bad crank

[dan2288]

ok, so i spun a rod bearing and it really messed my crank up. Would a machine shop be able to fix it ? Do they grind it down or what? Or should i just look for a used crank? Thanks

 

[TwoLiterLaser]

A picture would help in making this kind of judgement call. Your best bet regardless of what we say is to talk to your machinist and follow his directions. Or you could drop a little dough a bone-yard crank and call it finished.

 

[dan2288]

well if I would get it machined would I need different size rod bearings. Would the stock rods work or would I need speacial ones?

 

[gsx951]

Find a clean used crank, it's going to be a better and cheaper fix.

 

[dan2288]

well if i would get the crank machined and get oversized bearings, would it make the motor any less reliable?

 

[gsx951]

Yes.
There is a nitride layer n the outside surface of the crank. It does not extend very far into the surface and is mostly ground away when a crank is reground. The nitriding is done to provide an extra hard wear resistant surface for the bearing. To a very small degree, it also tends to strengthen the crank. In addition, the transition at the ends of the journals feature radii that are formed by a roller. The material of the crank makes a smooth transition, free from tool marks that is not easy to replicate. Tool marks in the radii can and often result in the formation of cracks.

If it were me, I'd find a good used crank and polish it because it will be better and cheaper than a reground crank.

 

[->PrOjEcTGS<-]

I had my crank ground on the advice given by my machinist. He said not to worry about it and that it's done all the time without problems. I took his word for it. 11,000 miles later it's still running strong. I think it cost me around $150 to get the work done.

BTW, it's undersized bearings you need when you get the crank turned since the bearing inside diameter is then smaller.

 

[gsx951]

I had my crank ground on the advice given by my machinist. He said not to worry about it and that it's done all the time without problems. I took his word for it. 11,000 miles later it's still running strong. I think it cost me around $150 to get the work done.

BTW, it's undersized bearings you need when you get the crank turned since the bearing inside diameter is then smaller.

Yeah, it was about 10K miles when the ground crank that I had broke....

Some people have no issues but everything that I've learned as a machinist is that you are better off not doing this, especially with a 100mm crank.

 

[->PrOjEcTGS<-]

I'm not saying that is the preferred way to do things. But, only time will tell... I've got a stock block with a good crank in it sitting in the garage waiting for a buildup if something goes wrong with this one. Just letting the OP know that it can be done if he doesn't have the cash for a new or used crank.

But yes, Mitsubishi claims the crank to be a Non-Serviceable part.

 

[fartz012]

the dealer is full of crap... you can weld and grind if its to screwed to grind for undersized barings