What should I do with my crankshaft?

[gearhead13]

I bought an '83 crankshaft to replace the possibly twisted, flaky crank that is in the bike now. It has a crazy vibration at 4000 rpm that was never there before.
1. I could run the crank like it is and keep my fingers crossed
2. Bring it to a local shop and have them weld the areas that the factory didnt weld.
3. Send it away and have it welded/trued.
Shipping a ~50 lb crankshaft isnt cheap. Is there anywhere in the northwest or western Canada that does this work?

 

[Steve]

Shipping a ~50 lb crankshaft isnt cheap.

Rebuilding an engine that shook apart because it wasn't true isn't cheap, either.

Just pick the amount you would rather pay.

.

 

[gearhead13]

Rebuilding an engine that shook apart because it wasn't true isn't cheap, either.

Just pick the amount you would rather pay.

.

Thats why i bought a new crank and I am going to tear the engine down again.
The question is how long will it last with the stock welded replacement crank?

 

[SqDancerLynn1]

Once trued and welded it is as good as new well almost. If it is in good shape to start with should be OK

 

[TheCafeKid]

How much power you putting to it?

 

[streetfighters]

I bought an '83 crankshaft to replace the possibly twisted, flaky crank that is in the bike now. It has a crazy vibration at 4000 rpm that was never there before.
1. I could run the crank like it is and keep my fingers crossed
2. Bring it to a local shop and have them weld the areas that the factory didnt weld.
3. Send it away and have it welded/trued.
Shipping a ~50 lb crankshaft isnt cheap. Is there anywhere in the northwest or western Canada that does this work?

Yeah, I vote for #1. Seriously, is that a consideration?
streetfighters

 

[gearhead13]

Ok, how about I buy a cheap stick welder and an indexing rod and weld it myself
How much power? I dont know, but it will wheelie when giving it less than half throttle in first.

 

[TheCafeKid]

Ok, how about I buy a cheap stick welder and an indexing rod and weld it myself
How much power? I dont know, but it will wheelie when giving it less than half throttle in first.

Well so will a lots a bikes, that's a product of torque. Or "torques" if you're Jeremy Clarkson.
I dunno, I think you'd prolly be ok until your other crank comes back. Chef was putting 1066 kit to his without even a pin welded crank and didn't twist it..I know yours is prolly more than that....
Wheelies are fun though...I especially like the "drop out" kind when you're powering out of a corner over a hill and the hill drops off on the back side and the wheel just hangs in the air...like a roller coaster

 

[gearhead13]

Well so will a lots a bikes, that's a product of torque. Or "torques" if you're Jeremy Clarkson.
I dunno, I think you'd prolly be ok until your other crank comes back. Chef was putting 1066 kit to his without even a pin welded crank and didn't twist it..I know yours is prolly more than that....
Wheelies are fun though...I especially like the "drop out" kind when you're powering out of a corner over a hill and the hill drops off on the back side and the wheel just hangs in the air...like a roller coaster

Ya, Bill's was an '80? unwelded crank with the 1166, cams carbs etc mostly the same as mine except mine has a larger bore (5mm). And the crank in there as I found out is a factory welded large taper '83 crank. I hope I just got unlucky with this crank. The PO messed with that crank for some reason. I have a few pics of it where it was taken apart and rewelded. You can see on the left end where it was rewelded, and the factory welds at other places:

 

[TheCafeKid]

Was it rusty like that from the get?? Even surface rust is not good on roller cranks...it may not eat the bearings but they'll skip on the surface and sing like Ella Fitzgerald...

 

[gearhead13]

Was it rusty like that from the get?? Even surface rust is not good on roller cranks...it may not eat the bearings but they'll skip on the surface and sing like Ella Fitzgerald...

The engine sat rebuilt in a guys basment for 25 years before I got it, I guess some condensation. I never thought about the bearing surfaces. The valve springs had surface rust too. If the guy had run it at least some there would have been more of an oil film on the parts to protect from rust somewhat.
Pretty much everything in the engine has been replaced, except for the cases. Tranny, block, complete head, valve cover and now the crank.

 

[gearhead13]

I have thought about why someone would take the right end off that crank and I cant see a reason other than to either weld the pin covered by the primary gear that the factory never welded or that one of the bearings and/or the rod on that end had a problem.
I am going to pull the clutch basket out tomorrow and have a good look, might just be that the clutch hub nut loosened off. I might be lucky. I also might try to measure the piston heights to see if there is a measureable twist.

 

[Guest]

I have thought about why someone would take the right end off that crank and I cant see a reason other than to either weld the pin covered by the primary gear that the factory never welded or that one of the bearings and/or the rod on that end had a problem.
I am going to pull the clutch basket out tomorrow and have a good look, might just be that the clutch hub nut loosened off. I might be lucky. I also might try to measure the piston heights to see if there is a measureable twist.

A twisted crank would result in significant vibration at all rpm, not just @ 4000. I'm guessing the culprit lies elsewhere.