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DR350 Carb help needed!

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Hey everyone!

I'm new here and just picked up my first dirt bike about a month ago. 1991 Suzuki DR350M. I've been dying to get on the trails here and enjoy the season before the snow comes, but i've been having a heck of a time getting the thing to run consistently. When i first got it it ran ok, it was a beast to kick start but when it got running it stayed running. Ran it around town for a few hours and then parked it. tried to start it up later and it wouldn't go. So I took the opportunity to do all the usual maintenance on it: Oil change, spark plug, repack exhaust, clean and oil air filter, valve clearances, and gave everything a good clean. Got it running again but broke the pumper carb lever so I waited on that for a little bit and now i'm trying to get it to run again.

After all that work and pulling the plug i found that the bike was running lean. spark plug came back almost completely white. Oddly enough, it seems that the bike perfers to start without the coke applied even when dead cold. I don't want to damage the bike, and therefore I need to tune the carb. 

The bike is mostly stock, however the air filter and exhaust have been changed. Here are all the details on the current set up of the fuel/air system

Exhaust: Supertrapp Exhaust (i think it has 5 plates on it)

K & N airfilter

Pilot Jet: 35 and Main: 122.5 Pilot screw is turned out 2 turns (stock of this bike is (Pilot 37.5, main 127.5 and 1 1/8 turn).

Here are my questions now that i've covered all of that:

I live in Boulder, CO at elevation ~5,000'. Most of where i want to ride is between 7,000' and 10,000'. Does anyone know a good starting point for tuning to that elevation? I realize that carb work is an art and a pain, every bike is different and unique, but i'm still hoping i can find some starting spot.  My preference would be have it tuned more for around 7,000' as long as it would still run ok at 5,000' without going too lean. I've heard to reduce the main jet from stock by 2% (which would put me at 125. How would the aftermarket exhaust and air filter affect this? On my other bike I jumped up two pilot jet sizes from stock (which would put it at 42.5). Any idea of this is the right way to go with this bike as well?

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