misfire

[macfreebe]

HI there ,well got my engine rebuilt after cct failed and replaced bent valves on front cylinder,put bike back together and she started up ok ,but i had to adjust idle speed a fair bit cause it kept stalling then when the bike warms up she idles to fast. i get a misfire every 20 seconds or so aswell
I lifted up the tank and removed air filter and see that its the front carb thats misfiring when the bike is running.Don,t understand why as i never adjusted the carbs .anyone got any ideas?

[AMCQ46]

Could be a number of things given the work that has just been done.
Assume the cam timing is correct, so my first thoughts would be an air leak. Has the front carb been seated properly, or has the vacuum takeoff screw been removed, or has the pipe to the vac adaptor not been fitted back on.

[tony.mon]

It's also easy to disturb the carb balance when tugging them off the engine, so check balance as well.
But I agree with Alastair, sounds like a vac leak or poss air leak.

[benny hedges]

I lifted up the tank and removed air filter and see that its the front carb thats misfiring when the bike is running.Don,t understand why as i never adjusted the carbs .anyone got any ideas?

you mean its spitting back through the front carb a lot???

did you replace the front exhaust or inlet valves.
if you replaced the inlet valves, did you reseat them, ie lap them in?
if you replaced the exhaust valves, are you absolutely sure the inlets are not bent or sticking?
could be a simple set-up problem but tbh i think the inlets aren't seating properly on the front pot.
maybe a compression test.

with carb balance, the front cylinder revs stay the same, and adjusting the balance screw adjusts the rear cylinder speed in relation to the front so i really dont think it's balance.
could be air leak though. did you make sure the carbs were sat tight down on the rubbers (they sit at an odd angle, not straight like you'd expect)
and also did you use a screwdriver to tighten the clips?? maybe try a 1/4 drive 8mm socket instead as you can get them well tighter.

go for the obvious first, check the rubbers are proper tight, top & bottom, check the vac hoses etc.

if it's just an occasional misfire you can probably get round it by upping the idle speed over 1500.

[macfreebe]

Well guys thanks for the tips .I laped in all the valves new and old so i ruled it out,I checked timing about 5 times befor to make sure it was spot on as didn,t want to open engine again .checked all the pipes (tank + carb) and they seemed fine .Got to the front carb clips and ah ha i hadn,t tightened them enough doh.Bike running very well now and is pulling great today.For some reason the fuel light won,t go of now must have done somthing when i lifted up the tank to check misfire .Goes of when i disconect it though maybe the sensor is stuck or something .Just waiting on my replacement shock from ebay as the one in is starting to get a bit bouncy .btw i have a clear screen and red tail pod cover for anyone that wants them .I replaced screen with tinted db and prefere the look of the bike without tailpod .

[benny hedges]

For some reason the fuel light won,t go of now must have done somthing when i lifted up the tank to check misfire .Goes of when i disconect it though maybe the sensor is stuck or something .

is yours the digi gauge then????
mine stays on when it's disconnected.
give it a shake about inside m8.... dont bother unbolting it from the tank unelss you really have to - it will leak.

[AMCQ46]

glad you got it fixed

[macfreebe]

THANKS WILL GIVE IT A GO ON SUNDAY BEFOR MY RIDE