cr 125 compression test

P

Pippin5267

Member

Dec 19, 2007

30

0

• Feb 11, 2008

• #1

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

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Jul 18, 2006

5,548

2

Amo, IN

• Feb 11, 2008

• #2

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...

 

Z

zaneyzrex

Member

Jan 9, 2007

77

0

• Feb 11, 2008

• #3

150psi plus is a good top end. 100psi is a dead top end

 

B

BigRedAF

Member

Jan 9, 2005

739

0

• Feb 11, 2008

• #4

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.

 

C

chevyss_98

Member

Feb 26, 2006

59

0

• Feb 12, 2008

• #5

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

 

B

BigRedAF

Member

Jan 9, 2005

739

0

• Feb 12, 2008

• #6

chevyss_98 said:

when its 120 its unpredictable and can pretty much blowup anytime

Click to expand...

NOT!

 

G

griffbones

Member

Sep 12, 2006

329

1

• Feb 12, 2008

• #7

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.

Click to expand...

The best advice that I have read in this thread!

 

Y

yz125MArider

Member

Feb 12, 2008

17

0

• Feb 12, 2008

• #8

just ride that **** till it BLOWS!

 

Y

yz125MArider

Member

Feb 12, 2008

17

0

• Feb 12, 2008

• #9

you will know it needs a rebuild when it wont run anymore,,,,,,correct? then the compression will be like 0,,,,,then u rebuild.lol

 

S

sixds

Member

Mar 25, 2007

779

0

• Feb 12, 2008

• #10

you will know it needs a rebuild when it wont run anymore,,,,,,correct? then the compression will be like 0,,,,,then u rebuild.lol

Click to expand...

:coocoo:

 

IndyMX

Crash Test Dummy

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Jul 18, 2006

5,548

2

Amo, IN

• Feb 12, 2008

• #11

They really need to have an IQ test to get in here..

 

C

chevyss_98

Member

Feb 26, 2006

59

0

• Feb 12, 2008

• #12

BigRedAF said:

NOT!

Click to expand...

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

 

IndyMX

Crash Test Dummy

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Jul 18, 2006

5,548

2

Amo, IN

• Feb 12, 2008

• #13

When the piston is worn, it doesn't matter what kind it is, it's probably going to break under those conditions.

 

C

chevyss_98

Member

Feb 26, 2006

59

0

• Feb 12, 2008

• #14

IndyMX said:

When the piston is worn, it doesn't matter what kind it is, it's probably going to break under those conditions.

Click to expand...

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

 

B

BigRedAF

Member

Jan 9, 2005

739

0

• Feb 13, 2008

• #15

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.