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Discussion Starter #1
Hey guys,

This is really a post for my buddies machine. I will give you the history and what we did to it so far.

It is a 1989 Polaris Indy 650. Tune Piped, Racing Clutch. Triple, Liquid Cooled.

We had it all warmed up and we taking turns seeing how fast we could go down the strip on the lake. One of our buddies went on it and when he was trying to get back he blew a belt. The engine died before the belt blew, but that all happened within seconds.

Well, I towed him back with my machine and we continued ice fishing ( We were ice fishing while we were having some fun)

Well, he tried something stupid which I think caused more damage to the engine. He decided to see if it would start up. No belt on or anything. It started, he let it run for about 20 seconds on idle then shut it down. I really think that was a big mistake. Read on you'll see why.

So, machine is at my house now. We too off the exhausts and the spark plugs and as I expected to see, damage. The back wall of the cylinder 1 was scored like a cat scratching at a wall. It was bad, the piston looked bad as well. We took the engine out of the machine and put it in my semi-heated work area. We numbers and layed out for taking apart the top ends of the engine. Cylinder 1 was disaster. It was scored bad. The piston was a right-off. Piston 2 and Cylinder 2 was okay. NOW. This is where we kinda got a little confused. I was kinda under the impression that there should be NO anti-freeze(coolant) near or in the bottom end. It wasnt in where the rockers and piston area. But there was fluid all around the head bolt bottoms and the machine areas that are like little trianble bowls where the heads and bottom end meet. I don't think thats a good thing. We looked for any visible cracks, didn't find any. SO, I think there is a crack inside the cooling shroud thing on the head.

So, That is our whole story. What do you guys think. What should he do. Etc..

Cheers,

Giger
 

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Hmm, intersesting. Well, the only way to test the coolont lines are to start the engine, which you can't do so i suggest draining the coolant out and either pressurize the lines and feel for air, or you could hook an air hose to the line, then spray soap water on the coolant head atop the engine block and in the suspected area of the crack, if you see bubbles you got a problem.

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Edited by - paulxlt on 11 Feb 2002 09:19:14
 

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I've got a few 650's - great power and in good supply. The heads and cylinders are cooled. When you removed the coolant manifolds and jugs (front and rear), the coolant probally fell down in to the "triangles", I wouldn't worry too much about that. Idleing without the belt - no problems unless it was overheating. Don't accelerate hard without the belt or you'll lose a clutch (and mabye some body parts). As to the engine, has it ever been rebuilt? If not, and it has some hard miles on it, it probally is due for a top end at the least. Bored over, fresh wiseco's, and I'd look at the crankshaft bearings and connecting rods. With no crankshaft problems, about $500 in parts. With a crankshaft rebuild, you are getting closer to $1000. Keep her around - those 650's are great.
 

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[/quote]The piston that you have pictured shows signs of overheating or swelling thats why the bore is scuffed so badly.... Was it low on coolant ? If it was only the one cylinder did the engine have a low RPM bog if it did you can almost be sure there was a case leak this will cause the engine to lean out on whatever cylinder the leak is at this results in piston overheat or meltdown. One other thing are the jets all the same size or do you stagger them ? Oh and one last thing I disagree with the idea of using wiseco's in this particular engine...... Your further ahead to run a set of Kimpex I know this from experience. Let me know what you find out but it looks like a rebuild is in order.
 

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Discussion Starter #11
The machine did have a low RPM bog. I do suspect that it was riding lean. Once its fixed I'll be sure to get the carbs set.
Why do you like Kimpex instead of wiseco's.
 

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The Wisecos while a very lightweight piston are very prone to swelling prematurely in the cast cylinder. The result is a toasted set of pistons in short order. I've had this problem personally and found that the Kimpex pistons while a little heavier don't have the same expansion problems as the Wisecos. If you want to run the Wisecos I'd be inclined to run the sidewall clearances wider than what the manufacturer recommends.....They are especially prone to the expansion on the hard wide open throttle runs you mentioned you were making.
 

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SnoDawg is right about the pistons. I almost bought a set of 3 Wiseco's, but luckily i learned about their wide expansion capability. Wiseco's run higher tolerances than your average piston. I ended up putting in new Kimpex pistons in my XCR 600. In addition, i can also say that i had to re-clutch after putting in the Kimpex, because they gave me a slight rise in HP over stock. They worked great for me, and there more reliable than Wiseco IMO. Good luck!

Ripperd2, that picture looks like the circlip fell out causing all the gouges. Is that what happened?? I'm just curious.
 

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megaman-

right on. Luckly it went right out the exhaust port after trashing the piston... THe bottem end was fine.

I did have to bore out the sleve though, and put oversize pistons in.

There is a thread about it somewhere in the shop.

-Dean
 

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Just wanted to add a ruel of thumb,

Damage above the pistons pin indicates overheating. Damage below the pin indicates lack of proper lubrication (not enough oil)

This may help someone out there with their diagnosis, so i thought i would throw it out there.


Polaris is my way out - Other people just use a door.
 

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<BLOCKQUOTE id=quote><font size=1 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>Originally posted by erick:

I don't know if any of that could have happend because there was no belt on there. It never over reved. did it, when there what no belt on it. I think it would be by the speed runs.


Vote for Snowmobile Fanatics.com[/quote]

Ya I agree with Erick on that one. I fire up sleds that are in the process of being built just to see if it runs and I never have a belt on it. Since its and old triple i'd say the speed runs are what did it.




Loud Pipes Save Lives
 

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A lot of times if the engine locks up at a high rpm that will cause the belt to break. My guess is that the engine siezed first from being to lean and that caused the belt to blow. Also if you do use Wiesco pistons gige them about 7 to 10 thousands clearence. Quite a bit more than OEM. It seems like a lot but they need it or they will sieze if you don't.


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Discussion Starter #19
*** UPDATE ***

Well, My buddy has had his heads machines 15/1000 over bored. New OEM pistons and seals and stuff. His question is, should he go for flat toping and something like that to get more power. Does flat toping or anything like that help?
Or for more power and speed should he look at other things.

Keep in mind, he does have a high perf clutch, and triple pipes.

Thnx

Giger
 
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