600cc Matchless twin, worn crank splines.

[piman]

Hello all,

my son in law's 600 twin matchless engine has badly worn splines on the crank.




One suggestion I have had is to use Belzona. Has anyone had a successful cure for such a repair?
I have MMA, TIG and Oxy/acetylene at my disposal.

Thanks,

Alec

 

[lchris21]

Weld it up and re-cut the splines. Belzona is not really a power transmission product, unless you glue the sprocket/gear/clutch on......not recommended

 

[Pete.]

Belzona would be a waste of time. I would weld, turn, mill if it truly is scrap the way it is.

 

[Chris Stevens]

Hello all,

my son in law's 600 twin matchless engine has badly worn splines on the crank.

View attachment 79251


One suggestion I have had is to use Belzona. Has anyone had a successful cure for such a repair?
I have MMA, TIG and Oxy/acetylene at my disposal.

Thanks,

Alec

See if you can find a good used crank. Unless you can do the machining work yourself, the cost of repair will be quite a bit more than a used part.

 

[cumbriasteve]

A job for a professional machinist in my opinion unless you can find a replacement, they will be out there sitting and going dusty on some shelf but finding it is the nightmare.

You should be able to locate someone near you but if not:

This guy is a magician with restoring engine parts, he is also a lover of classic bikes and I would trust him 100%, obviously you would have to post the part to him but worth a phone call I would think, nothing to do with me other than I have had work done and admired his skills for years.

http://www.192.com/atoz/business/wh.../05c5793fe358f3c0ab171457bf3e62014c8cf50e/ml/

 

[piman]

Hello all,

thanks for the comments. Regarding welding and I'm assuming the crank is cast iron what rod would be suitable, I only have a few basic rods, (MMA stainless ( I forget the number), some dissimilar cast rods and 6013s, 3016 stainless tig rods and mild steel tig rods plus some brazing rods (Nothing special)?

I have no problems with doing the machining.

This You tube video is something I found :-

I do appreciate that the point loading on a small section could be greater than on a very large machine and that the mass of plastic repair will be very small so will be relatively weaker. (I know it is an advertising video)

 

[winchman]

Coupe of options I suspect the bit that fits on is also worn?
I would just weld it and file / grind it back in to shape, I have done it a few times at work and never
had any issues.
Cost of Machining would possibly kill any other repair.
If its not a keeper I would just weld the other bit on and look for another crank to replace at a later date

 

[Screwdriver]

Might be easier and cheaper to effect a repair on the mating part.

 

[Chris Stevens]

Hello all,

thanks for the comments. Regarding welding and I'm assuming the crank is cast iron what rod would be suitable, I only have a few basic rods, (MMA stainless ( I forget the number), some dissimilar cast rods and 6013s, 3016 stainless tig rods and mild steel tig rods plus some brazing rods (Nothing special)?

I have no problems with doing the machining.

This You tube video is something I found :-

I do appreciate that the point loading on a small section could be greater than on a very large machine and that the mass of plastic repair will be very small so will be relatively weaker. (I know it is an advertising video)

I seem to remember the cranks on AMC twins were nodular iron, and had problems with breakages? I guess that means used parts are going to be very difficult? However if they are iron, repair is going to be far more difficult than steel, and I would suggest contacting the owners club and asking if they might be able to assist.

 

[octo0072000]

i doubt the crank end is cast iron
I would also suggest contacting the owners club

 

[jordan1]

I use Belzona for suitable applications, this certainly ain't one of them. I restore bikes [when I get the time] and find owners clubs invaluable, especially in situations such as yours.

 

[Seadog]

The twin crankshafts are all cast iron, including the spline. The later ones, very sought after, which were used on the CSR models were also cast but were nodular iron (also known as ductile or spheroidal graphite iron) for increased strength, to match the performance increase for, what was after all, originally a 500cc engine.

 

[Pete.]

Aah well forget my solution then. My next best offering would be cut the raised spline to be sunken ones and braze in some keystock, then turn it down.

 

[Seadog]

That's a good solution. A lot of work though, so could be costly if you're not in the position to do it yourself.

 

[jordan1]

Aah well forget my solution then. My next best offering would be cut the raised spline to be sunken ones and braze in some keystock, then turn it down.

Won't that weaken the shaft?

 

[Bill Edwards]

Aah well forget my solution then. My next best offering would be cut the raised spline to be sunken ones and braze in some keystock, then turn it down.

I think that's an excellent idea.


For welding it, if you're worried about it being cast iron (which I wouldn't expect) touch it to a grinder, red sparks are cast.
Regarding MMA, for steel of unknown composition 312 dissimilar is the choice (i.e if it's weldable it'll weld it), for ordinary steel 6013 is fine. But TIG is probably a better method I'd have thought, and whatever welding method you'd need to put thought into distortion.

Btw, cast iron rods aren't the same as dissimilar.

 

[piman]

Hello Bill,

a poor description about the cast rods, they were given to me by a welder friend and are designed to weld cast iron (Which I have done a few times) but will weld mild steel to cast iron also?

While I like Pete's idea of letting in key steel, that is a lot of work and I'd prefer to just build up the worn areas, SIF bronze maybe? The drive sprocket has a spring loaded device which I assume is to cushion the drive. I've never seen on ebefore but I'm more of a car than bike man.

Alec

 

[Pete.]

I think the hardest bronze is only about as hard as the softest cast iron.

 

[Bill Edwards]

Cast rods have a high nickel content, whereas dissimilar are stainless. As to welding mild steel to cast I've done it with cast rods, but when buying them I've been told there are two kinds - i.e one for cast to cast and one for cast to steel. I don't know the difference between then, perhaps it's one for @TechnicAl - I'd be interested to know myself.

As to building up the worn splines with braze, I'd say no. After all, it's basically brass and isn't up to it, the best places for braze are joints where there are two parts close (i.e just touching) where the braze is drawn in by capillary action and fuses it everywhere but not relying on being built up for strength. I think I'm explaining badly!
Pete's idea would have it where the keystock is being held in position with the braze and the power transmission isn't relying on the shear strength of the braze. As to how much work is involved in that I don't know, I'd have thought it as easy as a slot drill to make the slot, drop it in and after brazing just clean up much like you would if it had been welded. But, I'm not a machinist.

 

[Chris Stevens]

Hello Bill,

a poor description about the cast rods, they were given to me by a welder friend and are designed to weld cast iron (Which I have done a few times) but will weld mild steel to cast iron also?

While I like Pete's idea of letting in key steel, that is a lot of work and I'd prefer to just build up the worn areas, SIF bronze maybe? The drive sprocket has a spring loaded device which I assume is to cushion the drive. I've never seen on ebefore but I'm more of a car than bike man.

Alec

If you can find anyone to do it for you, powder welding with some sort of hard facing powder would be the best possible way to rebuild those splines. Second best and something you can do yourself would be Tig brazing, using the appropriate rods.