Run with no oil!!

[jasonbc]

It's not a good sign. It's called blow-by. It's a likely source of your oil burning.

The proper way to measure rings is to remove them from the piston, slide them into the bore and measure the gap between the two ends of the ring. Trying to slide a feeler between the ring and the barrel won't tell you a lot as they are springy.

That is a simple test that will proove if anything is leaking past them, instead of getting over technical in a home garage scenario this is a good indicator that the rings are not doing what they should be doing. End of the day they won't be very spring when they are on the piston, i should have said that i did miss that bit off i did mean (but did not mention) to put the rings on the piston slide th ebarrel over th episton and rings and then measure with a feeler guage. If there's any doubt about wear in the liner get a rebore or another liner pressed in. Supplying and fitting a new liner can be done locally here for about £70 inc the fitting all sizes of liner can be supplied.


I went through the same things as you are going through when i bought my XR some years ago. MIne had the 440cc kit, heavy duty clutch drilled air box, snorkel removed, hugely jetted up then one day outwent out to practise filled up with fuel somethig went bang and i found this.





cracked liner


bent piston




When i rebuilt it i put it back to a standard 400 as these motor can't cope with the 440 kits i've not heard of any that live very long using these kits this was fitted to the bike when i bought it and i wasn't told about it or i would have walked away. This one was the weisco 12.5:1 kit (high compression). The over revving was what caused the rod to fail. After the bike was put back to standard it went for quite a few hard years of use effortlessly untill it started smoking, then i opened it up pressed and cut a new set of valve guides in it, new valves seals fitted, cut the valves to suit the new seats then lapped them in threw it back together and like a new one. Then shortly after the wife got pregnant so i sold it and my beloved GAsgas EC250 gave up competion racing and now i only have my Trials bike and Varadero. Now waiting for the baby to be 2 years at next Christmas and he can have his new little OSET as soon as he's walking.

absolutly loved my XR one of the best bikes i've owned and wish i never sold it, that was a big mistake the punishment they can take and pleasure they give is unreal





This is what came out after i flushed it and it ran sweet as a nut

[Michaelb]

Thanks Alan and Jason - all good info.

I will do some more work on the bike today. Think the rings and seals might do the trick with maybe a valve seat regrind.

Cheers
Mike

[Michaelb]

Great pics Jason, mine has been wet before, but nothing like that.

Didn't leak any paraffin when I tested the valves so will just go with the decoking and the new valve seals and rings (one of the rings snapped as I was trying to get it off).

The previous owner told me it had a 440 kit fitted, but I'm not so sure now. The piston od is 84.88 which seems to be within the service limit of the oem piston, and, the piston is stamped with kyc which is also on the oem piston shown in the service manual (don't know what kyc stands for, but no signs of any wiesco markings. What do you think?

I put the piston back in the cylinder without the rings and could get a .2mm feeler gauge in there, but think this might be okay?

Cheers