Polaris 300 2 stroke - Polaris ATV Forum
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post #1 of 11 (permalink) Old 04-24-2012, 10:43 AM Thread Starter
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Polaris 300 2 stroke

Polaris 300, compression was 30 psi, bored/ honed to 75mm installed new piston and rings to match, new gaskets, check compression after and it's at 60psi
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post #2 of 11 (permalink) Old 04-24-2012, 10:50 AM Thread Starter
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I squirt oil on top of piston and it put compression up to 110-115psi
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post #3 of 11 (permalink) Old 04-24-2012, 10:50 AM
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It needs to be broken in. It's not going to seal up until the rings wear into the cyclinder.

'96 Xplorer 300 Aftermarket CDI box, K&N filter, jet kit, reworked expansion chamber from dirt bike, 1" taller + 1" wider rear tires, dual wenches, Rack on rear/w cargo pac, polaris box on front, Mossy Oak cover on seat, back-up lights on rear, aux. power source for GPS,"Theft deturent's", hand protectors, new clutch springs coming! Would love to find GURU style bumpers! By the way, I'm also a graduate of AMI with over 20 years of motorcycle mechanical experiance. New to quads, but the same basic engines. 2 stroke or 4 stroke!
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post #4 of 11 (permalink) Old 04-24-2012, 11:13 AM Thread Starter
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How would you get it to start with only 60 psi?
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post #5 of 11 (permalink) Old 04-24-2012, 04:30 PM
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barely, it needs a lil layer of oil on the cylinder walls to help seal the gaps in the rings. Another squirt or two of oil won't hurt.
Make sure you have fresh gas and clean carb.
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post #6 of 11 (permalink) Old 04-24-2012, 10:54 PM
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I've had two strokes run on as little as 30 P.S.I.!! Not great, but it ran! And ,yes the oil trick works.

'96 Xplorer 300 Aftermarket CDI box, K&N filter, jet kit, reworked expansion chamber from dirt bike, 1" taller + 1" wider rear tires, dual wenches, Rack on rear/w cargo pac, polaris box on front, Mossy Oak cover on seat, back-up lights on rear, aux. power source for GPS,"Theft deturent's", hand protectors, new clutch springs coming! Would love to find GURU style bumpers! By the way, I'm also a graduate of AMI with over 20 years of motorcycle mechanical experiance. New to quads, but the same basic engines. 2 stroke or 4 stroke!
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post #7 of 11 (permalink) Old 04-25-2012, 05:15 PM Thread Starter
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Compression problem solved

I beleave I found the problem, 76mm piston with 75mm rings in a 75mm bore
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post #8 of 11 (permalink) Old 04-25-2012, 10:50 PM
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Ok , that's a new one! How did you get a 76mm piston into a 75mm hole????? It has to be a 75mm piston in a 75mm hole or the other way around. I believe the wrong rings were included. Happens a lot.

'96 Xplorer 300 Aftermarket CDI box, K&N filter, jet kit, reworked expansion chamber from dirt bike, 1" taller + 1" wider rear tires, dual wenches, Rack on rear/w cargo pac, polaris box on front, Mossy Oak cover on seat, back-up lights on rear, aux. power source for GPS,"Theft deturent's", hand protectors, new clutch springs coming! Would love to find GURU style bumpers! By the way, I'm also a graduate of AMI with over 20 years of motorcycle mechanical experiance. New to quads, but the same basic engines. 2 stroke or 4 stroke!
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post #9 of 11 (permalink) Old 04-26-2012, 05:22 AM Thread Starter
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I'm sorry this how it goes... Part number on piston matches to 75mm, piston size matches to 74.5mm and it was in a 76mm box
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post #10 of 11 (permalink) Old 04-26-2012, 08:58 AM
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Should be getting mine back friday, intake boot ripped and melted piston, sent it to summit racing, $145 for a bore and new piston
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