Crankshaft polishing

[zookrick]

I have a '90 GSXR 750 crankshaft that is chewed up some, picture included. Is this too far gone or could it be polished without opening up the bearing clearances too much?

The top journal I have worked on some with a shoelace, 400 grit and wd40. the bottom one is pretty much the way the rest look.

Edited June 1, 2017 by zookrick

[Gixer1460]

Depends on what size bearings it has presently - I believe there are 3No bearing sizes to allow for factory machining tolerances - if the relevent journal is undersized already and there isn't another undersize bearing to go then its either leave well alone, metal spray and re-grind or scrap it. I wouldn't try DIY crankshaft re-facing! LOL!

[zookrick]

The bearings are all toast, I will be buying new ones, probably would use one size smaller on each to make up for any material removed.

[Fazz711]

You would need some plastigauge to check the clearance. And a manual for the tolerance to work to. It won't be easy to polish to an accurate degree. Especially if you do it by hand. 

[dupersunc]

Step away from the tools and put the emery cloth down.  No Suzukis need to get hurt here son.

[kja.busa]

I think I have a 750M crank in the shed, complete with shells if you get stuck.

[Swiss Toni]

I have a 750 J/K crank here too, if needed!

[zookrick]

Well a used replacement would be better if shipping is not too much. I am located in Canada.

I ordered a crank off fleabay, but it is unusable for me and not worth the shipping cost to send it back, which is frustrating.

[Swiss Toni]

I'd get a crank local to you if possible. Postage from UK will make it expensive. Didn't realise you were in Canada! Try Eblag, or Craig's List?

[no class]

12 hours ago, zookrick said:

Well a used replacement would be better if shipping is not too much. I am located in Canada.

I ordered a crank off fleabay, but it is unusable for me and not worth the shipping cost to send it back, which is frustrating.

It would make a nice coffee table lamp .....

[canamant]

I've seen worse  than that and put it back together.  Suggest you check what shells you have fitted already and buy the next tighter shell and test fit it.  Note that there are no "undersize" shells just different toleances.

Also remember that a 90/91 crank cant be swapped with a 88/89 crank.

 

Edited June 2, 2017 by canamant
additional info

[ktalgsto]

When I did my crank it looked almost like yours , and I took it to my local machine shop which I have been going to for years , and he said polishing will not take any material off it will just take the high spots off and polish it , I put all new bearings in that the bike came with color coded and numbers on the crank and block , and it came out perfect , but always plastic gage them , I did just to make sure.

[strima]

A bit more costly would be get the crank away to someone who does crank chroming and grinding. Should come back good as new.