Balanced Exhaust==>Un-Balanced Swap?

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Tornado

Tornado

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I'm planning to swap out the MKII 850's balanced headers with a nice unbalanced set I acquired recently. I do plan to get fresh crush seals....but is there any issue re-using my existing finned lock nuts and the underlying bits & bobs?
 
Twister,
You would probably need to re-jet your carbs on the main's. If you reuse the cross-over style finned rose nuts then you stand a chance of stripping out your head over time. These are shorter and are used with collars. So the thread engagement is less. I would get the 750 style bronze ones as the threads on those are longer and give you more engagement. Tell me how I know. o_O
Cheers,
Thomas
 
Does it depend on what the replacement unbalanced pipe heads look like? Can't be certain of their heritage (750 or 850, MK??)? I have never removed the existing locknuts so don't know what is underneath and if compatible with replacement pipes yet.
Re. Re-jetting, yes, that will be addressed as will opening up the heavily muted rear exit points for all the LOUDNESS ;-)
 
The separate downpipes are louder than the balance pipe ones
So give it a try first before you mess with the silencers
Of course it all depends how loud you want the bike!
Be warned it's not unusual for downpipes not to fit right on commandos, make sure nothing is under strain when you bolt them up
 
Tornado said:
Does it depend on what the replacement unbalanced pipe heads look like? Can't be certain of their heritage (750 or 850, MK??)? I have never removed the existing locknuts so don't know what is underneath and if compatible with replacement pipes yet.
Re. Re-jetting, yes, that will be addressed as will opening up the heavily muted rear exit points for all the LOUDNESS ;-)
Click to expand...

You have this with the cross over: https://andover-norton.co.uk/en/shop-drawing/194/850-exhausts-muffler-mutes-passenger-footpegs
#17 collet and 25 exhaust lock-ring chrome short. 26 and 27 seal washer. when you run single down pipes off the head you don't have the collets. as per the 750 type exhaust: https://andover-norton.co.uk/en/shop-drawing/79/750-exhausts-muffler-mutes-passenger-footpegs
#10,11 and 12. notice # 10 is long. Or go to the early 750 type #10: https://andover-norton.co.uk/en/sho...kring-chrome-long-early-type-d12-167-nm18092-
You can get these in Chromed bronze which expand and contract the same as the alloy head which doesn't have a tendency to loosen from vibration.
Hope that helps.
Cheers,
Thomas
 
baz said:
The separate downpipes are louder than the balance pipe ones
So give it a try first before you mess with the silencers
Of course it all depends how loud you want the bike!
Be warned it's not unusual for downpipes not to fit right on commandos, make sure nothing is under strain when you bolt them up
Click to expand...
My understanding is that the balance pipe helps reduce back pressure when the silencers are heavily restricted with mutes. Running non balanced pipes with the MKII muted silencers would be a lot more restrictive...basically 2x as restricted...since one silencer per one cylinder exhaust path, instead or two silencers per one cylinder.
I plan to ream/cut out the welded in mutes to match an unmuted silencer opening.
 
I think the balanced exhaust was an effort to unleash equivalent power with less noise than the individual pipes and the beancan silencers were a further effort to reduce noise. The balanced pipes came with peashooters at first and only acquired the bean cans later. The balanced exhaust with peashooters on the '73 850 was matched with 260 main jets.
 
In the Dunstall norton tuning guide, circa early '70's, balanced pipes produced an increase in power and (as a side effect) reduced noise. At that time, the balanced pipe was not used on production Nortons, it was was cobbled together for performance purposes. Norton later incorporated the identical design for production. It's a win/win deal with more power and reduced noise. Obviously it's not as convenient to deal with as far as installation/removal and there are complaints about welds cracking. It also does not look as "clean" as the individual pipes. On my '73 I switched the individual pipes it had when I purchased it in '06 for a balanced set a few years ago and have had no issues at all so far but I'm thinking of going back to singles because I prefer the look of the singles.
 
Torontonian said:
Sounds experimental but good luck to ya.
Click to expand...
Yes, but Mexico Mike told me in another thread this cutting out the welded mutes was a common practice back in the day. My silencers are not in great shape to begin with so I'm not sweating over mucking them up.
 
Tornado said:
Yes, but Mexico Mike told me in another thread this cutting out the welded mutes was a common practice back in the day. My silencers are not in great shape to begin with so I'm not sweating over mucking them up.
Click to expand...
If thine mutes offend thee pluck them out
 
Yep, even the local Norton dealer in Memphis, TN would cut them out for you for a small charge.

Many locals with Norton just cut off around 2" of the muffler with a hack saw! That beat the heck out of paying 10 bucks to have it done at the shop! It also gave the muff more of a megaphone look. ;)

One guy did that and painted the muffs flat black. It was a cool look that many of us admired!
 
Updating this old-ish thread.
Earlier this week I spotted the dreaded header crack at the balance pipe weld. It was about 1/2 way around the pipe circumference and appeared as a hairline yet could easily snag a fingernail moving across it.
Accelerated my plans to swap over to unbalanced 750 pipes and did the deed today. Biggest disappointment was the nice new RGM Stainless roses (063555S) although longer 3/4" thread, the thread diameter is too small for my R10 head! The roses just slide right into the head ports without any threading!
Reviewing the older threadlines on these nuts, could not find any mention of a difference in diameter, just the 3/4" vs shorted 850 balance pipe type.

Anyone know whats up?

I went ahead and return to service the original beat-up/bent-up roses, using RGM's steel sealing washers and high temp copper-laced exhaust RTV. Got a good solid clamping to the headers. Should be OK to run, no?
 
I don't know what's up with the smaller diameter roses. You know the old roses work in your head, so you should be able to use them if the new pipes are the same outside diameter as the old ones. ditto for the sealing washers, they need to fit the diameter of the seat in the exhaust port. If you can get the whole thing together and feel it's solid, give it a test ride. If when you back off the throttle the bike goes, "pop, pop, pop..." then your exhaust isn't sealing properly. Usually you tighten the roses, then go for a short ride to heat up the head then retorque the roses, Lastly, you bend the roses' retaining rings into place after the heat cycle and retorquing...
 
Pipe flanges and the RGM steel sealing washers are all proper fit to the head and both new/old roses. Only difference is longer thread length and small diameter thread than original...the bore in the new roses is the same diameter as the old ones.
New SS nuts are 1.932" diameter at thread. Can't check old ones as I've now installed them.

Is there such a thing as a repaired head port with oversize rose nuts?
 
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If you use the search function here, there seems to be a difference in sealing washers too. The worst thing you could do is bottom out the rose nuts and NOT have sufficient pressure on the flange of the exhaust pipe. Then the pipe will hammer away at the rose nuts and screw up the threads in the head. I've only owned a 750, so if you assemble the new exhaust and something seems amiss, you may need to check further into the differences...
 
Tornado said:
Biggest disappointment was the nice new RGM Stainless roses (063555S) although longer 3/4" thread, the thread diameter is too small for my R10 head! The roses just slide right into the head ports without any threading!
Reviewing the older threadlines on these nuts, could not find any mention of a difference in diameter, just the 3/4" vs shorted 850 balance pipe type.

Anyone know whats up?

I went ahead and return to service the original beat-up/bent-up roses, using RGM's steel sealing washers and high temp copper-laced exhaust RTV. Got a good solid clamping to the headers. Should be OK to run, no?
Click to expand...

Mike; did you try and fit the new nuts first without the exhaust pipes? may need to laya dial calper over both nuts to double check the OD. and thenin its still wonky time to get a hold of the supplier. the thread od should be the same...
 
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I'd say, in the longagopast, some clever machinist repaired stripped threads by making custom nuts... or made a sleeve/bushing. Look at the nut carefully.
 
I did attempt to fit a new nut without pipe just see how they went...but it just slide right into bore fully.
Oh, one other point I have not seen in other rose nut posts...my old ones are left hand thread. And the single wide lug fin actually has "L.H." stamped on it. Is that usual?
 
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