Update: I put the 15 pilot jet back in it after a ride testing for something else and I felt the "hit" just wasn't as hard with the 12.5pj in it. It was still running very good-just seemed to be lacking the knockout punch of the 15pj.

Which seems to mean that the pj is contributing to more than the range one normally sees for a pilot jet in a Mikuni jetting graph. But then again why wouldn't it?

Maybe it's a hint that I do need to put in the P8 needle jet instead of the P6, but I'm just not in the mood to start guessing about needle position all over again. It's running better than expected as it is now-and I have verified that the cams haven't had the MCM done to them, so that's always waiting in the wings as well.

Plus my box of XR200 and KLX250 goodies from the USA is due literally any day now giving me more options if I get itchy to 'fix something'

 

Richard, running a P8 needle jet sounds really big IMO. I run a P4 just like Mustang and Dan Moore did with their bigger bore kits.

 

It's .01 mm larger than the P6 that's in it now with the clip in the richest needle at the bottom groove. I am not using an air jet-which is the way the carb is delivered, so compared to a bike that uses a .7 or .9 air jet what seems a rich setting would be effectively leaner? (no air jet= more emulsion air mixing into the needle jet?)

I'd want to move the needle clip way up from its full rich position if I ever tried it the P8, back to the middle or second groove.

 

I'm no help here. When you stray this far away from Mustang's and Dan Moore's recommendations, I'm not sure where you are.

 

I know where I am at right now after richening mj and needle a week or so ago and finding more power. When the a/f meter gets here in 3 mos and I weld a bung onto my pipe I'll know more.

The settings of the others using TM36-68 were a great starting point for me. Too bad I can't start with someone's else's jetting findings when I start playing with the 40mm. I think that's in the same box as the a/f meter. So at least I'll have the meter to tell me quickly what's happening.

With my drilled air box and straight through muffler at the end of an exhaust system a little shorter than most after market systems I am in new territory.

I did see my cams haven't been done yet. Odd that the Ex and INT markings on the cam gears seemed much smaller than the photos we've been seeing here. I'll have to count some teeth or whatever to make sure this Thailand bike is using cam gears that let me do MCM.

I think the China megabomb will be here this week along with the CRF250f ebay dual exhaust, so I won't be running out of farkels any time soon

 

Well, an A/F meter will tell you a lot. Keep us informed.

 

As a general FYI, I ran across this comment over on TT in a 5yo thread from the guy who was building 60hp DRZs to someone who was asking about TM36-68 air jets..

Some applications could use a main air jet. You are thinking about it to much really.

If you ended up with a huge main jet without the air jet you could install air jet and go to a smaller main jet.



-I'd say use no air jet when you can-if you can jet for it, and get as much atomization of fuel as you can

 

Ah here we go; 159 series (TM36-68) needle jet diameters and a chart showing where those dimensions are typically measured

 

Using a counter-sunk 5mm screw (that won't hit my fuel line) and a couple nuts I had on hand, I made up an easy throttle stop that opens the carb to exactly 1/2 throttle when I hold it to the stop and the nut hits the front of the TM36 bracket as indicated by the black arrow



Doing some testing on the very slight uphill grade nearby, I found I had to hold the throttle at the stop in a high enough gear that the engine just didn't buzz through the rpm range.

With my needle still set at full rich, I noticed some burbling and the plug was dark, so I moved the clip up to the 4th groove, put in a new plug and went for one test ride chopping the ignition and coasting to a stop before pushing it up the driveway.

The new plug didn't look like it'd been run at all other than the ground electrode having a tan color on part but not all of it.. so next time I'll warm it up with the old plug and switch back to the new plug...I might put the needle at full rich again just to double check the new plug

OR put the leaner "51" needle in it at full rich? Hmm it might clear up that burbling

 

Maybe I missed it , Why the throttle stop ? Try that 51. I can feel the taper working. Or maybe I just think I can.