rear shock getting hot and sticking

[MREED]

I have a 03 yz 250 that is new ( a hold over) I race woods so I changed the valving. I added 1 38 mm shem to the rebound and took out 5 32 mm shems on the com. The bikes does good for about 30 min. and then it gets harsh. The shock will get hot enough you can't touch it and will stick like the linkage bearings are bad.( I have went through all the bearings and greased and all are in great shape) once the shock cools down the rear will free up. I use sprecto verry lite oil and I have the nit. pressure at 155 psi. Does any one have any ideas on what I sould check or change? Thanks for any help. Mack

 

[marcusgunby]

Ive seen this on kybs -its like the shock distorts as it heats.I think eric gorr honed one while heated up to make it stay round?

 

[mop]

I have seen this problem several times, and more often than not, it is when a particular oil is being used (not SPECTRO, though). It is a problem where the piston ring expands from some kind of reaction to the oil. Try changing oils, for one, and the other thing you should do is replace the piston ring with a new one, but before you install it, drill a small 1.0mm hole in the center of it between the two o-rings. This will relieve any pressure that may build up between the o-rings and expand the outside diameter.
Regarding your valving change, I have no comments because there are no 38mm O.D. vavles on the rebound stack (the larges diameter is 36mm), and there are not 5 pcs of 32mm O.D. valves on the compression side in stock configuration.....

 

[marcusgunby]

good info mop-not heard that idea before-learn all the time.

 

[MREED]

Mop
Thanks for the info. I will try that. As for the size of the shems I thought that was the sizes. I will have to look at my log book to give you the correct size. I took five of the largest shems off the com. and added one of the largest rebound size to the rebound. Thanks Mack

 

[mop]

REED:
The largest dia shims on the comp side are 40mm.......the largest on the rebound side are 36mm.....you cannot exchange them.

 

[MREED]

I didn't exchange them. I had shems from other shocks. I added one 36 mm to the rebound and took out 5 40 mm shems from the comp. ( I used your numbers ) I came up with that stack from a shock that I had done by Factory Connection. It works great for me. (until it gets hot) Thanks Mack