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Can't Get Engine Running Right

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Sorry to post another ‘my bike isn’t running right’ questions but I’m really at my wits end now.....let me explain.

 

I bought a 2009 KTM 250 EXC about 6 months ago and the first thing I did was a top end rebuild as hadn’t a clue when it had been done previously.  I am satisfied I did this correctly and the bike runs well enough to ride both on and off-road but not perfectly and this is what I’ve noticed:

 

If you are in second gear and at low revs and try to clutch is out of a corner it will struggle to pick up, if it has been at low revs perhaps over a technical section then it will struggle to pickup and I have to rev the nuts off it.  I could also be riding at reasonably high revs and then open the throttle fully and quickly and the engine will die requiring me to back off and allow it recover for a second or two.

 

My friend has the 2008 version and his runs flawlessly so have copied his carburettor settings but have also noticed that in comparison to his my drinks a lot of fuel.  His also idles so slowly whereas mine needs more revs.  And finally, my can be very hard to start both hot or cold but equally start first kick occasionally!

 

I’d love to resolve this as have spent a few pounds and so much time since buying this bike. 

 

Can anybody suggest what I should look at?

 

Thank you in advance.

 

Andy 

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My yz125 has been bogging out when I try to take off after going slow lately and I found that the oil level was too high. Also check your spark plug either clean it or replace it

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My yz125 has been bogging out when I try to take off after going slow lately and I found that the oil level was too high. Also check your spark plug either clean it or replace it

 

Thanks YZ_Rider48 

 

I am using a good quality Castrol oil and mixing at the correct ratio (25ml of oil per 1 litre of fuel) and fitted a new spark plug during rebuild.

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No I meant your gearbox oil sorry, it's super easy to just put in a bit more oil then needed and it was causing the same problems

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Check your power valve, see if it's working.

 

Seemed ok when I rebuilt top end, as in it all moved ok.  Is that you mean?

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No I meant your gearbox oil sorry, it's super easy to just put in a bit more oil then needed and it was causing the same problems

 

Gotcha!

 

Seem impossible to over fill a KTM as you fill with oil until it leaks out of a port then insert a bolt to plug the hole so any excess drains out.  

 

Thank you for suggestion though.

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How was it running before the te?

 

Don't honestly know as I didn't ride it enough to tell.

 

I get the impression the seller didn't exactly look after it and was dishonest so thought I would do the top end as a precaution so I knew where I was with it.

 

Don't get me wrong, my bike works but just not as it should and I can't figure out why! 

Edited by fury84

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Im going to say reeds or the powervalve. Check both and get back.

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Im going to say reeds or the powervalve. Check both and get back.

 

When I rebuilt the top end, I stripped and cleaned the power valve and was happy with its operation (as best as an amateur can be).

 

What am I looking for when checking the power valve and reeds and will do so?

 

Appreciate the advice :-) 

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take the reed cage out, hold up towards the light and see if they are sealing 100% , next hold them up level and pour gas into the cavity- they should hold the gas, a occasional drip or two is ok.

do a compression test and a leak down test -then you know what it is not.

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Check the carb float height.

 

Was thinking of stripping the carb and rebuilding to check for anything strange.  Does anyone know of any good how to videos for this?

take the reed cage out, hold up towards the light and see if they are sealing 100% , next hold them up level and pour gas into the cavity- they should hold the gas, a occasional drip or two is ok.

do a compression test and a leak down test -then you know what it is not.

 

Thank you.

 

Whats a leak down test?

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Was thinking of stripping the carb and rebuilding to check for anything strange.  Does anyone know of any good how to videos for this?

 

Thank you.

 

Whats a leak down test?

 

Answered this myself:

 

An engine leakdown test is a compression test in reverse. Instead of measuring the engine's ability to create pressure, compressed air is introduced into the cylinder through the spark plug hole.

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It's had several tanks of fuel but will do some more diagnostic work and report back.

Thanks everyone   👍

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try a new spark plug, try your friends carb, try new fuel , just try some thing

THIS. I had carb that worn, messed and messed with jets, Electrical etc to no avail, put my buddies carb on that setup identical and all of sudden I knew exactly what the problem was.
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take the reed cage out, hold up towards the light and see if they are sealing 100% , next hold them up level and pour gas into the cavity- they should hold the gas, a occasional drip or two is ok.

do a compression test and a leak down test -then you know what it is not.

Cant leak down test a pv engine.

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