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Need jetting suggestion for Colorado, stock 400s

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Hey guys, I am getting ready for a trip to the San Juans. I want to jet it for 8000 feet as this will be our low altitude and I dont want to run it lean. I will purchase a JD kit at a later date, I've already spent a bunch of money on some other goodies.

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Going up to 8000 feet will make the motor run rich not lean.  Pilot jet and needle are probably fine.  Needle is not adjustable anyway. Mixture screw hidden under a anti-tamper cap will probably like being turned in a little.  Probably a 135 main jet is about right.

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Going up to 8000 feet will make the motor run rich not lean.  Pilot jet and needle are probably fine.  Needle is not adjustable anyway. Mixture screw hidden under a anti-tamper cap will probably like being turned in a little.  Probably a 135 main jet is about right.

Thanks, 135 is what I came up with but I wasn't sure, I am going to put the stock pilot back in. Should I make ant adjustments to the fuel /air mixture to compensate for altitude?

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All jet changes affect the air/fuel mixture.  The only analog screw adjustment is the fuel screw under the anti-tamper seal.  It affects idle mixture and transition off idle.  Yes it should be adjusted for a smooth steady idle.  It is best to adjust with the motor running but is difficult to reach.  If you set it with the carb off, I would set it 1 to 1.5 turns open.

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Hey guys, I am getting ready for a trip to the San Juans. I want to jet it for 8000 feet as this will be our low altitude and I dont want to run it lean. I will purchase a JD kit at a later date, I've already spent a bunch of money on some other goodies.

 

I will offer you an alternative......Depending on whether you want to mess with the carb or do the 3x3 mod 

 

Yes, a 135 main jet is what to use with stock air intake OR  just leave the carb stock and do the 3x3 mod....

 

My thought is that as your going to install the JD jet kit at a later date, run with the 2nd suggestion.... :excuseme:  :)

Edited by Craig-o
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Craig-o,

Do you thonk the 145 main will be lean enough at 12k with the 3x3?

 

9 to 12 K = 140mj with stock exhaust and 3x3 mod  OR  135mj with stock exhaust and stock airbox opening

 

But as I said in previous post ,you would get away with leaving the stock jetting and just do the 3x3 mod..stock main is 142.5

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Thanks,

I am going stock for now with the 135. When I get back I will do some work on the bike, 3x3 and a jd jet kit. I also have a dia a jet I might install.

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Thanks,

I am going stock for now with the 135. When I get back I will do some work on the bike, 3x3 and a jd jet kit. I also have a dia a jet I might install.

 

Dia a jet..?

 

In some people's opinions it would be an easier chore to do the 3x3 mod than pull the carb, that's why I offered the "don't pull the carb " option... :)

And when you return from the trip you could tape up the air opening to match the stock opening for non lean running ..

All just as a temporary fix until you install a jet kit...

Edited by Craig-o
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Dia a jet..?

 

In some people's opinions it would be an easier chore to do the 3x3 mod than pull the carb, that's why I offered the "don't pull the carb " option... :)

And when you return from the trip you could tape up the air opening to match the stock opening for non lean running ..

All just as a temporary fix until you install a jet kit...

Thanks for the advice,I need to pull it anyways, I jetted the bike for sea level with a 150 I think.

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Sorry, I meant dial a jet. My friend has one on his Husky 510 and it works pretty good. His bike it jetted lean and he uses the dial a jet to enrichen the bike for sea level or he can dial it back for altitude. Never rejets.

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Sorry, I meant dial a jet. My friend has one on his Husky 510 and it works pretty good. His bike it jetted lean and he uses the dial a jet to enrichen the bike for sea level or he can dial it back for altitude. Never rejets.

 

Dial A Jet = Snake Oil

 

Dial a jet is not as good as all the hype...They are inconsistent with their fuel deliver system..the design of the feed circuit in the float bowl relys on the fuel keeping the pickup fully covered all the time...When the fuel sloshes around the feed cavitates....I wouldn't bother wasting you money....

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