If you are thinking of using a wiseco piston.........
I have just stripped a rather rattly XR6 engine.
The rattle was due to the gudgeon pin having slipped out sideways past the circlips and out of one side of the piston.
The circlips are the correct type - the problem seems to be due to the clip grooves in the piston being machined too deep.
Spoke to Wiseco Tech Dept and astonishingly they seem to be aware of this type of problem.
I am promised a phone call tomorrow.
Check your wiseco circlips - this engine now needs a piston, liner and crank.
D L

I recently bought a 1vj with a wiesco piston. Just fitted in the last 2000km. But I've just started to notice a bit of a rattle... that wasnlt there a few 100ks ago. Is there any particluar way of telling if its the piston problem you refer to without stripping it down... I guess not, but any advice welcome.

Dave, if i bring it down in the autumn will make an assessment for me ? (bike is in the Pyrenees at the moment),

Simon

Simon.
Oh dear, I think Ive got you worrying now!!!
Highly unlikely its the same problem.
This XR6 engine could be heard rattling over the phone and riding behind it.
Small rattles on XTs are pretty common really.
Yes, bring it down & ill have a ride & a listen.
A bientot.
David Lambeth.

I rebored and put an oversize Wiseco piston in my 1989 XT 600W back in 1989. That was 14000 miles ago and absolutly no problems. Rode it across the U.S. right after. Lots of power and tops out at 101 mph. It sounds like Wiseco just had a bad batch recently. The engine does rattle, but all XT's sound like the head is ready to fly off anyway. Best bike I've ever had. I would never want to sell it.

Was it std or oversize ? eg 620 or 640 and does it make a lot of difference to the power? I've got a TT600 and wondered about giving it a bit more go.
I've got a DR350 bored out with a Wiseco 385 piston and I've had no problems with that

It was the first oversize after std, but so long ago I've forgotten the number. I have the specs in a file and will look them up later. I also put in a Crane high lift cam(reguires different valve clearances), R&D valve springs, and a Super Trap exhaust. I allways use Golden Spectro 4 engine oil 20w50(works for me, but I ride in very hot and humid weather). After the performance work vibration does increase. Just recently had to replace the intake manifolds(rotted)and all the o-rings in the carb(hard and brittle). Power is great. Another bonus is Progressive Suspension in the front. It makes a noticable difference.