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Discussion Starter #1
I am running an 2001 800 Mountain cat. It runs great from about 3000-8000Rpm's, but I can't make it idle. It has bored carbs, v-force reads, pipe, and can. It idled fine until I ditched the stock air box and began running filters. at the same time I rejetted the mains from 320 to 420 in the TM 40's. Now it makes awesome power but seems to load up and bog on the bottom. I can't go back to the air box, I am addicted to the power.
Thanks for any help in advance.
 

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have you tried addjusting your fuel screws?in is leaneri think i might be wrong but 420 sounds pretty big, hows your piston wash?
 

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Discussion Starter #3 (Edited)
The dealer suggested I run 450's with the mod's I've done. I started with the 450's but was going to foul plugs so I dropped it to 430's and road it again, plugs still black no wash, now I am at 420's and am riding it again this morning. I moved the needle down one clip and it idles now(kinda, 1000rpm max). It seemed to idle better with the 450's than the 420's but neither is right. I am suspecting the dealer was crazy on the 450 idea and will probably find bigger power and an idle between 400's and 390's. I just don't want to jump the gun and find a hole in my piston(s) instead. The sled is ridden between 7000 and 10000Ft so I think it is still just rich and gets leaner as the rpm's climb. Does my logic sound right or am I crazy?
 

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Thumper said:
The sled is ridden between 7000 and 10000Ft so I think it is still just rich and gets leaner as the rpm's climb. Does my logic sound right or am I crazy? [/B]


:D crazy as a loon!!! just kidding. anyways you have to find the right setting for idle and part throttle before you go crazy dropping the mjs. i would try putting the stock box on it and see if it idles. my guess is it wont. the main jets have squat to do with idle . if it does for some strange reason put the filters back on and start turning in your fuel screws(white ones on the side) a 1/4 at a time does it start to get better? once you get your idle figured out do a 1/4 to 1/2 throttle cruise for a 1/4 mile if you can when you shut it down do not let go of the throttle untill the engine has stopped. now check you wash and plugs(tan like cardboard) adjust the needle untill it is right. now go 3/4 and recheck if too lean raise needle back up and retest. due full throttle run and check plugs and wash. adjust main jet accordingly

where did the carb vents go ?into the airbox? if so you may want to put them in at the bottom of the air filters. if you do this do it prior to checking the plugs and wash as this will have a big effect on your jetting
 

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What about the pilot jets?????????They control the bulk of fuel mixture at idle.With your mods it seems to me that your pulling to much air for the stock pilots to keep up(too lean )at idle.When you make the transfer to the mains(open up throttle)it probably takes a while for the transition, makin a bit of a bog.I would up the pilot 2 or 3 sizes and then play with idle mixture.
 

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When the sled is started and warmed up a lil' ,put your choke half way and full if the sled idles up you need a bigger pilot,and adj. your air screws and idle screw,not as difficult as it seems.
start with a bigger pilot then air screw
 
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