Ok so i have jus done a complete rebuild (crank, pistons cylinders recoated etc) on my 92 model 21. After a few hiccups getting it back together the engine is now bolted in and running. my problem is the front cylinder doesnt fire until the bike hits 6500-7000 revs. It runs fine over that but as soon as revs drop back past 6500 front cylinder dies?? there is heaps of spark, tried different plugs, looks to be plenty of fuel.. I really have no idea ?? any help would be great!
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Hesitation is Fatal!!

If you're happy it's got a good spark, and the compression is good, i think you need to strip the carb and give it a good clean out. It could be a blockage of the slow running system.

Thanks jeff. There is definatly heaps of spark... i did have the top off the carbs and cleand what i could but didnt go too far inside as they scare me a lttle bit! what exactly is the slow running system because that does make sense.
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Hesitation is Fatal!!

The slow running system controls the first stage of throttle opening, before the main jet comes into play.
You need to remove the float bowl and remove the jets. Blow through all the jets and drilling's. You can use compressed air, or carb cleaner at a push.
I think if you look in the tuning section, you will find some pictures to explain more.

ok awsom thanks jeff.. i think i can manage all that, a job for tomoro. i shall report back. thank for your help!
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Hesitation is Fatal!!