Does this sound right? ( 5K' plus jetting )

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jacmmaxwell
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Does this sound right? ( 5K' plus jetting )

Post by jacmmaxwell »

New to the forum, not new to the KDX... in fact this is a bike ( 95 ) my wife bought me new as a hold over for my B-day in 96. Loved the bike for 4-5 years then had to be sold to pay the bills. Long story short it has been with her brother who never really rode the bike till this fathers day my wife surpised me with the bike.

Now the trouble is the bike was set up for sea level, now I live a 5,400 ft ( Central Idaho ) and ride up from there. The bike runs good but lacks punch and was not idling when warm. I backed the air screw out to about 3.5 turns, opened up the air box a bit and added some idle screw and it just stays idling.

I used candian daves jetting guide and went on the safe side ( I thought ) and ordered a 148, 145 main and 42 pilot. Tonight I pulled the stock jets and they are 48 and 160, seems to be a big jump.

Did I go to low? Any input on those of you running around near 6K would be great... bike is stock motor, slightly opened air box, FMF turbine core silencer, stock pipe. I run 40 to 1 with synthetic and non-ethonal 91.

Got a couple fresh plugs to do some plug chops but would hate to squeck the top end on the ride out.
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Julien D
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Re: Does this sound right? ( 5K' plus jetting )

Post by Julien D »

Nah, I think you'll be alright. For the record, a jetting guide like that is kind of a crappy way to go. It's basically telling you what jetting the author thinks you should have simply based on the fact that you ride a KDX, without taking into account your individual bike and your individual riding style. The best thing to do is to actually jet it. There is a process to it, and there are no shortcuts. Being that you have what you have, I think if you start with the needle in the middle clip position, the 148 main and 42 pilot, you will be safe. It won't be "right", but it should be an improvement over the stock jets and you SHOULD be giving it enough fuel so as not to cause any damage from a lean condition. No promises there, without testing each circuit.

Oh, and welcome to KDXRIDER!
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jacmmaxwell
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Does this sound right? ( 5K' plus jetting )

Post by jacmmaxwell »

OK, I know there will be tuning to be done and other jet changes I'm sure. Not afraid of jetting and spend a crazy amount of time tuning my snowmobiles so no stranger to plug readings, piston wash... would be even easier if I had EGT's and an AFR gauge like my sled.

I'm just looking for a safe starting point, that guide called for a 145 main and 45 pilot so I low balled it to a 148 and 42 pilot but ordered a 145 main just incase it runs fat up top.

Never tuned a motor after this much of a base line jump in altitude.

And thank you for the quick reply.
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Re: Does this sound right? ( 5K' plus jetting )

Post by bufftester »

As Julien said, 148/42 will be ballpark. Air density at 5k is lower than sea level, so would expect to be on the smaller side. Follow this jetting guide http://kdxrider.net/forums/viewtopic.php?f=105&t=1156

Canadian Dave's method has you settling on main jet size and clip positions before you even look at the idle circuit, which is just silly since the idle circuit is always in play. Follow the guide and you'll be screaming in no time. A quick search on here about jetting and you'll see how proper jetting works wonders...no shortcuts.
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Does this sound right? ( 5K' plus jetting )

Post by brian1014 »

Isnt that super lean? I thought most people run 155/45 not 145/45?
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Re: Does this sound right? ( 5K' plus jetting )

Post by UI Vandal »

I believe I am running a 152 or a 150 main (depending on season and location) at a 40:1 ratio on Interceptor. I am in Eastern Idaho so I ride from +5500 and up. My pilot is a 42 and the bike idles fine. I'd say stick the 148 in there. Make sure everything else is in order though (filter, gaskets, fresh premium gas and good mix, etc).
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