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2 stroke crankshaft machining?

S

Swagonmaster

Regular Contributor
I want to verify that 2 stroke cranks can't be turned due to a lack of oversize replacement needle bearings. Could one of you guys that work on these things regularly comment please.
Thanks Bob
 
Crankshafts are ultra precision parts.----Hardened and run at full load at say 5500 RPM.----Some claim they can be rebuilt & rehardened,------I would not trust it on my own motors.----After welding / building up the may be bent / stressed etc.-----But technology changes and I could be wrong.
 
Many, readily available used cranks are out there since they outlive the blocks (usually). Look for a good, used replacement on E-Bay or etc.


Jeff
 
That is pretty much what I thought, the expense of getting a shaft repaired is likely more than the cost of a used shaft as long as a used one is available. Back when I was working on Mercedes-Benz diesels they had a nitride hardened crank but that could be redone if the journal needed to be repaired and I guess that the merc crank could too but you a are back to "you have to build it up you can't grind it down" which is much more expensive.
 
I just got a used crank delivered to find out that #6 had a pitted place that the seller had missed and that was what brought up the question but have since found another one that will hopefully turn out better.
Thanks for the help, Bob
 
I did a " test buy " off E-bay 2 years ago.------Part was described as " in good usable condition " by seller.----I took one glance at the bearing surface and was disappointed.-----I suppose could say ----" Bayer beware " with some of these parts sellers.----New parts only from now on off Flea Bay for me.
 
eBay you gotta be careful, some sellers are misleading.....check their feedback. There are many competent new/used parts retailers out there. My favorite is Tim's Outboard in Hackensack MN.....over 50 years in business now.
I have an old racing Johnson 33 hp speedi 4. Crazy with 4 megaphones out the back. A Big Four lower unit had been adapted to fit. If I ever catch up, I would like to restore it. Needs crank work.....can't find one. Thanks Pappy, will Google them up.
 
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I called them to get an idea of what it would cost to repair a shaft and they said for my inline six it would likely be about $500. Since on this one I can get a used crank there would be no need to go that way but if there is no used available then it would make sense. Expensive but beats no shaft at all. I wonder what that crankshaft would cost if it could still be bought new? Probably would put that repair cost in the "cheap" category.
 
This is what happened when when crankpin bearings went on walk about and the reason I was in need of a new crank.
 

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Yikes, you need more than a new crank, my friend......sure you know that. When working on old cars and trucks we often said..."jack up the hood and pull another car under it".
 
Yup, I am really glad that replacement cylinder liners are available or I would be in a world of hurt. It's bad enough as it is, my budget on this boat went out the window a while ago. I had heard years ago that the definition of a yacht is "a hole in the water that you pour money Into", I guess that I Just have a little smaller hole.��
 
Cylinder would have to be bored.----Then sleeve installed.----Then perhaps the sleeve bored and honed to proper size.-------B.O.A.T.-----Bring on another thousand.--------A parts / donor motor would be the best way to go.----Lots around in my area.-----Perhaps not where you are.
 
No not any that I've been able to find. Fortunately a local machine shop I've used had bought the special boreing bar needed to bore the marine blocks that have to be cut all the way to the "head". They said about $325 depending on the freight for the sleeve and $80 for a piston, as you said i might be close to 1K all in. It will run better than it did though, I was really glad I had a trolling motor that day it locked up.
 
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