09-10-2011, 07:37 PM #1
95 Polaris SLT 750 under performing
Looking for some guidance. This is my first post, hopefully I am in the right spot. I have been using the site for about three months now. Here is my issue.
I have a 95 slt 750 that will only do about 5600 rpm and about 39-40 mph. Every once in a while it goes up to 6200 rpm, and its correct top speed of 45, but only for 10 seconds or so at a time, and this only happens a couple times in an hour of riding. I have read almost every post on the hulk about slt and sl 750's, and whenever I find someone with similar problems, they string me along with info, and then never post the final results of how they fixed their problem. The threads just dead end.
History. Bought ski in June. Did compression test before I paid. All cylinders at 120. Maiden voyage starts rough, slow to get going then goes 45 for about 20 minutes and then drops down to 20mph for ride back to dock. Change spark plugs. Next day takes off like a champ all day. Three rides later it goes back to 20mph and 3500-4000 rpm. Change plugs again, no dice. Carb cleaner. Doesn't help. Mess with carbs a little, check the cooling water, charge battery, air inlet valve on gas tank, check fuel lines, fuel filters, install three outlet fuel pump and install different carb rack from a good running machine. Clipped spark plug wires and re-thread on the wire heads. New thru-hull drive shaft seal, grease everything. All of this was done with help of the hulk posts. Again, every post ends without a final result.
Currently-machine accelerates nicely. Idles nicely. Starts great. Compression is good. No vibrations or weird noises. Doesn't over heat. Only thing is it seems to be a little on the smoky side, but plugs look pretty good when I take them out to check them.
I am assuming that it is in the carbs or it is electrical. I will be installing new diaphrams, but I don't know how soon. If anyone has insight into this, or has corrected this problem in the past, I would appreciate the help. And...I will post my results when I fix the problem. Thanks. Jason
09-10-2011, 08:25 PM #2
- Join Date
- Oct 2006
- Cleveland OH
Welcome to the hulk.
What does your piston wash look like?
What impeller is installed in the ski?
09-10-2011, 10:18 PM #3
Thanks for the quick reply.
I haven't checked the piston wash, but I will tomorrow with a snake light and let you know what they look like. I really don't want to pull the heads off.
Impeller is stock.
09-11-2011, 09:41 AM #4
Okay, so I pulled the heads...I want to do this right, and I appreciate your help. Here are the pictures hopefully...
What do you think about the way the spark plugs look? The PTO is totally different looking from the other two. I read a bunch of other threads last night and one reminded me that my PTO cylinder seems to be much cooler than the other two when I touch them after running. Also I gapped the plugs and the are all gapped correctly. I felt around the return line for the restrictor and it is there. Also, when airbox cover is off, and machine is running, the pto seems to have slight misting coming up. Could this be a reed problem, and if so would that cause my problem? If I think of anything else that might help, I will reply again. Thanks.
One other thing. Should my pto and mag pistons be at the same height in relation to the top of the cylinder block? Right now the mag is 1/8" higher than the pto. I haven't rotated the drive shaft to watch them move, this is just how they were when I removed the covers.
09-11-2011, 10:48 AM #5
- Join Date
- Oct 2006
- Cleveland OH
First, your PTO (back) piston looks about perfect. Your CEN is dangerously lean (lack of fuel) and the MAG doesn't look much better. Actually almost looks rusty on top????
You need to get some more fuel to the CEN and MAG cyls pronto!!
My Q to you is how soft are those red fuel hoses you installed? And did you use that for your pulse hose?
How long is the pulse hose?
Next Q is can you see any air bubbles inside the fuel lines when running? Not a real big fan of those zip ties for hose clamps.
Any air leaks inside the fuel lines can cause you to run lean.
You said you installed the carb rack from another machine. Did you go through them carbs and check for obstructions and proper size jets for your year?
Did you set the carb screws accordingly?
Spark plug reading means nothing. Looking at those is just a reading of what the motor was doing right before you shut it off. Most likely idling back to the dock.
As for the crank Q, you can do a index test, but you are prob fine.
09-11-2011, 11:59 AM #6
Red hoses are pretty rigid. Regular black fuel line for the pulse line. Pulse hose is about 7" long. I have the triple outlet pump mounted in the factory pump location. How long would I need to run the machine to re-check the piston wash after any adjustments? Besides the air bubble thing, what can I do to get more fuel to the CENTER and MAG?
There are some small air bubbles in the fuel lines. I wiggled them around by the pump and fuel started leaking out. I will replace zip ties with hose clamps today.
I went through the carbs before I installed them and they seemed really clean. Little filters and everything. Diaphrams seemed a little stretched, and that is why I want to replace them. I set the carb screws to factory settings from my manual.
I did your "redneck" index check, and they were off by about 1/32. My caliper is MIA.
I think the rusty look of the MAG was from the flash. I looked at it again and it looks like the other ones. The head bolts are rusty though.
I ran it this morning with the airbox cover off, and the PTO carb was definitely spraying up, Center was fine, and MAG was spraying just a little tiny bit. Reeds? Or nothing to worry about?
09-11-2011, 01:47 PM #7
I replaced the zip ties with hose clamps on the fuel lines. There was definitely air in the lines. I'm having trouble bleeding the air out of the lines. Big bubbles turn into little champagne bubbles when it runs, but it doesn't go away. When it runs I'm not seeing much fuel go into the Center carb. How much should I be seeing? I don't have a flush adapter on the cooling system so I can only run it for 10 seconds or so at a time in the garage.
09-11-2011, 10:09 PM #8
- Join Date
- Oct 2006
- Cleveland OH
As long as the lines are air tight, the bubbles will work themselves out.
Triple outlet fuel pump should feed the CEN just as much as other 2 providing there is no obstruction.
09-12-2011, 01:51 PM #9
09-12-2011, 07:51 PM #10
I am going to bring the beast the to the launch tomorrow, and I will post back how it runs. I am hoping that getting the air out of the fuel lines will solve my lack of rpm problem. Thanks for the input so far.
BLUEFISH-I don't know about the PTO and MAG cylinder carbs spraying up with the airbox cover off. From everything I have read on these posts it means that there is reed problem. I really don't feel like pulling everything apart to replace them, but if that will help it run better, I will. It will be a little fall project. But I will try it as it is for now.
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