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Old 01-10-2013, 09:54 AM   #1 (permalink)
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400 Indy huge Issues

Hey yall, I have a 1988 400 indy Liquid. Now in previous years this sled has been insane! Would easily show you 95-100 mph. I have NEVER taken anything apart that hasnt needed so. So Im not sure if its been bored to the walls or anything. Dug her recently and put some fresh gas and plugs, got her fired up, but is bogging something crazy. Despite the problem i took it for a ride, in hope it would come out of its daze. Well, If you hold her wide open, she bogs up to 6-7 grand then takes off like a scared rabbit. for about a mile, then it over heats. I have topped up antifreeze and bled the system so its not an airlock. Put the compression tester on it and get this(mind you i think the testers bad) about 50-55 pounds each side. WTF? I thought you needed a good 90lbs to make an engine run? Head gaskets? Waterpump? Im at a loss. Still starts relatively easy and will idle, when u try to rev it, it bogs till it engages at 4 grand, then stays at a high idle almost engaging.
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Old 01-10-2013, 10:31 AM   #2 (permalink)
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Something is defitinitly amiss. if your compression IS really that low - it will not run. For the record .. I used to have a '88 Indy 400 - It was one of the best sled Polaris ever made back in the day. Anyway .. when you put fresh gas and new plugs - did you clean the carbs before taking her out? If not .. its possible u may have a riding it with a dirty carbs and you may have done some internal damage to the engine .. like melting the piston(s) SO one step at a time - you already know you have low compression - you will need to take the head off and see what happens there, check the pistons and check the cylinder walls for the condition. Without seeing it directly - sounds like you may have to do top end rebuild .. providing the crank is ok. While doing the top end .. might as well change the crank seals as well. When that is all done .. clean the carbs well so it doesnt happen again. Your compression should be in the 120 range. Anyone? WL
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Old 01-10-2013, 01:16 PM   #3 (permalink)
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Did you do the comp test correctly?
Throttle wide open, both plugs out and pull till the gauge stops rising?
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Old 01-12-2013, 09:41 PM   #4 (permalink)
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Problem mostly solved, believe its just minor clutching issues now. replaced rad cap w/ new one I happened across in the shop. All is now good other than a bog on the get up. Lots of Go though! Will have a look at the clutchs when time finds me. Thanks all.

by the way, new comp tester revealed it has 125 both sides. not bad for never being freshed up.
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Old 01-12-2013, 10:26 PM   #5 (permalink)
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Why does the throttle need to be wide open RJ?


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Old 01-13-2013, 02:38 PM   #6 (permalink)
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You want as much air going into the cylinder as possible for an accurate reading.
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Old 01-13-2013, 02:42 PM   #7 (permalink)
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Is that the difference between a wet and dry compression test?


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Old 01-13-2013, 03:23 PM   #8 (permalink)
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No. A wet/dry test is used in a 4-stroke engine to determine if a lack of compression is due to rings or valves. If you do a dry test and it's low and squirt oil in the cylinders and do a wet test and it's high, the oil has helped seal the rings so the test would indicate rings are needed. If the compression is low both wet and dry, it would be time for a valve job.
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Old 01-14-2013, 05:02 AM   #9 (permalink)
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You can do the same in a two stroke too to determine if you low compression is rings or a holed piston.
It it's rings and you add oil, the compression will come up, but if it's holed or chunked it will not.
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'93 Wildcat 700EFI
w/ Comet 108 Pro-4 clutch & 01 ZR skid

'90 Wildcat Project in progress.

Vintage (sorta)
1980 Indy Trail 440 (for sale)
1980 AC Pantera (donor engine to the 90 wildcat)


http://www.dcdrifters.net/


Worshipful Master; F&AM Dryden Lodge# 472
http://www.masonicdryden472.org/

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