Custom/Hybrid Dual carb mismatched high jets

blasterDrey

blasterDrey

Location
Erie, PA
I've got a interesting problem. Just bought a 2002 superjet this past Saturday. Took it out riding a few times and it would seem to randomly bog down at times. I pulled the carbs and the main carb has a 130 main jet while the secondary has a 120 main. I only have an extra 135 main at the moment. Could I run a 130 in one and 135 in the other for a bit? If I can, which jet in which carb? The ski is stock. Thanks for any advice y'all.


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Robbie8984

Robbie8984

Location
Uk
I'm sure it would be better than what you have but personally would just order up the right jets.

I think stock is 70 low and 135 high.
 
AAlamo

AAlamo

Location
Dalhart, TX
Check your compression too. I bought a banshee that came with different main jets. Turned out the cylinder with the smaller jet was almost 20 lbs less compression. Rebuilt the motor, jetted it correctly, runs perfect now.
 
blasterDrey

blasterDrey

Location
Erie, PA
I did order proper jets. I'll try adjusting the screws accordingly and hopefully it runs decent for the weekend.
Compression was 150 in both cylinders. Guy said he just rebuilt the top end and cleaned the carbs. Lol. Hopefully this top end holds up.


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Robbie8984

Robbie8984

Location
Uk
just measured a set of 38's and with the adaptor ring on the bottom they measure 40, and at the top they measure 40.

Take the adaptor/space off the bottom and they will measure 38
 
JetManiac

JetManiac

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orlando
SJ dual 38s stock came with 70/130. It sounds like your 38s may be from a raider/venture or other couch and they had staggered mains. Check your pilot jets also. The couches came with 67.5 not 70 like the SJ.
 
blasterDrey

blasterDrey

Location
Erie, PA
JetManiac said:
SJ dual 38s stock came with 70/130. It sounds like your 38s may be from a raider/venture or other couch and they had staggered mains. Check your pilot jets also. The couches came with 67.5 not 70 like the SJ.
Click to expand...

They were 67.5. I'm not going to change them yet because it idles nice and doesn't give me any low end throttle issues. The bogging would happen after being over half throttle for about a minute. Are dual carbs that run off of one pulse line supposed to have staggered jets? Or is it just a raider/venture thing? Should I buy carbs that actually came off of a sj? What are the advantages of running 2 pulse lines? I know I can tap my case for a second. This is my first sj and dual carb ski so I'm still learning.

I hope to have it running right soon so it's all ready to be transplanted into my AM hull in a few weeks.


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JetManiac

JetManiac

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blasterDrey said:
They were 67.5. I'm not going to change them yet because it idles nice and doesn't give me any low end throttle issues. The bogging would happen after being over half throttle for about a minute. Are dual carbs that run off of one pulse line supposed to have staggered jets? Or is it just a raider/venture thing? Should I buy carbs that actually came off of a sj? What are the advantages of running 2 pulse lines? I know I can tap my case for a second. This is my first sj and dual carb ski so I'm still learning.

I hope to have it running right soon so it's all ready to be transplanted into my AM hull in a few weeks.
Click to expand...

All Yami dual 38s regardless of model run a single fuel pump and single pulse. The staggered jets is a tuning thing for couches, they have staggered jets on dual 44s with dual fuel pumps as well. Leave the sgl fuel pump setup as it is, they work fine.
 
Freakie

Freakie

Location
Cape Town
I believe the staggered jetting for couches had to do with pronounced crankshaft twist causing the rear piston to run way hotter than the front one under WOT...so they richened up the rear HS jet to prevent lean seizure under WOT....I could have dreamed this up though, so others please chime in.
 
kev.t

kev.t

Location
Braapp Factory
Freakie said:
I believe the staggered jetting for couches had to do with pronounced crankshaft twist causing the rear piston to run way hotter than the front one under WOT...so they richened up the rear HS jet to prevent lean seizure under WOT....I could have dreamed this up though, so others please chime in.
Click to expand...
^^^ that is correct^^^
 
JetManiac

JetManiac

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Freakie said:
I believe the staggered jetting for couches had to do with pronounced crankshaft twist causing the rear piston to run way hotter than the front one under WOT...so they richened up the rear HS jet to prevent lean seizure under WOT....I could have dreamed this up though, so others please chime in.
Click to expand...

Correct and even worse issue on yami triples
 
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