No Top End Power

[cello]

Can anyone give me some advice on the following problem ?

I recently had my Husky WR250 2stroke (1996) re-nicosil plated , after rebuilding the bike with the old piston ( Had problems with the nicosil plating first time round which caused a engine seizure, resulting in the plating company re-coating the barrel and me trying the engine with the old piston ) , and running the bike for about a week all was well - Low and Top end power as expected.

After ordering a brand new replacement piston ( Wiseco ) I stripped the bike down and the barrel was dispatched with the new piston to the plating company to hone the barrel to fit the brand new piston.

The problem is after the bike has been rebuilt and run in there appears to be a no top end power , the power builds as expected then just appears to tail off as if the power valve is not opening properly.

I have checked that the valve does actuate and it appears to be opening fully when reving the bike at a standstill.

The only difference appears to be the NEW WISECO PIston . THe piston looked identical to the factory husky unit it replaced but was noticed to be somewhat lighter.

Can anyone suggest anything to check next ? Already tried the plugs , cleaned exaust and checked power valve ?

Thanks

 

[cello]

HUSKY wr250 enduro no Power

I,ve just had my WR250 Husky 1996 renicosil coated and replaced the original piston with a Wiseco replacement.

Since fitting the new piston and after running in the engine I have noticed that the engine now lacks top end power - the engine @ high revs appears to be running as if the power valve is not opening properly and struggles to rev higher than a certain level.

THe bike use to run fine with the old piston and I am wondering if the New Wiseco Piston is not quite compatible with the one it replaces . It was marked for a WXC not a WR but I believe that the WXC was the US name for the European WR .

Can anyone confirm or deny this or suggest a alternative cause for the problem .

THanks

Cello

 

[Layton]

I doubt that the piston is the problem. Find out if the power valve is opening properly.

 

[cello]

Certainly it does appear to open when reving the bike at a standstill. I cant check that the valve is opening on the move , but it certainly feels as if the engine is blowing against a closed valve. Theres plenty of low down grunt just it wont rev out and splutters at a particular rev point.

HELP !

 

[Layton]

Is there any chance the main jet is way too rich? That would cause the bike to sputter and flatten out at high rpm.

 

[cujet]

I would take the power valve assy apart. The Husky power valve can be improperly assembled and will appear to be opening, however it is being held in the closed position. I had this problem with my bike when I first purchased it.

Might even want to wire the valves in the open position for testing.

In addition, you can hear the difference in exhaust tone when the valves open.

Chris

 

[a454elk]

You'll know when it kicks in, if it doesn't, see cujets idea. If you wire it open, it'll be dead on the bottom end but kick in shortly thereafter.

 

[it175man]

Before you wire things down...I have probllems with my carburator that soounds a lot like this no high end power. I have some old Yamaha it175's. The caarburator floats are made out of float materials that absorb fuel ovver time and screw up the flow of gas iand air into the engine. It does not happen at the low end. I changed out the floats and all is well.