SOHC.co.uk Forums > CB500/550
I need a carb sync - Anyone in North London?
michtag:
--- Quote from: K2-K6 on August 12, 2020, 09:46:30 PM ---
To help in the interim, it's sounds possible from your above observations that you may have a cylinder not firing. The points each run two cylinders so if either is a problem you get both from that supply stopping and it's even hard to pull away, so doubt if it's that.
More likely it could be just one. If you start it from cold and run for about 20 seconds, switch off and then feel each of the exhaust pipes youll tell if you've a cold one ( that will feel more like the "something stuck in your throat" you describe) if that's the case then ordinarily you're looking at a fault of the HT part of the system from coil through plug cap to plug itself as initial suspect.
Anyway, post how you get on and shout if you wish to have help.
--- End quote ---
Thanks K2-K6, all 4 are firing, I check by default every time I run the bike for 20 secs or so as I did have that problem in the past (but it was carb related).
michtag:
--- Quote from: paulbaker1954 on August 13, 2020, 07:55:22 AM ---Are you positive you don’t have an air leak between carbs and head. That would also cause similar problems. Try spraying carb cleaner around the joints when running. I had exactly the same tickover issues with revs suddenly rising and fixed it with new inlet rubbers. I also used jubilee clips (thin stainless ones) as opposed to the old Honda clips as even the replacement ones I got (not aftermarket ) from DSS were no sealing well.
From the sound of it this is more likely the problem
--- End quote ---
Thanks Paul, I have not really tried spraying carb cleaner because I have new inlet rubbers and new O-rings on the inlet manifolds, so I believe I have taken care of that possibility. I still use the old clips though, so I may as well give it a try. FYI, I will soon post a video of how erratically it idles today, just to give as much info as I can.
michtag:
Update of the day:
Just before thunderstorms hit (although it's still well sunny here) I decided to have a check at the timing.
-Points gaps were at 0.3mm and 0.35mm, so I made them both 0.3mm now.
-Static timing is spot-on for 1-4 and 2-3
I have tried using my strobe but the idling seems too unstable that I am not sure about anything, so I have not tried to adjust anything. I will try again just to see if I notice it being too far advanced at higher revs, but from first examination it does not look that way. It may be that it advances too soon though. I have tried in the past to use different spring combos in the advance mechanism but never really solved anything, so I reverted to the original setup (I was probably jumping the gun anyway).
Here's a video I shot today, just to give you an idea of what it sounds like when idling. Note that unless you see my hand on the throttle or idle screw, she's doing everything else by herself!
https://youtu.be/ESx_E8mv2vM
Carbs are standard PD46A with. standard jetting, This may not be ideal for the Delkevic 4 into 1 the PO put in, but it should not give problems when idling
As suggested above, I will try spraying carb cleaner on and around the inlet manifolds to check for air leaks there, but I have new manifods and o-rings so I doubt it will be that.
Nurse Julie:
What spark plugs are you using?
michtag:
--- Quote from: Nurse Julie on August 13, 2020, 01:30:21 PM ---What spark plugs are you using?
--- End quote ---
Just plain NGK DR7ES they are fairly new, maybe have 30 miles on them. I cleaned them from carbon deposit because the mechanic I trusted to solve my troubles actually made it incredibly rich (4th groove on et needle!!) and as a consequence exhaust and plugs just got covered in black soot. BTW, I moved the needles back to the 2nd groove...
Not sure I have a new set of plugs to try if any difference now, would that be worth it?
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