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Jetting Advice


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Am looking for suggestions on where to start w/jets. Have std. bore weisco's, fmf fattys w/power core 2's, boyseen reeds, pro flow system w/k+n, snorkel only removed, boost bottle, approx 6hrs on rebuild. Am assuming the 200's the guy set my carbs up w/before is way too lean after reading some of the advice on this great site. was loosing power in 5th, and couldn't even get into 6th. had a stumble off the idle, to 1/4 throttle, but already purchased 30's for the pilot, will see if that takes care of the low end. Please help!

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when I had those similar mods my jetting was 290 mains, needle in middle position, stock pilots, air screw 1.5 turns out and it ran awesome. I was at sea level.

Start with what 1800bigk said to do. I bet you will be right on. 200 mains is way to lean. FMF usually sends out 260 mains with their pipe kits. I had the exact same mods as you and I ran 280 mains without a problem.

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Thanks guys for the advice, I had started out at 260's, per advice from fmf's website, runs great off the idle, but just try to get into the power band, power drops right off, hesitates and sputters. am assuming it has something to do w/the needle clip position, sounds like i need to lower it to richen up 1/4 to 3/4 throttle. Any further input would be appreciated. Will pickup some larger mains also, just sputters w/ throttle w/o.

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Thanks guys for the advice, I had started out at 260's, per advice from fmf's website, runs great off the idle,  but just try to get into the power band, power drops right off, hesitates and sputters. am assuming it has something to do w/the needle clip position, sounds like i need to lower it to richen up 1/4 to 3/4 throttle. Any further input would be appreciated. Will pickup some larger mains also, just sputters w/ throttle w/o.

Don't rely solely on the "sputter" or "hesitation". 260 sounds pretty lean just from my experience with them, but the ONLY way to really tell is by reading the plugs. If it's sputtering, so be it, run your wide-open-throttle test anyway and see how the plugs color. That will tell you what you need to do. If it were me, I'd just go ahead and throw in a set of 300s and hope your rich, then you can work down for the ideal main jetting.

 

The way I see it, if you start lean and work up, you won't really know if you need more fuel without trying it, but if you start rich, then you know your rich and you can work down into the ideal air/fuel mixture. If your a tad on the rich side, your fine, but if your a tad on the lean side, and something happens or it overheats or something, you'll be running the risk of some nasty shit.

 

Once your main jetting is where it should be, based on plug readings and bike performance, then dial in the main by trying several clip settings. Try the 3rd, and the 4th and see which runs better.

 

Then you'll be flyin... B)

Edited by sredish
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Went to 300 mains, and moved needle to fourth clip, have 30 pilot jet. starts hard, but idles great once it starts, have hesitation in 1/4 to 3/4 throttle, screams w/o. did plug test w/ new plugs and ended up w/ a dark tan to chocolate color. after riding 90 minutes plug was pretty dark to almost black, but not wet. does this indicate my needle is too rich, I moved it because i couldn't get any go at all 1/4 to w/o w/260 mains. do I need to move it back to stock position. Sort of confused now. also does it sound like I'm good w/300's. :wacko:

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my .02, You are still rich. If you are still running with the AIRBOX LID ON I would drop the needle back to the stock setting and work down on your mains. try 290s and then 280s and see how it performs and how the plugs look with each. Let us know how it turns out. Sounds like you are getting real close.

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