99 Kx 250 problems?

Question

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Hi, i recently rebuilt the top and bottom end on my 99 kx 250. I used a Hotrods crank kit, a Wiseco prolite piston, resleeved the cylinder with an L.A. Sleeve as well as replaced all necessary seals and gaskets. The bike was broken in properly but in all gears just before powerband i seem to be getting what sounds like really bad detonation. Once in powerband it's fine. Has anyone experienced this problem before? I checked the powervalve and it seems to be moving freely. I am using Castor 927 premix mixed at 32:1 along with Exxon 93 octane fuel with octane booster. Is it a possibility that the octane is still not high enough? Also when the new sleeve was installed it was bored to fit the piston fairly tightly, i think there was something like .003" clearance so i don't believe it's piston slap. Any help and suggestions will be greatly appreciated, thanks!!!!!!!!!!

Answer 1

After you change the gas and spark plug -
Try moving the clip on the needle, up or down one position to rule out carb problems.
Check the specs of the piston against stock.
The piston dome may be a little taller to raise the compression,
which could cause pre-ignition.
Call Wiseco to see if you should re-jet when using that piston.

Answer 2

Why are using Octane Boost? Quit using that, Drain the fuel from your tank and take a cup of clean fuel(no mix) and pour it into your tank and shake it up and dump that out. put your tank back on and mix up a new batch of fuel mixed right(32:1) without octane boost. Then run it.

Take that mixed fuel with octane boost and make a bon-fire.

Answer 3

It is a good idea to take the top end apart and visually inspect the piston for scuffing. This is not a difficult job and the only cost is the gaskets.

Answer 4

for a starter piss the octane booster off and stop using caster oil change the oil to a good synthetic oil then check the heat range of your spark plug sounds like it might be to hot try a colder plug and see how that go's how are the reeds they may have become stiff and not letting enough fuel in.

Answer 5

I have used Castor for 20 years just because I like the smell.
93 pump gas is fine,but you can try a 50/50 blend with'VP Race gas.
Check the plug and make sure it is clean or replace it and see how it runs.
You many need to go up/down one number.

Now go drink a beer and relax.

Answer 6

try going to a fuel ratio of 50:1