Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: Moleskins on October 26, 2019, 03:18:00 PM
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Sorry about this, I’ve gone through various posts and can’t find any answers.
I’ve got 022A carbs on my CB550K0
I’ve stripped them cleaned and replaced the O rings but not jets, just cleaned those. They’re stock 100 and 38
I’ve replaced a dodgy rubber which was leaking
I’ve had gauges to set the vacuum
I’ve static and strobed the timing
I’ve ditched the pod filters and got a used airbox, filter is dirty though
I’ve got it to run but it runs very rich, the air screws are out about 3 1/2 turns!!
Nothing seems to make a jot of difference. Needles have been up and down, currently in the middle.
I’ve read there are fine holes in the carb body which block, I did blat carb cleaner down the ones I could see. Had this problem on another bike which took 3 goes to get them cleared finally using a guitar string.
So any suggestions and how do I get the bloody carbs off now it’s connected to the air box??
Ppl
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You probably need to change the filter as if it looks dirty it'll be having more of an effect than appreciated.
It's one of these non-linear scenarios as it'll cope with quite a lot of dust before getting the flow exponentially affected. Difficult to judge without swapping to test it, but run it with filter out just as reality check first.
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What would be the consequence of having too much fuel in the float bowl?
Not enough to cause it to overflow but too much?
I’ve set floats at 22mm.
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That would bias it toward richer mixture, but its a very subtle change and more apparent right at the lowest revs. Probably unnoticeable at higher rpm.
With the jets you've stated, it's unlikely to be able to run rich as they control maximum flow. Leaving a reduction of air to give you rich mixture the most probable cause. Without confirming the airfilter you may go round in circles.
To check the primary circuits, with it running and warmed, you should hear a response as you wind each one of the screws in and out individually like a small throttle for that cylinder. If no response is present it would indicate that circuit was impaired. But again that response is dependent on having normal airflow in the first instance.
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I don’t notice any change as I alter the air screws.
Definitely runs richer set anything less than 3 1/2 turns out. It was on pod filters so no shortage of air.
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I don’t notice any change as I alter the air screws.
Definitely runs richer set anything less than 3 1/2 turns out. It was on pod filters so no shortage of air.
There is a spider in the slow running jet and the main jet if, you have pocked anything down the hole, the spider is destroyed and air mix disrupted. The clip should be second down on the needle.
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Thank you for that Trigger. I have no idea what’s been poked down holes over the last 45 years, this makes it interesting though doesn’t it.
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Hi
Sounds like you have a blockage in the idle fuel/air circuits. I had this issue until eventually I ultrasonically cleaned the carbs and cleared them all out with compressed air.
If you want to read about how and where these very fine ilot circuits go have a butchers at the post I did a while back
http://www.sohc.co.uk/index.php/topic,16351.msg138049.html#msg138049 (http://www.sohc.co.uk/index.php/topic,16351.msg138049.html#msg138049)
As to getting the carbs off I have found that the best method is to push the airbox rubbers back in to the airbox as far as you can (you can even push them right through if you want, just a bit harder to get them back on). This will give you enough wiggle clearance to get them off.
I have had many gos at this over the years and I can have the carbs off in around 30 mins now !!!
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Paulbaker1954
Thank you, I’ve finished the ultrasonic clean today. I gave up and bought one.
During the rebuilding I kept thinking’this doesn’t make sense, it’s running rich, I’m cleaning fuel ways out’.
Anyway I fed a bit of guitar string into the slow jet. This measured 17 thou. From memory that equals .43mm the jet is marked 38 so I think there lies the problem.
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Why did you use a steel string that is harder than the jet's brass? Anyway, that's probably what the PO did...
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I understand why you’d say that. However I can’t imagine it would be possible to make a bendy guitar string go through a hole which was smaller than it.
Anyhow, I’ve replaced the slow idle jets with 38’s and balanced the carbs. It’s much improved but coughs a bit going up the road, lacking power. Once revs are at about 3500 it’s much better. That’d be Main jet though at that stage.
The exhaust still indicates running rich, any attempt to put a filter in the airbox makes that worse.
I’m contemplating dropping the needle to lean that off, currently needles are on the middle setting.
Vacuum gauges are on about 8 inches which if I’ve converted correctly equates to the book 16-24 cm HG
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There is a lot of overlap of jets when going from idle jets to main jets, so at 3500 rpm it could be either jet. Nigel (K2-K6) posted a brilliant graph showing the overlap but i can't find it again now. Also, as long as the vacuum gauges are showing parity, it doesn't matter what the reading is within reason.
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I understand why you’d say that. However I can’t imagine it would be possible to make a bendy guitar string go through a hole which was smaller than it.
Anyhow, I’ve replaced the slow idle jets with 38’s and balanced the carbs. It’s much improved but coughs a bit going up the road, lacking power. Once revs are at about 3500 it’s much better. That’d be Main jet though at that stage.
The exhaust still indicates running rich, any attempt to put a filter in the airbox makes that worse.
I’m contemplating dropping the needle to lean that off, currently needles are on the middle setting.
Vacuum gauges are on about 8 inches which if I’ve converted correctly equates to the book 16-24 cm HG
If you’ve measured 8 inches of water, then that’s about 1.5 cm of mercury. 16cm of mercury is about 85 inches of water !
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There is a lot of overlap of jets when going from idle jets to main jets, so at 3500 rpm it could be either jet. Nigel (K2-K6) posted a brilliant graph showing the overlap but i can't find it again now. Also, as long as the vacuum gauges are showing parity, it doesn't matter what the reading is within reason.
I can't find that either Julie even though I thought I had a copy tucked away somewhere here.
For your current jetting though, as you plan, put the needles down a notch to try it and see what you get. Obviously you've got progress with the new idle jets and it's just moving something else now to bring in other sections of mixture to where you want it.
If you've got room to bring the idle screws out another 1/4 turn it's worth trying that. It should delay the point at where the idle jet gets to full flow at it's 38 capacity and be matched with the throttle slide being a little higher when it occurs. That and dropping the needle a notch combined will effectively lean out the middle range throttle opening and may get you into range.
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An additional point to consider, the airbox on these can have different configurations I believe from other's experience on here. Deltarider? They have a different air entrance to make some market models quiter I think, these are paired with smaller main jets, from memory, and run at slightly smaller mains it seems.
Someone with that knowledge may be able to help here in identifying the parts you have.
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There is a lot of overlap of jets when going from idle jets to main jets, so at 3500 rpm it could be either jet. Nigel (K2-K6) posted a brilliant graph showing the overlap but i can't find it again now. Also, as long as the vacuum gauges are showing parity, it doesn't matter what the reading is within reason.
I fo[attachimg=1]und this chart some time ago that may help
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An additional point to consider, the airbox on these can have different configurations I believe from other's experience on here. Deltarider? They have a different air entrance to make some market models quiter I think, these are paired with smaller main jets, from memory, and run at slightly smaller mains it seems.
Good you brought this up. BTW, on the international forum I also follow the thread about airflow with interest and I find some intuitions that I had, confirmed. http://forums.sohc4.net/index.php?topic=179850.0
Actually my first post in that international forum, I believe in 2006, was a question: why did the CB500 models for most countries on the European continent (France being the only exception) have the 649A carbs? These carbs have #78 main jets and for the rest everything the same as in the 627B carbs: #40 slow jets, needleclip in the 3rd (middle) position and an advised airscrew setting of 1 turn ± 1/8. These models also have a socalled airduct over the airfiltercase. Realise that at the time there was no legislation on emission in these countries, Germany, Holland, Italy and Switzerland to mention a few. Realise also that none of these countries had a national speed limit and were very competive markets indeed. I have one source that states Germany had legislation on air intake noise however. Hence that cover over the airfilter case and I can assure it works as such. How could it be these models performed equally good as the ones with the 627B carbs? At first I have thought it had something to do with the quality of gasoline. Countries like Germany, Holland, Italy and Switzerland always have had the better gasoline, the US about the worst, a finding that's shared by more. But that still could be subjective. From all what I've read, I can only conclude it must have been related to this legislation on air intake noise. The cover does NOT restrict airflow such (if it restricts at all!) that power output is less. Tests including my dyno test have proved this. Ofcourse I have, like some Germans, experimented with #100 main jets and the airduct removed. It brought nothing but extra intake noise. What the airduct maybe does, is reducing turbulence at the intake, resulting in a more laminar flow, who knows?
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Can't read that as it's in german but I'm wondering why it's saying the bike has 2.15 rims front and rear when it came with 1.85 rims from the factory. Unless of course you've changed the rims at some time.
It's not about my bike. I live in The Netherlands. :) Listed are the max. rims widths that are allowed on this model in Germany. TÜV is the German test agency. In Holland we have no such thing, not for motorcycles. Hurray! :)
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Thank you Nurse Julie and K2-K6 there’s a few things for me to go at there.
Currently (pun intended) I’m sorting out a wiring ‘situation’ because the new battery went flat.
This made me wonder if combustion was going off because of a weak ignition circuit.
I’ll get back onto carbs tomorrow / the weekend.