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Discussion Starter · #1 ·
I recently cracked a small section of my cases when disassembling the motor on my '68 T120R. It's the part beneath the timing cover that protrudes out to hold the shaft that the idler gear rides on. I'll post pics. I'm pretty sure it can be fixed with acetylene or tig, however I have absolutely no experience with either. I searched around on the site and didn't find much. I also searched around online and found a few shops that claim that's what they specialize in but am not sure who to trust, I want it done right. Any suggestions? Also does anyone have experience fixing old cases themselves? I'd like to know what is the best method for doing this so I can read up on it, Tig, Braze, Heliarc, Exc. Also what material should be used for filler. One site was saying "super alloy 5".
 

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That could be tig welded, if you mouthed the cracks out. How your going to machine it back round? Clean it before you bring it to a welder.

Edit: A good welder will know what he wants to fill it with.
 

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Man that blows! I wonder if you'd just be better off replacing that whole case half? They're cheap enough, and easy enough to find... and the numbers are on the other half, so no one would ever know.

Just a thought. Good luck!
-BK
 

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Eeek. You're sunk. Don't replace a case half, you're just waiting to split your crank in half. Cases are line bored from the factory in matched pairs. Mismatching halves will insure your main bearings are not in line with one another, putting undue stress on THE most stressed member in your motor.

You crack is also very close to your timing side main bearing. Too much heat around that location could cause huge problems with bearing fitment after repair is done. Stuff a rag with ice in it in the bearing recess while welding, or you'll regret it!

Keep us posted.
 

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Discussion Starter · #6 ·
Does anyone have experience repairing cases themselves or know of anyone on this site that might? Or know know of a good shop for it? Ive seen it done on countless cases so I'm sure it can be done...
 

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Eeek. You're sunk. Don't replace a case half, you're just waiting to split your crank in half. Cases are line bored from the factory in matched pairs. Mismatching halves will insure your main bearings are not in line with one another, putting undue stress on THE most stressed member in your motor.
Didn't think of that! I was SURE swapping the half was a no brainer! Is it possible to have them re-bored to match? Just trying to think of what is the safer and more time/cost efficient solution.

Thanks for the info!
-BK
 

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Didn't think of that! I was SURE swapping the half was a no brainer! Is it possible to have them re-bored to match? Just trying to think of what is the safer and more time/cost efficient solution.

Thanks for the info!
-BK
We swap case halfs all the time, the reason there is a ball bearing on one side and a roller bearing on the other is to allow for some mis-alignment of the crank and the cases. all Triumph and Norton cranks flex at high RPM and the roller or super-flex bearings allow for this. It's not the main bearings you need to worry about it's the cam bushings that need to be line bored, a very simple process with the proper tool.
Case swapping is the answer.
 

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Anything metal can be fixed, welded then aligned with a mill if a person knows how to do it. The guy I use locally for this sort of thing is quite expensive because he is extremely good, but not compared to a mismatched case in my opinion. Also try Don Hutchinson Cycles, I understand he has done these specific fixes before. And although it is preferrable in my opinion to keep matched cases, they can be mismatched with success as long as mating surfaces are good such as where the cylinder bolts on. Also remember when switching cases to get both sides with the same thread type on the covers. Nothing is peskier than having 26 TPI on one side and 20 TPI on the other.
 

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We recently repaired a 1955 Speed Twin engine where that hole had worn out, and the idler gear spindle was moving around. Welded the cases up, milled them, and installed a new spindle. Engine runs great now, but I have no idea what it ran the customer (not my department). You are welcome to call up the shop and inquire as to whether or not we would be willing to do it again. I would imagine that you should be able to find someone local to do the work, but if not, just ask for Dennis when you call.

I have to agree with most everyone else though, case side swapping would be the easier, and cheaper route.

-Shaggy
 

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We swap case halfs all the time, the reason there is a ball bearing on one side and a roller bearing on the other is to allow for some mis-alignment of the crank and the cases. all Triumph and Norton cranks flex at high RPM and the roller or super-flex bearings allow for this. It's not the main bearings you need to worry about it's the cam bushings that need to be line bored, a very simple process with the proper tool.
Case swapping is the answer.
Ya don't mention the need to remachine the barrel deck.Surely if you are going to replace one side would it not be easier to replace both cases with a matched set?
 

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Ya don't mention the need to remachine the barrel deck.Surely if you are going to replace one side would it not be easier to replace both cases with a matched set?
and then you would replace your registration with the new numbers
 

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That case is weldable it will take more than just welding. It will need to be machined down a bit then build back up with weld solid and remachined. But even before that what I think I would do is machine down the boss a bit then bevel out the cracks and fill them in, then proceed to continue building up weld from there (Tig welding with 5356 wire)
 

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When I found my 67 650 the front motor mount was broken off and was looking for new cases. Brought the motor to a guy in WI and he said they could be fixed and I believe they were heliarked. You can't even tell they were repaired. Resurfaced after repair and no leaking. If I remember to do both cases it was about 150.00
 
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