Cutting back ?
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I would Flush the carb via the drain screw on the carb bowl. It could be shite in the carb. Condensation is the usual, especially if the tank is near empty.
when was the last time you put fresh petrol in?
Is it only on full throttle? Or is it stuttering on lower throttle positions?... -
Ah okay. When I said full power I mean I have moved the Reed switch away and the power Valve is working properly. It’s a french import with the better cdi from what I can remember researching. It’s was revving perfectly in the past, right up to 11000rpm. It just seems to be at full throttle between 8-9000 RPM. Maybe I’ll give the card a clean first and go from there.
Thanks
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@spookdog is doesn’t stutter low down at all just top end at full throttle. It always has fresh petrol I take it for a good run each month. It used to be fine so maybe I’ll try flush the carb and see if it helps at all. If not I’ll have to get more involved.
Thanks
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I’ve checked the power jet pipe and that was clear and drained the carb and put new fuel in and it was still cutting back at higher RPM. I checked the HT lead and that seemed good so I changed the spark plug and I think that has sorted it although I’m yet to take the bike out properly. What I did notice is that the spark I took out was oily so I’m guessing that’s stopping it from sparking properly which could of caused it?? Obviously changing the plug now will only temporarily fix it until this one gets oily. Where should I be looking l next to sort out the lean running issue. I did notice my number plate was covered in splattered oil from the exhaust, ! which I’m guessing isn't healthy ??
Any help appreciated
Thanks
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@dtlee Examine the oil pump settings, make sure they are correct.
It might be the right hand crank shaft seal has gone bad, seaping Gearbox oil into the combustion chamber. Which I'm afraid, is a engine out cases split jobby to fix, since access to it can only be got at from behind the main bearings.
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the power valve pipe needs to be air-leak free. If it looks old and dry or cracked, replace it..
My number plate is dripping with shitty old 2/ from the silencer. It’s just the way it is with 2/‘s. Even if you pre-mix your fuel & oil...
Wet plug could just as easily be to much fuel or the ignition breaking down. It also depends if the engine was up to temperature? Cold engine makes for wet plug, in my experience...
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@spookdog thanks for your advice. I moved the Reed switch out from the Rev counter a long time ago and it’s always been fine. The problems I’m having now are more recent. Will have a look into the ignition and carb jets and see how I get on cheers
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That’s an electronic rev limiter isn’t it? I think the 1997 onwards bikes have them? Y/N? Maybe that connectors the problem?
I have an 1988 onwards wiring loom/CDI. So I wasn’t sure what you meant
A little back history is really helpful. When (& if!) it last ran proper, any changes you’ve made, Bada bada, bing bing! You get the pic? Helps diagnose problematic changes...
Carb jets won’t be the problem, they don’t change from right to wrong. Air leaks will, as will crank seals. I doubt that it’s that though. Not if the bearings aren’t noisy...
Seriously, I’d check the rev limiter mod
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Is there a way to check if the ignition is breaking down? I’ve checked everything mentioned above and cleaned the carb out etc. But still the book it’s cutting back intermittently at about 8000rpm. Before I split the casing and check seals I want to make sure I’ve checked everything else.
It seems to run perfect for about 20mins riding the then seems to start and progressively gets worse. Could this be as it warms up the ignition is failing
TIA
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@dtlee as electronics warm up the resistance changes I'd hazard a guess with the problems your having you might have a faulty ignition coil as the coil warms up it might be out of spec this is easily checked with a multimeter via the Haynes manual, my bike cuts back at the same rpm never been able to remedy it- edit when I say ignition coil I mean the physical coil on the stator not the ht coil although that also can be an issue when it warms up
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