JD Jetting Jet Kit

The kit will include the stock jet sizes and in most kits (depends on the machine) it will usually include one or two jets close to the stock size for re jetting.

Here is a list of all the items included in the kit:
Keihin Main Jet - 152
Keihin Main Jet - 158
Keihin Main Jet - 162
Keihin Main Jet - 165
Keihin Pilot Jet - 38
Keihin Needle Clip
Blue Marked Needle (Richer Needle)
Red Marked Needle (Leaner Needle)

The JD kit makes it easy. They enclose specific instructions that tell you exactly what jets to use at the specific elevations. They also have nemorous jets for variation's of elevation. I think it is an overall good deal for the price and content you get with the JD jet kits. Along with the various jets they have a chart to tell you what jets to use.

The kit for my 07 yz250f did come with a new leak jet size 45. The kit i got for my 07 CRF450R did not come with a new leak jet.

There are multiple variations allowed with the kit. Follow the instructions for altitude etc., they should be close. You might have to do some testing to fine tune your jetting but it won't take long. I have an aftermarket pipe and am at altitude (Wyoming). I followed the instructions but had to fine tune (lean out) my jetting as the recommended settings were a little rich.

I can say for a fact that it will work on almost all the CR series carburetors that are found on all of the 450s of that time frame (some mods need to be completed on the California carbs). It will possibly work on yours as well, but it is a smaller carb. I would suspect that the jet selection in the 450 kit would be a bit on the large size, and I'd be particularly concerned about the needle profiles contained. They may also fit, but may be too long, or not have the right shape. That is assuming that you are talking about the YZF250 (4 stroke). If you actually have a YZ 250 (2 stroke), that is a totally different carb than the kit you are referring to. I bought one for a 2007 CRF450X from Rocky Mountain ATV/MC, which is why this question was directed to me. In short, I would say NO. This is not the right kit for you. I would get on line, and look up JDJetting dot com, tech at jdjetting dot com, or call them at the number on their website. (I am not allowed to include email addys. or phone #s in this reply) They will direct you to the correct product from their line, which is most likely also available from Rocky Mountain ATV/MC. I hope this helps. Good Luck!

Yes, it's got everything you need I've used a JD kit in my last 5 carbureted bikes I've bought.

I also own a xc 300 2012 (third owner so a lot is unknown about the bike, 450 hours on it) as well. My jd jetting kit came with a pilot. I had tried to put a fatty on previously with the jets the previous owner had and it flooded the engine. The guidelines in my manual allowed it to turn over so I threw my fatty on to see what would happen and the bike immediately turned over. I ride enduro style stuff and between the jd kit and the fatty it turned it into exactly what I wanted it to be. A ton of low end is exactly what I needed and I have no worry about it not idling or fouling a plug now. hope this helped.

Me personally, unless you live in areas where in one ride you will make over a 1500ft elevation change, then go with jd jet kit. If you do ride more than 1500ftelevation in a ride then lectron.

Your issue is likely the internal gasket on the Mikuni carb. look this up on KTM talk, It is a jet block gasket failure. JD jetting sells a kit to fix the issue.