What's wrong

I'm having one hell of a time dialing in my jetting :applause::lol: I have done all free mods, removed AIS, 04 wr needle mid postion,cut out the top of the air box, removed most of the baffle, (left in the spark arrester) I have tried 168 main, 45 & 48 pilot, 40& 50 leak, zip-ty 2 turns out, and checked out the AP squirt, at about 1 sec. I have a low end bog :banghead: the idle hangs high, and when I turn off the engine I get a light back fire. What do you guys think could be wrong or what am I doing wrong. :lol:

You're still too lean. Three things I can advise you on. First, spend the money and get the JD Kit. I know it's not the cheapest thing in the world, but what quality item is nowadays? Secondly, get a #50 pilot jet and a #170 main. Thirdly, use all of these goodies and apply them to Indy's jetting chart...first page of the jetting database. Like you, I had one hell of a time getting the jetting to work. After I did the above, things are working great with my '05.

There are a couple little housekeeping things you need to do as well. You need to make damn sure your exhaust connections are all tight and not leaking a bit. Also, you may need to re-route your hot start cable. Mine looked like it was not binding, but it was which mimicked a hanging idle caused by a lean pilot...that was very frustrating until I finally found it! You may also want to really lubricate the hot start cable in the housing and the plunger in the carb. If you're still using the plastic hot start nut, plan on spending $20 and replacing it with the Zip-Ty aluminum one...well worth it. And finally, set your idle to around 1900 and NEVER TOUCH IT AGAIN! I can't stress that enough. It will likely fluctuate a bit, but set it after about 30 minutes of serious riding and then forget that little idle screw even exists.

I'm confident that if you do these things, you'll get there. I went through a meticulous process a couple of months ago, documenting each little change as I tried to figure out each jetting circuit and what each tweak affected. Good luck bro...SC

Thanks for the info, I do have a 50 pilot and a 170 main, I'll try them. The confusing thing is this morning I started the bike and idled for a couple of minutes and then I decided to check my plug and it was black, not sure if it was because it had been idling or if it was from the other day when I went riding when it was in the mid 90's & @ 500 ft. and my current jetting was too rich. I live at 2000 ft.and have been jetting for my elevation. I typically ride at 2000-5000 ft.

Figure out what your average elevation and temp are and jet according to those numbers. If you're jetted right, you should be able to compensate throughout the day with your fuel screw...SC

I changed the jets like you said and she idles down perfectly and seems to have a little more pep, the only thing left is the 1/4 throttle stumble :banghead: I just ordered the JD kit and I will follow Indy's guide and see if I lose the stumble. Oh yeah, it appears that most of the bog is gone. I saw your post thanks it has allot of helpful 411. Thanks again for your help. :applause:

When you say "1/4 throttle stumble", are you talking about wicking open the throttle from idle? If so, it's likely due to the leak jet, the AP squirt or a combination of the two. If you're talking about a surging with the throttle 1/4 of the way open, then try unplugging your TPS. If it goes away, then the surge is a normal function of the TPS. If it doesn't, then you really need the JD Kit needles which work well in cleaning up things in that throttle range. With regard to the TPS, it's really a matter of personal preference whether to leave it plugged or unplugged. I don't notice mine surging unless I'm at a steady throttle, but since that only happens when I'm on asphalt on my way to the singletrack, I don't worry about it. I NEVER notice it when I'm in the dirt, and I figure it's there for a reason...SC

I'm talking about when you are riding along at about 1/8-1/4 throttle and it stumbles and runs kinda rough. I'm excited, I finally ordered the JD kit and it should be here in a few days. So the needles make that much of a difference do they. Well I'll soon find out. :banghead:

The JD needles are triple tapered and make a big difference. The blue needle is for cooler temps and is noticeably richer in the 1/8-1/4 throttle range. I run the red needle at #5 most of the time, but switch to blue #3 once the temps reach into the 60's consisistently...SC

Thanx, I also ordered the JD AP diaphram kit, so we'll see how she runs. Of course only one change at a time.

Bad move on the diaphragm kit...I talked to them about it when it first came out and it's primarily for KTMs 'cuz they don't have leak jets. I'd see if you can cancel that part of the order...SC

Bad move on the diaphragm kit...I talked to them about it when it first came out and it's primarily for KTMs 'cuz they don't have leak jets. I'd see if you can cancel that part of the order...SC

My 426 does not have a leak jet... would the diaphragm kit be a bonus?

(I don't have the jetting kit)


For the 426, I don't know for sure, but it makes sense. Give JD a call and they'll give you the heads-up...SC

Bad move on the diaphragm kit...I talked to them about it when it first came out and it's primarily for KTMs 'cuz they don't have leak jets. I'd see if you can cancel that part of the order...SC

Thanks for the heads up, I called and canceled this morning. :banghead:

For jets, do you get those from TT's store or a Yamaha dealer? I have the JD kit on the way, but that is needles only, right?

Do the jets come in a package of several or do you pick them up individually?

You get needles and mains with the JD Kit, but I'm not sure how many of the mains. You can usually get Keihin mains and pilots from any reputable bike shop and for a lot cheaper than the dealer. For everything else, you can get it through Zanotti's. A lot of people go through SudCo, but I've never had any luck with them. Here's a list of the Yamaha p/n's for the jets specific to the '05...SC


4MX-14943-88-00 .JET, MAIN (#152) AP 1

4MX-14943-38-00 .JET, MAIN (#155) AP 1

4MX-14943-89-00 .JET, MAIN (#158) AP 1

4MX-14943-39-00 .JET, MAIN (#160) AP 1

4MX-14943-90-00 .JET, MAIN (#162) AP 1

4MX-14943-40-00 .JET, MAIN (#165) STD 1

4MX-14943-91-00 .JET, MAIN (#168) AP 1

4MX-14943-41-00 .JET, MAIN (#170) AP 1

4MX-14943-92-00 .JET, MAIN (#172) AP 1

4MX-14943-42-00 .JET, MAIN (#175) AP 1

4MX-14943-93-00 .JET, MAIN (#178) AP 1


3TJ-1494F-12-00 .JET (#62) AP 1

3TJ-1494F-13-00 .JET (#65) STD 1

3TJ-1494F-14-00 .JET (#68) AP 1

3TJ-1494F-15-00 .JET (#70) AP 1

3TJ-1494F-16-00 .JET (#72) AP 1

3TJ-1494F-17-00 .JET (#75) AP 1

3TJ-1494F-18-00 .JET (#78) AP 1

3TJ-1494F-19-00 .JET (#80) AP 1

3TJ-1494F-20-00 .JET (#82) AP 1


5TA-14943-15-00 .JET, MAIN (#70) AP1

5TA-14943-19-00 .JET, MAIN (#80) STD1

5TA-14943-27-00 .JET, MAIN (#100) AP1


4MX-14948-01-00 .JET, SLOW (#35) AP 1

4MX-14948-02-00 .JET, SLOW (#38) AP 1

4MX-14948-03-00 .JET, SLOW (#40) AP 1

4MX-14948-04-00 .JET, SLOW (#42) AP 1

4MX-14948-05-00 .JET, SLOW (#45) STD 1

4MX-14948-06-00 .JET, SLOW (#48) AP 1

4MX-14948-07-00 .JET, SLOW (#50) AP 1


4JT-1494F-01-00 .JET (#35) AP 1

4JT-1494F-03-00 .JET (#40) AP 1

4JT-1494F-07-00 .JET (#50) STD 1

4JT-1494F-11-00 .JET (#60) AP 1

4JT-1494F-15-00 .JET (#70) AP 1

4JT-1494F-19-00 .JET (#80) AP 1

4JT-1494F-23-00 .JET (#90) AP 1

4JT-1494F-27-00 .JET (#100) AP 1

ANy idea how the jetting would change if all the free mods were done except leaving the pipe stock, including the baffle? I will remove mine soon, but from an learning perspective, I'm curious.

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