Thread: '94 750 sl wont go above 30mph
07-06-2010, 08:43 PM #1
- Join Date
- Jul 2010
'94 750 sl wont go above 30mph
Added 07.07.2010Where u from?Just recently purchased a '94 Polaris 750 sl from a guy and it has an issue with getting up to speed, it wont.
North Idaho (Sandpoint), this particular ski came from Moses Lake Washington
what kind of ski
This ski is a '94 Polaris SL750
what kind of engine
750 triple blue fuji engine
how many hours on the meter?
500+ A lot..
how long did it sit
I was told it was out a few times this year before I picked it up, I took it out twice on the lake to test it.
any new/modified parts on it
triple fuel pump, aftermarket flame arrestors, oil injection removed
recent tune-ups or rebuild
Forward most cylinder is new, not rebuilt by me.
general history of the ski if you know
Owned by a guy in Moses lake and he claimed it was his wifes ski, one of 3 Polaris skis he had
comes with trailer?
live on water?
a few minutes away
did the ski run on saltwater or normal lake water
Freshwater only from what I can tell
130 on all cylinders
does it run?
Not much two stroke know-how. I work on cars and trucks mainly.
Basic items, no special tools.
The max speed I can get it up to is about 30mph.
Compression is 130 across all 3 cylinders. It's been rebuilt in the past by someone.
It has the aftermarket fuel pump that splits into three separate lines.
It also has aftermarket flame arrestors.
It seems to vibrate a bit, and the idle is a bit high, it didn't idle as high as it does until I took it to a shop to get checked out and it had this same issue before then.
My guess is a vacuum leak.
The shop I took it to replaced the nozel that was on it with the correct nozel (previous owner replaced trim nozel with manual nozel that angled downward), and he found that the engine was not completely bolted to the plate that connects to the hull so he pulled the engine out and connected it to the plate securely and put it back in.
The guy at the shop said that the jet pump looks fine, and a visual inspection shows no gaps between it and the wear ring but could it be the culprit? What else should I consider?
Thanks in advance for your help.
07-06-2010, 09:48 PM #2
sounds like only 2 cylinders are firing
07-06-2010, 10:04 PM #3
Welcome to the Hulk!
yeah i was thinking he holed a piston. but i guess thats not the case. maybe the wrong prop. do you know the type and pitch of that impellor in it?
if the blades are bent. it may be hard to tell without putting it on a pitch gauge. maybe the timing is way off.. how do the plugs look? light tan? or white? did you check the electrodes on the plugs? what doo they look like?
maybe the crank is rusty... how long was it sitting? was it fogged before storage?
coils could be getting weak.. did this ski ever get swamped?
a clogged pipe could cause it too. was it ran in salt water?
or baffles breaking in the water box could cause it to not perform right.
does it run hot? to the point where you cant touch the clyinders? they should be around 140. not 180 degrees.
maybe cut back the spark plug wires a 1/4 inch and see what happens.. maybe just a weak spark..
Idle will be around 3000 rpms out of the water.(no load on impellor). 1250 in the water.
07-06-2010, 10:08 PM #4
- Join Date
- Jul 2010
Thanks for the replies.
The plugs all look fine and all are the same colors.
The vibration goes away at higher speeds.
How would be a good way to test for combustion on all three?
Not sure of the prop, but it doesn't really look like a new one so I wouldn't imagine it's been replaced and then riden like this for a long period of time.
07-06-2010, 10:39 PM #5
take the plug off and put the electrode on a clean head bolt and look for fast bright blue sparks. wear a glove, or else youll get a little buzzing! ive dont it.. not too bad.lol
could you post pics of the plugs? try answering all my questions if ya can.. others can read the answers and help too.. any info we can get is important to diagnose things..
i put a sticky on the front page for new members to answer some basic questions about yourself and your ski and the condition.. check it out...
it says" before you repair or buying a ski for newbies"! that will help us out more too..
can you do a compression check? when was the comp test done? after you rode it or before?
i mean you could of had 130 across the board, then hole a piston and wonder what happened..
i see you said it has the triple pump on it.. thats good. who did the routing of the fuel lines? theres a restrictor in the return line. if its gone, youll loose fuel pressure.
does the gauge work? its called a MFD-multi-function display.. if it works, is there a light blinking?
07-06-2010, 11:32 PM #6
- Join Date
- Oct 2006
- Cleveland OH
Welcome to the Hulk.
What kind of RPM are you getting?
What's the part number on the impeller?
Does it have 4 or 3 blades?
How much clearance is there between the impeller and the wear ring?
07-07-2010, 06:48 PM #7
- Join Date
- Jul 2010
Pictures of fuel pump:
Pictures of Fuel Lines:
Pictures of plugs: (sorry, should have used a better camera)
I think they closely resemble the "Normal" plugs pictures here:
Picture of inside of jet pump: (3 blade)
I checked spark and am getting spark on all three plugs.
Can't remember what the RPM gauge was saying while riding it (didn't feel like it was spinning out on itself though like cavitation).
The MFD works but the numbers are fading away on the lower part of the gauge.
No light is flashing unless it tilt the ski in such away where a low fuel reading shows up. or I push the "Mode" button it flash for a second or two.
The compression check was done a couple days ago, after the problem was already present.
Also note that the ski has had the oil injection removed and it takes mixed fuel. I forgot to mention this in my first post.
The impeller is a 3 blade as pictured above, with zero clearance. Unsure of the part number.
Where is the restrictor in the return line suppose to be?
The previous owner did this.
I've added the "Newbie questions before you rebuild or buy a ski" questions+answers to the first post of this thread.
Thanks for your help.
07-09-2010, 01:32 PM #8
Hey Maxaud. I remember this ski on craigslist... was interested in it myself. I ended up with a pair of broken SLTs that I made one good one from. I'm down on Newman Lake.
I notice your fuel lines are still "T-eed" between the carbs even with the triple pump. Folks here say that is not the ideal supply line routing. It's preferred to have a single line feed a single carb and cap off the extra fittings. And it looks like you still have the original return hoses between the carbs. You should check those. All that said... I don't see this as your issue for slow top end speed.
The return fuel line restrictor is a little brass plug with a small hole in it inserted INSIDE the fuel hose. It should be located on the long fuel return hose that goes back to the fuel tank just a few inches down the hose from where it connects to the carb rack. There is usually a ziptie around the hose to mark it and keep it from moving inside the hose. Make sure you have it.
Good luck getting it running right!
07-09-2010, 04:26 PM #9
- Join Date
- Jul 2010
I'll check for the fuel line restrictor and report back.
Is the slow top end a sign of this not being present?
07-09-2010, 04:43 PM #10
the restrictor is in the return line going back to the tank, its the top hose off the carb rail going to the tank.. the restrictor should be about 1 inch away from the carb rail with tie wrap on it.. if it isnt there, it needs to be.. that is what builds your fuel pressure in the system.. that could be contributing to your lack of power... low fuel pressure.
ill find a pic of it for and also a pic of what your carbs routing should look like.. hold on a sec
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