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Mikuni jetting

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I have the stock carb with 3x3, full FMF powerbomb q4 exhaust. 700 ft altitude. 

 

I looked in the carb a little while back and made a thread about it.

 

I believe the stock pilot jet is in there, with a 155 (Dynojet?) main jet, and a needle with the clip on the second position from the top.

 

Right now the extended screw is turned out over 3 turns and runs pretty well.

 

However I feel like it may be lacking power at higher RPM.

 

Can I increase my main jet to 160 and order a 25 pilot jet fairly cheaply from a general jetting store or something? If so, links to where to buy? I don't feel like spending 75 bucks on a JD jet kit if all I need is 2 jets...

 

Thanks.

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I have the stock carb with 3x3, full FMF powerbomb q4 exhaust. 700 ft altitude.

I looked in the carb a little while back and made a thread about it.

I believe the stock pilot jet is in there, with a 155 (Dynojet?) main jet, and a needle with the clip on the second position from the top.

Right now the extended screw is turned out over 3 turns and runs pretty well.

However I feel like it may be lacking power at higher RPM.

Can I increase my main jet to 160 and order a 25 pilot jet fairly cheaply from a general jetting store or something? If so, links to where to buy? I don't feel like spending 75 bucks on a JD jet kit if all I need is 2 jets...

Thanks.

i have a spare 25 pilot jet but i think its pointless me posting it to you. Order it off ebay . Mikuni 25 pilot jet long jet type.

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You can get Dynojet main jets individually from Dynojet.  You will want the "DJ"160.  There are many places you can get pilot jets from.  You can get them from the TT store on this website or Jets R Us for example. 

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The problem is with the needle and jetting to suite. Arbitrarily throwin in jets or needles wont tune it to be the best it can. You can chase your tail for a long time trying to get it right. Mixing stock Mukuni jets with Dynajets or others is yet another problem because their flow is measured differently between brands. Best to stick with one brand. The 75 bucks spent on the JD Jetting kit is money well spent for a stock carb. Gets you real close to where you want to be out of the box. Just fine tune from there. Stock engine and carb with 3x3 a/b mod and say a MRDssw sys will get really good performance with a JD kits Blue needle 3rd or 4th clip, 25paj and 155-160 main. About 2-2 1/2 turns out on the a/f screw. Getting a Kientec fuel screw also helps because of its design and compliments the JD kit. Choice is yours of course. I like the KISS method to keep my bike running good.

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Well, he has the Dynojet kit already installed.  A 155 main and the needle clipped second groove from the top is the standard set up for the Dynojet SM stage 2 kit.  Personally, I would leave the 155 in and just get the #25 pilot.  I have that same kit and it works beautifully.  I had to raise the needle to clip #4, which is probably because of the powerbomb, and I got a #25 pilot, but as it is now, it purrs and pulls very cleanly.  You would probably have to fiddle with the JD kit to get it dialed, too, so you really won't save any work by getting that kit.  You would just have to spend the money on a whole new kit and re-do everything.  Jets are cheap.  I got my pilot for less than 8 bucks.  I think Dynojet mains are like 6 bucks apiece.

 

Still, if I had it to do over, I would probably go with the JD kit since it includes the float bowl screws and pilot jet.  It costs like $15 more, but the included parts are worth more than that.  It's a better deal.

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I have the stock carb with 3x3, full FMF powerbomb q4 exhaust. 700 ft altitude. 

 

I looked in the carb a little while back and made a thread about it.

 

I believe the stock pilot jet is in there, with a 155 (Dynojet?) main jet, and a needle with the clip on the second position from the top.

 

Right now the extended screw is turned out over 3 turns and runs pretty well.

 

However I feel like it may be lacking power at higher RPM.

 

Can I increase my main jet to 160 and order a 25 pilot jet fairly cheaply from a general jetting store or something? If so, links to where to buy? I don't feel like spending 75 bucks on a JD jet kit if all I need is 2 jets...

 

Thanks.

 

Well, he has the Dynojet kit already installed.  A 155 main and the needle clipped second groove from the top is the standard set up for the Dynojet SM stage 2 kit.  Personally, I would leave the 155 in and just get the #25 pilot.  I have that same kit and it works beautifully.  I had to raise the needle to clip #4, which is probably because of the powerbomb, and I got a #25 pilot, but as it is now, it purrs and pulls very cleanly.  You would probably have to fiddle with the JD kit to get it dialed, too, so you really won't save any work by getting that kit.  You would just have to spend the money on a whole new kit and re-do everything.  Jets are cheap.  I got my pilot for less than 8 bucks.  I think Dynojet mains are like 6 bucks apiece.

 

Still, if I had it to do over, I would probably go with the JD kit since it includes the float bowl screws and pilot jet.  It costs like $15 more, but the included parts are worth more than that.  It's a better deal.

 

I don't see where the OP has indicated which Dynojet kit is installed....He may wish to confirm whether he has DJ3109 or DJ3110 fitted..

Changing out the pilot jet will have no effect on his apparent top end lacking power...

Edited by Craigo 485sm

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I don't see where the OP has indicated which Dynojet kit is installed....He may wish to confirm whether he has DJ3109 or DJ3110 fitted..

Changing out the pilot jet will have no effect on his apparent top end lacking power...

He didn't.  It was just an educated guess.  A DJ155 main and the needle clipped in the second groove is the suggested starting point setting for the DJ3110 "stage 2" kit.  They suggest clipping the needle in the fourth groove with the DJ3109, and if using a Dynojet main jet, it should be a DJ144 with the 3X3 mod.  (At least that is what a Dynojet tech told me, I never tried it...  I installed a DJ3110)  Of course this is only assuming that the PO knew what he was doing...  It may very well be that he has a DJ3109 needle paired with a DJ155 main or a 155 Mikuni,  That would certainly explain a lack of top end power.  It would probably choke on itself at WOT.

 

Yeah, a #25 pilot won't affect WOT, but it does eliminate popping on decel.  At least it did for me!

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He didn't.  It was just an educated guess.  A DJ155 main and the needle clipped in the second groove is the suggested starting point setting for the DJ3110 "stage 2" kit.  They suggest clipping the needle in the fourth groove with the DJ3109, and if using a Dynojet main jet, it should be a DJ144 with the 3X3 mod.  (At least that is what a Dynojet tech told me, I never tried it...  I installed a DJ3110)  Of course this is only assuming that the PO knew what he was doing...  It may very well be that he has a DJ3109 needle paired with a DJ155 main or a 155 Mikuni,  That would certainly explain a lack of top end power.  It would probably choke on itself at WOT.

 

Yeah, a #25 pilot won't affect WOT, but it does eliminate popping on decel.  At least it did for me!

 

 

When it comes to jetting assumptions don't mean much.... 

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