173psi

K

KDXMAC

Member

Sep 13, 2004

79

0

• Oct 30, 2004

• #1

i did a compression test on my recienlty purchased 98 kdx200 and it registered 173psi, the service manual said normal operating level 95-151psi, so why is mine so high? the bike runs fine in over the whole rev range. In saying this though I have never riden a kdx before to compare the engines power level! what do you think it could be?

 

S

skipro3

Mod Ban

Dec 14, 2002

902

0

• Oct 30, 2004

• #2

Could be some carbon built up on the head, reducing the volume and increasing compression.

 

B

BRYDEN1

Member

Sep 22, 2003

97

0

• Oct 30, 2004

• #3

How trustworthy is your comp. tester? Do you have a baseline to compare it to from a different bike?

 

K

KDXMAC

Member

Sep 13, 2004

79

0

• Oct 31, 2004

• Thread starter
• #4

there was very little carbon build up on the piston or head, the compressioner tester in brand new and of good quality and measured my friends reciently rebuilt 01 YZ250F fine.

The only thing I experienced on my bike was when ridden at a constant 3/4 throttle and I backed off very very slightly there would be like a knocking noise in the engine.

 

L

lankytim

Member

Feb 26, 2004

62

0

• Oct 31, 2004

• #5

Was the bore really oily from rich jetting or something? Just a thought... I'm not even sure if that could raise compression above the service limit?

Hey, at least it isn't reading 73psi ;)

 

B

BRYDEN1

Member

Sep 22, 2003

97

0

• Oct 31, 2004

• #6

The head and cylinder may have been milled by the previous owner. If the jetting is close and there is no sign of detonation, leave her be and go riding.Good luck.

 

K

KDXMAC

Member

Sep 13, 2004

79

0

• Nov 1, 2004

• Thread starter
• #7

thanks for the help guys, bad news though- I pulled the head and barrel off and WHAT A MESS- looks like previous owner must have semi siezed the engine there is a patch about 1inch square on the piston where chrome has stuck to it and some bad scoring on the barrel and a fine crack on the inlet side. God knows how she kept running, funny thing is she was running ok. Anyway barrel is off to get a new sleeve, piston and ring and while it's there Im getting the power valve cleaned and matched to new sleeve. Can't wait to get back on.

 

S

skipro3

Mod Ban

Dec 14, 2002

902

0

• Nov 1, 2004

• #8

If you think the seller knew about the condition, it might pay to appeal to his conscience.

 

K

KDXMAC

Member

Sep 13, 2004

79

0

• Nov 2, 2004

• Thread starter
• #9

yeh, thanks but it's my problem, thats what happens sometimes when you buy 2nd hand. Anyway it will be nice to have a fresh engine to run the way I want.