Balanced or unbalanced headrers?

What's the difference between these two? Was looking at complete exhaust from Commando Specialties for my 850.
I see that they don't have the balance pipe between the two headers. Does this make a differnce in tuning or idling or anything else?

I also don't see how they mount without the built in brackets that accept a bolt. Can anyone help me out with these questions before I decide if this is a wise purchase.

Many, many thanks.

That's a good question. I've been told that the exhausts with balance pipes are more dificult to install. I've also heard that the balance pipe helps performance. I've heard it hurts performance. Lots of automotive applications use a balance pipe for performance gains to control exhaust backpressure between two banks of cylinders.

I went with no balance pipe although my 1973 Roadster came with them.

The balance pipe was introduced on the 850 models purely to reduce noise levels. This subject has been discussed before, and the general consensus was that there is little, if any, performance benefit between either system.

Blue noser said:

I also don't see how they mount without the built in brackets that accept a bolt. Can anyone help me out with these questions before I decide if this is a wise purchase.

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The pipes are secured to the head by the finned exhaust rings and there are two lugs on the silencers/mufflers that bolt to plates which fit to the passenger footrest plates with metalastic bushes.

The lugs appear to have been positioned out of sight in the Commando Specialties photos, but their reflections can be seen, so they are there. Apart from those lugs there are no other fixing brackets. http://www.commandospecialties.com/

Ages ago , when my balanced oipes needed replacement , I asked myself the same question .
So I made a valve in the balance tube that I could open and close with a choke lever on the handlebar .
Riding at different speeds , but keeping the throttle in a fixed position , I opened and closed the valve .
If the balance pipe would have made any difference in power , I should have seen the bike accelerate or decellerate .
I felt NO difference whatso ever !
Only a little difference in sound : not quiter , not louder , just different .


If someone is interested to repeat this test , I'll be happy to send him the valve .

This has probably been conquered now but friends who had the balance tube seemed to have more pipe and flange problems. In theory it is a good idea but I'm not sure it worked well on Nortons.

I thought it depended on the type of silencers used, ie, reverse cone no balance pipe, non-reverse cone use balance pipe, that's how i've always understood it for my '73 850 Interstate,
Dave.

Hi,
You may or may not experience some sort of gain with the balanced pipe, BUT you certainly WILL have to look at it and compared to an unbalanced pipe it is UGLY. That is of course my humble opinion, others are welcome to form their own opinion no matter how wrong they are.
GB

daveparry said:

I thought it depended on the type of silencers used, ie, reverse cone no balance pipe, non-reverse cone use balance pipe, that's how i've always understood it for my '73 850 Interstate,

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All 850s originally had the balance pipe system, and for peashooters it doesn't seem to make any noticable difference to the power, (I changed to balanced pipes from unbalanced pipes and couldn't tell if there was any difference in power) however I believe the black cap Annular discharge silencers do need the balanced pipe system in order for them to breathe properly.

daveparry said:

I thought it depended on the type of silencers used, ie, reverse cone no balance pipe, non-reverse cone use balance pipe, that's how i've always understood it for my '73 850 Interstate,
Dave.

Click to expand...

That"s possible .
I should have added I did the tests with peashooters .

daveparry said:

I thought it depended on the type of silencers used, ie, reverse cone no balance pipe, non-reverse cone use balance pipe, that's how i've always understood it for my '73 850 Interstate,

Click to expand...

This is a bit of a myth. From the Norton Owner's Club website:

http://www.nortonownersclub.org/support ... -silencers

I quizzed Phil Radford at Fair Spares years ago about this, and he said no way. I bought a set of black cap silencers from him for my MKIII along with unbalanced pipes. I needed everything from front to back on the bike, wanted the black caps, and knew Phil wouldn't steer me wrong. I have no idea what the problem was with the bike mentioned on Mr. Patton's post. But I can say in my case, my MKIII has plenty of top-end and is deceptively fast, as a friend of mine with a Vincent Rapide found out. I have heard mention of the later black caps being different and possibly not as quiet as the early ones, so that may enter into some of this.

don. w

Thanks everybody for the helpfull replies. Especially L.A.B., he seems to know all and see all. I'm looking over my shoulder right now.

When I'm wrenching on my bike, I can hear him say, "no, you idiot, that's wrong!" :lol:

One thing to keep in mind is the balance pipes need to use split collars to install the nuts.This takes away approx. 1/8" of thread from the nuts which usually means sooner or later the ports are stripped. When I originally started to repair them many years ago they were 850's with the balance pipe.They replaced there exhausts then with single pipes without the balance.Nobody ever had any tuning or power issues.I would have to say of the hunreds of ports I have repaired 75% were 850 ports. Also use the norvil bronze nuts.They don't come loose.
Bruce

So what I'm picking up from the previous post is that my 850 has split collars under the exhaust nuts (which I found) but I also found two copper looking circular gaskets setting in the exhaust outlet (one so squashed that I could barely tell it was there). Should I leave out the collars during the reassembly so as to get more thread contact?

Diamondjet said:

So what I'm picking up from the previous post is that my 850 has split collars under the exhaust nuts (which I found) but I also found two copper looking circular gaskets setting in the exhaust outlet (one so squashed that I could barely tell it was there). Should I leave out the collars during the reassembly so as to get more thread contact?

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The collets should not be necessary if you're using the 850-style exhaust nuts on 750-style pipes. Check to make sure the nuts don't run out of thread without them. The copper washers seal the exhaust pipe to the head. Sometimes folks put two in to get a better seal - sometimes the old one is left in by mistake, and a new one put in on top of it.

The split collets are what holds the 850 pipes in the exhaust port. Because 850 pipes have the 'Y' for the balance pipe, the only way to install the exhaust nut was to use the collet. The downside of this is the fact that the 850 pipe and collet arrangement is deeper that the simple flange on a 750-style pipe, leaving fewer threads in the head available for the exhaust nut.

Another disadvantage of the balance pipe is cracking at the 'Y' due to vibration. I went through two left-hand pipes before going to the 750-style pipes. I did notice a few decibels increased sound when I changed to the unbalanced pipes.

The only positive thing I can say about the balance pipe is that I lost a few miles per gallon in fuel economy when I switched to 750 pipes. Commando exhaust has always been a trouble spot for me, and the cross over pipes just make it that much more aggrivating. Not a fun thing to deal with.

I have balanced pipes and Dunstalls on my '72 Combat. I've found that the idle seems even more stable, the exhaust note is deeper and the front-pipe assembly, once tightened, stays that way with the whole exhaust system dancing around less, at the expense of a touch more vibration. The setup practically doubles pipe volume, allowing a short-coupled pipe/muffler configuration with the scavenging effect Dunstall otherwise sought with the muffler tips extending past the rear wheel. His '60's-era tuning guide recommends the balanced-pipe system for "fast road work."

I haven't had much normal-weather experience with fuel economy and high-rpm performance. I reduced the main jets from 230's to 220's with good results and may experiment with 210's and 200's when things warm up. I've tried all kinds of exhaust configurations over the years and find I like this one as well as any.



Tim Kraakevik
kraakevik@voyager.net

Brithit said:

daveparry said:

I thought it depended on the type of silencers used, ie, reverse cone no balance pipe, non-reverse cone use balance pipe, that's how i've always understood it for my '73 850 Interstate,

Click to expand...

This is a bit of a myth. From the Norton Owner's Club website:

http://www.nortonownersclub.org/support ... -silencers

I quizzed Phil Radford at Fair Spares years ago about this, and he said no way. I bought a set of black cap silencers from him for my MKIII along with unbalanced pipes. I needed everything from front to back on the bike, wanted the black caps, and knew Phil wouldn't steer me wrong. I have no idea what the problem was with the bike mentioned on Mr. Patton's post. But I can say in my case, my MKIII has plenty of top-end and is deceptively fast, as a friend of mine with a Vincent Rapide found out. I have heard mention of the later black caps being different and possibly not as quiet as the early ones, so that may enter into some of this.

don. w

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Don, that would be me. Talk about a blast from the past. It's really not a myth. As usual the devil is in the details, and since it's raining like hell and blowing 40knts outside, here goes.

The engine I was running at the time was not stock. It had 10:1 compression and a Megacycle 560 cam. Even when it misbehaved at it's worst with the Beancans it made more power than a stock 850, which is in a pretty low state of tune. The important issue is that this cam has a lot more overlap than the stock grind. You live and die by the sword when it comes to overlap. 4000rpm is right when the engine should be coming on the cam, so when I said it couldn't get out of it's own way at 4000rpm it has to be taken in context, compared to before the Beancans. Overlap needs a freeflowing exhaust to work well. I put the Beancans on because I wanted to do some crosscountry riding and the noise of peashooters gets tiring. I wound up taking the Beancans off and getting a set of RGM 'Beancans'. Which basically look like a Beancan but are a straightthru design with a glasspack silencer. They are more quiet than the peashooter. All the power came back. A stock 850 probably wouldn't notice it one way or the other, with or without a crossover.

Speaking of crossovers, This is from Smith & Morrison (1962):

"An interesting modification to the exhaust system of a 650cc twin-cylinder motorcycle engine with exhausting intervals at 360 crank degrees, involved coupling the two separate pipes by means of a cross-pipe located close up to the port outlets. The intention was to improve silencing by doubling the silencer capacity available to each individual cylinder, since flow through the cross-pipe would have such effect. However, the improvement in power output obtained by this simple modification was such as to indicate that the cross-pipe was functioning to some extent as an interference pipe, though the the lessened resistance to mass flow as a result of doubling the silencer capacity could also have an advantageous effect."

By "interference" they mean the reflection of the exhaust pulse as a vaccum pulse back into the head, which jumpstarts the intake process during overlap. Dunstall ran them on his race bikes and the modern aftermarket header makers do it too. Even on headers that are 4 into 1's. down the line. The way it was explained to me, it would take a dyno and the throttle at WFO to tell.

bpatton said:

Don, that would be me. Talk about a blast from the past. It's really not a myth. As usual the devil is in the details, and since it's raining like hell and blowing 40knts outside, here goes.

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Interesting post, Bob. Thanks for taking the time to expand on that!

Judging by this thread I think I see why friends who had the balance pipe mostly dumped them, It just does seem that they cause you more trouble one way or another.

I got rid of mine, and now run 750 pipes with 750 flanges. "And I am well pleased."