I have a frustrating problem where my VF1000FF will only run on 3 cylinders at idle and low revs. Above about 3000rpm all is fine but below that #2 cylinder is not interested.
Any thoughts and possible solutions would be appreciated.
First thing to try would be a check for spark at low revs, if all good there, then check to see if your your carbies are gummed up or not balanced.
Then a compression check since it sounds like the beginning of a burnt valve.
Also check for vacuum leaks, it really could be a range of possibilities, but first you need to do some basic checks.
The more information that you can provide, the more help this forum will be to you.
Is the header pipe for No.2 cold when the others are hot?
Thanks for the response, Yes, the No.2 header is still cold when the others are hot. The No.2 header heats up once it’s run at higher revs and that cylinder starts firing.
I’ll check for spark at low speed but my initial thought was that the low speed jet on the No.2 carb might be blocked. Is it possible to access these jets with the carbs in place or do they have to be removed from the engine?
I was hoping to avoid taking the carbs off as I have bad memories of trying to refit the carbs on a VFR400 a long time ago.
I hadn’t thought of vacuum leaks or a burnt valve.
Yeah, you are on the right track, if it were a burned or tight valve or a vacuum leak, that pipe would be hot. It’s either not getting fuel or spark if the pipe is cold. Spark is easiest to check, so eliminate that first, then if it is jets blocked, its a carbies off job.
Tony
Unless there is a method I haven’t thought of? You can remove the diaphragms with the carbs in place, can anyone tell if they would cause that symptom? If you remove the tank and air cleaner element, you should see if the slides are all working evenly.
Check your pulse generators with a digital multimeter for correct resistance
check my latest post for details