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Discussion Starter #1
04 660 , 10.75 piston, stage 1 can no airbox and k&n filter, .5 inch carb space.
I'm having trouble getting this dialed in. I'm suspecting head issues but don't know. I'm at 5509 ft in Colorado. I have a problem with upper mid to top end power. It falls off and starts to POP. If I'm in neutral and rev it then rev again fast it'll POP, and rev it up it starts to POP at hi rpm. To low for limiter. I also have an rm stator rev box just FYI. I've tried bigger jets and combs from the stock all the way up to 180/185's . It feels a bit better with the large jets but same issue. I've tried different needle locations with all these jets. I've tried different mixture screw settings, and different pilots. No matter what I do I cant get rid of the POP. It's a stock head with a lot of hours . The carb are completely cleaned. Ideas?
 

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Every symptom you mention suggests running a bit lean on the needles. Are you using stock or aftermarket needles? Your mods would lead you to aftermarket (GYTR, DG, Vitos)...

You don't mention pilot jets - you need 25's. At your elevation with your mods, I'd guess at 155L/160R or 160L/165R mains, aftermarket needles with clips either just above or just below center, fuel screws at 2 to 2.5 turns out. The 5500 feet makes you want to run a bit leaner than those of us down near sea level - everything a step or so leaner.
 

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Discussion Starter #3
what about a moose racing stage 2 kit with springs?

I tried the 25s for the pilots and no difference. so i decided to tare the motor apart and fresh it up. I just slapped that piston in when i got the bike and did no work to the motor other than the stage 1 cam. i think i was having head problems. i just ordered my +4 stroker crank, hotcams stage 2 cam and springs, timing chain and a 12:1 piston. and getting the head rebuilt. then i will try out these settings you gave me unless you think they will change far from this. I just found it weird that nomatter what i did it seemed lean on the top. even all the way up to 180/185. but that was with stock needles.
 

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Just remember that carb has three circuits (with a bit of overlap): the pilot jets control from idle to 1/4 throttle, the needles from 1/4 to 3/4 and mains from 3/4 to WOT... so where ever you have throttle issues, this tells you what carb circuit needs attention.
 
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