polaris sl 750 idles good and starts good but stutters and wont go.

[mogyver69]

Hey guys. I have a 1995 polaris sl 750 I just put a engine in. all new gaskets and seals. Rebuilt carbs pop off 16. Starts right up and idles fine. compression 115 all cylinders. When I give it gas on the trailer it has a bog or miss it feel like. I put it in the water and it idles and runs fine in the 5 mile zone but as soon as I go to take off it surges and sputters baddly. I trimmed 1/4 inch of the wires and opened the electrical box and checked connections. I pulled the plug wires off one at a time while driving in the water with the seat off and each cylinder dropped. I feel like it maybe a coil pack breaking down under a load but can not pin point issue. I took it out one time and it started running normal then after a few minutes it dogged out again and did not recover . Anyone have this issue before... I have went as far as taking another set of carburetors of my other ski and put them on just to be sure.. I now have the carbs off this ski on my other ski. So I know it is not carburetor related. I replaced all the fuel lines. checked the on off switch by removing the hoses and blowing threw with my mouth to verify it has no restrictions. I swapped fuel pumps with a extra one I had sitting around.

[stimpsonjcat]

I was gonna say rich on the carbs, but if you tried a known good set...

Do you have a cheap spark indicator to put in-line to the plugs?

[Octoarms]

Are your carb settings correct for the 95 year? 93/94/95 all had different adjustments.

[mogyver69]

I was gonna say rich on the carbs, but if you tried a known good set...

Do you have a cheap spark indicator to put in-line to the plugs?

I opened the electrical box yesterday. Unplugged every single wire and reconnected everything and it started up and ran correctly. I took it to the river and drove it and after about 3 good jumps it started crapping out again.. Has to be something in the electrical box. Poor ground or bad wire. I have replacing all the ground connectors and the wires coming from the cdi unit and stator wire connectors. If that does not work I will replace the other connectors. I was also wondering if that reset fuse/resistor could be a issue with corosian inside. it supplys all the power to everything inside there.

[mogyver69]

Thats kinda funny you mention that. The carbs them selves are exactly the same between those years, Even the jetting is the same. The only difference is the 94 the oil injection is under the carbs and 95 the injection is above the carbs. The small changes they made I am sure were performance changes. In either case my settings are good.

[K447]

I was gonna say rich on the carbs, but if you tried a known good set...

Do you have a cheap spark indicator to put in-line to the plugs?

I opened the electrical box yesterday. Unplugged every single wire and reconnected everything and it started up and ran correctly. I took it to the river and drove it and after about 3 good jumps it started crapping out again.. Has to be something in the electrical box. Poor ground or bad wire. I have replacing all the ground connectors and the wires coming from the cdi unit and stator wire connectors. If that does not work I will replace the other connectors.

I was also wondering if that reset fuse/resistor could be a issue with corrosion inside. it supplys all the power to everything inside there.

The circuit breaker can fail. I have seen more than one that was cracked, often around the threaded snout. If water gets inside or the flexible cap dome is missing then corrosion can happen.

I have posted sources for replacements, see my signature links.

Sometimes the wires outside the electrical box can have issues. Look for corroded grounds, wires rubbing on the engine, etc.

The blue Fuji engines can have issues with the engine bed plate electrical connection to the engine. The battery negative cable bolts to the engine bed plate, not to the actual engine case. Corrosion under the engine at the big bed plate bolts can interfere with the electrical contact between bed plate and engine crank case.

Try relocating the battery negative cable to attach directly to the engine. One possible location is a PTO intake manifold bolt. If you use a longer black battery cable you can ground the battery to one of the starter motor bolts.

Sometimes the actual engine kill switch goes bad. Or your finger is accidentally hitting the Stop button while riding.

[mogyver69]

You hit it on the nail. I missed your post and came on this evening to post the fix and read your reponse... The 15 amp circuit breaker failed on top of the electrical box.

I bypassed the circuit breaker with a wire lead and problem solved. I had another old eta 15 amp circuit breaker laying around from a old machine I parted out. So i threw it on and we are back on the water.

A little advice, my ohm meter read .05 at 20 ohm setting but if I pushed down on the connectors my resistances changed. On my new circuit breaker the readings stayed the same as they should. The readings should not fluctuate. If they do you have corrosion or worn terminals.

Thanks Guys

[mogyver69]

Still not fixed!!!

[mogyver69]

SO AS i INDICATED EARLIER WE THOUGHT WE HAD THE ISSUE SOLVED. i REPLACED THE CIRCUIT BREAKER WITH A INLINE FUSE AND TOOK THE SKI OUT FOR ABOUT 1 1/2 HRS RAN GREAT THE HOLE TIME. RIGHT AT THE END THE FUEL LIGHT STARTED FLASHING INDICATING LOW FUEL. jUST BEFORE PULLING INTO THE 5 MPH ZONE i DID A 360 AND AS i WAS DOING IT HE MOTOR STARTING SURGING AND BOGGING. i LET OFF THE GAS AND STOPPED THEN HIT THE GAS AGAIN AND IT RAN GOOD i AGAIN WENT TO DO A 360 AND IT BOGGED AND SURGED. I STOPPED AGAIN AND THEN TOOK OFF STRAIGHT AND IT RAN FINE. I ASSUMED IT WAS GOING INTO LIMP MODE DUE TO A LOW FUEL LIGHT AND WHEN TURNING SHARPLY THE SENDING UNIT WAS PROBLY READING ZERO. SO i PULLED THE SKI FROM THE WATER. LET IT SIT FOR 3 DAYS AND THEN FILLED IT BACK UP AND TOOK IT BACK OUT.. THE SKI IS NOW BOGGING AND SURGING AGAIN. i PULLED IT BACK OUT. DISCONNECTED THE BATTERY OPENED THE ELECTRICAL BOX AGAIN CHECKED ALL THE CONNECTIONS AGAIN AND PUT IT BACK TOGETHER.. iT RAN GOOD FOR AWHILE THEN SURGED AND BOGGED ONCE. i STOPPED TO IDLE FOR A MINUTE PLAYED WITH THE STOP BUTTON JUST IN CASE THAT COULD BE A ISSUE AND THEN TOOK OFF AGAIN AND IT RAN GOOD AGAIN... COULD MY CDI UNIT BEING GOING BAD? iTS RUNNIG GOOD AGAIN NOW...

[K447]

Surging and bogging is typically a fuel system or carburetor problem, not electrical. It could be electrical, but do not assume so.

Did you relocate the battery ground cable to the engine case as suggested?

Thinking along the electrical vector, another member had an issue with the cylinder head grounding not being 100%. He ran a ground wire across all three cylinder heads and then down to the cleaned up engine grounding bolt, which solved his particular problem.

On the fuel system, you really need to make sure everything is 100% correct. Air leaks into the fuel feed will cause troubles, for example. And of course the carburetors themselves must be set up correctly.