SOHC.co.uk Forums > CB500/550
I need a carb sync - Anyone in North London?
michtag:
--- Quote from: Bryanj on August 15, 2020, 02:11:48 PM ---PD46, just about guarantee the pilot jets or pathways are blocked
--- End quote ---
Yes, I've known about the pitfalls of PD46s for a while now....but these have been gone through/into/over so many times that I feel confident they should be fine. Of course I could be wrong so if I find myself at a dead-end I will start from the carbs over again.
I will triple-check for air-leaks as soon as I have the chance :)
cheers guys, much appreciated!
michtag:
Small update:
Bike runs fine from cold, for about 2-3 minutes. Then, once warmed up, the erratic idle starts showing. I have (abundantly) sprayed carb cleaner on intake manifolds with no change at all, so for now I tend to exclude an air leak as I could not find any evidence of it (and both rubber intakes and manifold o-rings are new).
I keep on thinking it could be something in the timing (or rather advance mechanism springs, maybe kicking in too soon) and/or unbalanced carbs (only bench synced visually, with a drill bit).
Maybe I'll start playing with the spring combination again, after all I am keeping the original ones as they are and just adding different ones, so anything I do can be undone quite easily.
Cheers
paulbaker1954:
--- Quote from: michtag on August 18, 2020, 01:03:27 PM ---Small update:
Bike runs fine from cold, for about 2-3 minutes. Then, once warmed up, the erratic idle starts showing. I have (abundantly) sprayed carb cleaner on intake manifolds with no change at all, so for now I tend to exclude an air leak as I could not find any evidence of it (and both rubber intakes and manifold o-rings are new).
I keep on thinking it could be something in the timing (or rather advance mechanism springs, maybe kicking in too soon) and/or unbalanced carbs (only bench synced visually, with a drill bit).
Maybe I'll start playing with the spring combination again, after all I am keeping the original ones as they are and just adding different ones, so anything I do can be undone quite easily.
Cheers
--- End quote ---
This was exactly the same as mine, I sprayed carb cleaner all over and didn’t show a leak but there must have been one there. I replaced the clips with thin stainless jubilee clips. Word of warning is not to over tighten the clips or there is a danger of the clips splitting the rubber.
I am convinced you have an air leak. One thing you can try is when bike is running get hold of the carbs and pull/push them up and down. Give em a really good waggle around
michtag:
--- Quote from: paulbaker1954 on August 20, 2020, 08:50:40 AM ---
This was exactly the same as mine, I sprayed carb cleaner all over and didn’t show a leak but there must have been one there. I replaced the clips with thin stainless jubilee clips. Word of warning is not to over tighten the clips or there is a danger of the clips splitting the rubber.
I am convinced you have an air leak. One thing you can try is when bike is running get hold of the carbs and pull/push them up and down. Give em a really good waggle around
--- End quote ---
OK, that is good info, thank you Paul, I will definitely give it a try. One more question, what do your Jubilee clips look like?
cheers
michtag:
I have tried to wiggle (vigorously) the carbs when the engine was warm and indeed it did rev up when I pulled the left side up and rev down if I pulled it back down....4-5 times, so there seemed to be a connection there. Other than that it kept on being erratic by itself.
I will definitely have a look at the rubber manifolds and get some new jubilee clips: could I have put them on backwards (front to back)? They seem to be fitting snugly and properly, but hey, I am a novice what do i know? More stuff to re-check....again :-\
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