250-500cc first time at track...problems

[Travis Thompson]

i took my wxe 260 to a track saturday for the first time and was having a ton of fun. after over an hour of riding my bike started bogging and then shut off. I rolled it back to the truck and it was really low on compression. It was running rich so I knew it couldnt have blown or anything. I took it home and pulled the head off and piston looks really good and also through the exhaust port looks great. Im pretty sure one end of my piston ring got stuck in somehow. I stuck a feeler gauge between the piston and bore and right where the 2 ends meet one side is stuck in piston. How could this happen? Only thing I can think is air filter not sealing properly and let a couple pieces of sand in and got jammed. Gonna pull it apart later but just wanted to know if anyone has had this happen before?

 

[Dirtdame]

The only time that I ever had rings stick in the grooves is when I ran castor bean oil in my bike. It just didn't burn cleanly enough for the type of riding and service intervals that I was doing. I switched back to a petroleum based oil and didn't experience any more problems. These days, I run a high dilution mix of a synthetic for the cleanest results.

Did you actually throw a compression gauge on the machine to check it? It is not likely that dirt got stuck in the rings. If the air cleaner was not doing its job, the first evidence of that would be a scratched cylinder wall, somewhat more on the exhaust side than the intake.

 

[Travis Thompson]

The cylinder is perfect...I'll pull it apart and see what's really going on...just wierd to loose compression like that. The kicker was real easy to kick over but still had a little compression where I might have been able to roll start it

 

[Travis Thompson]

Ok pulled it off and never seen this before...after only ten hours my piston ring is wore way down...why would this happen? Bad ring? My ring gap was fine when I installed it...I'm gonna contact wossner to see about a new ring..

 

[Dirtdame]

Ok pulled it off and never seen this before...after only ten hours my piston ring is wore way down...why would this happen? Bad ring? My ring gap was fine when I installed it...I'm gonna contact wossner to see about a new ring..

I had a ring locator pin come loose in a piston one time. This allowed the ring to move around till the end gap lined up with the exhaust port. Then the end kept catching in the port, until that part of the ring was completely blunt and worn out.

 

[Travis Thompson]

well mine was still lined up but alot thinner especially at exhaust port. heres a pic

 

[Travis Thompson]

Ok so got new ring installed...cleaned up everything...started it and broke it in and then today went for a ride and 1 mile away it lost all compression again!! I'm gonna measure the bore again but don't see why this happened!!

 

[Travis Thompson]

Ok got it all apart and it siezed...Could this have happened because I was sent the wrong ring. I didnt even think to double check it when I got it but looked the same. It seized on the sides with the wrist pin bearing. It wasnt very bad but gonna require a new piston. The cylinder looks fine other than needing bored because it has a steel sleeve. Heres some pics. Why would it have seized since it seemed to be running rich. Maybe an air leak? Not sure since its the first time ive had one seize on me.

 

[Aviduser]

weird, are the circlips still in place? (you probably checked this)

 

[2premo]

that is odd, all that comes to mind is a cooling issue

 

[2premo]

might be time to buy that NOS top end I sent you the link on, the price is about the same as a piston so you get a barrel and head for free
as I recall you had an o-ring at the head issue to boot

 

[Travis Thompson]

Yes everything is in place...had plenty of coolant...the problem is mine has been resleeved with a 250 sleeve so it won't fit..any other ideas? Too tight maybe? That's what I'm thinking...

 

[Travis Thompson]

The more I think about it I think my ring expanded to much and ends met and thus got to tight and seized. It was dumb of me to not check ring gap...completly spaced that out..I think thats what happend is my best guess since it seized after about 8 min of riding...just enough time for it to expand enough..If anyone else has any ideas let me know. Thanks...

 

[juicypips]

get the top end 2 premo mentiond.
ive never checked ring gaps but ive not run in my 250 yet its a wossner piston too so im going to check that before i run it in.

i feel for you

 

[Travis Thompson]

Haha...I emailed wossner and that's what they said..the way it seized definitely felt like it expanding because it surged real bad but didn't lock up...any body know what a good ring gap and piston to bore clearance should be? I didn't check ring gap this time cause last one was good. To late now lol.