbs Dave. I thought I was getting somewhere with mine as well having made up a float height gauge similar to the one Chris described in an earlier post. I set the floats to 21mm, checked, checked again and once more for luck, all in order, bowls were re-fitted (a number of the screws had to be helicoiled as the threads felt 'weak'). I bench tested the carb bank with fuel and still two of them leaked!!!! I took them apart again and rechecked. I blew out all the airways with compressed air and checked each fuel valve with a magnifying glass. I must admit the quality of finish on the new valves looks a bit rough, not the smooth finish I would expect for something that is supposed to seal against fuel. I fitted the two 'best' of the old valves as these looked in better condition then the new ones! Carbs back together, bench tested and all was fine, happy days :).
I refitted the carbs back on the bike on Saturday having bench sync'd with a 1mm drill bit (fiddly!). Everything connected, all cables lengths correct, idle screws set at 2 turns, fast idle clearance set, all good. Morgan carbtune connected and I started her up. I was greeted with very rough running, carbtune only registered a reading on no.3 and no amount of adjustment brought the other three carbs to life although the engine note improved. By now it was getting dark so I gave it another go yesterday. I took the carbtune apart and re-polished the stainless rods and brass guides in case they were sticking (it made no difference anyway). Yesterday was going well, the engine was sounding better but I could only get a reading on the carbtune if I turned it upside down??? Reading was 20hg, and was in the range stated in the manual. I balanced all the carbs to the same setting +/- 2hg. Problem I have now is the engine races to 400rpm if the throttle is 'blipped' and it feels 'flat' when slightly revved. Just to add to the frustration no.2 carb became incontinent and gushed from its overflow. I also noticed exhaust no.1, 3 and 4 are yellowing at the head, is this a sign of running hot and a weak mixture, no.2 header is fine. Just a note, as the carb balancing was taking a while I stopped a few times to let the engine cool down. The bike was also a pig to start from cold on both days.
Any thoughts would be appreciated, I noticed I have a lump hammer in the toolbox, it might come in useful soon...... >:(
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Sounds like progress anyway! Are the carbtunes worth getting? Do they come with the adaptors to screw into the balancing ports? I'd like to have a bash at balancing mine further now.
My new brother in law popped round a few days ago, turns out his first bike was a 400. Happily mine started on demand with no air box/filter on and he seemed to think it was running OK. I have to admit being used to more modern bikes sometimes I don't know if something sounds rough, or it's just the age of it.
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Laverda120, I believe you've gone away from where you need to be.
I think you were right to bench sync them, are you making sure while you do that the slides are "hanging " on the throttle mech and not being supported by the drill? If so then at that point I would not adjust the slides again, at all.
The even slide height should make a healthy engine run correctly at all parts of throttle opening and it doesn't need these moving from each other.
I've always seen the carb "balancing " routine as a bit of theatre, which can cause more problems than it solves.
With the slides set accurately to the same height, then if it doesn't run properly at tickover these are not the tool to correct it. You just put an error on all other rpm operation that is not desirable.
The part you need to adjust is solely the idle screws. If you turn each screw while running at tickover, you should get a change in rpm, if not, then that one idle circuit is not clear and operating as it should. Again, the throttle slide adjustment just will not correct this. It needs the idle circuit to be cleaned properly.
There is a well documented routine in Honda manuals to carry out the idle circuit adjustments, and it works well. You may end up with slightly differing screw set points, this will either be because of the jets and passage being partly blocked or a real difference in the hardware. it's here that differences are adjusted out and not the slides.
Think of the idle circuit as a microbore carburettor in itself, and it should respond to opening and closing exactly the same as any whole carb, just at low speed. If they are not right, you'll chase your arse for ever on the main slides, and never get it ok. What's more, the wide open throttle is then incorrect which will give you another whole set of problems.
I'd say, step away from the carb balancers. Go back to basic checks.
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OK k2-K6 I'll give it a try although I can report I had the slides adjusted onto the drill bit like a feeler gauge, just felt a bit of resistance as I pulled the drill out. I will take the carbs off again and have another look, they were ultrasonically cleaned so I guess they would be clear of crud, never assume anything! I've bought a large can of carb cleaner and will give them a blasting with this before refitting and trying again.
I shall report back on progress.
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I'd say your bench setting was bang on then, I do think you've stepped back a bit from there though.
The Honda procedure for idle jet setting calls for you to change a single screw at a time and to observe the engine revs going up or down to determine how you eventually reach a good setup for each cylinder. I guess this is the real acid test for idle circuit impairments as if you fail to get a response from each one of them, then it would indicate a problem with that carb body.
I don't think Honda could envisage the ultimate problems we have in getting these carbs clean. In general use they are pretty good, but leave them not running with modern fuels and you'll soon run into certainly some minor problems if not completely blocked.
I know it feels very frustrating when they are not going right, but once you get sorted they are maintained with ease.
Generally to eventually think about carb balance gauges you'd need to be very sure everything else is set up well first. If you use them with any significant setup issues unresolved they'll just add to your problems.
Hope you are able to make a little more progress.
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Hello again!
I'm sad to say that shortly after my last post above, the bike hasn't been touched - life caught up with me in the form of having a nipper and house refurb works. Hopefully @Laverda120 has had more luck than me!
Apologies to resurrect this thread, but I figured it shows the history of what i've been up to so far with this bike. This weekend I had a rare moment to have a play with it again, so I thought i'd look at some of the minor issues that I had never got resolved before, so I now have throttle and clutch cables hooked up, and all the lights are working again :o
I've fitted the hondaman Ignition unit and a new battery, it's now sat on the optimate so at least I know it'll have juice when I go out to play with it.
So, with 2 year old fuel (with some fuel keeper additive) and a bit of luck...it actually did fire up first time since my post above! Plugs 1 and 4 have sooted up immediately so assume these are rich, but 2 and 3 lare minty clean...bugger. Looks like I have spark on all plugs so I've pulled the tanks on all the carbs again, given all the jets etc a good blow through with carb cleaner. Hopefully that will help things after it's been standing.
I'm doing all this with the airbox out, tried to refit but my rubbers are knackered. Am going to try the 'wintergreen' method to soften them up as DavidSilver doesn't seem to have them in stock at the moment.
:)
Dave