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+--- Thread: High rpm misfire... (/showthread.php?tid=75195)
High rpm misfire... - Motopsycho87 - 20-03-16
Hi guys, been out for a 100 mile play today, towards the end of the ride me and a mate decided to drag race (on a privately owned airstrip...), after the first couple gears the bike started to fall flat. Now no matter what gear I'm in it seems to misfire over about 7-8krpm. It ran perfect in recent weeks doing the same, but all of a sudden today it struggles,it sounds more like it's on 3 cylinders than 2.
So besides the obvious, clean connectors, snip the HT leads, replace the plugs. Any other thoughts? Coils are pretty cheap so I'll snatch some up while I'm at it. Are there any common faults that would act like this?
Cheers!
Re: High rpm misfire... - PieEater - 20-03-16
Check the air intake to make sure nothing is obstructing it or has been sucked into the snorkel.
Re: High rpm misfire... - Motopsycho87 - 20-03-16
Ridden over a few leave but would be damn surprised! Added to the checklist though...
Re: High rpm misfire... - Motopsycho87 - 20-03-16
Apparently a white block of wires behind the left hand panel can be a problem?
Re: High rpm misfire... - mick chiz - 21-03-16
check your exup valves working,(take cover off and move it with your hand)also a dry air filter can cause all sorts of problems if you have an aftermarket one,k+n or pippercross,make sure that they are oiled correctly.another thing it could be is the fuel filter,very easy and cheap to replace.ive learnt over the years to start replacing the servicing parts on a bike before going full technical if any running problems arrise
Re: High rpm misfire... - Motopsycho87 - 21-03-16
No EXUP on bike I'm afraid!
Re: High rpm misfire... - Motopsycho87 - 26-03-16
Right, so changed the sparks plugs, ignition coils and leads. Still no different. There was a lot of corrosion everywhere, but nothing obvious.
So now my next possible thought is the carbs. What can go all of a sudden and stop a cylinder running at high RPM? When I installed Ivan's I fitted new carb rubbers, everything was to spec, and it ran perfect. All of a sudden, one cylinder seems to be not firing, but only at high RPM, its perfectly smooth at low revs...
Cleaned out that 'white connector' with contact cleaner too, then slapped with white grease and re-assembled. Nothing.
Only thing that makes sense atm is a blocked main jet... in which must be a big lump of shit to achieve that!
Re: High rpm misfire... - Motopsycho87 - 26-03-16
A fucking dead ant in my main jet...
Re: High rpm misfire... - PieEater - 26-03-16
Mice in the airbox I've heard about before but that's a first !!!
Re: High rpm misfire... - AyJay - 26-03-16
Got to be a first!
Still, it's always good to find the problem so you can be confident of a fix.
Re: High rpm misfire... - Motopsycho87 - 26-03-16
The fix being poison pellets in the vent hoses...