Is my crank toast?

[Matt_martians]

So the story behind this engine(1995 spx 657x) is that was I was doing electrical diagnostics and opened the stator cover to make sure everything is in tact. Found tons of oil. Tore down engine to replace crank seals, found the cage on the front bearing is gone and there's remnants of the cage melted into the front seal. When I lifted the crank up a little bit the balls fell out and so did the outer race. The inner race on the outer bearing slid off when I grabbed it and the second one was also loose but there was a rough section that I had to air hammer it over. I did not run my air hammer very hard at all, I could have probably pushed that out by tapping it with a small mallet. That rough area feels like what a spun bearing on a 4 stroke feels like.

My question is should I replace my crank? Or should I sand down that rough area, make some measurements, and call it a day? Does anyone know what the min ID of these cranks are, as it does not say it in the service manual. If I can replace these bearings does anyone have any tips/videos on replacing these bearings? I'd assume you press it, but do you need to make special fittings for the press and is there anything to look out for? Thanks for the help in advance

 

[etemplet]

I'd be concerned about the bore size in the engine case. I happen to have a 657X engine disassembled that I'm never going to build. It ran but the internal crank seals on the rotary valve chamber were leaking pretty bad. I bought another bottom end from a guy so I don't need this one. I'd bet the crank and the engine casing are in very good condition. You'd have to replace the seals on the crank. $100 and I'll throw in the cylinders. You pay shipping and the box I'm gonna put it in.

 

[Matt_martians]

I'd be concerned about the bore size in the engine case. I happen to have a 657X engine disassembled that I'm never going to build. It ran but the internal crank seals on the rotary valve chamber were leaking pretty bad. I bought another bottom end from a guy so I don't need this one. I'd bet the crank and the engine casing are in very good condition. You'd have to replace the seals on the crank. $100 and I'll throw in the cylinders. You pay shipping and the box I'm gonna put it in.

are you saying i'd need to replace the center seals? in that case I'd just buy a SBT crank at that point. I will measure the bore and then get back with you about that engine. But you think I should

I'd be concerned about the bore size in the engine case. I happen to have a 657X engine disassembled that I'm never going to build. It ran but the internal crank seals on the rotary valve chamber were leaking pretty bad. I bought another bottom end from a guy so I don't need this one. I'd bet the crank and the engine casing are in very good condition. You'd have to replace the seals on the crank. $100 and I'll throw in the cylinders. You pay shipping and the box I'm gonna put it in.

Appreciate the feedback. This is what my pistons look like. The grooves are noticable with my finger nails, but aren't that bad. I'll measure the bore with a bore gauge and if it's out of spec(or if the cylender-bore clearance is out of spec) I'll get back with you about buying that engine. But you would conclude that it needs a new crank, right? The engine ran when I disassembled it.

 

[mikidymac]

Get out the butter as that crank and pistons are toast.

 

[etemplet]

From the pictures I can't see anything I'd reuse on the bottom end.

 

[AKnarrowback]

I'd be concerned about the bore size in the engine case. I happen to have a 657X engine disassembled that I'm never going to build. It ran but the internal crank seals on the rotary valve chamber were leaking pretty bad. I bought another bottom end from a guy so I don't need this one. I'd bet the crank and the engine casing are in very good condition. You'd have to replace the seals on the crank. $100 and I'll throw in the cylinders. You pay shipping and the box I'm gonna put it in.

Sounds like a deal to me.

 

[AKnarrowback]

If you can slide an inner race off then it is time to replace the crank. It's worn out of spec and will work for a short time if you monkey with it in some way to hold the inner race, but if you want a good rebuild it has to be replaced.

As everyone has said, it looks like everything is needing to be replaced. Sorry to tell you that.

But to answer one of your questions. If you ever are in a situation where only an end bearing needs to be replaced you can do this if you are VERY careful. Score the races and break them with a chisel. New bearings can be put on without a press. You can heat the bearings in an oil bath just like cooking. An old pot, 2 stroke oil and a small cook stove. Heat the bearing, gently grab it with some needle nose pliers and drop the bearing down on the crank. Not too much heat or the bearing can be damaged. You have to get it out of the oil and dropped straight down on the crank as fast as possible or the bearing can start to contract and lock onto the crank before it is seated properly.

That is the basic idea.

Spacing between bearings??? That is where it gets more technical. But the key idea is an end bearing can be replaced without a lot of trouble if you feel comfortable doing it and know what to look out for.

Inner bearings? Not a chance at home, send it out to get rebuilt.