200 psi of compression still!!!???

[georgieboy]

Goodmorning longsleepers,
In march this year when i putt in this new vertex piston and after some riding( say 3 hours)i tested it i came to a nice 210 psi.
yesterday i compression tested my huskie cr125 '99 again, and came to 200psi. :yeehaw:
I think after all this rding i did, i think approx 50 hours of trailriding, i find this amazing.
When i looked tru the exhaust there were no signs of carbon builtup and the cilinder was looking very nice.
I mix 1:50
Do i need to change my piston, just to be safe, because there cld be flaws i don't see or can measure?
Any opions pls, thnks in advance.
Yes, i know i am not worlds most fastest rider either :)

 

[marcusgunby]

Pistons do break with enough hours, we found just the same on a ktm 125 -1 hour after a new ring it broke the intake skirt off, it looked perfect when it was apart-put a piston in they cost so little compared to a complete engine rebiuld.

 

[georgieboy]

hi Marcus, thnks for the reply.
On my way to the mxshop as we speak ;)

 

[georgieboy]

Just heard from the dealer/shop that because huskie cilinders have such a wide exhaust bridge the compression will always be up to parr, due to less ring wear, but that the pistons will break of fatique.
So a comp test is not saying anything about the condition if don't know the actual running hours.
Anyone wants to comment on the above? Just for second opinion.

 

[marcusgunby]

Thats kind of like what i said before:) comp tests tell you the trapped compression-not the state of the piston.

 

[RM_guy]

If you want to feel safer next time, try a Weisco forged piston. They will last a lot longer than any cast piston (ie Vertex, oem, etc). I have at least 80 hours on mine right now with 200 PSI (was 210 with fresh to end). I'm going to change it this winter to be on the safe side though.

 

[darringer]

I ran the same piston/rings for 2 years and compression remained constant at 215psi. In a 2 stroke, compression testing is a poor indicator of actual wear. Better to tear down and measure everything than picking out piston shrapnel... or worse.

 

[georgieboy]

Thnks for the replies, guys.
Rm and Darringer you are still talking about a 2 stroke, 125cc one ring piston? How were things with the cilinder, still nice cross hatch of the hone stone?
I find 50 hours more or less, pretty strong, but i now realise that you guys done better :cool:
Today i opened the vertex box and the leaflet inside stated 10 hours max for race use :)
You guys were pushing the envelope, or do you disagree?
O btw, i always bevel the piston skirt to avoid oil scraping off the cilinder wall. I even bevel the edge of the pistonpins. Heard it once of a race mecanic. You guys do it?

 

[darringer]

This applies to either 125 or 250 I have owned. I put the piston in "as-is". Always have had very good luck with Wiseco pistons. I never go by mfg recommendations as I am not that hard on them. I do alot of single track trail riding. However, when I hillclimb, it's very hard on the engine. I periodocally tear down the top end to measure wear, so I usually have a good idea how things are going.