1997 Superjet bogs down when I hit the throttle

Shayne Dugan · Sep 20, 2014

My suprjet will run ok for a few minutes and then after a while when I hit the throttle to jump a wave or just speed up, it will bog down and die. If I have enough time to reach the primer I can pump it and it will run ok for another few minutes before it bogs down again. Seems like its not getting the fuel that it needs. Any suggestions? Thanks.

blastin603 · Sep 21, 2014

check fuel lines... bypass fuel selector, check pickup tubes, change fuel filter, check internal carb filters

All stock 701 · Sep 21, 2014

Are you sure you don't have a flat spot? Is there a certain amount of throttle it always bogs at?

Shayne Dugan · Sep 21, 2014

Yeah it definitely isn't a normal thing. It would bog down when I hit the throttle all the way to jump. It also didn't happen every time. It seemed like there was no gas getting to it. If I felt it starting to bog down I would hit the primer and it would keep it alive for a few more minutes which made me think it is a fuel system issue.

Shayne Dugan · Sep 25, 2014

I took the carburetor apart and cleaned it. The diaphragms looked in ok condition. I blew out the pickup tubes, and sucked up the gas incase there was water in it. There is spark on the spark plugs, and I have a compression of 130-140 in both cylinders. Does that compression seem ok for a 1997 stock superjet?

All stock 701 · Sep 25, 2014

From the factory they are 150 per hole. May be your gauge or may be age and wear

Shayne Dugan · Sep 25, 2014

Is there anything I can do to raise the compression, or would that require an engine build?

All stock 701 · Sep 25, 2014

An aftermarket head will raise compression but it sounds like it wouldn't hurt to do a top end

Shayne Dugan · Sep 25, 2014

What exactly do you mean by a top end?

All stock 701 · Sep 25, 2014

Piston, rings and home the cylinder.

Shayne Dugan · Sep 30, 2014

I just water tested in this past weekend. It's still bogging down and stalling. Does it sound like it needs a carb rebuild?

Midlake Crisis · Sep 30, 2014

The dreaded intermittent bog. . ..
I hate this issue, never seems to go away.
Basics

Shayne Dugan · Sep 30, 2014

Any suggestions? I don't know what else to do.

Midlake Crisis · Sep 30, 2014

Shayne Dugan said:
Any suggestions? I don't know what else to do.

Adjust idle, high and low screws to make sure it is at least close to being tuned (See Mikuni Manual)
Change external fuel filter
Clean out small internal fuel filter inside carb
Clean carb thoroughly, blow out passages with compressed air
Check every inch of fuel lines and pulse line for cracks, brittle ends, bad connections
Bypass fuel selector to verify no air leak there
Fresh plugs gapped correctly
Test coil specs with ohm meter, wiggle wires to see if consistent, trim wires and replace terminals if needed
Check thoroughly for exhaust leaks, cracked water box, hose, bad connections
Verify tank check valve works right and installed properly
Swap CDI with "known good" CDI
Swap Stator with "known good"

These are basics I have tried, I have thought it was fixed after different things and then had the problem return. Good luck and report success if you find it. . .

Shayne Dugan · Sep 30, 2014

Ok. I'll look at these things. I have already: changed the external fuel filter
cleaned the internal ones
Took the carb apart to look at the diaphragms and check jets, gaskets etc.
checked the spark but not with an OHM meter, just by unplugging the plugs and trying to start (they sparked)
How do I bypass the fuel selector?
How do I check the tank check valve?
How do I adjust idle?

I noticed while riding that when the fuel selector is in the "on" position it bogs and stalls more than when on "reserve". Does this have any significance?

Midlake Crisis · Sep 30, 2014

How do I bypass the fuel selector?
Run the reserve line directly to the carb, plug the other one.

How do I check the tank check valve?
Make sure the arrow on the valve is pointed toward the tank, blow through the valve make sure it lets air in to the tank but won't let air out (one way valve).

How do I adjust idle?
Google for the Mikuni manual, need a tachometer to adjust idle and mix screws properly

I noticed while riding that when the fuel selector is in the "on" position it bogs and stalls more than when on "reserve". Does this have any significance?
I am thinking that may be a good sign - if it is just an air leak in the selector you could be in good shape for an easy fix.

Shayne Dugan · Sep 30, 2014

If it's an air leak in the selector is there a fix or would I need a new one? Also, where would the reserve line go into the carb when I bypass the switch?

Midlake Crisis · Sep 30, 2014

Shayne Dugan said:
If it's an air leak in the selector is there a fix or would I need a new one? Also, where would the reserve line go into the carb when I bypass the switch?

I haven't looked in to repair kits for selector switches, I would think you could buy internals for it but don't know for sure.
To bypass the selector disconnect the fuel line coming from the selector to the large external filter and plug it off. Take the reserve line off of the selector and stick it directly on to the filter.

Shayne Dugan · Sep 30, 2014

Ok and what do you block the line coming from the selector off with? A zip tie?

Midlake Crisis · Sep 30, 2014

Shayne Dugan said:
Ok and what do you block the line coming from the selector off with? A zip tie?

I usually stick a 1/4 hex drive screw bit into 'em. :0)