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290 smells like it on fire

Featured Replies

  • Author

Another update, bike starts and rides lovely however after a short test ride, I came to a stop and when I put it in neutral there was an audible hiss and now it's p****** oil out of the crank breather. Any ideas anyone?

6 hours ago, Backerlee said:

Another update, bike starts and rides lovely however after a short test ride, I came to a stop and when I put it in neutral there was an audible hiss and now it's p****** oil out of the crank breather. Any ideas any

Is there a breather on the crankcase ? Gearbox breather ? 

  • Author

There's a clear tube I'm assuming comes from the crank case or gear box and thats the oil source. 

It may be the right hand main bearing seal is failing and pressurising the clutch basket side of the caseings, the hole that feeds the breather pipe is behind the top of the clutch basket. I had a sherco 125 chucking out oil from the breather it wasn't hissing though, that sounds like a complete seal failure. It may not be thow as I was always under the impression that the seals were to stop the crank sucking oil in and not the other way around. 

A good test is to attach a longer pipe to the breather pipe, warm the bike up put the pipe in a bucket of water and if it bubbles like crazy when you rev the bike your main baring seals have worn-out. 

  • Author

The hiss was one brief noise as I put the thing in neutral it hasn't hissed since but that was definitely the start of the leak. I'm thinking a seal somewhere but haven't the faintest idea where

  • Author

It would definitely bubble if I put it in water cos it's bubbling as it's forcing oil out

Did you fall off the bike and the bike end up landing on its right hand side for a while, as the gearbox oil could pool in the clutch side then get sucked in the breather hole as you stand the bike back up straight and carry on riding. there is a small cavatiy behind whare the breather attaches to the caseings if that has filled up with gearbox oil it might spray oil out for abit until its cleared, I used a vacume pump to clear mine. 

  • Author

No but if I shake the bike about a bit ie push down on the front end hard the drip gets faster if that helps 

  • 2 weeks later...

what colour is the oil coming out of the breather 

Try running the breather to a small transparent catch tank of some sort, maybe a large fuel filter or something, se how quickly it fills up. Mount it higher than the breather outlet then the oil will run back in to the gear box if it fills up the filter in mins you definitely have a air leak if its just abit of spatter you probably have to much oil in your gearbox. 

  • Author

I've definitely got a leak of some sort, I've been informed its probably the crank seal wet side which I understand is not an easy fix 

  • 3 months later...
On 1/11/2021 at 9:25 AM, Backerlee said:

I've definitely got a leak of some sort, I've been informed its probably the crank seal wet side which I understand is not an easy fix 

Did you get it sorted? If you changed the oil before your last ride and added more than 450 the excess may be pumping out the breather hole. Keep us posted on progress. Cheers.

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