Simply put, is this a show-stopper?
http://i.imgur.com/5GIJ01b.jpg
http://i.imgur.com/ybYAfuE.jpg
http://i.imgur.com/oDqD3gH.jpg
http://i.imgur.com/5GIJ01b.jpg
http://i.imgur.com/ybYAfuE.jpg
http://i.imgur.com/oDqD3gH.jpg
Crack in the case...
- Thread starter Aleks
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It's not really a show stopper, but it should be addressed at some point and at your earliest convenience. This is repairable and although you will have to pull the motor, you may not have to split the cases.
In the mean time, make sure things are tighten properly( not too tight nor too loose) and make sure the isolastics are adjusted properly.
In the mean time, make sure things are tighten properly( not too tight nor too loose) and make sure the isolastics are adjusted properly.
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J.B. weld . :shock:
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Some semi stiff set up JBW put place with tape dams then a spriz of grey sliver paint would cover it up and not prevent later removal. But JBW has nano iron particles so may contaminate to alu weld later. This is not near sealing surface so nil sealing distortion if welded. But if not a big deal for a non racer structurally then pretty easy and permanent to JBW cosmetically. When almost set up so no sag can remove tape and press-tap sand paper in to mimic the cast texture enough only your hair dresser will know for sure. JBW in such rough textured area will definitely beef it up some. Might want to turn bolt a once before full set up just to ease it later removal but would not risk getting JBW inside the exposed hole. JBW only adheres to surface texture by pure grip lock not much by just stickyness.
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Regarding Mr Goforths broken crank.....I cannot help but wonder where his crank broke...would I be right in thinking it occurred to th drive side at the point of the big ends outer 90 thou radius??? If so I do hope the replacement crank was first checked inside to see if the STRESS RAISER the stress raiser not been left directly beneath the big ends outer 90 thou STRESS REDUCING radius but correctly as per the drawing within the flywheel web where it would not cause a problem......and if it was directly in line with the 90 thou radius that the crank was x rayed BEFORE using it to ensure it was not already starting to fail.......and if not already on the way to failure that the stress raiser was removed so ensuring the crank had a much better chance of staying as a 3 piece lump rather than a 4 piece one!!
Mr Hopwood summed up the position of the STRESS RAISER the idiots at 'Norton' had introduced when shoving a big drill upthe inside of the drive side half and not doing the job as per the drawings rather well when he looked at the sketch showing its position I sent him..... Mr Hopwood wrote .......'it leaves something to be desired in technique'. Mr Hopwood (and Mr Hele) were very polite Gentlemen. Personally it was NOT the description I have ever used but I am never polite where incompetence is concerned,especially my own!!!
Mr Hopwood summed up the position of the STRESS RAISER the idiots at 'Norton' had introduced when shoving a big drill upthe inside of the drive side half and not doing the job as per the drawings rather well when he looked at the sketch showing its position I sent him..... Mr Hopwood wrote .......'it leaves something to be desired in technique'. Mr Hopwood (and Mr Hele) were very polite Gentlemen. Personally it was NOT the description I have ever used but I am never polite where incompetence is concerned,especially my own!!!
My crank broke at the junction of the left main bearing journal and crank cheek. I had found the inner race was loose on that side and the guy who rebuilt it sent it off to be built back up and reground to size. I'm guessing the shop that did it didn't radius the journal properly. He rebuilt my engine again for free and doesn't use this approach any more for cranks with loose main bearings.
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Always only one best answer to almost all Commando issues, start from sludge trap and spend your way back out.
To repair-fill that big an area will distort and intrude alu into the hole so redrill-ream likely required. There are likely other hidden cracks below surface at other corners of the mounting flats. Might consider 7/16 bolts as many racers have done. To get oil pollution out must heat over 600-700 F for some time to move-evaporate oil vapor and burn off. I and my welder appreciated the effective use of propane pancake heater on a hose to hand direct heat and aim at another area while welder does his ugly thing. Bolting cases together may help seam distortion but makes need of copious heater to over come the large heat dispelling mass of both cases. A small torch like that used to cut say 3/4 inch steel just can not keep up so thermal differences will increase distortion.
Likely other hidden cracks at the other mounting flats and each one ground out to then be melted deeper, ugh, then filled back in adds its lip curling to seam matting. The corners proud fill ins must be ground back to a radius and maybe beaten on to get seams to close enough for goop to seal. If welder gets its a bit wrong a thumb sized area can just flow away...
To repair-fill that big an area will distort and intrude alu into the hole so redrill-ream likely required. There are likely other hidden cracks below surface at other corners of the mounting flats. Might consider 7/16 bolts as many racers have done. To get oil pollution out must heat over 600-700 F for some time to move-evaporate oil vapor and burn off. I and my welder appreciated the effective use of propane pancake heater on a hose to hand direct heat and aim at another area while welder does his ugly thing. Bolting cases together may help seam distortion but makes need of copious heater to over come the large heat dispelling mass of both cases. A small torch like that used to cut say 3/4 inch steel just can not keep up so thermal differences will increase distortion.
Likely other hidden cracks at the other mounting flats and each one ground out to then be melted deeper, ugh, then filled back in adds its lip curling to seam matting. The corners proud fill ins must be ground back to a radius and maybe beaten on to get seams to close enough for goop to seal. If welder gets its a bit wrong a thumb sized area can just flow away...
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Aleks. My crank case did the same thing but on the other crankcase half to what yours is shown. Half the lug broke of broke off completely. I had noted Jim Comstock had mentioned about not heating up the cases too much while welding. His advise was to preheat the case to about 100 degrees C and weld carefully and not get the area too hot or it would soften the alloy. He also mentioned drilling out to the next size bolt.
In my case, I chose to use new bolts where the unthreaded part went through all the way, necessitating using some plain washers to enable the new lock nuts to tighten. Have a look at the first photo you supplied and you will see where the nut is on the bolt, I would guess that the threaded portion of that bolt went all the way into the alloy by probably 1/2 inch. Threads are not good bearing areas, and will chew into the steal g/box frame as well as the alloy case.
I went with the standard bolt sizes but went to a lot of trouble making up shims to take up the slack. Now my cases are tight on the g/box frame before tightening the lock nuts.
the difference was noted in the fact that I had to loosen the primary adjustment quite a lot to get the primary gear back on, and then had to loosen the rear chain as well to get the rear drum and wheel on.
I noted that when I pulled the engine out, those bolts were still bloody tight. The design is not ideal for bolting 2 structural pcs together.
Dereck
In my case, I chose to use new bolts where the unthreaded part went through all the way, necessitating using some plain washers to enable the new lock nuts to tighten. Have a look at the first photo you supplied and you will see where the nut is on the bolt, I would guess that the threaded portion of that bolt went all the way into the alloy by probably 1/2 inch. Threads are not good bearing areas, and will chew into the steal g/box frame as well as the alloy case.
I went with the standard bolt sizes but went to a lot of trouble making up shims to take up the slack. Now my cases are tight on the g/box frame before tightening the lock nuts.
the difference was noted in the fact that I had to loosen the primary adjustment quite a lot to get the primary gear back on, and then had to loosen the rear chain as well to get the rear drum and wheel on.
I noted that when I pulled the engine out, those bolts were still bloody tight. The design is not ideal for bolting 2 structural pcs together.
Dereck
hobot said:
Thank you kindly for the wisdom you shared. I'll reference this thread repeatedly once I start talking to welders. If anyone knows any who'd be able to undertake a repair such as this AND they happen to be in Canada, by all means, share their whereabouts.
kerinorton said:
Imagine my relief Dereck to hear that I'm not alone. Thank you for the reply. If you don't mind me asking, do you recall what size bolts you ended up going with? Any photos of the finished product I may be able to spy?
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That crack has really progressed. When you zoom in on the pictures the crack appears rather wide open near the engine mount and goes nearly all the way up to the next engine case through bolt. It looks like there was significant displacement in the crack (open) near the engine mount where the chunk is missing.
Since you are pulling it down, assess as you go along with the dismantle and have a contingency plan "B" (replacement cases) or at least a replacement drive side. There is a fair chance you may be able to weld repair it. Please keep us posted.
Since you are pulling it down, assess as you go along with the dismantle and have a contingency plan "B" (replacement cases) or at least a replacement drive side. There is a fair chance you may be able to weld repair it. Please keep us posted.
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Best Alu welders to take it too might be a traditional auto machine shop that welds up ugly distortions and missing parts in Alu heads then takes it back down to perfect again. They are pretty good at tracking down or predicting where to melt into and build back. Maybe better to remove most the busted boss to start new then grind to shape, texture then drill.
If mine to use like I do plain ole 72Trixie > drill out hole some, tape ends squarish, mask around the boss warm till about oil smoking then fill with fresh free flowing JBW to flow into expanded cracks, helped by super magnets pulling it outward into cracks to set up under great compacting tension cooling then finish off with hand tools and drill press.
If mine to use like I do plain ole 72Trixie > drill out hole some, tape ends squarish, mask around the boss warm till about oil smoking then fill with fresh free flowing JBW to flow into expanded cracks, helped by super magnets pulling it outward into cracks to set up under great compacting tension cooling then finish off with hand tools and drill press.
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kerinorton said:
Imagine my relief Dereck to hear that I'm not alone. Thank you for the reply. If you don't mind me asking, do you recall what size bolts you ended up going with? Any photos of the finished product I may be able to spy?[/quote]
Hi Aleks. I stuck with the standard sized bolts [ 1 x 5/16" and 2 x 3/8 " ] but made sure the plain shanks on the new bolts were a wee bit longer than the combined length of the crank case and the g/box frame. I used 2-3 washers to make up the difference as needed. I made up tubular shims to take up any slack between the bolts and the housings. [ please not, I made up shorter ones to fill the gaps in the steel frames ] I also used lock nuts on the threads.
Not so good in the photo department.
Hope this helps. PM me if you need to.
Dereck
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- May 22, 2015
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My upper mounting lug was cracked , right side. Some fool over torqued I'm sure. I took it to an automotive welder who works w/ AL a lot. My fear was he would heat the case seal and it might leak afterwards but since the crack is at the top, there's no oil laying in there. He welded it fine. Looks like new now. Now I sleep better. I will say, I kept the piece that broke off. He had to add a lot of AL anyway and grind it back down so I'd say this is an easy fix for a crack welder as long as you take the motor out.
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- Nov 18, 2005
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When my crankcase cracked near to where yours did, I took it to someone who really knew British bikes and welding.
He took the crankcases to a chroming plant who put it in a trichloroethylene degreasing solvent for TWO WEEKS! An engine that has been soaking in oil for 40 years needs all that oil sucked out of the porous castings.
When he welded it, he bolted both halves together to make sure they expanded and contracted together .
He took the crankcases to a chroming plant who put it in a trichloroethylene degreasing solvent for TWO WEEKS! An engine that has been soaking in oil for 40 years needs all that oil sucked out of the porous castings.
When he welded it, he bolted both halves together to make sure they expanded and contracted together .
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