That TM36 is a bit tantalizing. I guess the only thing stopping me from trying one is that I don't want to go through the hassle of the jetting routine.

I've used the 5 gas analyzer on the KLX in the shop a couple of times but essentially at idle. The bike has to be tested under operating conditions, either with a brake dyno or being ridden to get loaded results. It's kind of embarrassing to admit this, but I don't have a brake dyno (or an inertial dyno, for that matter).

It's problematic taking exhaust readings on a single cylinder bike. Single cylinder exhaust pulses have pronounced positive and negative pressure components. There is no issue with the positive component but the negative component draws outside air back into the muffler. On a multi-cylinder engine the pulses are close together and the negative pulses don't have time to pull the fresh air very far into the muffler. Usually about 6-8" is about average. This air mixes with the exhaust and results in exhaust readings which are much leaner than the actual exhaust. Most exhaust probes are a minimum of 12" long to get to the undiluted exhaust.

On a single cylinder the negative pulse extends deep into the muffler, almost always below the baffles/screens. The exhaust probe can't be inserted far enough into the muffler to test pure exhaust. To get a true reading, the rear of the muffler must be extended, sometimes as much as two feet with a very long probe being used.

That is mostly acceptable in a shop, but is really cumbersome on the road. That's why I usually only take idle measurements.

Now, aren't you sorry you asked?

Ron

 

Nope, Ron, not sorry at all. That part about a single cylinder's characteristics and the problem having to get way into the pipe was interesting. On TM36 jetting, Dan Moore and Mustang pretty much plowed all the ground. Using their numbers, all I changed was one step richer on the pilot air jet. Pretty easy. On my recent CO trip, I dropped the needle one notch and one step leaner on the main...but I had to do basically the same on my OEM CV unit.

 

That does sound pretty interesting. I hate having to re-invent the wheel!

Ron

 

Well, I put the stock snorkel back in and took a test ride. The bike felt a little flat after a short warmup of about a mile and a half, not crisp in throttle response and pulling power seemed less by the butt dyno. Still running the 120 main and the Dynojet needle in the bottom notch. After the bike fully warmed it was even worse, blubbering at lower throttle openings and mushy at larger openings, some stumbling as the throttle was closed from full.

So the stock snorkel restricts airflow a lot it seems. I will go back to the KDX200 snorkel and continue to work with jetting the get the lean surge at cruise worked out. L D

 

I did the regulator ground mod and no change at all in the way the bike runs, still a lean surge at cruise throttle at 6 to 7K RPM. Waiting for KLX300 carb to arrive before any more changes.

 

Still got the stock clutch? I had the symptoms of lean surge at peak torque only to find out it was the stock clutch slipping only at peak torque. Did the ground mod and it did nothing.

 

Clutch is still stock but I can tell it is not the problem, the surge is occurring at cruise throttle settings and at full throttle the surge goes away. Thanks for the tip though. I had no surge when the engine was still 250cc. Nothing has changed except the larger 330cc. It is definitely a lean fuel surge which has gotten less and less as I moved the needle clip down but is still there a little bit, just enough to be good and annoying. :-) The needle is in the bottom clip and that actually makes it a little too rich at around 1/2 throttle or less.

I'm hoping the 300 carb will have closer fueling with the NT1C needle than the 250 carb with the Dynojet needle. The 300 carb should be here soon and the history is that it is stock, no needle or jet changes according to the seller.