125-200cc Jetting issues with the TMXX - aware of the jet block gasket failure?

http://ktmtalk.com/showthread.php?543163-Mikuni-jet-block-gasket

Just to know if some of you have been confronted with the same problem?

jeanjean

KTM Talk won't let non-members view the page linked above.

Is there some way to paste the pertinent information here?

Heath

I started that thread. There is a rubber gasket under the jet block that has been failing. It appears to be squeezing out and messing up the idle/off-idle circuitry. It may well be why some riders love the Mikuni while others can't get it to run worth a darn. My own 150xcw ran very will with just the usual jetting, then began getting funky after several months. A carb teardown showed that the jet block gasket had failed. The part is not shown on the fiche so no way to order it. I fixed it (made my own) and the bike ran well again. Several of us on KTMtalk have been working on solutions that don't require a homemade gasket, and Cometic agreed to produce a replacement. There is now a rubber-metal-rubber replacement available from Cometic. These pics show what was in my carb when it was acting funky.

I assume that as the japanese bikes sharing this carb, the HVA's have the single-hole-design and the gasket doen't fail as fast as by the KTM's.

jeanjean

Picklito, that's a great find. Thank you for sharing it.

You can buy the prototype now, available 10, 14, 20 thou thick. It's looking like the 0.014" will be the way to go, as most of the jet blocks are recessed .010-.011":

CB559010RC
CB559014RC
CB559020RC

The other VERY common failure in the Mikuni is the O-ring for the float needle seat. It shrinks, cracks, then leaks and your fuel level is too high. Check it out!

O ring failures as well as gasket failures became common since ethanol showed up in the fuel... so yes a really long time.

I just received a jet block gasket from JD jetting.
https://jdjetting.com/product/jdmk05-mikuni-tmx-jet-block-kit/

Hi There,
Does this apply to the 2012 wr 300 ?

It would apply to any Miknui of same design, but we oddly hadn't heard much about it until KTM/Husky released the 17's with Miks. Can only speculate why that would be. I've now installed several of the Cometic gaskets with no further issues.

Just opened my carburator (125 WR '14). The gasket didn't look nice...

The replacement gasket is available by JD jetting in the States https://jdjetting.com/product/jdmk05-mikuni-tmx-jet-block-kit/

and by Bergos (Germany) in Europe https://www.bergos.de/technik/motor...nadelventil-abdichtung-jdmk05?number=11102011

jeanjean

Finally got around to checking mine. Yup gasket was bad. Also found my main jet laying n bottom of bowl! Explains the sudden massive spooging issue that developed at the end of last ride. Blubbering bad at WOT. Will take her ouT tomorrow for a test run.