power valve

R

riggermode

Member

Aug 25, 2008

21

0

• Sep 2, 2008

• #1

hey guy's what exactly does the power valve do i seem to have lots of oil coming from that area on my 1990 yz 125.

another ??? i have is i changed the antifreeze flushed it out and put in prestone premix from Canadian tire was that a mistake or is that fine thanks for you help.

 

J

_JOE_

~SPONSOR~

May 10, 2007

4,697

3

• Sep 2, 2008

• #2

The power valve is basically a mechanical exhaust restrictor. What kind of premix oil are you using? I hope not the auto parts store stuff. Cheap premix can cause excessive oil in the power valve area.

You should use antifreeze for aluminum engines if you need freeze protection.

 

R

riggermode

Member

Aug 25, 2008

21

0

• Sep 2, 2008

• Thread starter
• #3

pre mix for the gas is yamalube racing oil at 32:1
the antifreeze was the cheep stuff but good for aluminum engines

 

J

_JOE_

~SPONSOR~

May 10, 2007

4,697

3

• Sep 2, 2008

• #4

Those fluids are fine.

Are you also seeing oil at the pipe connections and outlet?

 

R

riggermode

Member

Aug 25, 2008

21

0

• Sep 2, 2008

• Thread starter
• #5

yes lots i think it might be the power valve

 

J

_JOE_

~SPONSOR~

May 10, 2007

4,697

3

• Sep 2, 2008

• #6

Naah. Either your jetting is too rich or the tranny side crank seal is starting to leak. Eventually the oil build-up will cause the power valve to stick making the bike run terrible in the top end. A leak down test is a pretty cost effective way to check the crank seals. Do that then clean out the power valve and repack the silencer. How old is the top end? After that you can start jetting to get that sloppy pig cleaned up, lol.

 

R

rmc_olderthandirt

~SPONSOR~

Apr 18, 2006

1,533

8

• Sep 2, 2008

• #7

The power valve changes the exhaust port timing with engine RPM. At lower RPMs it makes the piston travel farther down the cylinder before the exhaust port is opened, which improves low end power. As the RPMs increase the power valve rotates, exposing the exhaust port earlier in the stroke to give the exhaust more time to exit the cylinder, which is required for higher RPMs.

It is not unusual to have the exhaust goop leaking out from the ends of the power valve shaft. It is possible for this goop to clog things up and cause the power valve to jam, which can mess up either the top end or or bottom end power depending on what position it jams in.

Rod

 

S

Screamn200

Member

Aug 30, 2008

25

0

• Sep 3, 2008

• #8

Ride it harder :D. When I first started riding a 2 stroke I had gone from a CT125 to a KDX200 with quite a bit of work done to it and oiled it up quite a bit because i didnt have the bike revving enough. It also made the bike gutless. Don't have any trouble now, I keep it screaming all the time :)