High Fuel Usage On '89 Kdx200

[mrowe]

I HAVE JUST BOUGHT AN 89 MODEL KDX200F.
IT RUNS GREAT, FULLY RESPONSIVE THROTTLE AT ANY POSITION,
BUT ONLY GETS ABOUT 50KM TO A TANK FULL OF FUEL
FLOAT LEVEL IS OK, NO FUEL LEAKS, SPARK PLUG IS A LITTLE BLACK,
EXHAUST (PRO CIRCUIT PIPE FITTED) IS NOT EXCESSIVELY SMOKEY,
ANYBODY HAVE ANY IDEAS ON WHY IT USES SO MUCH FUEL ?

 

[David Trustrum]

Well either it is leaking or going through the engine at twice the rate normal!

Would seriously suspect the jets have been damaged or worn at some time in their long life. Time to replace &/or rejet, check site for starting point.

PS turn your caps off, people get a bit pisy about it.

 

[dirt bike dave]

Have you ridden another one to compare to? It's possible that the powervalve is stuck open, but that should prevent it from running 'great' at lower rpm.

 

[mrowe]

Thanks for the comments guys. (And for the "caps" tip - sorry)
I haven't ridden another one to compare it to.
I'll have to check the jets, but can you help me with something that i don't understand; if they were worn badly enough to use so much fuel, wouldn't that just make the bike run really badly (as it would do with way too rich a mixture) ?
Thanks again.

 

[David Trustrum]

Only compared to one that was running better. I mean there has to be a reason why you get half the economy that I do. Are you sure of the distances? I mean 10km/L is a pretty sorry economy but I accept that because it is a performance 2 stroke & is given a hard time. Add that to a [memory fading here a bit] 12l tank means you should get 120km.

 

[mrowe]

Yes David,
Unfortunately i'm absolutely sure of the mileage.It just goes through fuel like crazy.
The difficult part to understand, is that it runs so well, which makes me a little bit reluctant to start changing jets etc.It starts within a couple of kicks pretty well every time and has no "flat spots" in the throttle response.Problem is, that it's costing a fortune to run it.
I've seen a problem similar to this on this forum before, but nobody seemed to have any specific suggestions as to what the cause was.