Pippin5267

Member
Dec 19, 2007
30
0
my friend has a cr 125 that hes wanting me to rebuild the top end in. he dosent have a manual and i was wondering what the compression psi is supposed to be for a stock bike. its a 2000. im guessing it should be between 100-175 but i wanna be sure. if anyone can has a manual for that bike and could tell me i would sure appreciate it.
 

IndyMX

Crash Test Dummy
~SPONSOR~
Jul 18, 2006
5,548
2
Amo, IN
I've looked all thru my manual, I can't seem to locate it.

I have found the compression ratio, but that's not gonna help...
 

BigRedAF

Member
Jan 9, 2005
739
0
I like to see 180+ in a fresh stock top end. Be sure it's a warm engine and hold the throttle open when you kick it. Kick it until the gauge stops rising.
 

chevyss_98

Member
Feb 26, 2006
59
0
ya 180+, if its severly below 150 like more than 10, then itll need a rebuild ASAP, or itll blow basically lol

what happens is you start out around 185, then after a bit you drop down to 150 for quite a while, then itdrops to 120, and when its 120 its unpredictable and can pretty much blowup anytime
 

griffbones

Member
Sep 12, 2006
329
1
BigRedAF said:
I like to see 180+ in a fresh stock top end. Be sure it's a warm engine and hold the throttle open when you kick it. Kick it until the gauge stops rising.
The best advice that I have read in this thread!
 

chevyss_98

Member
Feb 26, 2006
59
0
BigRedAF said:

seen it happen alot, more with the 125's

cast pistons are the worst

you get a hot day, beating on a 125 with tolerances not as tight in a cylinder, rings get hung, and everything goes to crap

had it happen to me on my first bike

dont know bout you, but thats my own personal experience, maybe ive just been unlucky
 

chevyss_98

Member
Feb 26, 2006
59
0
IndyMX said:
When the piston is worn, it doesn't matter what kind it is, it's probably going to break under those conditions.

true that, bit of vibration and off come some circlips lol, and its off to the races with a floating wristpin lol
 

BigRedAF

Member
Jan 9, 2005
739
0
circlips come off when the open end is installed in the 3 or 9 o'clock position at very high RPM. They should be installed in the 12 or 6 o'clock position. Some pistons use a better full circle clip design that are a real mother to get off. Some people squeeze the clips when they install them and cause the clips to loose their temper or spring. That will make them fail very soon.
 


Top Bottom