An Exhausting Question

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robs ss

robs ss

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PURISTS - AVERT YOUR EYES!

Without wanting to start a discussion on what the "correct" pipes and mufflers are for different Commandos I have one question which, hopefully, someone can help me with.
Is there anything fundamentally different between 750s & 850s and between Roadsters & Interstates that would prevent an unbalanced set of pipes and peashooters fitting them all?
I'm not interested in the nuances of post '74 bikes (LH change & e-start).
 
I have a similar question.
I am rebuilding my MK 3 at the moment and want to use non balanced headers, mainly to keep costs down.
Is there a difference in performance and which year should I use?
 
Seagull said:
I have a similar question.
I am rebuilding my MK 3 at the moment and want to use non balanced headers, mainly to keep costs down.
Click to expand...

Some non MK 3 headers foul the primary chaincase on Mk 3 , Mk 3 specific non balanced header pipes are available .
 
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Thanks Sam - my last line in the opening post was trying to eliminate confusion with Mk3. Maybe topic for another thread.
How about everything - post 70 - before that?
 
robs ss said:
Thanks Sam - my last line in the opening post was trying to eliminate confusion with Mk3. Maybe topic for another thread.
How about everything - post 70 - before that?
Click to expand...
Yes, I just replied as Seagull had asked. In response to yours, I'm sure all pre mk 3 will fit each other and you will be aware that genuine early Interstate down pipes levelled off at the end so the silencers gave clearance to any luggage fitted.
 
robs ss said:
Thanks Sam - my last line in the opening post was trying to eliminate confusion with Mk3. Maybe topic for another thread.
How about everything - post 70 - before that?
Click to expand...
AN seem to list only one part number for unbalanced upswept Roadster type pipes.
 
And obviously the appropriate exhaust rose and fittings
 
Leaving the MKIII out...
All commando pipes WILL interchange using correct matching mounting hardware
The main consideration is the port/rose hardware compatibility.
All ports are 3/4 deep.
1. early thick flange style =long rose
2. 850 collet = short rose
3. aftermarket flare/cone (oem MKIII style) = short rose

Is there a difference in performance and which year should I use?
Minor difference yes, normally beyond the technical capability of most to notice or compensate.
 
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The difference between balanced and non balanced is the sound.

I have a MK3 with peashooters, with the balanced pipes it is quieter than with unbalanced.
But I haven`t measured it.
With balanced pipes the sound is still present.
 
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The really early fastback unbalanced pipes tucked in a lot more. These are the ones with low level Atlas style mufflers. Here’s the comparison.

An Exhausting Question
 
I have a right side pipe like that.

Compared to a shitty aftermarket bend -

An Exhausting Question
 
Thanks very much Sam and others that have assisted me.
Now to find the Headers for Mk3, if anyone has suggestions of a supplier that would be wonderful.
I have also posted a question on a replacement Starter if someone could assist.
Thanks again Ian
 
Thanks everyone for your combined input - the situation with exhausts is much clearer to me now.

What I take from this, in summary (excluding Mk3s), is that it appears we have almost complete freedom to fit whichever style we choose/like.
  1. There may be a performance and noise difference with/without balance pipe.
  2. Different flange thicknesses will require different roses.
  3. Dimensions of support bracketry may differ between systems.
Other than that, ignoring (at my/your peril) period/model correctness, we have complete freedom of choice.
 
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Seagull said:
Thanks very much Sam and others that have assisted me.
Now to find the Headers for Mk3, if anyone has suggestions of a supplier that would be wonderful.
I have also posted a question on a replacement Starter if someone could assist.
Thanks again Ian
Click to expand...

In the US Commando Specialties sell them from time to time, I'm pretty sure they are LF Harris manufacture in the UK, so that will mean they are produced in batches and so dealers can run out of stock. Keep an eye on ebay UK, and your usual suppliers in Australia.
 
Also can recommend Viking in New Zealand. J not sure if this is still current but there used to be a problem with pattern headers [possibly 3rd world sourced] that fowled the kickstarter not sure if that is still relevant.
 
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illf8ed said:
The really early fastback unbalanced pipes tucked in a lot more. These are the ones with low level Atlas style mufflers. Here’s the comparison.

View attachment 19853
Click to expand...
I have a new timing side like yours with the inward kick at the weld. I would like to find a new one like it for the drive side. these are for a roadster with the upswept peashooters.
 
I wonder if the newer style that goes straight out might give a bit more power than the kicked in type. Or it could work the other way around.
Test required.

Glen
 
I think this pipe angle isssue is somewhat of a carry over from the early NHT heads 20degree splay/pre down draft heads.
Of course does every one knows all NHT down draft heads exhaust ports are splayed 40degrees from straight ahead...It took a while for the pipes to get to 40 degrees=straight out of the port.
 
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