785 Flat Top Jetting and Carb Settings

hjm1

hjm1

Location
Spokane
Guys I need some help. I bought this engine off my buddy and it ripped in his ski. Only thing that really changed is the carbs that were on it. He had dual NOVI 48mm and Im running dual stock 38mm. It will start and idle fine but when I punch it, it has no power. Its like riding a JS440. BUT if I hop the back end out of the water, It will rev up and do 55-60 mph. I think it is loading up in the mid range but I'm not sure. I'm running 130 main 115 pilot 1.8 needle and seat with 35 psi pop off. Running a Factory B-Pipe at about 2000 feet.
Things I have tried...
-Bought new MSD ignition system
-Tried 75 pilot jets
-Tried upping the pop off to 45 psi
-Checked stator and flywheel

The only thing that made any difference at all was upping the pop off, and it made it run even worse.

Any more help will be greatly appreciated.

Thank you.
 
Big Kahuna

Big Kahuna

Administrator
Location
Tuscaloosa, AL
Also, find out who built the motor. contact them. They may have specs for that motor. But Most flat tops were built as race motors and ran with 46's or larger. 38's may be on the small side for it.
 
hjm1

hjm1

Location
Spokane
Just re jetted to what everyone has suggested and still the same exact issue. I throw my friends coil in and same thing. I feel like I've gone through everything.

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Citizen

Citizen

Location
Coeur D' Alene, ID
BK may be right and the carbs are too small, but i dunno.

If your buddy is down, i would swap his known working electronics into your ski, whole thing. See if it works. If not swap his novi carbs in too. Those were known working with that motor. Would at least let you narrow it down.
 
hjm1

hjm1

Location
Spokane
So I pulled my manifold and found this. About 1/4 of the epoxy port work is broke off. I realise it was a mistake now but I pulled both of them out.
I also put the original intake manifold and carbs on it that were on it last year and it still doing the same thing.
a1e748889df666f5b5d9ec053b7454d1.jpg


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hjm1

hjm1

Location
Spokane
Has anyone ran a cooling line from the pump to the bottom of the headpipe? I just saw a diagram of it being routed that way.
954d144d135e4e0c2fe4c950426d1b4c.jpg


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hjm1

hjm1

Location
Spokane
Okay I've officially tried everything. Tried a new stator today and flywheel and still doing the same exact thing.

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Big Kahuna

Big Kahuna

Administrator
Location
Tuscaloosa, AL
Your missing something. What is your compression? Have you pressure tested the motor? Have you checked plug wires? ****** If you have broken strans, if you hopped the ski out of the water this may have reduced load and allowed enough spark energy to jump the broken strans. Check this. I have had the same issue where hopping the ski would temporarly fix it. ended up replacing the coil wires and it fixed the problem.
 
hjm1

hjm1

Location
Spokane
Big Kahuna said:
Your missing something. What is your compression? Have you pressure tested the motor? Have you checked plug wires? ****** If you have broken strans, if you hopped the ski out of the water this may have reduced load and allowed enough spark energy to jump the broken strans. Check this. I have had the same issue where hopping the ski would temporarly fix it. ended up replacing the coil wires and it fixed the problem.
Click to expand...
Compression 170/170.

Haven't pressure tested it.

I have tried two different coils that I know work.

Tried two stators

Tried two flywheels

Tried 2 cdi boxes

Tried 3 different sets of carbs

Tried 3 different ways of routing cooling



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