Were balanced exhaust pipes used on late model 750's?

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comnoz said:
Danno said:
I have some unrestricted short peashooters on my hybrid SS clone and they are LOUD!!!!! with lots of backing honk on off-throttle such as when one shifts.

I always thought any kind of connected exhausts, such as the 850 and early Dunstall crossovers had the potential to enhance performance via added extraction. Paul Dunstall and Gordon Blair obviously thought so when they produced the 2-into-1-into-2 pipes.
Click to expand...

It will enhance performance if the mufflers are restrictive or if the crossover is in the correct place to work with the wave activity in the exhaust.
Unfortunately the 850 crossover is not in the right place to help with wave tuning so your not likely to see much difference unless you have restrictive mufflers.
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Makes me wonder what Dunstall was thinking with his pre-Blair crossover pipes for 750s? My '71 750 had one on it when I bought it in 1973. The crossover pipe was an inconel flex-pipe like you used to see on old Harleys, but otherwise very similar to the 850 type.
 
Be interesting to see the dyno charts that backed up these choices/decisions, wouldn't it....
 
Rohan said:
Be interesting to see the dyno charts that backed up these choices/decisions, wouldn't it....
Click to expand...

Be interesting to pick Dunstall's brain, were he still with us.
 
The old Dunstall tuning book had a drawing of an exhaust system for racing. It had a crossover pipe and he specified how many inches it needed to be from the cylinder head.

I built the exhaust system to his drawing once and it worked very well. Jim
 
Danno said:
Be interesting to pick Dunstall's brain, were he still with us.
Click to expand...

He is still with us ?!

I understood/read he has gone into the property business....
 
Rohan said:
Danno said:
Be interesting to pick Dunstall's brain, were he still with us.
Click to expand...

He is still with us ?!

I understood/read he has gone into the property business....
Click to expand...

If he is still alive, he's around 80 and he's likely retired from any sort of gainful employment. I'd love to hear from him on this subject.
 
Danno said:
Rohan said:
Danno said:
Be interesting to pick Dunstall's brain, were he still with us.
Click to expand...

He is still with us ?!

I understood/read he has gone into the property business....
Click to expand...

If he is still alive, he's around 80 and he's likely retired from any sort of gainful employment. I'd love to hear from him on this subject.
Click to expand...

78 and still working, I believe.
 
Whether they are stock, produce power, or reduce noise, I never use balanced pipes on a Commando. They are too hard to take off or put on, and they always crack around the welds at the spigots for the crossover pipe.

Stephen Hill
 
Agree. The crossover type are simply a bother in every way. I put on single pipes and
straight through silencers from Andover. Work well but they are rather loud when you
run it up.
 
Stephen Hill said:
Whether they are stock, produce power, or reduce noise, I never use balanced pipes on a Commando. They are too hard to take off or put on, and they always crack around the welds at the spigots for the crossover pipe.

Stephen Hill
Click to expand...

I think the cracking is obviously a product of the combinations of stress and vibration. Though the 'black-caps' were replaced with straight through EMGOs the otherwise all original balanced system on my '75 cracked on one side at the down-curve about 25 yrs. ago. Had it welded and have not had an issue since. Though nothing can be done about the vibes, I think maybe the crack was a symptom of installation stress and re-welding it relaxed that stress. The cross connector parts are always well cleaned and coated with an anti-seize so it all comes apart and goes together pretty well.

I have ridden Commandos identical to mine, EMGO mufflers included, but with individual pipes. The take-away for me was no discernible power difference but the balanced system had a somewhat 'rounder' or 'softer' sound. Less of the ear splitting rap the individual pipe system seems to produce, particularly when 'on the cam'.
 
Same experience here. My Mk3 cracked somewhere around 10,000 miles. I used the TIG welder and some stainless rod and welded it right on the bike. You would have to look really close to tell. No more cracks in the last 17,000 miles.
Removing it may be a chore. I do not believe it has ever been removed since it was built. Jim



Biscuit said:
I think the cracking is obviously a product of the combinations of stress and vibration. Though the 'black-caps' were replaced with straight through EMGOs the otherwise all original balanced system on my '75 cracked on one side at the down-curve about 25 yrs. ago. Had it welded and have not had an issue since. Though nothing can be done about the vibes, I think maybe the crack was a symptom of installation stress and re-welding it relaxed that stress. The cross connector parts are always well cleaned and coated with an anti-seize so it all comes apart and goes together pretty well.

I have ridden Commandos identical to mine, EMGO mufflers included, but with individual pipes. The take-away for me was no discernible power difference but the balanced system had a somewhat 'rounder' or 'softer' sound. Less of the ear splitting rap the individual pipe system seems to produce, particularly when 'on the cam'.
Click to expand...
 
John Favill , invented the "Bean Cans"

John Favill , invented the "Bean Cans", his name is listed on the patent. He told me that the "beans" made more power than the "peas"( :mrgreen: ). He factory dynoed them back to back ,back in the day.He also told me that the beans needed the cross over to work correctly. The owners "back in the day" took off the beans because they were too quiet. The aftermarket "beans" are not made the same as originally designed so all bets are off on them.
 
Re: John Favill , invented the "Bean Cans"

jimbo said:
John Favill , invented the "Bean Cans", his name is listed on the patent. He told me that the "beans" made more power than the "peas"( :mrgreen: ). He factory dynoed them back to back ,back in the day.He also told me that the beans needed the cross over to work correctly. The owners "back in the day" took off the beans because they were too quiet. The aftermarket "beans" are not made the same as originally designed so all bets are off on them.
Click to expand...

Be interesting to sight those dyno charts then, wouldn't it.
(or have someone verify them with a stock bike).

That statement doesn't sit too well with magazine tests though ?, that couldn't get
Mk 3 Commandos to anything like the speeds & 1/4 mile times of earlier Commandos.
Witness too folks here who have discarded the plastic airboxes and beancans to get the performance back...

??

There are quite a variety of peashooters around these days too, when you compare them all...
Ditto not all performances are the same ?
 
Re: John Favill , invented the "Bean Cans"

jimbo said:
John Favill , invented the "Bean Cans", his name is listed on the patent. He told me that the "beans" made more power than the "peas"( :mrgreen: ). He factory dynoed them back to back ,back in the day.He also told me that the beans needed the cross over to work correctly. The owners "back in the day" took off the beans because they were too quiet. The aftermarket "beans" are not made the same as originally designed so all bets are off on them.
Click to expand...

Still begs the questions of why Dunstall used the crossover and why the factory did also, before the bean cans were included.

If Norton included it to quiet the exhaust, okay, but I can't imagine Dunstall giving a rat's ass about quiet in the days before sound regulation. Flat track Nortons back in the day were known for their "softer" sound than the other competitors Harley, BSA and Triumph and those pipes were straight-through with megs.
 
Re: John Favill , invented the "Bean Cans"

Danno said:
jimbo said:
John Favill , invented the "Bean Cans", his name is listed on the patent. He told me that the "beans" made more power than the "peas"( :mrgreen: ). He factory dynoed them back to back ,back in the day.He also told me that the beans needed the cross over to work correctly. The owners "back in the day" took off the beans because they were too quiet. The aftermarket "beans" are not made the same as originally designed so all bets are off on them.
Click to expand...

Still begs the questions of why Dunstall used the crossover and why the factory did also, before the bean cans were included.

If Norton included it to quiet the exhaust, okay, but I can't imagine Dunstall giving a rat's ass about quiet in the days before sound regulation. Flat track Nortons back in the day were known for their "softer" sound than the other competitors Harley, BSA and Triumph and those pipes were straight-through with megs.
Click to expand...

In 1973 at least some of the 850s came with a removable mute held into the end of the muffler with a screw.
It was quite restrictive and would have needed the crossover to make the bike run very well.

I have dynoed a bike with open, straight through peashooters with and without the crossover. There was really not enough difference to say one was better than the other.
 
In 1973 at least some of the 850s came with a removable mute held into the end of the muffler with a screw.
It was quite restrictive and would have needed the crossover to make the bike run very well.
Click to expand...
My '73 750 came with the removable mutes (and non-crossover pipes) along with a pair of 220 main jets to be used with mutes and 230's to be used without them! I still have the mutes, but the mufflers disintegrated years ago.
 
How did it go though ?

I had a 73 850 with those peashooters with mutes, and the original balanced pipes.
Felt pretty strong - but there were no real hills anywhere near where I lived then.
It was quite a bit louder with the mutes removed, but didn't seem any faster or stronger.
Not that I measured it in any way - or changed the jetting - one size is none too significant ?
 
Rohan said:
How did it go though ?

I had a 73 850 with those peashooters with mutes, and the original balanced pipes.
Felt pretty strong - but there were no real hills anywhere near where I lived then.
It was quite a bit louder with the mutes removed, but didn't seem any faster or stronger.
Not that I measured it in any way - or changed the jetting - one size is none too significant ?
Click to expand...

Frankly, I didn't notice any difference and only a slight reduction in noise with them in. Of course I was a 23 year old kid at the time and wanted as much growl and grunt as I could get.

I found the 230 to be a little too rich without the mutes, so I installed the 220's. They are still in there.
 
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