Another PJ34 jetting thread

You talking a 2nd gear launch gibson?

Also I asking him yesterday about performance on the track (always good to do that after emotions have cooled!) and he said he was in 3rd and 4th most of the time. He was unable to hit 5th due to a lack of acceleration at that point. I noticed 4th was a bit flat (long time to pull to 5th) the other day. Does that sound rich or lean?

Midrange power is where this motor should really be pulling so obviously I don't have it quite right yet.
 
Yes start in 2nd. My son also spends most of his time in 3rd and 4th with occassioal 5th. Our carb settings are the same except I am at a 155 main. So maybe you are alittle fat.
 
Sure 3rd and 4th would be normal on most twisty tracks, especially with a higher gear ratio. But it stills pulls with the 155? I kept giving it more main because the plug still looked lean and I'm kinda paranoid about lean-seizure. The lack of acceleration power would seem to say fat tho, and you are at sea level while I am at 4000ft.

I see a smaller main in it's future. I was running a 160 at first and that seemed good. It currently bogs on a 2nd gear launch, maybe I will lean the pilot a bit too. How radical is your porting, for comparison purposes?
 
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UPDATE: I went out yesterday and played with the jetting some more. I'd come to the conclusion that I needed to resist that "more is better" attitude and just pay attention to what it likes.

Started out again with 50 pilot and 160 main, 3rd step on the needle. Low end was poor, boggy. Dropped the needle, #2 groove, or so I thought, really my son moved it to #4, oops. Still boggy right off idle, duh. Started moving down on the pilot, 45 was better, 40 I really like. Decided it needed more on the top, put in the 170 and moved the needle back to #3. Re-adjusted the idle (I love that the knob works now).

Final jetting 40, 170, DGH needle on 3rd groove, 1/2 turn out on air screw. Good low end now, lifts the front end 1st, 2nd, 3rd, and I'm a big guy. Hard to steer like that, but damn, at least it wants to wheelie. Strong mid and good top. Runs like a raped ape, especially with the 14/40 gearing. I feel like I'm finally getting my money's worth out of this motor.

So, some observations about PJ's and jetting in general. A PJ does not need to to have the slide open at all to idle. Somehow it gets enough air through the idle circuit (3/16' hole!) and maybe leaking around the slide. The pilot does indeed affect idle to a small degree, everytime I changed it I had to reset idle, and this makes a bit of sense since the pilot outlet is on the motor side of the slide. The main is completely blocked by the slide at this point and therefore has zero effect. Any hesitation or lack of power off-idle probably indicates a fat pilot. Big carbs on small motors seem to like smaller pilots. More main is great as long as it responds to it mid-high, it won't really affect the low much to speak of. Set idle first, then pilot, then main.

I would like to have done more testing with the needle, I believe that's where the real fine tuning is, they control how the mid comes on. For now I'm happy to leave it alone.
 
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