misfire question

[nc30chris]

chaps, just another question regarding my misfire from cold, ive now narrowed down the problem to the lhf cylinder,
and two possible causes,
firstly i adjusted the float heights on the bike, and two were out, one considerably at 9+mm, which i believe was that cylinder. i wanted to know if the float height was this far out would it allow fuel in to the cylinder when the engine was not running, thus flooding that cylinder?
i think its either that that's the issue, or the coil pack. the bike has new plugs fitted, but its that cylinder which takes a good few mins to heat up. so my two questions are...
1, will an incorrect float height allow fuel in to the cylinder when turned off
2, is it possible for a coil/lead to be faulty, and get better once warmed up??

sorry if this sounds a bit stupid, but its baffling me a tad now, im about to restart it from cold tonight for the first time since i adjusted the float heights, but wanted to get a few ideas.

[CMSMJ1]

swap a good plug to that cylinder to rule that out..nice and easy

float heights and dodgy float needle valves can cause a mess of your running

Coils supply two plugs so more likely a lead at fault.

My money is on a dodgy plug btw

[nc30chris]

thanks for the reply, ill try swapping the plugs round tonight, i should of mentioned in the earlier post that it ran like a sack with the old plugs in also, though at that point i hadnt identified which cylinder it was. so if its not a plug, is it feasable that fuel could leak in to the bore if the float height was way off? or that a plug lead would start to work when its warmed up?

[nc30chris]

right, ive moved the plugs around, and looks to have made no difference!, only i have noticed tonight that its the l/h/f and r/h/r cylinders that appear not to be firing, the other two pipes steam straight away when squirted with water where as the water just runs down the other two pipes. throws my float bowl or coil theory out of the water!
the bike was bought as a restoration project, and since ive had it its never run right.
any advice guys ? im out of ideas.
its got new plugs, and the speedo is connected, and it misfires from idle.

help!!

[Cammo]

Blocked idle circuit in the carbs is common if the bike was left sitting for any time with petrol in the carbs, can lead to issues as you describe.

Only way to really unlock them is to ultrasonically clean them

[nc30chris]

cheers cammo, would that cause them to misfire just at idle or all through the rev range? looks like thats the next step i guess, do i have to fully strip the carbs for that?

[Cammo]

It's usually only an issue at idle, if yours has this problem through half of the rev range or so then it probably is something else responsible for the problem.

The haynes manual has checks for the coils and HT leads, easy to do, get hold of a multimeter and check them.

Sounds like a PITA problem but a bit of sleuthing should find the culprit.

Just read your original post - have you had the engine at operating temp and ridden the bike yet? It might just need the cobwebs blown out of the engine...

[nc30chris]

cheers cammo, ill be honest, the bike hasnt moved under its own steam for nearly 5 years! i really thought id cracked it the other day with my last carb clean and float height adjustment, id does run a load smoother even though it misses from cold.
i think ill take your advice, ill get it insured and give it a good run ant take it from there. ill post back in a few weeks once the old girl has had a run.
thanks for all the advice guys.

[simon rc51]

sounds similar to the problems i am having with my rvf ? not had the carbs off yet but i have a feeling that is were i am heading please let me know if you got to the bottom of your problem ..

[Neosophist]

sounds similar to the problems i am having with my rvf ? not had the carbs off yet but i have a feeling that is were i am heading please let me know if you got to the bottom of your problem ..

it will be blocked carbs... 5 years of not running will gum up your pilot circuit