SX/SXi/SXi Pro constant bog PROBLEM!!??

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Ready To Rip
Location
Grand Rapids, MI
I have a 93 750 sx it has ran great for years then all of a sudden half way through a day of riding i went to take off but the ski wouldn't even go fast enough to stand up it barley goes fast enough to ride on your knees.

It Has
a mikuni sbn 38 carb
coffmans exhaust
150 psi in each hole
both cylinders have spark
just rebuilt the carb

Things I've Tried
rebuilding the carb
new needle and seat
pop off at 16 psi
pop off at 25 psi nothing changed with any of the different pop off pressures
pop off at 32 psi
pop off at 46 psi
checked spark when running and when not running
gave it can extra shot of gas in the carb but it bogged more (so its not running lean)
ran it with no air filter
ran it with no hood

i can hold it pinned wide open and it will never get on plane, its running on both cylinders, its not caveating. it just feels like something is restricting the motor from gaining RPMs


any info or suggestions would be greatly appreciated

my friend had the same problem on his and some guy fixed it but i cant get a hold of the guy to ask him what he did to it, so i know there is an answer out there
 
JHD

JHD

Site Supporter
Location
Colorado
Have you tried easing into the throttle. My SXi will run great the first part of the day but when I let it sit for a while I have to ease into for about 30 seconds it to get it to open up and run. Once it opens up it's good. Fall off, kill it and it will rev right up untli I let it sit again. I'm thinking water might build up in the exhaust or even into the water box and just needs to get cleared out.
 
M

mikekilleen

Location
Deerfield ma
I believe I am having the same issue with a 93 I just purchased that hasn't been run in years. Tested the stator, failed, borrowed stator from other ski. Ski ran but had same symptoms as yours. I have a stator on the way, oil block off kit, drain block. Planning on doing a leak down test after installation of parts. if you solve this issue can you let me know what it was. Thank you.
 
Blue

Blue

Judging your cheapness
Location
St Cloud Florida
I had same issue with an sxi pro 10 years ago. Ended up being leaking crank seals and leaking case sealer. Bad vacuum leaks. I found the problem by spraying the side of the engine with brake cleaner or starting fluid the engine will either bog down or rev up. Spray a little bit directly into the carburetor first so you can see how the engine reacts then sprayed the side of the motor and the back of the crank seal while its running and see if it revs up or dies.

Sent from my SAMSUNG-SM-N900A using Tapatalk
 
Quinc

Quinc

Buy a Superjet
Location
California
Do not use brake cleaner! Stuff will kill you... Starter fluid is fine.
Edit: Do not use brake cleaner with chlorine.

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Magyar68

Magyar68

Really!!!
Location
Lewisville
Start with the easy stuff
Spark Plugs
Plug wires
Fuel filter screens, and check if the fuel Pickup is cracked
Check Value
Are you getting pressure in the gas tank after you ride?
Do you have the service manual to test the electronics?
 
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