Hi all could someone tell me what the symptoms of crack seal failure is?
The reason I ask is I've been out for a few hours today on my totaly standard mc21, and while sitting at traffic lights the tick over went from 1300rpm to somewhere near 1800 rpm without me even touching the throttle, then it would be fine for the next dozen times this happened 3times today, does anyone have any ideas? Is it something to worrie about or is it just something they somtimes do, the bike is fine starts goes well no noises
Any advice? Thanks

Hi Tom,

I remember mine racing MC21 back on 1998 that was dropping revs very very slowly... That was my symptom... But check it very well before you go and start disassembling the engine... You could do an Air Leak Test in order to find out...

Cheers
Michael

Hi micheal
The revs drop straight away to 1300rpm, but if I watch the rev counter they pick up to 1800rpm without touching the throttle, but then could pull up at a dozen lights and have no problem (ticks over 1300) then next lights 1800rpm then ok for 6sets of lights, then next two sets of lights 1800rpm and so on but always drops to quickly to 1300 and goes up from there any ideas or am I just worried for nothing? Thanks

Might be some dirt in the fuel gas or a partially clogged pilot jet causing a weak mixture.
Not a big issue but prepare for a carb strip and/ or fresh gas if the problem remains.

Crank seal failure is way more thrilling that the issue you describe.
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Is your clutch dragging a bit an not so much when its warm?
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it wouldn't be fun if it was easy!

Thanks for putting my mind at rest about the crank seals, I tend to look for the worst case in every fault I have, I think im a (hypocondriact) and bad at spelling, I've read somewhere about fuel tank breather maybe bloked but I don't have the rubber tube from the tank so can't be that, like you say looks like a carb strip,it,s all a learning curve. As for clutch dragging I can't see it being that as im in neutral when it happens

Thanks for putting my mind at rest about the crank seals, I tend to look for the worst case in every fault I have, I think im a (hypocondriact) and bad at spelling, I've read somewhere about fuel tank breather maybe bloked but I don't have the rubber tube from the tank so can't be that, like you say looks like a carb strip,it,s all a learning curve. As for clutch dragging I can't see it being that as im in neutral when it happens

Mine hops around at idle. It runs very rich down there too, which is probably why. A bit rich does no harm...except to your pocket.

Good to know it's not just mine then, i was just worried i was causing more damage by ignoring it, but it does sound sweet no knocks,rattles,and it goes well,im going to give it a good carb clean, rc valve clean etc in winter
so for now im going to stop thinking the worst and enjoy

Thanks Mark

Just a quick update, I decided to remove carbs to give them a clean and there was a load of gunk in the bowls so cleaned out with carb cleaner and blow them out with the compressor, so had a look at air filter while I was there an found that somone has made a filter From one of them foam filter sheets you cut yourself but has been made very badly, doesn't even fit the airbox there is half inch gap most of the way round, so I've just ordered a new one see if that helps