1994 SL 750 won't rev up

[petereric]

I have a Polaris 1994 SL 750 3-cylinder jet ski that wont rev up. It has an aftermarket head on it and a aftermarket waterbox as well. The center cylinder piston rings were toasted. I replaced the rings and put it back together. After completing this I started it up. It ran fairly well. I put it in the water and took it for a drive. After starting, I went to rev up, upon my surprise, it bogged down and stalled. I started it again and made sure it was warmed up. When I hit the throttle it stalled. I thought it wasn't getting enough fuel so I pulled the choke and drove. This worked very effective to get it going. When I was on plane I let off the choke and it revved up to full throttle. It worked. I came down off plane and tried no choke this time and it bogged down and stalled. I went to the manual for carb. settings and set them. The symptoms still persist. After getting frustrated I took off the carbs to clean them. There was some varnish in the internal fuel filter, but not much. I put them back on, set the jet settings, took it for a ride and it still does not come up on plane without choke, but it runs good at full throttle. Please Help!!

[Bryan Glynn]

Rings don't just 'go' - and whatelse did you repair? Just throwing new rings on a damaged piston and sleeve doesn't solve anything.

[Rider X]

sounds like your to lean on your low speed screws for your head you are running. here is surefire way to tell, when it bogs and dies, pull plugs, see if lean, take new set with you, install them, restart see if planes easily and if starts to bogg, pull the choke, then if starts to rev up, shut off, pull plugs and see if rich or lean.

[dank]

We know it is way too lean since it will rev with the choke and not without it. Sounds like it is in need of another carb clean. pour the fuel that comed out of the carb bodies in a contained and check for water. This will come back to haunt you if you don't find it the first time. Also make sure the fuel is not old and the fuel valve it letting good fuel flow you can bypass it for testing.

[dank]

After your engine repairs what was your compression?? Is it running on all 3?

[petereric]

Would old fuel lose its volatility and only run at a high RPM and not a lower RPM? How do you tell if there is water in the fuel? Compression was at 120 and it is firing on all three cylinders.

[ November 05, 2002, 03:39 PM: Message edited by: petereric ]

[dank]

I have had old fuel cause it to idle bad and not accel off idle properly. I don't know about the top end because I was concerned about burning a piston or worse. You can look at the gas in a container after it has been sitting for a few min. The water will go to the bottom and form a puddle.

[petereric]

I have tried all of the things suggested here and I even added an extra fuel pump. And the machine still doesn't run like it should. Also would low vacumm pressure to the fuel pump cause this?

[Bryan Glynn]

Yes low vaccuume to the pump would cause that.

[Wet Wolf]

turn your low speed screws out 1/8 to 1/4 turn. If you can grab the choke and it helps, then itsa lean bog.

[petereric]

How do you get better vacuum pressure. Or can i use an electric fuel pump? [img]graemlins/cwm3.gif[/img]

[Technical Support]

You cannot alter the vacuum pressure. Just make sure the pulse lines and fittings are not leaking. Other than that, it's the pumps themselves that are damaged, if they are not pumping sufficient pressure.

[petereric]

I have replaced the vacuum line, and put a new pump on it. I also checked the fittings and they are all fine. Tha symptoms still persist.

[Technical Support]

The next thing to check is the rest of the fuel system. make sure you have everything routed correctly, that there are no obstructions in the pickup tubes, the fittings, the fuel switch, filter, etc.

[cameron da river rat]

i had that problem with my doo one time. it would only run with the choke on and yes it was lean but the reason behind it was an air leak at the carb to manifold gasket. somehow the gasket got offset and was sucking air in through the manifold. u might have an air leak somewhere, carb put back together wrong or something very simple like pop off. u just gotta go one by one and find the culprit.

id start at the tank, remove all the old gas and check for water, blow all the fuel lines out with an air compressor and check the fuel switch while your doing it, check the fuel filter bowl for water, bad o-ring, cracked fuel line, when thats all good go to the carbs, manifold, and so on till u find it.