34mm Jetting help

Oct 11, 2020
10
12
44
38
Having a little bit of issues getting my jetting right since I upgraded my carburetor to a 34 mm PJ. I think I'm pretty close but it's a little on the rich side. I feel like when it's about half throttle or maybe when I jump on the gas. I noticed it is mainly rich when I try to pop a third gear wheelie when I should normally be able to easily pull it up and when I switch into fourth gear is when I really notice it.

I'm listing all the specs below-

14t front sprocket
40t rear sprocket
Cylinder head port and polished via Ken O'Connor's instructions
Vito's high compression head gasket
Keihin 34mm PJ carburetor
#6 slide
Float height is perfect
CEL needle on 3rd clip
55 pilot
156 main
Custom high flow intake
Vito's reed valve spacer
K&N air filter
Fmf fatty pipe
Fmf powercore 2 muffler
HPM Exhaust Coupler
Holeshot Tires (22" Front / 20" rear)
Tors delete
Motion pro throttle cable
New brake pads and shoes

I had to go all the way up to 55 on my pilot jet otherwise it would be way too lean especially on cold start but seems to be working okay like that it's just issues mentioned above. Plug chop looks great btw.

I live in Raleigh North Carolina right now it's October about 68°, 65% humidity, elevation 315ft.

Thanks in advance!
 
Has this engine been proven air leak free with a leakdown test ?

You're close with those carb #'s including the slide and needle
(155 main, not 156) < have you plug chop confirmed that ?

I run almost the exact same mods and jetting except KOR did the goodies himself, a richer DGH needle for my higher elevations, right bend CT pipe which requires richer jetting than an FMF, but you're at lower elevation which needs richer.
I've also have never had luck getting it to idle good with that stupid choke knob turns, I use the cable to hold the slide up slightly for idle, then fine tune with the choke knob or adjust as needed. yes it revs slightly when I turn the bars, but starts easy, idles all day, and runs perfect.

but the 55 pilot doesn't sound right, I run a 48 pilot, and know others near your elevation run a 50.
did the airscrew turns tell you to increase the pilot to a 55 ?
what turns out on the airscrew gives you the highest idle ? that will tell you pilot required.
if highest idle is between 1/2 and 2-1/2 turns out you're good. 1-1/2 turns out is best and allows adjustment either way to compensate for temp changes.
have you played with the pilot doing 1/8 turns either way while riding it until it revs clean past 1/2 throttle and pulls hard ?

revisit the airscrew/pilot tuning DIY and recheck the airscrew turns .............
https://www.blasterforum.com/threads/adjusting-your-airscrew-pilot-jet.51060/

that 14/40 gearing is also hampering your low/mid torque.
 
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Has this engine been proven air leak free with a leakdown test ?

You're close with those carb #'s including the slide and needle
(155 main, not 156) < have you plug chop confirmed that ?

I run almost the exact same mods and jetting except KOR did the goodies himself, a richer DGH needle for my higher elevations, right bend CT pipe which requires richer jetting than an FMF, but you're at lower elevation which needs richer.
I've also have never had luck getting it to idle good with that stupid choke knob turns, I use the cable to hold the slide up slightly for idle, then fine tune with the choke knob or adjust as needed. yes it revs slightly when I turn the bars, but starts easy, idles all day, and runs perfect.

but the 55 pilot doesn't sound right, I run a 48 pilot, and know others near your elevation run a 50.
did the airscrew turns tell you to increase the pilot to a 55 ?
what turns out on the airscrew gives you the highest idle ? that will tell you pilot required.
if highest idle is between 1/2 and 2-1/2 turns out you're good. 1-1/2 turns out is best and allows adjustment either way to compensate for temp changes.
have you played with the pilot doing 1/8 turns either way while riding it until it revs clean past 1/2 throttle and pulls hard ?

revisit the airscrew/pilot tuning DIY and recheck the airscrew turns .............
https://www.blasterforum.com/threads/adjusting-your-airscrew-pilot-jet.51060/

that 14/40 gearing is also hampering your low/mid torque.
Has this engine been proven air leak free with a leakdown test ?

You're close with those carb #'s including the slide and needle
(155 main, not 156) < have you plug chop confirmed that ?

I run almost the exact same mods and jetting except KOR did the goodies himself, a richer DGH needle for my higher elevations, right bend CT pipe which requires richer jetting than an FMF, but you're at lower elevation which needs richer.
I've also have never had luck getting it to idle good with that stupid choke knob turns, I use the cable to hold the slide up slightly for idle, then fine tune with the choke knob or adjust as needed. yes it revs slightly when I turn the bars, but starts easy, idles all day, and runs perfect.

but the 55 pilot doesn't sound right, I run a 48 pilot, and know others near your elevation run a 50.
did the airscrew turns tell you to increase the pilot to a 55 ?
what turns out on the airscrew gives you the highest idle ? that will tell you pilot required.
if highest idle is between 1/2 and 2-1/2 turns out you're good. 1-1/2 turns out is best and allows adjustment either way to compensate for temp changes.
have you played with the pilot doing 1/8 turns either way while riding it until it revs clean past 1/2 throttle and pulls hard ?

revisit the airscrew/pilot tuning DIY and recheck the airscrew turns .............
https://www.blasterforum.com/threads/adjusting-your-airscrew-pilot-jet.51060/

that 14/40 gearing is also hampering your low/mid torque.
Thanks for the quick response! I remember doing a leak down test last fall (which was the last time I've messed around with it until a few weeks ago) and it did hold over night, I don't remember what psi I left it on maybe 10psi ore something close. I will put in a 50 pilot and play around with the air screw and see if that helps. Right now it's exactly 1 1/2 turns out and doesn't hang or anything. Idle screw is all the way in and I do adjust with the cable so that's good that I'm not the only that does that lol. I went up on the front sprocket since blasters are already short geared and hoped it would spread it out some. I may upgrade to a pwk if the 50 pilot doesn't work and see what happens.
 
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Idle screw is all the way in

Give it some fuel with that choke knob/idle screw, I don't know the effects of having that turned all the way in ? .... close off that circuit altogether ?
I'd start with it out 1-2 full turns out, or turn it up to get it to idle a little high while playing with the 50 pilot and see what the airscrew tells you.
 
Well my idle circuit works correctly:).
I run the cel needle also. Really picks it up in the middle
 
Has this engine been proven air leak free with a leakdown test ?

You're close with those carb #'s including the slide and needle
(155 main, not 156) < have you plug chop confirmed that ?

I run almost the exact same mods and jetting except KOR did the goodies himself, a richer DGH needle for my higher elevations, right bend CT pipe which requires richer jetting than an FMF, but you're at lower elevation which needs richer.
I've also have never had luck getting it to idle good with that stupid choke knob turns, I use the cable to hold the slide up slightly for idle, then fine tune with the choke knob or adjust as needed. yes it revs slightly when I turn the bars, but starts easy, idles all day, and runs perfect.

but the 55 pilot doesn't sound right, I run a 48 pilot, and know others near your elevation run a 50.
did the airscrew turns tell you to increase the pilot to a 55 ?
what turns out on the airscrew gives you the highest idle ? that will tell you pilot required.
if highest idle is between 1/2 and 2-1/2 turns out you're good. 1-1/2 turns out is best and allows adjustment either way to compensate for temp changes.
have you played with the pilot doing 1/8 turns either way while riding it until it revs clean past 1/2 throttle and pulls hard ?

revisit the airscrew/pilot tuning DIY and recheck the airscrew turns .............
https://www.blasterforum.com/threads/adjusting-your-airscrew-pilot-jet.51060/

that 14/40 gearing is also hampering your low/mid torque.
Well, I put the stock 26mm carb and boot on with a 270 main and the performance is unbelievable! Not sure what the deal is with the PJ but I guess I'll keep the stock carb on.
 
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It's more the pipe than anything, and the stock carb is perfect for the FMF and all the other low/mid pipes.
the 33+mm carbs don't shine until they're matched to a high rpm pipe.
 
It's more the pipe than anything, and the stock carb is perfect for the FMF and all the other low/mid pipes.
the 33+mm carbs don't shine until they're matched to a high rpm pipe.
It's doing awesome now! lots of low/mid power and was actually able to get it up to 63mph yesterday! Not bad for a 220lb rider with moderate mods I guess.
 
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