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Old 04-03-2010, 06:58 PM
Prembird's Avatar
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Exclamation Need help with issues on 97 400l sport

First off this is my first post... So hello all... Im hoping someone can help me out since i dont have alot experience with 2 strokes. I do have a lot of experience with automotive mechanics just not these motors.

A little history..

1997 Polaris 400L Sport

Was told it has...

Big bore kit
Larger needles
K&N air filter

There might be more but not sure...

The problem...

I bought it from a friend of mine about a month ago... My wife has riden it alot since then and everything seemed to be good. Then last week she said that there was anti-freeze coming out of a little tube on the left side and there was quite a bit of it coming out. I checked everything out and didnt see anything wrong. Then she tells me this week that the temp light flashed at her a couple of time. I checked and it seems to be a little low on fluid so i toped it off and everything seemed fine...

Then comes today....

She takes it and rides around a bit and was coming back when it backfired and bogged down on her and then died. The temp light came on. She happened to be at the top of a hill so she was able to cost down to the house.

I checked it and it was hot. Pushed the starter button and it clicked. Pulled the manual pull and it acted like it was seized up. Push button and it turned over.

I checked radiator and it was pretty much empty. Added water and it the whole system was still hot and the water actually was poping back up... got it filled up and let things cool down.

Tried starting again and it just cranks over. I pulled the plug and found that as you crank it over water is spraying out of the hole and soaking my hand.

Found a local polaris dealer and got a top end kit right before they closed so that I could replace the head gasket thinking this was gave out due to the heating problem.

Got home and started in on removing the head of it. I found that 5 of 6 bolts on top where probably just a touch over finger tight. Got everything worked around and got the head off and the metal gasket was warped pretty good and looked in bad shape.

Got it put back together with a new head gasket installed and a new plug as well. Removed the crankcase drain plug (atleast that is what i believe it was) and had just a touch of oil come out. Not sure if this is normal or not given my limited knowledge of these motors.

Cranked it over without the plug installed and am no longer getting water on my hand. Slight mist of gas. Seems to have good pressure if you try to hold your finger over hole. I installed plug and went to try to start.

I noticed that the temp light is still on. It cranks over without a problem but doesnt start. As I cranked it over a little more it does backfire out the exhaust but nothing happens. I looked at the exhaust output and notice that every time it backfires there seems to be water that shouts out from around the donut gasket. I removed springs and pulled it back and cranked some more till backfire. You can see the flame from it backfiring into the exhaust. Not sure what the water was about. When I pull the plug you can tell that it is getting gas. I even pulled the fuel line to verify fuel was getting to it.

So.... A quick recap...

1. overheat
2. water spraying out of spark plug whole when removed
3. replaced head gasket and spark plug
4. cranks over and backfires out of exhaust
5. wont start

Short of taking the engine completely out and doing a complete rebuild is there anything else that you all might know that I can try? Is there something that I might have missed in the whole process.

Thank you in advance for any and all help you can give along with taking the time to read the whole novel I typed.

Greg
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Old 04-03-2010, 09:37 PM
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First off, welcome to the board!
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I tried setting my password to "penis" but it said my password wasn't long enough...
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Old 04-03-2010, 09:42 PM
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I would eliminate all the easy stuff before a complete overhaul. Are you getting good spark and have you checked compression? You are getting spark if it backfires, but is it constant and good? Just a few suggestions.
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Old 04-04-2010, 06:12 AM
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Just remember that you are working with aluminum and the torque specs are not as harsh as one with an iron head.
The oil drain(for the front?) was for the counterbalancer and it only holds 4.5 ounces.
The temp sensor is on top of the head ,is it plugged in??
try a compression test ,if it's less than 100 ....................did you peek inside and look at the cylinder walls when you had the head off?
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Old 04-04-2010, 11:47 AM
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Little update...

I went ahead and pulled the head off of it since i didnt have access to a compression tester. What I found was what would be metal shavings coating the cylinder wall... Metal flakes like those that you would find in automotive engine when rings are going out. Im assuming its the same case in these as well.

So it seems as though I will end up having to overhaul the whole engine. So since I dont like leaving anything stock if I have to rebuild. What would be some suggestions on upgrades to get the most out of it without sacrificing to much reliability.

There is a saying in the automotive worlds...
Three goals to modding
1. Reliable
2. Fast
3. Cheap
The catch is you can only choose two....

So what all would you suggest????


Thanks for your help
Greg
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Old 04-04-2010, 01:17 PM
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you may want to look up rick ritter.... rcr racing.......you may be able to have all three
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Old 04-17-2010, 04:29 PM
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well just an update.. Finally after a couple weeks I had the time to pull the top end off... What i found was the piston itself started to break apart up at the ring area... The top of the piston also started to break apart.. The area between the rings up at the exhaust area is almost totally gone. The part the piston rides up and down in (forgot name of it) looks like it is ok and just needs to be honed. When i pulled the exhaust off there was water/antifreeze in it as well. I checked the bottom end and there wasnt any mixing with the oil so its fine. Just need to figure out which piston I need cause I was told it has a big bore kit in it...

So a quick question... What is the standard size of the piston so I can figure out what size this one is... Thanks for all your help so far

Greg
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Old 04-17-2010, 05:07 PM
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wiseco is the best piston rings circlips wristpin and gasket kit for 130 and its reliable. you also might consider getting it bored a lil and getting an oversized piston to make sure you get all the knicks and stuff out. When your all done make sure you break it in right. that is critical to long engine life!!!!
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Old 04-17-2010, 05:11 PM
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Quote:
Originally Posted by 450rracer22 View Post
wiseco is the best piston rings circlips wristpin and gasket kit for 130 and its reliable. you also might consider getting it bored a lil and getting an oversized piston to make sure you get all the knicks and stuff out. When your all done make sure you break it in right. that is critical to long engine life!!!!
Whats the recommended break in procedure?

Also like I said.. it might have already been done.. The "big bore" kit I was told about.. Thats why i need to figure out what sizing I need. As for boring it out more... The side are not marked up at all.. Just flakey stuff from the piston going out but no grooves or anything.. was gonna hone it and check it again though..
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Old 04-17-2010, 05:15 PM
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yea i like to run heat cycles on mine. let it get hot then let it sit for an hour or so and cool down and do that 3 or 4 times. Then i usually run a tank of gas through at no more than half throttle. that is what dan lamely of DASA racing in cali to me to do for my 450r's and it has proven to work. never had a motor problem. i have done it on 2 2-strokes now to and they are running good.
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