Help! XTZ660 3YF engine problems
 

Hi, I was hoping someone could offer some advice to get my bike running again. I've just changed the head gasket, and when i ran the bike for the first time, there was a fair amount of noise coming from the top end. I checked that oil was getting up there, so decided it must be the valve clearances. So i rechecked these, ensuring the engine was at TDC just after the intake valves had shut. I tried to set them on the tight side, by tightening them down onto a 0.1mm feeler gauge for the intakes, and 0.15mm on the exhaust side. There was a fair amount of drag on the gauges as i pulled them out. When i went to restart the engine, it wouldn't; instead it occasionally produced a sound like a gunshot. I'm now unsure what to do - i didn't alter the valve clearances that much, maybe half a turn each, and suddenly the bike won't run. Have i made a classic mistake somewhere here? I'm pretty sure i got the cam back in the right position, as i marked the cam sprocket and before i took it out, and it went back in the same position. And it did run and rev up ok when I initially tried it. Any suggestions woud be appreciated.

Did you mach up the timing marks on the sprockets or just your own timing marks? Check your compression, i think you might have screwed up your timing and hit a valve. I hope i'm wrong... Having never worked on this motor, i'm not sure if you have a timing chain or gears, but the marks must match up in the right position at TDC, or something catastrophic may happen. Is this the new Tenere? Head gasket already?

Cheers for the reply.

There's a plug in the crankcase that you take out and you can then see when the engine's at TDC as there's a mark that you line up with a notch. So i did that, then i marked the cam sprocket before i removed it so i'd be able to reloate it. It all looked fine once i'd reassembled it, and the cam chain was nice and tight. I cranked the engine a few times by hand to make sure it turned ok and the valves moved as expected. it did run ok when i first tried it, it just made a tapping sound like the top end was dry or the valve clearances were too wide. So thats when I adjusted the clearances, which appears to have been a backward step. I didn't adjust the clearances that much, so I'm surprised if they've gone from too loose to too tight. I'll try and get a compression meter....

It was a spare engine i got with the bike, I think its a 1992. I swapped the engines as the original (1991) one was burning a fair amount of oil. This engine ran fine for about 500 miles then the gasket started leaking.

Okay, so it sounds like the timing is fine, but you need to confirm this by looking at the machined marks on the sprocket. Are you sure you adjusted the valves on TDC of the power stroke and not the exhaust stroke? Also, any chance you may of blocked off an oil passage by placing a gasket up-side down? It sounds like you may have to start tearing into the motor again and find your problem before you create more damage. Are you following a book, like clymer or Chiltons? They're sound investments and very handy.

Hi again, yes I'll have to have another look. I'll compare the valve clearances / cam position at TDC etc with a spare engine i've got in the garage (the bike's original one which was using a bit of oil but was otherwise sound). Thanks for your help, i'll let you know what the problem is when i eventually find out.

Just thinking
 

Hi - I was just reading your posts since I ride the same bike.

I have always been inclined to keep the valve clearances towards the upper limit (ie. wider)
If you make them too tight then you don't allow for thermal expansion.
There is the chance that when the engine gets hot, and the clearances get taken up, you might perhaps end up holding the valve open a little fraction.
This in turn would let hot gasses past the seat and valve face burning these and destroying the good seal.


Mine are set at 0.15mm for the inlets and 0.2mm for the exhausts. And no rattly noise.