Nonsense Found Building Bikes

[Triton Thrasher]

I'm about to start wiring a Commando - what fuses and holders should I use? I just bought a couple of these blue things above
I am thinking I need a 15amp main fuse, then a 5amp specifically for the electronic ignition.

Use inline fuses that look something like this.

 

[cliffa]

Lol, better than a Scotchlok piggyback with NO fuse

And to be fair, the wiring ( when done properly) and the fuse, are held pretty securely.

 

[johnm]

Yesterday I was taking a Combat engine apart to rebuild for a customer. While doing that I inspect things to see what I need to buy, service, or fix. This engine has over 78k miles and was apart once when almost new for a bad piston and never since.

When I took the oil pump off it turned very freely, already means worn, but then I noticed that when I looked into the return port turned the drive gear, it appeared that the gear was not turning and was broken. Took the pump apart and it turned out that the gears were all turning and there were no broken teeth but there was a chunk of metal stuck in that port that looked like the end of a Woodruff key. Also, the gear nearest it had small marks from hitting that metal.

Since the oil pump bolts were not staked and there was nothing to tell me otherwise, I assume it left the factory with that metal in that port. The metal blocked about 60-70% of the passage so the pump could work. The metal came out easily by pushing inward once the gears were out of the way.

It is clear that the metal could not go through the pump, so it was in the pump when the pump was assembled.

My brother bought a new Trident sometime in the early 1970s. When the gearbox failed after 1000 km he pulled it apart to find machining swarf in the box. There was definitely industrial sabotage taking place in the industry at that time.

 

[Richard Tool]

Rode my Commando for a couple years before rebuilding and discovered this when I removed the oil pump - a bit of piston ring must have been in the sump as the rings were all intact. A small piece was forge welded to the pump gears from passing between the gears . I could not turn the pumps past this spot by hand yet it apparently was no problem for the engine to do. I have no idea how long it had this condition. What’s more how did that piece of ring get through a couple of 90 degree turns in the oil way ?

 

[dobba99]

Rode my Commando for a couple years before rebuilding and discovered this when I removed the oil pump - a bit of piston ring must have been in the sump as the rings were all intact. A small piece was forge welded to the pump gears from passing between the gears . I could not turn the pumps past this spot by hand yet it apparently was no problem for the engine to do. I have no idea how long it had this condition. What’s more how did that piece of ring get through a couple of 90 degree turns in the oil way ?
View attachment 122925
View attachment 122926

And another thing is the crack in the crankcase around the main bearing....

 

[concours]

And another thing is the crack in the crankcase around the main bearing....

....where a prybar was used instead of a pinion gear puller.

 

[Richard Tool]

And another thing is the crack in the crankcase around the main bearing....

Looks like a crack but it was a chip on surface.

 

[dobba99]

Looks like a crack but it was a chip on surface.

Yeah right... I think you need glasses mate

 

[marshg246]

I'm rebuilding a Combat engine and gearbox for a guy. When I did the first phase on my cleaning process on the drive side crankcase, I could not get it to like that they usually do at that point. Today, I did the timing side, which was very dirty, but it came out looking exactly as expected easily like normal. So, I redid the drive side. It came out a little better (I have put in new glass abrasive for the timing side). In the end, it will look fine as very little of the drive side shows when in the frame and he primary is installed.

I think the issue is a slightly different alloy mix at the foundry. They are a matching pair but that matching I'm sure happened long after the sides were cast. For one thing, a quick glance and you would think the drive side is a 1974 850 case it is so porous in places. The timing side it more porous than is usually for 1972 cases but no where near as porous as the drive side. Also, the color is slightly different between the sides. I'm sure once I've finished with the final bead blasting and cleaning the will look the same if you don't look too hard. I've done lots of Norton, Triumph, and BSA cases and while these started out nowhere near as bad as some, the drive side has been a real challenge.

 

[cliffa]

I'm rebuilding a Combat engine and gearbox for a guy. When I did the first phase on my cleaning process on the drive side crankcase, I could not get it to like that they usually do at that point. Today, I did the timing side, which was very dirty, but it came out looking exactly as expected easily like normal. So, I redid the drive side. It came out a little better (I have put in new glass abrasive for the timing side). In the end, it will look fine as very little of the drive side shows when in the frame and he primary is installed.

I think the issue is a slightly different alloy mix at the foundry. They are a matching pair but that matching I'm sure happened long after the sides were cast. For one thing, a quick glance and you would think the drive side is a 1974 850 case it is so porous in places. The timing side it more porous than is usually for 1972 cases but no where near as porous as the drive side. Also, the color is slightly different between the sides. I'm sure once I've finished with the final bead blasting and cleaning the will look the same if you don't look too hard. I've done lots of Norton, Triumph, and BSA cases and while these started out nowhere near as bad as some, the drive side has been a real challenge.

Wasn’t there a discussion some time ago questioning whether some of the cases were painted from the factory? And it think it was agreed that some were. Maybe that’s why.

 

[marshg246]

Wasn’t there a discussion some time ago questioning whether some of the cases were painted from the factory? And it think it was agreed that some were. Maybe that’s why.

I've seen painted cases that AFAIK were factory painted but not on 750s that I remember. This engine is one owner. When brand new, it had a piston problem and was dealer repaired and then never apart again until I took it apart with 78k miles.

BTW, the paint on painted cases I've seen was very thin and generally about half missing.

 

[batrider]

My 72 combat cases 2020xx had a thin coat of paint on them from new.
I read long ago that the look can be recreated by spraying aluminum paint onto a rag and rubbing the cases with it. It works well. Spraying it on directly makes it way too thick.

 

[marshg246]

My 72 combat cases 2020xx had a thin coat of paint on them from new.
I read long ago that the look can be recreated by spraying aluminum paint onto a rag and rubbing the cases with it. It works well. Spraying it on directly makes it way too thick.

Was you head also painted?

 

[batrider]

Was you head also painted?

Yes it was

 

[marshg246]

Weird main bearing (06-4118) problems today I've never seen. I heated the cases to 100C and dropped in the new FAG bearing outer races from AN. The to make sure I didn'1t mix up the inner, I dropped them in the outers. Once everything cooled off I tried to take the timing side inner race out of the out race to install it on the crankshaft. It turned smoothly but tighter than usual. With a lot of effort, I got the inner race out. Even though I checked it before installing I figured it was somehow defective so I tried the drive side inner race in the timing side, and it also would not go in without force. That convinced me that the bearing was bad from the factory, so I heated the case and dropped the bearing out and installed another new one - same issue! They are from the same batch made in India but I've never had a problem with FAG bearings before, and the drive side has no trouble from the same batch. The damned things cost over $120 with tariffs, and I have only one more in stock to try. It makes me think that somehow the aluminum is compressing the outer race but that seems like a silly thought.

OK, next problem. The drive side bearing that came in the engine was quite rough and the inner spun on the crankshaft. It wouldn't rock but you could turn it on the crankshaft. OK, Loctite bearing fit 620 should do it. 1st try: Read the instructions put the bearing fit on the leading edge, heated the race normally and it went on half-way and stuck hard. After a lot of effort with a bearing puller got it off and cleaned up the race and crankshaft. 2nd try: Put a thin smear on the crank shaft, heated the race and it dropped on fine. Let it cool and the race would still turn on the crankshaft. Ok with a GREAT deal of effort, got id off and all cleaned up again. 3rd try: Same things but more bearing fit and re-read the instructions - takes time to setup after cooling off! Full curing is about 12 hours. Will check it tomorrow. If this doesn't work will be looking for a crankshaft.

 

[mdt-son]

OK, next problem. The drive side bearing that came in the engine was quite rough and the inner spun on the crankshaft. It wouldn't rock but you could turn it on the crankshaft. OK, Loctite bearing fit 620 should do it. 1st try: Read the instructions put the bearing fit on the leading edge, heated the race normally and it went on half-way and stuck hard. After a lot of effort with a bearing puller got it off and cleaned up the race and crankshaft. 2nd try: Put a thin smear on the crank shaft, heated the race and it dropped on fine. Let it cool and the race would still turn on the crankshaft. Ok with a GREAT deal of effort, got id off and all cleaned up again. 3rd try: Same things but more bearing fit and re-read the instructions - takes time to setup after cooling off! Full curing is about 12 hours. Will check it tomorrow. If this doesn't work will be looking for a crankshaft.

Hard chroming and re-grinding to 0.0005" interference is what Seager Engineering regularly does to crankshafts with loose bearing inner races. Initial plating is between .005 and .020" thick and masking of crankshaft is required for the plating process.

- Knut

 

[mdt-son]

Weird main bearing (06-4118) problems today I've never seen. I heated the cases to 100C and dropped in the new FAG bearing outer races from AN. The to make sure I didn'1t mix up the inner, I dropped them in the outers. Once everything cooled off I tried to take the timing side inner race out of the out race to install it on the crankshaft. It turned smoothly but tighter than usual. With a lot of effort, I got the inner race out. Even though I checked it before installing I figured it was somehow defective so I tried the drive side inner race in the timing side, and it also would not go in without force. That convinced me that the bearing was bad from the factory, so I heated the case and dropped the bearing out and installed another new one - same issue! They are from the same batch made in India but I've never had a problem with FAG bearings before, and the drive side has no trouble from the same batch. The damned things cost over $120 with tariffs, and I have only one more in stock to try. It makes me think that somehow the aluminum is compressing the outer race but that seems like a silly thought.

It's probably not the bearing which is at fault, considering it has a C3 clearance. My suspicion is crankcase deformation. Please measure bearing bore at various depths, circular angles and report back. Did the engine suffer a bang in previous decades?
These open-mouth crankcases are fragile and easily warp as a result of impact or overheating. The good news is that bearing seats can be restored my machining and insertion of a steel sleeve.

- Knut

 

[marshg246]

It's probably not the bearing which is at fault, considering it has a C3 clearance. My suspicion is crankcase deformation. Please measure bearing bore at various depths, circular angles and report back. Did the engine suffer a bang in previous decades?
These open-mouth crankcases are fragile and easily warp as a result of impact or overheating. The good news is that bearing seats can be restored my machining and insertion of a steel sleeve.

- Knut

Engine has 78k miles, apart when brand new for a piston problem, never apart since. Was running fine but smoking a little on the drive side, had a top-end noise, and gearbox had a problem so the owner wanted it checked over. Cylinders are out for a bore. Had the middle version "Superblend" bearings it left the factory with so installing current. Of course, it should not have this problem - this is a LONG way from my first Commando bottom end. Will do some measuring but since the old came out at about 100C and then new dropped in at about 100C and then inner went in the outer with no problem when still hot, I'm a little confused. The outer should not collapse when the case cools enough to overcome C3 or really at all.

 

[marshg246]

Hard chroming and re-grinding to 0.0005" interference is what Seager Engineering regularly does to crankshafts with loose bearing inner races. Initial plating is between .005 and .020" thick and masking of crankshaft is required for the plating process.

- Knut

Way too many good crankshafts available to spend the time to find someone to do that here! I've already got one good 750 crankshaft out for a minor Gorilla-caused repair that has been over three years waiting its turn - no more of that and the other one I sent with it just recently came back costing more that any used crankshaft I ever bought! Better to buy 2-3 used and find one gem! Most I've bought are fully in-spec. In the US, the majority of Commandos are very low milage and there are a couple of "breakers" that can be trusted and a couple more that usually are OK.

 

[mdt-son]

Greg

Re. bearing problem: Clearance while heated is insignificant. If the bearing bore has become slightly elliptical (at ambient temperature) for unknown reasons, the bearing will be pinched diametrically. This may be sufficient to deform the bearing in the elastic domain, causing a locking effect at the inner race. The outer race - although steel - isn't that solid!

- Knut