KTM MIKUNI JETTING THE EASY WAY: MR. KNOW-IT-ALL

JET SETTER
Dear Mr. Know-It-All,
I recently purchased a 2018 KTM 250XC-W and am having some issues with the jetting. I’m running Bel-Ray 60-1 premium gas, clean filter, etc. The plug fouls when the engine is first started and doesn’t idle down properly if I go leaner on the pilot and needle. Now I am one size leaner than stock and have dropped the needle one clip. I am at 3500 feet elevation and ride in the eastern slopes up to 7000 feet. The dealer said some of the OEM reeds can be a problem and wants me to switch to Moto Tassinari or Boyesen. Any suggestions on which would work better for this application? The dealer claims the Tassinaris are better quality, but I have used Boyesen on other bikes with no issues.
Be easy on me, as I am old and grumpy like you.
RR
Alberta Canada

Hey, Grumpy, we got with our buddy Jeff Slavens from Slavens Racing for his input here. He’s a two-stroke aficionado and a KTM devotee:
“The Tassinari brothers put out a great product, but so does Boyesen. You can’t go wrong with either one. Your jetting dilemma is common with the 2018 KTMs and Husqvarnas. Mikuni missed the mark on the setup, and consequently they make better paperweights than they do fuel atomizers. The biggest part of the problem is the needle design and the needle atomizer, both of which were improved in 2019. James Dean at JD Jetting has a kit that will get you on track. Don’t waste your money buying more brass.

PSYCHOGENIC FUGUE
Dear Mr. Know-It-All,
Must have been a typo in the May issue. In your discussion about leaning out or enriching the mixture with oil, you describe 4 ounces to a gallon of gas as a 40:1 ratio. Here in Michigan, we have 128 ounces of gas in our gallons, so it would be 32:1.
At least you know people are reading.
RB
Via [email protected]

I have no proper response. To be honest, I’m gutted. I’ll return home, smack my dog, pound my head in with a claw hammer and refrain from watching “Big Bang” reruns. This brain-dead aficionado offers his sincerest apologies. The proper ratios are as follows:
20:1 — 6.4 ounces to 1 gallon (of fuel)
32:1 — 4 ounces to 1 gallon
40:1 — 3.2 ounces to 1 gallon
50:1 — 2.6 ounces to 1 gallon

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