Thread: paranoia or reality
03-25-2010, 09:54 AM #1
paranoia or reality
Im in the middle of a 94 slt 750 rebuild & yesterday I googled polaris 750 w/ hole in pto or mag piston & I was surprised at the number of people who made the repairs & still burnt another hole before they even got out of the no wake zone. I have completely rebuilt fuel sys. from tank pickups all the way back to rebuilt carbs.& fuel pump. There was about 6 individual problems in fuel sys. to cause a lean cond. Ive Indexed the crank & that is not a factor here, from what Ive been able to learn is that the one last factor would be leaking main seals. I dont want to waste the money Ive got wrapped up in this project & have to tear it down again & spend more good money. Ive been financially commited since about $6-700.00 ago! So to answer my own question I guess I play it safe & split the cases & replace crank seals.or I have the motor tore down to shortblock cyls. off,exhaust off,reeds & intake off. How do I perform a leak down at this point.
03-25-2010, 10:02 AM #2
im not sure if this test works for that or not but what about doing a leak test or pressure test? again i dont know its possable for main seals.. but maybe some on will chime in that knows about that stuff..
i be you are fine though pretty much everything on your ski is new.. how do your carb too intake mani gaskets look?
Last edited by ryandi2; 03-25-2010 at 10:03 AM. Reason: spelling
03-25-2010, 10:06 AM #3
Yes a leak test will show if the seals are leaking
03-25-2010, 10:10 AM #4
You can certainly do a leak down test and you don't tear the engine down, to do it. Just do a search on it and you will get way more information then I can quickly write in this post. If it does leak, you can use some soapy water around the rear seal, cases, etc. to try and spot it.
The crank seals do go bad so yes, it can cause a lean condition. The rear of the crank has 2 seals placed back to back. There is only one in the front.
03-25-2010, 10:36 AM #5
I completely understand that cases do not need to be split to perform leak down test, My question is what do I use or where can I get the material to use for blockoff . Not wanting to be another 750 fuji casualty,Thanks
03-25-2010, 10:41 AM #6
03-25-2010, 10:55 AM #7
03-25-2010, 10:59 AM #8
I thought that was a joke, the raquetballs & duct tape! Jokes on me. Learn something new here everyday.
03-25-2010, 01:52 PM #9
Pull a vacuum. You'll need Plexiglas, RTV, and a hand pump.
I let it sit for 24 hours and then applied some RTV around the intake and exhaust manifold and used Plexiglas to seal the openings. I used a mityvac hand held pump and applied 10" of vacuum and watched the clock. I started at 1:07 and at 1:21 I had only lost 1/2" inch of vacuum...not to shabby.
03-25-2010, 02:14 PM #10
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You need air pressure and soapy water to see the bubbles where it is leaking.
With a vacuum, it will just draw the soapy water inside - not really what you want.
When applying air pressure, you just need a few PSI
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