I had the missfortune to see my Hobbico SU-31 break apart in mid air the other day. Wings came off and the rest went in like a high speed yard dart . I thought I was going to have to go get a shovel to get the engine out of the ground. It broke the block where the muffler bolts on taking some fins with it. I tore it down and cleaned it up, but the question is it's a Tower 75 and is it worth fixing. A new casting is about $35.00. If so how do you get the seleve out and how do you remove the crankshaft?

Here's [link=http://www.youtube.com/watch?v=TuzEco3EDUM]a vid that will help[/link] (YouTube)

Fix it if you can get the parts.

The sleeve is usually stuck and you have to heat the block up a little to push the sleeve up with a wooden stick.

With the sleeve up and out, you can remove the piston/rod from the crank.

Remove the prop drive washer.

Push out the crankshaft.

Buy new bearings. Forget the old ones.

Get back on here with any problems.

The rod goes onto the crankshaft in a certain direction.

The cylinder sleeve has a definite orientation but you can determine this by aligning the higher exhaust port with the exhaust stack.

You can get the bearings from RC-Bearings.com http://www.rc-bearings.com/

The Prop drive washer set on a tapered compression cone and with have to be removed with a gear puller

This ia a duplicate thread. []

You may find that the sleve is bent also. Some of the damage is not that obvious up front. I tore up an O.S 52 four stroke, really badly. I was looking at what I could salvage and then sat it aside. I took another peek a couple days back and found a lot more damage than I first thought, IE the valves were even bent. I thought the piston was OK, but on close inspection, the ring was pinched in the grove. I didn't bother to pull the liner out, but based on the rest of the damage, I wouldn't bet on it being any good either. Stuff like the liner and piston are not obvious when damaged some times. It it is slightly squashed, IE not exactly round any longer, it is trash. When you finish buying parts and if you value your time at all, it will end up being cheaper to just suck it up and buy a new engine.

Don

PS, I did save in internal workings of the carb. Had to buy a new body though.

Don

Carb is fine, and I got the sleve out by putting it in the frezzer first then slightly heating the case with a map gas torch then by holding the engine buy one of the engine mounts that was still attached struck the edge of my work bench with the front of the engine, and the seleve came right out. No other damage has been found yet the crank appears to be straight, but I will check it with a dial indecator before I order any parts. i havent pulled the prop washer yet.

Let us know about the crankshaft, Big Jim.

I'm locking this thread because there are two going by the same original poster. Flyboy Dave has posted some good pictures and advice in the other thread, and it is worth seeing.