81 intruder locked up

[Steven]

Here's a pic of the exhaust port. The engine was rebuilt bottom up. It doesn't look like a burn down, top of piston looks good, rings look ???. Perhaps a piston skirt? This is my buddy's sled. Not to sure what to tell him. He spent a bundle $ buying it. Yikes!

[Matt]

Nothing to do now but to tear it down and see what happened inside. With debris on top of piston I would think it has to be melted. If that's the case then maybe the crankcase wasn't sealed up right, there was an air leak on the intake, carbs still clogged, jetting wrong, something like that.

[ljm]

x2

[Steven]

Here's what I found inside.

Both c clips are still in the piston. Too much clearance between the piston & jug wall?

[Steven]

One more of intake plate gaskets

[Steven]

Here's the piston up close

[harleysportster]

Possible causes: wrong spark plugs, premix ratio wrong, overheated-bad thermostat.
You need to split the crankcase and inspect bearings and flush out chunks of loose aluminum.

[JDT]

Ouch!

What happened first? Skirt failure?

Was the piston orientated correctly in the jug?

[Steven]

I think the skirt failed first. It seems to have a bit of play where the rod connects to the crank. Pison is in correctly i think, both cerclips in, no play in piston pin. The crank was replaced when rebuilt. Maybe 4 tanks of fuel since rebuilt.

[Steven]

Will a Sportfire crank and rods work in the Intruder case? Or should I tell him to find another Intruder motor? The rod bearing looks like the culprit of destruction.

[JDT]

Always best to know exactly the chain of failure events so you can hit the root casue.

Otherwise one may experience de' javu.

As long as they are the same series engine the cranks should interchange.

[ljm]

Steve

Intruder cranks are different. They are longer to accommodate the gear box. A Invader or Liquifire crank would be a better fit. But they may have different bearings

[Steven]

Ok thanks Lloyd and Todd. I found a used Intruder motor, just need to put in some new crankseals. Then i'll have a spare Intruder motor to rebuild or pick parts from for my Sporty.

[Steven]

Got the used motor up on the bench. I'm going to try changing the seals with it up side down. I found a good write up on kawitrax. The exhaust ports look like someone has done some work to them. It rolls over smooth. I hope the crank is good. We'll see how it looks when I pull the bottom off. I'm feeling confident i can do this. I want to get my Sporty in the shop next to pull the skid and check things over. Snow is disappearing quickly.

[Steven]

A couple electrical questions. Motor is resealed back in the machine and runs good. The old motor had e start the new one doesnt. I used the old fan tower and harness connector. The lights don't work. This machine needed the battery for the lights to work before so how do I eliminate the battery and have it just get juice from the regulator?