Under engine Balance pipe

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Steve, if you make a two into one using those header pipes and a collector that you can cut back to increase the size of the tail pipe, you will find that as you increase that size you will reach a point where the bike take a leap forward. A lot still depends on the back pressure imposed by the muffler, however if you get it right with no muffler then you can try fitting a bit of restriction and see if you can adequately control the noise while still getting a performance boost. I suspect the Laverda cross manifold might be the best option for road use. Two nice light Termignoni mufflers ?
 
If was easy to fit id run cross over on Trixie Combat as like the tire spins play not going very furious. I'm going to buy a TIG at some point to experiment along you lines Al as well known its mainly the exit side that helps boosted applications and expect what works w/o boost works even better on boost. There's something to the stepped header desing so may hydrid with pipe dia and length volumes. Will have a G force monitor for road going dyno tests. Noise definitely a factor so more fun experiments to mellow. I'm not above putting in old fashions exhaust dump valve or spring operated flaper valve to see what happeens,
 
Steve, A friend of mine originally owned my Seeley and had a 750cc Laverda motor in it with the SFC cam. He was too lazy to make a decent exhaust for it, and had one just like yours. It killed the performance stone dead. I raced my Triumph 500 against it while it was being ridden by my main rival and absolutely creamed it. When I bought the Seeley, I tried to get the Laverda motor, however the guy who had it wanted too much for it. It probably would have been more powerful and reliable than the commando, however it was extremely heavy.
 
Steve, if your bike ends up as loud as my Seeley, the police will lock you in jail. I think it would be very difficult to make a quiet 2 into one which provides decent performance. I love the way my bike performs, however it is not for road use. I've wanted to video a start-up for a long time, however I'm worried about upsetting the neighbours even though I live in a country town.
I will get around to making that video, you should really get a laugh out of it - you wouldn't think a commando could boom so loud. What really amuses me is that it actually performs well. I think Mr Norton might have done a lot of detuning to comply with the noise laws.
 
Ideally, 2 into 1 should have a symmetrical geometry. Otherwise, there will be an unequal assist by one cylinder vs the other.

I find it hard to believe a 4 - 5 hp gain is possible by a balance tube joining the pipes at a 90 degree angle to each.
Such a junction does not yield much cross sectional area for the high speed flow of one pipe to suction the other.

But the dyno should not lie!

Slick
 
Hickjacked? Well add something apropriate to it Ludwig. I don't claim to know what I'm dooing but do know a cross over does not need to be same dia as the main pipes, IIRC 1/3 is plenty. Just because one confirguration sucks on one type engine don't mean it will on another. My Cracked grin on 3rd eaier controlled blip up meant Peel gained such accleteration >t instantly re-kindled sports bike hunting similar too my P!!. Peels assymetrical lenghts bothered me when scabbing iit up but it ended up feeling like each cylinder saw it as one long pipe so could lug a slow load great. The weird thing to ponder on Peel vs P!! was when the Dunstall mega fell off roading Peel so open 1.5" single pipe loud Harley sound she'd hardly cross drag of pasture grass w/o stalling, could not take fast throttle at all and lost sense of fast cruiser as no passing power yet the P!! was romping stomping ilde to top out with open equal length pipes that were police bait enough they hunted the P!!. I behaved mostly in town but lent to a friend that dragged raced inside major univ. campus then dumped it there when corned so I had to retrive it next dawn light before discovered, Loud Pipes suck to sneak away on so just nailed the snot out of there through hedges and waks and hallways.

Under engine Balance pipe
 
A balance pipe coming off at right angles to a header pipe is bullshit. What is it going to do - resonate at what frequency and to what effect ? Dunstall was simply a profiteer. 'There you go sonny - she'll be right, Mate' and another wood duck bites the dust. Have a look at what has actually been proven to work.
Ludwig, stick your 'hi-jack'. It'll be a big moment when you actually contribute something constructive.
 
acotrel said:
Ludwig, stick your 'hi-jack'. It'll be a big moment when you actually contribute something constructive.
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I feel I have to chime in here, Aco. The many threads to which Ludwig has actually contributed over the years are the ones which have real data from real road testing, proven ways to make street Commandos more reliable, lighter, suspension and braking improvements, etc. They are among the most useful and constructive references for anyone who wants to get the best out of his or her Commando.

It's easy to write stuff but do people actually want to read it? Sticking to the subject of the thread and writing brief posts and fewer of them make those posts more interesting to read, instead of scrolling down to avoid them. Think about this before writing your next post.
 
Most Harley motorcycles have small mufflers relative to their engine displacement. Those small mufflers must also be quiet, and that combination results in limited airflow which, in turn, limits power output. A crossover pipe allows the exhaust gasses from one cylinder to flow through both mufflers, thus reducing the restriction and adding a bit of power. Crossover pipes can also improve mid-rpm torque if they are properly located. Triumph first discovered this when they introduced an exhaust crossover pipe to their American Triumph Bonnevilles in 1964. The original purpose was to increase the airflow through the smaller mufflers that we Americans preferred. However, they also discovered that the crossover added performance in the mid-rpm range.
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just a fwiw, early goldwings (1100-1200) used a balance pipe underneath, prob more toward the back of the engine,

not sure what the story is 1500 & up,
 
BMW, Honda, Yamaha have all fitted cross-over systems to their bikes at one time or another (two pipes in the case of some BMW twins) and Suzuki even tried it on their early GT series 2-stroke triples!
 
This is Ducati headers which is very similar to my SV650 so confused if X or H or Y type mergers.

Under engine Balance pipe
 
this is SVtwwin 650 after market upgrade with same plumbing connnections as factory confusion flow enhancers helping to make the famous Vtwin low to upper mid range advantage. Its does reveal the differences between plain cross over connection vs Y into one pulse extraction principles. Does not compute why there'd be an advantage with them this close together but apparently the extra hassle & expense is worth it.
Under engine Balance pipe
 
L.A.B. said:
BMW, Honda, Yamaha have all fitted cross-over systems to their bikes at one time or another (two pipes in the case of some BMW twins) and Suzuki even tried it on their early GT series 2-stroke triples!
Click to expand...

Have had a 2 into 1 on my BMW 1000 racer for the last year or so, put the stock headers back on with some Commando reverse cones with the balance pipe deleted and it ran the best it ever has, was able to pass a Commando and some other Brit bikes on the straights. :D , and on some of the corners.
Mind you running up to 8000 RPM, road bike might be different.
I'd like to make a 2 into 1 to 2 next.
 
Hi John, sounds like it is running great, how did Adrian go?
Damn work in the road again so will miss a few meetings1
How did Paul do on his Commnado/
Regards Mike
 
Brooking 850 said:
Hi John, sounds like it is running great, how did Adrian go?
Damn work in the road again so will miss a few meetings1
How did Paul do on his Commnado/
Regards Mike
Click to expand...

Adrians bike is going well, should do with all the $$$ spent on it. :roll:
If you mean the Paul on the Maney powered, TT gearbox Commando he was going well, about 3 seconds a lap faster than me.
other Paul with the T140 is suffering from false neutrals :cry:
http://files.marktime.co.nz/nz-classic- ... 1/BEST.TXT
Hampton Downs this weekend will be good, a much better track.
 
Thanks for that John, i see there was a couple of other Commnado's there as well that we don't normally compete against.
Are they new to the register?
My should be all going again by the end of Feb

Regards Mike
 
There was a 17 year old lad riding his Dad's from Welly, 1st time on a rh shift and used to a Honda RS125. He liked it ... " goes a lot better than I expected " he said. :D

See the Register is looking at moving with the times and letting .......gasp Jap bikes in .....and later than 1976....
Your alright as they have a Grandfathering rule so all Commandos are pre 72.
 
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