JD Jetting KTM High Performance Mikuni Jet Kit

What it is

• Jet kit for Mikuni equipped KTM two-strokes.

JD Jetting has a kit for the 2017 KTM two-strokes now using the Mikuni carburetor. It consists of two proprietary needles, a spare needle clip, detailed instructions with a jetting guide and a selection of main and pilot jets. The James Dean custom jetting kit is designed to improve throttle response throughout the range by using specially made multi-taper needles. The kits are dyno tested and claimed to work from sea level to 12,000 ft.  The kits are bike and sometimes model year specific. They retail in the area of $85.

How it works

• Great instructions.
• Improved performance with little fuss.
• Takes the thinking out of jetting.

KTM and Husky two-strokes with the Mikuni carb are jetted a little funny from the factory. Depending on the model they can be rich on the bottom and then between rich and lean in other spots. The bikes are picky about fuel to oil ratios and in all of our testing generally difficult to get just right. We wanted to change the nozzle, which is difficult to source and played with different needles and jets tyo comer to a satisfactory setting but it took some time and was never perfect. Then we got hold of a JD jetting kit. Straight off, installation is bike dependant and once in the carb everything is very simple for even a novice mechanic. Getting at the carb on some bikes is difficult especially with larger tanks. On the 2017 KTM 300 XC-W we tested it was a little tighter to remove the carb than in the past with the counterbalanced engine, but not by much. It is very simple to twist the carb out of the intake boot and get at the float bowl. It is also possible to twist the carb the other direction and get at the slide and needle. Having the right length screwdriver or even replacing the slide cover bolts with the supplied allen head bolts and using a rounded tip allen wrench makes it even easier the second time around.  

The instructions will walk you through the steps and has a jetting chart that uses altitude, temperature and riding style to determine the setting you will use. The biggest choice for some is the difference between technical/trail and racing/open desert. Basically the more aggressive of a rider you are and the more you want the bike to have snap more than clean chug, then go for the race setting, even if you are riding technical trail. The slightly richer setting also lessened detonation especially if the gas was not of the best quality or when the bike gets hot.

We set our bike for the 2000-7000 ft. setting and hit the trails. First with the trail setting and then with the race setting which required just a needle swap. Both jetting settings were spot on and an big improvement over the jetting that came in the KTM stock. It was even better than the improved setting we had come across with a jetting change detailed in our first test (2017 KTM 300 XC-W Test). The 300 was cleaner off the bottom especially--and did not go through this lean/rich/lean segment in the throttle as the powervalve opened and closed. And though the overall jets are much leaner in numbers compared to stock jets, the needles make up for it. The settings are so specific that there is an included washer that will raise the needle a half-clip position if needed in the setting. The Kit for 2018 is also changed as KTM altered the needle jet inside the carb, so JD compensated again. We have not tested the 2018 bike yet.

Overall the power character does not really change, but the consistency in throttle response is much better. We’d even go as far as to say the bike actually makes a little more overall power at any throttle position. In doing this it also became a little more fuel efficient. And it was good for at least 5 more miles per tank with the trail setting in the XC-W. The bike will pull from a lower RPM in any gear and it makes power a little farther out on top with the racing setting in the bike. In the trial setting the bike will lug on the bottom cleaner for a longer time before loading up at all. The biggest improvement is that the jetting is less affected by temperature and especially altitude. It is more along the lines of a well jetted Keihin carb now with a little more snap when on and off the throttle.

We tested the bike with both stock and FMF exhaust systems and spark arrestors, swapped to slightly different reeds and ran fuel mixtures at both 40:1 and 60:1 and the chart and jetting were spot on. We always ran 92 octane pump gas and experienced little to no detonation even in deep sand. If there was any fine tuning it was simply make a half-clip adjustment with the washer (which stays on the bike either on top of or below the needle depending on position) on needle position as detailed in the instructions.

Price wise the hassles you save by just dropping in the recommended parts, and having the ability to change the bike’s jetting to perfect no matter where you ride, is worth every cent. And if you have ever purchased genuine carburetor parts then a couple of needles can run you easily $50. If you have a carbureted KTM or Husky two-stroke this kit will save you a lot of time and make your bike run better.