Exhaust Headers (Down Pipes)

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HI - can anybody please advise if the down pipes on a 71 - 750 commando are symmetrical? My left hand pipe leaves the exhaust nut in line whilst the right hand pipe is angled allowing the pipe to run closer to the bottom frame rail which is OK but it skews the silencer at a different angle. The pipe fits but looks odd.
 

concours

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Left is aftermarket replacement, RH is original design.

“looks odd” compared to a Triumph?;)
 

maylar

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HI - can anybody please advise if the down pipes on a 71 - 750 commando are symmetrical? My left hand pipe leaves the exhaust nut in line whilst the right hand pipe is angled allowing the pipe to run closer to the bottom frame rail which is OK but it skews the silencer at a different angle. The pipe fits but looks odd.
The right side tucks close to the frame to clear the kickstart lever. Below, an aftermarket pipe on the left vs an original Norton pipe -

1596622296473.png
 

concours

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The OEM design requires the Fabricator to have an accurate angled jig to set up the spigot to the proper (compound) angle.
It appears most fabricators/purchasing agents cheap out and just make a self aligning slip fit like most other bikes use.
 
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How many commando owners know that from the 1949 model 7 that the exhaust ports and therefore the pipes were each angled (splayed ) 20 degrees from straight ahead. Starting in 61 with the manxman the semidown draft head splay was 40 degrees making the pipe bend more difficult to lay close and be tucked in to the frame rails. A Norton factory compromise was to have the pipes have a offset outlet at the head/ exhaust spud, I have seen it on 71, I think it was on 72. Original 73 750?

By the 850 the pipe skew was gone. Pipe part numbers have changed probably reflecting the factory changes. I doubt the aftermarket's recreations of early pipes are correct and are some of the cause of the kicker hitting the mufflers.
FWIW current aftermarket "SS" pipes have the skew in them.
The above is of course all speculation and if wrong, better factory documentation by experts will come forth. I hope
 

maylar

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I believe that the angled pipe in my photo above is from a 72 750. Very rare to find them now. I had it re-chromed and it's on my bike now.
I had an aftermarket set that was horrible. Not sure who made them. The right side absolutely would not line up with the silencer mounts, it was about 3 inches away. The vendor gave me a different brand that fit (but with kick lever interference).

1596631616597.png
 
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Since we know there are MkIII's out there factory fresh it would be interesting to see how they measure up and how much interference the kicker has.
 

maylar

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Since we know there are MkIII's out there factory fresh it would be interesting to see how they measure up and how much interference the kicker has.
The MKIII kicker is different.
 
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Since we know there are MkIII's out there factory fresh it would be interesting to see how they measure up and how much interference the kicker has.
MKIII is so totally different, cone seat in the port makes the flared pipe adjustable.
My 5 mile new original MKIII has no pipe problem and as mentioned the extended kicker offsset

Does not address OP question about early R/L symetrical spud/pipe skew.

Below are 750 pipes with symetrical skew
71 pipes RH061607/LH061606
???
72 pipes RH063376/LH063375 same for 73
I also believe my original 72 combat pipes had the skew. I still have them on the rack somewhere mixed in with about another 23+ sets of pipes
No evidence yet that low level interstate/interpol had any skew. They were obviously a new bend up configuration.
 
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Hi - does anybody have an idea what the noise level is for a standard 750 commando. I'm doing a track day at Cadwell Park next week & just wondering if I will have a problem with noise
 
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