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Another broken down sled

Dennis Steele

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Hey Guys,

My 89 Indy 500 fan was rebuilt with new pistons this fall after blowing a cylinder and scorching the other. Both pistons were replaced and the exaust ports bored.

She wouldn't start and found bad gas in the tank. Emptied the tank and put new gas in.

She ran great in the back yard but had trouble getting it to idle down. (had the same problem before the motor was blown last season)

We added a mixture of 50 to 1 oil to the gas for break in. She still ran good in the back yard but was not ridden.

First time out the sled ran fine for about 3 to 400 yrds then just died. We checked the plugs with one wet and one dry.

Carbs were rebuilt, new fuel pump and filter. She now runs rough and has a lack of power and will kill at idle.

What should I try next?

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Do you have the sled at home and what are you doing this week (nights)?

If you didn't blow another cylinder (I just can't imagine that), you are running on 1 cylinder. Wet plug/dry plug... could be a carb. Well, either one cylinder is firing or the other is not.

Pull the plugs keeping them in the plug wire caps and make sure the plug is grounded to a cylinder head and pull the rope. See what kind of spark you are getting. If they are both equal, it would have to be a fuel problem. If one isn't firing, replace the plug and try it again.

Sledhead- Would an 89 have bad enough crank seals to cause a loss of case pressure to pump fuel? My experience with crank seals is older (70's vintage) sleds rather than Mikuni fuel pumps & carbs. Any opinions???

Like I always say, This is easier to diagnose when looking at the sled in person so alot of the previous info is me thinking out loud.

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I'm thinking a carb (or both) problems. When you tore the carbs apart it could be possible the float may have stuck on one? I've had this happen when screwing the bowl back onto the carb. You can hear it make a click sound (lightly shake/rock it in your hand) inside to make sure it's working properly before bolting it back onto the engine. You can't have gas in the bowl, however, at the time.

I know you have an idea on how to set the lean/rich/idle carb adjustments sufficiently, so I'm not going there. smile.gif

Also I've seen on Polaris' where the choke cable is worn or stretched, or whatever, and the choke will be engaged at all times. Something to look at. My buddy had this problem we could not figure out his engine troubles for the life of us.

Get some new plugs too if you haven't already. Isopropyl in the gas tank, a little Sea Foam too.

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That high idle is worrysome, given it did that before your pistons met Mr. Squeaky last year. Do a case pressure check to see if a crank seal or base gasket is leaking. That will lean out a cylinder real quick, and could possibly have caused your problem in the first place.

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I tinkered a little with it myself today and here is what I found.

The sled is only running on one cylinder.

I did a hill billy (thumb) compression test and it seems that both cylinders have equal compression.

Spark in both cylinders

Gas in both cylinders

Carb settings are where they are supposed to be.

I'm going to mess with that a little tommorrow.

It is possible that both carbs were not rebuilt properly. My "mechanic" works for me and I know how he pays attention to detail. tongue.gif

If I don't get her running tommorrow then I might have to take it to a shop. I don't have the means to check crank pressure and all that stuff.

I hate to spend any more money on an older sled. I was hoping to get one more season out of it then get a new sled for next season. This year I get to spend the tax return!!

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I had the same problem, run on one cyl not the other, cause the crank seal sliped out of the case and was sucking air by the crank, most, can;t say all 2 cyl. engines have a seal in the middle of the case that seperates the two cyl. the seal on mine slid out on the torque con. side, can usually see if it;s out with a mirror and lite. or pull the t.c.

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I just wanted to thank everyone for thier advice here.

Its great to be able to pick the minds of those who know.

My sled did have a cranks seal blown. I took it to Indy Specialties in Shakopee and they fixed her up for a fair price.

My personal mechanic (nephew) will have the motor back in the sled and ready to ride next week!! grin.gif

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