1985 250r low compression causes?

[mrtwidster1]

What are the factors that will cause a water pumper R to have low compression?
I have very low pressure on my R *40lbs* I was riding it and its power output got very weak, died and won't start back. No funny noises and the motor is not seized. It did not get hot either.
I am going to rebuild it but want to find the culprit. I know it could be the cylinder bore, piston or rings. I think those things will be obvious. I would like to know what else to look for.
Thanks

[lazybiker79]

The same thing happened to my 86 250r it was a cooling problem

[harryredtrike]

new rings and gaskets should fix her up

[mrtwidster1]

Will any thing besides piston, rings, or cylinder cause low compression? I have not tore the motor down yet so it may very well be a piston or ring or cylinder issue. I was just wondering if bad crank seals or something else would cause low compression. I am running Klotz at 32:1 My R did not run hot so I do not believe that was the issue.
Thanks guys!

[Vootie]

Only other thing that could cause low comp than piston/rings/cyliner would be either a bad head gasket or a stripped plug hole.

[3wheelmecca]

possibly a pinched ring, I had a YZ490 do it to me.

[mrtwidster1]

Thanks for all the advice! I really appreciate it. Just want to start out in the correct direction.