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Power loss question

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I've got a 2008 ktm 250xc . Always non ethanol 40:1 w/ synthetic. New top end a year and a half ago. Has the Suzuki needle jetting mod. Jetting has been spot on always.

 

Last two rides I've had a hard time starting it off and on even when Warm and had to choke to get it to start.

 

In addition to that having major power loss/ fizzle out/ bog out 2/3rd off the way up big sandy hill at wide open throttle...was able to get up the hill just fine on my friends Kawasaki 250 four stroke...

 

New plug, clean air filter, fresh bel ray oil ...

 

Tried taking Float bowl off and doing quick carb clean/ check jets. Everything was clear and spotless. No varnish or sediment.

 

Noticed head pipe was slightly loose. Ordering new gasket and springs. Could that be causing that much power loss?

 

Power valve? Reeds?

 

I haven't changed anything....since it ran great.

 

Could I be losing compression?

 

Thanks!

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Depending how many hours of use and, how hard it's ridden

1-1/2 years on a top end could be way due for a refresh, take a compression reading.

 

Reeds as well are a wear item just like a piston & rings, despite not showing any damage and still sealing around the petals

with usage they loose their tension. Makes the engine less responsive (acts like it's running rich) and kills top end overrev.

If in doubt, replace them. Nothing fancy required (VForce etc.), stock replacements are fine.

 

Make sure the float / fuel level is set correctly. Over time that can change, making you think it's a jetting issue by either running rich or lean.

Check the powervalve's operation.

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Depending how many hours of use and, how hard it's ridden
1-1/2 years on a top end could be way due for a refresh, take a compression reading.
 
Reeds as well are a wear item just like a piston & rings, despite not showing any damage and still sealing around the petals
with usage they loose their tension. Makes the engine less responsive (acts like it's running rich) and kills top end overrev.
If in doubt, replace them. Nothing fancy required (VForce etc.), stock replacements are fine.
 
Make sure the float / fuel level is set correctly. Over time that can change, making you think it's a jetting issue by either running rich or lean.
Check the powervalve's operation.


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Thanks. Has the v force reeds in now. I'll check them and have a compression test done.

Not too sure how to check power valve operation itself.

Float was working well

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Float 'working well' (meaning regulating the fuel inlet) doesn't mean it's set at the proper height.

Sounds like a service manual would be a wise investment for you.

 

Edited by mlatour

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I haven't changed the height of the Float and it was working well prior.

I understand what you are saying.

I have a service manual...

Wouldn't necessarily consider myself overly mechanically inclined.

Thanks for your help

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Difficulty starting and lack of power are common signs of a worn top end.  Other things can cause the same problem, but for sure you would see this with a worn top end.  If it were me I would first do a compression check.  If it's low then definitely plan a new top end.  Riding in the sand, if any sand got by your filter then that could wear your top end extremely quickly.   

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