unexplainable sound - 250r high RPMs 4th 5th and 6th gear

[gravelord]

my 250r has been making a strange sound in high rpms in 4th, 5th, and 6th gear, i cant put my finger on it. ive narrowed it down to not just the jetting, but maybe the needle posistion or pilot jet - or coil/stator..... i really cannot explain the sound, it sounds almost like if you put positive and negative jumper cables togather from a car battery, in between detonations well in the gears at high rpms, thats the sound that i hear. best i can explain. fresh top end, broken in properly, it seems to be jetted correctly, warm it up before riding, new bearings in the case, exhaust flange springs are SUPER tight, i dont think too tight could be causing this sound ?, fresh packing in silencer. i cant pin point this sound.

[Dammit!]

Could be too rich or to low of an octane causing detonation. If you run with the airbox lid on, pop it off for a minute and see if it gets better or worse or stays the same.

[x.system]

If you can, do a compression check, detonation eats up pistons pretty quick, can cause alot of damage. Fresh build so it should have more compression, if you used a thinner gasket that will up the compression even more. Pull your plug out, might show signs of detonation if you ran it a long time like that.

[350xBomb]

It does not happen in the lower gears at high RPMs? if it was detonation wouldnt it make that noise at high rpm no matter what gear?

[Jason Hall]

The higher gears work the engine harder (more load) that will make detonation worse. Try running some premium gas. X.system Is right, check for small pieces of debry on the spark plug. Another thing to check Is the counter balancer bearings. Are all the motor mount bolts tight? My boys 85 vibtates the exhaust springs, but that will happen all the time If you rev the engine high.

[Bryan Raffa]

do a compression check if it's above 200 you need race gas,, under, 97 will be fine ,, pull the stator cover off and check the bolts for the counter balancer like jason said and red lock tite them

[oscarmayer]

it soulds liek spark knock, or jetting issues. (runnign to lean and detonating. till you get it tuned proeprly, don't go runnign it hard. i woudl say you need to move up 2 jet sizes to help resolve the issue.

[gravelord]

OK, heres what happened... i dont know why i didnt notice this right away.
well i lost my debit card, i usually run 100 octane low leaded av gas, but without a debit card ic ouldnt get it, i ran 93 octane for the past few weeks, for some reason i didnt notice the sound as much the first times running 93 octane, i guess since i wasnt wfo in higher gears, but i got my new debit card, got 100 octane - problem gone. hope i didnt ruin anything running that *Edited**Edited**Edited**Edited* haha...