Self same happened to my 99 back in 1969 ( UK) completely wrecked the motor , even the mag didn't escape . I finished with bikes and bought a car but still have the desire ( Norton ) Thanks Mike great vid .
Ouch Ouch & double ouch again, catastrophic is definitely not a word over used in this case Mike. That's a real shame so many components with damage & imo just not worth risking to reuse. As others have said, the cause is the important thing to discover, oil or lack of it has to be top of the list. Thanks for sharing guys. atvb t ..
That looks like a nasty big end failure. I like your engine stand though, much neater than the one I cobbled together. Keep up the good work, looking forward to seeing the next step.
Yes, it's going to take a while and some cash to fix this one Geoff. Luckily, Dave got the donor engine reasonably cheap and spare engine cases but the parts certainly start to add up quickly! Cheers, Mike
I owned 2 commandos both 750s both 72 back in the 80s keeping one till Y2K. I had a Norvil Proddy racer which smashed the gearbox completley by trying to select 2nd & 3rd at the same time, there was only a mainshaft left, every thing else was gone! replaced it with a standard 4 speed unit and sold it when they were worth pennies.The other was a MK4 750 roadster which was so unreliable I couldnt get it to stay together for more than 5000 miles, It ate cams like they were goinig out of fashion, one incident was when it was ticking over outside the garage while i was putting on my helmet etc, the motor just stoppedin a nano second and made a loud bang as the bike nearly fell of its stand, the cam follower stellite tip fell off the follower and jammed the cam! then there was the seizing at 80 mph on the M4 outside Reading UK, then there was the layshaft bearing failure, then there was the main bearins failure, then a 40 thou rebore, then the valves wore out with alarming regularity! I struggled on with that bike GF0 493K and finally got rid of it in 2000, it was found by my friend in 2012 after the guy I sold it to sold it to someone else who blwe it up and left it in his garden uncovered for 10 years, even the spokes had rusted away! I rebuilt it for my friend in 2014 and its been stood in his garage ever since. A fast bike ( I did tune it) and would see off Suzuki GS750s as my friend had one and couldnt stay with my and the Norton over the IOM TT. I Bought a Jota in 88 and have had it since, now that is the bike Norton should have built! Still I really enjoyed my time with my commando, I owned it from 18 years of age till I was 40, I'm now approaching 63 and gone all Italian though my daily ride is a Triumph sprint 955i, good channel, keep up the good work!
If the rest of the barrels is ok you could have them resleeved with new liners on a standard bore as you will need new pistons anyway. If the cost of new parts ie crank , rods and a pair of matched crank cases is prohibitive, maybe a donor engine rebuilt is the way to go So you will know what’s inside it . All the best nick
Thanks Grant. It's an inspection cover/cap for the timing chain. This timing cover is off a later MK3 Commando (1975 Electric start model). Best wishes, Mike
Back in '73 had a connecting rod fail and punched a hole through the case on my Commando while going about 85 mph. Not a good feeling when it happened.
Mine was '71, just at the end of the back straight at VIR (Va Intl' Raceway) just before the end of the AAMRR Labor Day 5-hour race. Broke the rod, but the broken case had a hole you could'a covered with your thumbnail; unfortunately, it hit just below the cam journal, timing side, trapping the cam. Welded the case, and line-bored the cam bearings and all was fine with the case. At the end of the first hour, it took 3 gallons of fuel and 1/4 tank of oil, after the second hour, 3 gallons of fuel and 3/8 tank of oil. After the 3rd hour, 3 gallons of fuel and 1/2 tank of oil, after 4th hour, 3 gallons of fuel and 5/8 tank of oil. Never made it to the end of the 5th hour. Valve guides got loose and let too much oil through -- very soon afterwards, I saw that guides with oil seals were available. I'm never run a Commando without seals of the guides since.
The big end obviously gave way but have you been able to see why? Blocked oilway or something? Shame about that crack - I'm sure somebody somewhere will be able to braze it up.
Hello from Germany, what a fatal engine damage! Could you say anything about what could have been the root cause? I am just building up a combat Commando too ( which once runs in Georgia US) and be happy for every tip to prevent such an error.
Rüdiger Schmitz. Hi Rüdiger, I have a new video publishing on Wednesday morning which should hopefully give the final explanation really the root cause of this failure. It’s a simple and very sad tale. Best wishes , Mike
Oh my gosh, my heart sank and this makes me feel sick. The crank can probably be saved, clean up the journal. Use lye or oven cleaner to eat the aluminum off, just please be sure to do so outside with gloves and face protection. Muriatic acid can be used as well but need to be extremely cautious.
My 850 has a delaminated lifter on the left exhaust valve train. Have you seen this before? Yet to pull Down. Nothing Major. Def Looks Like Lack Of Oil With Yours, Spun Bearing? My Vw Did The Exact Same, No Oil Except Case Ok.
Hi from the U.K, suggest you subscribe to Douglas MacRae and watch 72 Commando Racing Mid Ohio, unfortunately he has a similar experience to what your mate had.
Oh Geez! I do applaud Dave's attitude, I'd be crying.
Hehe. The beer helped!!Best wishes, Mike
Self same happened to my 99 back in 1969 ( UK) completely wrecked the motor , even the mag didn't escape . I finished with bikes and bought a car but still have the desire ( Norton ) Thanks Mike great vid .
Thanks very much David. There will be another video on Wednesday that confirms the root cause of this problem. Best wishes, Mike
Ouch Ouch & double ouch again, catastrophic is definitely not a word over used in this case Mike.
That's a real shame so many components with damage & imo just not worth risking to reuse.
As others have said, the cause is the important thing to discover, oil or lack of it has to be top of the list.
Thanks for sharing guys. atvb t ..
Thanks very much Terry. Yes, it’s a real mess, isn’t it! Thankfully he has a new donor engine that should work just fine. Best wishes, Mike
That looks like a nasty big end failure. I like your engine stand though, much neater than the one I cobbled together. Keep up the good work, looking forward to seeing the next step.
Thanks a lot, the video this Wednesday should explain the root cause of the problem. Best wishes, Mike
Expensive repair.
Yes, it's going to take a while and some cash to fix this one Geoff. Luckily, Dave got the donor engine reasonably cheap and spare engine cases but the parts certainly start to add up quickly! Cheers, Mike
I owned 2 commandos both 750s both 72 back in the 80s keeping one till Y2K. I had a Norvil Proddy racer which smashed the gearbox completley by trying to select 2nd & 3rd at the same time, there was only a mainshaft left, every thing else was gone! replaced it with a standard 4 speed unit and sold it when they were worth pennies.The other was a MK4 750 roadster which was so unreliable I couldnt get it to stay together for more than 5000 miles, It ate cams like they were goinig out of fashion, one incident was when it was ticking over outside the garage while i was putting on my helmet etc, the motor just stoppedin a nano second and made a loud bang as the bike nearly fell of its stand, the cam follower stellite tip fell off the follower and jammed the cam! then there was the seizing at 80 mph on the M4 outside Reading UK, then there was the layshaft bearing failure, then there was the main bearins failure, then a 40 thou rebore, then the valves wore out with alarming regularity! I struggled on with that bike GF0 493K and finally got rid of it in 2000, it was found by my friend in 2012 after the guy I sold it to sold it to someone else who blwe it up and left it in his garden uncovered for 10 years, even the spokes had rusted away! I rebuilt it for my friend in 2014 and its been stood in his garage ever since. A fast bike ( I did tune it) and would see off Suzuki GS750s as my friend had one and couldnt stay with my and the Norton over the IOM TT. I Bought a Jota in 88 and have had it since, now that is the bike Norton should have built! Still I really enjoyed my time with my commando, I owned it from 18 years of age till I was 40, I'm now approaching 63 and gone all Italian though my daily ride is a Triumph sprint 955i, good channel, keep up the good work!
If the rest of the barrels is ok you could have them resleeved with new liners on a standard bore as you will need new pistons anyway.
If the cost of new parts ie crank , rods and a pair of matched crank cases is prohibitive, maybe a donor engine rebuilt is the way to go
So you will know what’s inside it . All the best nick
Thanks for the reply Mike . Ps l came to the conclusion with my 99 that a timing side chain snapped .
Ouch David! Thanks for your note. Cheers, Mike
sorry for you! but now you have a nice start for a "shelf decoration engine" or as an "offering to the gods of speed".
Interesting rebuild. What is the screw plug to the upper left of the points cover? Don't see many of those.
Thanks Grant. It's an inspection cover/cap for the timing chain. This timing cover is off a later MK3 Commando (1975 Electric start model). Best wishes, Mike
Mike, that’s a mess 😔 hope you have a strong coffee to say the least 😂
Hehe. We have had a few beers over this one, David. Best wishes, Mike
Grrr! Who at Norton thought the Combat engine was a good idea? Good luck my friends.
My combat engine has been running for over 20 years without issue...though I fitted a decompression plate under the barrel back in '98.
Smart move.
If you understand the few shortcomings of the Combat engine they are easy to correct and the engine is as good as any other 750 Norton.
Back in '73 had a connecting rod fail and punched a hole through the case on my Commando while going about 85 mph. Not a good feeling when it happened.
Mine was '71, just at the end of the back straight at VIR (Va Intl' Raceway) just before the end of the AAMRR Labor Day 5-hour race. Broke the rod, but the broken case had a hole you could'a covered with your thumbnail; unfortunately, it hit just below the cam journal, timing side, trapping the cam. Welded the case, and line-bored the cam bearings and all was fine with the case.
At the end of the first hour, it took 3 gallons of fuel and 1/4 tank of oil, after the second hour, 3 gallons of fuel and 3/8 tank of oil. After the 3rd hour, 3 gallons of fuel and 1/2 tank of oil, after 4th hour, 3 gallons of fuel and 5/8 tank of oil. Never made it to the end of the 5th hour. Valve guides got loose and let too much oil through -- very soon afterwards, I saw that guides with oil seals were available. I'm never run a Commando without seals of the guides since.
The big end obviously gave way but have you been able to see why? Blocked oilway or something? Shame about that crack - I'm sure somebody somewhere will be able to braze it up.
Hi John, yes you are correct. I have a video coming out on Wednesday that explains/confirms the root cause of this failure. Cheers, Mike
Hello from Germany,
what a fatal engine damage!
Could you say anything about what could have been the root cause?
I am just building up a combat Commando too ( which once runs in Georgia US) and be happy for every tip to prevent such an error.
Rüdiger Schmitz. Hi Rüdiger, I have a new video publishing on Wednesday morning which should hopefully give the final explanation really the root cause of this failure. It’s a simple and very sad tale. Best wishes , Mike
Oh my gosh, my heart sank and this makes me feel sick.
The crank can probably be saved, clean up the journal. Use lye or oven cleaner to eat the aluminum off, just please be sure to do so outside with gloves and face protection. Muriatic acid can be used as well but need to be extremely cautious.
Thanks very much Wooley, will do. Best wishes, Mike
JB Weld will fix that, easy :-)
Hehe. Yes, that’s not going to buff out, is it! Cheers, Mike
Nice try...attempting to cheer up Dave by commenting that the hole/crack in the case makes a great handhold during engine removal.
Hehe, I try to do my best to help ;)
My 850 has a delaminated lifter on the left exhaust valve train. Have you seen this before? Yet to pull Down. Nothing Major. Def Looks Like Lack Of Oil With Yours, Spun Bearing? My Vw Did The Exact Same, No Oil Except Case Ok.
Hi from the U.K, suggest you subscribe to Douglas MacRae and watch 72 Commando Racing Mid Ohio, unfortunately he has a similar experience to what your mate had.
Hello street scrambler, thanks very much for this information. I will definitely take a look. Best wishes Mike