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Can't get this jetting right!
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Posted by: acw592

I have an 03 pred. with a full Big Gun race series exhaust and a uni filter clamped onto the carb. Iv'e went up to a 162.5 main jet and the needle is in the last (highest) position. A 162.5 main is fairly large. I thought it might be too big, or that I might have to move the needle back down, but it sputters at 3/4 or higher throttle. It's a little better since I went up to the 162.5, but still sputters badly. Does anyone have a larger than 162.5? It deffinately seems to be starved for fuel at the top,It runs strong until the 3/4-full range but I just didn't think it would take that large of a jet. HELP!
Thanks

Posted by: Live2Ride300

So your running no airbox correct? Is it a kehin or mikuni carburetor?

Posted by: acw592

Correct, I'm not running an air box. I was just looking at one of the jets but I'm not sure which one they are. Its the stock carb for the 03, If that helps. I did do some more searching and one post said to start at 170 mj and go down.

Posted by: forgiven

170 to 175...maybe higher

Posted by: acw592

Thanks forgiven, I'll hopefully give that a try tomorrow. By the way , I like your user name, reminds me of what Jesus did for me.

Posted by: MAaudioX10

First thing, move your needle back down. Right now, if I understand you correctly, you have your needle in the leanest position. (clip #1) You need to have your needle on clip #3. With a clamp on and exhaust the needle shouldn't need touched.

Then, up your MJ to a 170 and see what it does.

Posted by: acw592

I went to C&C Cycle today and the only thing they had between the 162.5 I had and 180 was a 177, so thats what I got. Haven't had a chance to fire it up yet. My needle is in the highest position out of the hole. I have it on the last clip closest to the tip of the needle. Correct me if Im wrong but that should bring it higher up out of the jet which will allow more fuel.

Posted by: acw592

Well, I put the 177 mj in and moved the needle back to the #3 position and it ran worse. It was about 1/2 throttle that it cuts out. I brought it back to the house and moved the clip to the #1 (top of the needle farthest away from the point-tip) and it ran better. Now Im really confused.

Posted by: acw592

I don't know what I'm doing! I went back down to the 162.5 then down to the 157. It doesn't seem to change much other than it seemed to cut out quicker with the larger mj. Now Im 157 with the needle clip on #3. It runs hard until about 3/4. Im about to take the new uni off and go back to the crap intake and stock mj. It wasn't right but it was better than it is now

Posted by: forgiven

I would say go richer on the needle if anything

Posted by: kc8pnd

You should try a way high jet like a 180 then work down. Also maybe up the pilot jet to a 47.5. To get your your mixture screw you need to remove the brass plug.
If its running like crap at idle and 1/4 then its your pilot, correct me if I'm wrong but your main jet don't kick in until 1/4 to WO.

Posted by: wolffie

you need to drill that little brass plug out on the bottom of the carb. that will allow you access to the fuel screw. if you tip the carb upside down with the intake port facing out from you, you will drill the lower plug (there are two)

i cant remember the drill bit, but just go a lil bit bigger than the plug and make sure you go slow with a varialbe drill! you could probably turn your fuel screw out a turn or so.

the predator carb is fun to jet

Posted by: wolffie

oh yeah, stop messing around with a few jets. go to www.jetsrus.com and get a whole kit from 150-185 or whatever. and then get a couple bigger pilot jets as well (47.5, and mabey a 50) jetting takes time unfortunately.

Posted by: kc8pnd

What I did to get my mixture screw plug out was take really course screw and started it in the little hole and then tightened it down, the screw will get tight and start to turn the whole plug then you can pull it out. You should do what wolffie said, www.jetsrus.com has the kit for dirt cheap.

Posted by: acw592

I'll check out jetsrus. I have gone back down to a 155 0r 157 mj and it runs better. Thanks

Posted by: Flyers-Own-All

Get the Kit for 35 bucks well worth it.

Im running a HMF Ironman and a Uni Foam cone on a Rath billet intake no airbox. Your not getting more air than that unless you do motor mods. Im running a 165 mikuni jet & 2nd to bottom clip (towards the point) Get your bike ideling and stick a screwdriver bit up in the air screw tube and turn it while its running. Your looking for the fastest idel without the idle getting all funky. Thats when its at its optimum fuel/air mix. Pilot Jet is Idle thru 1/4 throttle - Needle is 1/4 thru 3/4 throttle - Main Jet is 3/4 thru WOT.