Low End lack of power

[fbonneville]

I've posted something similar a few weeks back but never got underneath the problem.

here goes:

99 RM125 Suzuki, PC Pipe + Silencer, VForce Reeds, new top end, new plug, new clutch.

the last few weekends, I've been noticing a major lack in power in the lower end of the RPM range and verified this by cruising in 1st gear and turning the throttle WFO. The bike would be very unresponsive, sounding like it would load up then start picking up speed and HIT so hard the front wheel just wants to come off the ground and into my teeth.

I've had a friend try my bike and he agrees that my bike's powerband is definitely weird.

I tried turning the air screw in OR out but didn't notice much difference. Plug looks pretty good too.

Do any of you have any pointers as to where to start looking?

 

[Rich Rohrich]

Logical causes are:

- dirty or collapsed air filter element
- worns reeds
- worn rings/top end
- jetting as a result of a weather or fuel change.

First place to start is the basics, clean the filter, clean the plug wire and check the ignition grounds, put in a fresh plug and mix up some fresh gas.

 

[RM_guy]

One more to add to the list...check to see if the power valve is stuck open.

 

[Rich Rohrich]

Originally posted by RM_guy
check to see if the power valve is stuck open.

:thumb: :thumb:

 

[fbonneville]

So a dirty air filter would cause this? No low end with an evil kick on top?

It shouldn't be the top end, it has less than 2 months on it. Reeds, less than 2 months also.

Now for the powervalve, is there a way to check this without having to do too much surgery to the bike or do I need to remove the head for this?

 

[TM-Frank]

Ther should be a cover on the side of your cylinder. It is often a bit hard to reach because the pipe is in the way. Underneath that cover you can see the pushrod of the PV.
Remove pipe, remove cover, put pipe back on*, start engine, open throttle and watch if pushrod moves up & down or not.

* leave pipe off when you want to renew your friendship with your neighbors

 

[RM_guy]

You can see the valve with the just pipe removed. Don't start the bike with out the pipe and look in the exhaust port. The valve should be protruding from the top of the port when the motor is not running. If it is not all the way down or it is all the way up then it's stuck. You should be able to move the valve up with your finger and it should pop back down smoothly all be itself. If it is stuck you need to remove the cylinder and clean it.

Good luck