Thread: 780 COMPRESSION #'s
05-22-2007, 09:11 AM #1
780 COMPRESSION #'s
Looking at a '96 SLT 780.
Front cyl. 125-130 psi
middle cyl 105-110 psi
rear cyl 115-120 psi
What about the center cylinder? to low? any thoughts?
05-22-2007, 09:57 AM #2
A little off but that could be gauge related. Were these numbers with a hot or cold engine, did you crank the engine until the gauge no longer went up or just a few revelutions of the engine?
Was the battery completely charged and rotating the engine freely?
Can you look into the cylinder with a flexible light and inspect the cylinder walls?
The main thing is the cylinders all be within 10% of one another.
Oh and WELCOME to the Green Hulk Forums!!
05-22-2007, 01:44 PM #3THANKS FOR THE WELCOME
05-28-2007, 01:48 PM #4
Well I decided to take a chance and bought the ski last Tuesday. Ran it for about 4 hours on the lake. Seems to be running good and strong.
05-29-2007, 02:43 AM #5
This got past me while I was on vacation. Great ride in my book,
Cut 1/8 inch off of the spark plug wire and screw the cap back in.
Make sure fuel lines are not kinked over.
How about some photo's??
05-29-2007, 05:24 PM #6
What gauge did you use to test the compression. I need to do this also.
05-29-2007, 09:18 PM #7
I was so excited to ride it last weekend ( I hadn't even ridden one before) that I left the camera and GPS at home. I'll get some of it on the water next weekend.
05-29-2007, 11:02 PM #8
- Join Date
- Oct 2006
- Cleveland OH
They didn't abandon it completely... it got a little bit more stroke, triple pipes and some exhaust valves. Then it became the 145 HP PRO 785 which was built until 2000? Polaris just opted to go with the bigger Domestic engines (900, 1050, and 1200) rather than the Fujis for production models.
05-30-2007, 01:39 AM #9
Not only that, the basic design started as the 650, then the 750 and of course the 780. The bugs were worked out for the most part and the 780 power plant has proven to be extremely reliable.
A little maintenance and they run forever.
05-30-2007, 08:18 AM #10
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