Hodaka cold starts

[Bill2001]

Wombat 94, with new Mikuni carb. Possible loose end with a cold start.

In the warmth of Summer, it needs the Enrichener for a cold start. For the first 2-3 minutes it needs the enrichener for it to idle or take throttle. After that couple.of minutes, it will idle and you can blipntje throttle. But for the first run when the enrichener is cut off, the engines doesn't seem to catch, and it feels like it's trying to start off in second gear-- no "oompf". But once you get it rolling, it does run, and after a couple mor minutes of running, it feels OK starting off in first. I'm wondering if this is normal, and a 2-stroke needs more time to warm up the crankcase volume. Or if mine is abnormal and might still have a pilot jet mixture problem. The stock pilot jet is #25, I'm running a #30 for this break-in period. The main jet is increased from #160 to a 170. New piston and rings, honed cylinder. About 10 miles on this top end, about 2hr running time.

Otherwise, it runs well. But I need to get it on the open road to do the jetting.

[racerclam]

sounds like you still need a bigger pilot jet. How far out is the air screw? What position is it at to achieve the highest idle speed? From that point it should be turned back in about 1/4 turn. The record how far it is and report back.

Rich

[squid on a 300]

+1 on the lean pilot circuit.. Does turning the air screw in help? Try raising the needle by lowering the clip a notch? That may help your off idle response.
bob

[Bill2001]

I'll continue to tinker with the low-end settings.

I didn't say that the main jet was increased one step from #160 to 170. All other settings-- float level, needle and needle jet, and slide cutout are verified correct as "stock" Wombat 94, and the carb is new replacement from SH.

The air screw is set at betw 1-1/4 and 1-1/2.

Thinking it over, this does occur within the 1/4 to 1/3 throttle range, so it is in the pilot jet range. Either increase the pilot jet size or reduce "air correction jet" (air screw) size. I might even try a lower slide cutout. One thing I haven't tried is running the cool engine with the enrichener engaged.

I'll tinker. Big job today is to get the gauge bracket for the temperature gauge (EGT) finished and installed.

[Bill2001]

As an aside, here is the installation of the EGT temperature sensor.

EGT gauge sensor

[Bullfrog]

Pilot Jet range is zero to 1/4 throttle, quarter to 1/2 is slide cut-away range.

Ed

[Bill2001]

I'll evaluate that-- I've got the twist-grip marked off in 1/4-throttle increments. Better than guesstimating.

[Bullfrog]

Bill,
You've mentioned that the pilot air screw is currently between 1 1/4 and 1 1/2 turns out. Is that where it ended up as you searched for the setting which gives you the highest idle speed? Racerclam and I both want to know about that.

Ed
PS: Nice looking job on the EGT sensor.

[Bill2001]

Yes, that "1-1/2 turn" seems to be the optimum setting. But practice makes perfect, and I'll tweak it more.

[Bullfrog]

Then you have a pretty strong indication that the pilot jet size is correct. You've found the optimum setting and it is almost exactly where we'd like it to be - near 1.5 turns out. Therefore, I would shift some suspicion to other things.

A partially plugged exhaust system would be high on the "suspicion list". Moving the clip on the needle would be very low on the list since that change would have little to no effect down in the 1/4 throttle range.

Hm, it would be good to mention that it does take some time for a two stroke engine to warm up and operate properly on cold fall day. The real question is, how does it run after it warms up?

Ed

[Bill2001]

As much as it seems that I may be obsessing about this mixture, early-on I thought that things were good, and I ended up with a seized piston. I think that there were pre-existing reasons for that, but I'm wanting to be sure I understand jetting on the Mikunis. And it's more critical on the 2-strokes. I've read something about evaluating mixture by reading the piston top and examining the exhaust port walls or the inside of the header pipe. I need to learn more about that.