2 in 1 exhaust system (2010)

Anybody have any experience with 2 into 1 exhaust systems on Norton Commando's. Especially Steve Maney's system.
I've noticed that Norton's are very susceptible to exhaust pipe length, even with separate pipe systems. At about the half revs range the engine appears to act as if suffering from megaphonitis.
Any comments?

I ran an Axtell exhaust system, twin pipes with idividual reverse cone megas, on my reace bikes for a good numer of years. Worked great from 5500 to 7200 rpm on the race track, with a range of serious megaphonitis somehwere below 5000 rpm, but we never ran it down there anyway. I eventually switched to Steve's 2-into-1 on my 750 AHRMA racer. By then, I wasn't riding the bike anymore, but I had a friend riding it who was very good. He said the Maney exhaust gave noticeably better mid-range pull out of corners, and he couldn't tell any difference in top end, so that's what we kept. I ran the bike that way at Bonneville in 2001 and set three class records, with a best of 130+, so it can't be too bad.



And it never drags on the ground!

Ken

I scabbed up this DIY form standard 1.5" set. Put on stock Dunstall megaphone, bean can cigar tube baffle, and lost all spunk all around. Tried stupid SuperTrap, too dang heavy and loud by the time enough plates added to feel some power released. Got frustrated, 12 gauged 1 3/4" hole in just an end plate, and I got A Whole 'Nother Meaning to the term MEGAPHONITIS !!!!!!!!!!!!!!!!!!!!!!!!!!!
Small port head, light crank, 10CR, 2S cam. Exhaust weight ~9 lb.


hobot - how good was it spring of '04 >>> ***M-E-G-A-PHONE-ITIS***!!!

Medically any thing with "Itis" in its name
means its inflamed, as in red, hot, swollen
and painful. Not cold pale shrunken numb eh.

Last PM I took out the Dunstall perforated
baffle tube. It was a two part affair but
I'd not cut off my header pipe when I shoved
it in to mount, so with rough riding the
pipe knocked the near end of baffle tube cap
cap loose for annoying rattle, plus one of
the baffle bolts sheared off, so what the heck,
hollar'd it out to emptiness.

It was almost mid night, the storm and lightening
was heavy - who'd hear but me eh. First was open
pipe music, cool and proper real bike beat, but ho hum.
Lacked the distinct playing cards in spokes farts of
ripe Norton. Also stalled off idle and weak mid range.

Humphf, put on now empty, half again lighter,
hollar'd out Dunstall Decibel - fired Peel up on idle.
oh my felt as much as heard...


Rumbling Grumbling Growling, sheet metal shed
walls and roof began resonating, AWSOME,
idling, little blips, oh man it gave me sense of a big
block Rat motor in a Chevy Vega, the sound
was just too big for the size of the power
plant and made even me take on a whole
another level of respect for the Norton sonic
impressiveness. Whew wee I couldn't get
enough of it, it was such a voluminous sound
even as supercell front hit, it made me cringe to
disturb the peace with a WOT run up to
reline, which of course I did for ***Startled Spinal Shock***

CRACKKKKKKKKKKKKKKKKKKK!!!!!!!! BLAPPPPP!!!

: - O *** OH MY GAWD ***

It sounded like the cracking RIP of Lighting
Strike as it tears superheated air apart!!

Hehe So I did it AGAIN and AGAIN and AGAIN!

It took my breath away. I shut off, in a
tremblingly state came on in to dream on this
last revelation. Oh yeah shed, is 75 yards
from house. I asked wife if she heard me.
"Yes but I didn't know it was you at first."
"I saw the lighting flash real close and
heard this REALLY LOUD CRACK OF THUNDER
but it did it again w/o the lighting so
I knew it was you. Its was louder than
the thunder claps!" [of sad deadly] Supercell

Next day was even better, so good I've never really gotten off the trill since.
not the place for the 3 more pages of real road orgasms.
HEE HA hobot

I tried out a friend's 850 Hi-Rider with a 2-1 exhaust. Kind of anemeic. No sole ,,, :?
I have a Dunstall 2-1-2 with a 36 mm Mikuni on my 73' 750 and it's more better :mrgreen:


Tim

Mr Hobot, you do have a way with words

Steve Maney's system is really good on the track....maybe a little loud for the road depending on where you live , mine was tested at 108db. However like Ken said, it gives a lot more midrange and really good top end. I had a works spec 2-1for years, but had to put a straight can on the end to get around the noise testers, and it cost me a lot of power and screwed up the carburation. Putting Steve's pipe on transformed the motor.
He does also sell an "extra silencer" to add on to the endcan which would make the pipe acceptable for road use (noise wise!)

I had the Dunstall 2-into-1-into-2 setup years ago. Loved the performance, but was always hitting the center collector pipe on something. Changed to a Winning 2-into-1 with a Supertrapp baffle I added for some extra sound quality. Never liked the sound. Now on the resurrection, I have traded the Winning pipe for some SS high-mounts with Dunstall replica cans. I don't think anything sounds as good as the stock peashooters.

Hi John

My Maney pipe was tested at 104 at Snetterton (not) I have purchased the end can as Steve said you can mount it & not put any of the internals in it!
(supertrapp type discs also an end plate for road use) Then if & when we get pulled add a piece at a time!

See you at Cadwell with a 4 speed. as the Quaife ate itself! Well it was an original with out an oil seal on the high gear. ? 40 years old?
all the best Chris

To fix megaphonitis - use longer intake manifolds - go for 9-1/2 to 10" total from the head to the end of the velo stack.
Will also increase performance and is just important as the exhaust.

I have heard that twin pipes with megas show several more HP on the dyno than the 2 into one with silencer. Part of the problem is the silencer. Don't know the comparison without the silencer.

http://www.rgmmotors.co.uk/images/full/full_471a.jpg
You can add RGM's 2 into 1 to the mix. The primary pipe length must be at least 30'' so it might be a good choice for a street bike with a mild cam.

I had a 2 into 1 exhaust on my race Commando for a while. It stuffed up the pilot mixture and gave it a big hole in the mid range.

Other people have much better experiences, so it all depends on the system design.

I see two basic types of 2>1's, those that retain long single headers to the muffer and those that merge the pipes at front of frame. I only know effect of the later.
I liked it so much after some frustrating trial error on the muffler-megaphone exit part, i'm glad I tried it and its what I'll use on super duper breathing Peel engine.
Main issue in close to head joining its a joint to allow each pipe to insert into the angle apart exhaust ports. Narrower at head seat then at head threads. I lucked out by having just enough spring in the pipe to allow me to spread em to clear head
thread then release to pop in and nip up.
There is another issue to be aware of if pipe crosses in front of frame, must bend close enough to frame front mudguard don't smack pipe to dent the fender or fracture pipes.

Viking makes a "Dunstall" 2-1-2 that I would love to put on the bike but the centerstand and the ground clearance makes it a no-go.

Think kennys bike is proof that the 2 into one does very well. Not seen a norton run like that in a long time. If a two into two is better , we are in trouble. I have wanted to try one of steves systems on my bike but just can't part with that much $$$$ now and cut it up to fit a tri.

lcrken said:

Click to expand...

Are those dellorto carbs I can see there?

I've got a pair of 34mm I've tried on mine and can't get them set up.

Would you mind telling me the jetting? Do you still have the accelerator pumps connected?

Thanks

Hi John,

yes, they are 34 mm Dellortos. I've used them on that bike for something like 25 years now! With no air filters, and racing exhaust, this is the carb setup I use.

Slide is in between a 50 and 60 cutaway. I've filed a bit off the bottom of the slide to lower the cutaway and make it slightly richer for better response when opening the throttle from idle. It's been a long time, and I dont recall how much I removed. I just kept filing and trying it till it worked well.

The pumps are disconnected. Not allowed for AHRMA vintage racing.

Needle clip is in second groove from top.

Pilot jet is 65.

Main jet is usually 135 or 140, depending on conditions and circuit. We used 128 at higher elevations like the old Park City (Utah) and Steamboat (Colorado) street circuits, but those circuits are long gone now.

Hope that helps.

Ken

Almost exactly the same as I have, and can't get it to run well. A pair of 34mms on a race bike with twin supertrapps, ( open ends).

I have a 40 slide, that I had machined to 55, 130 main, 60 pilot, K18 needle, AB265 needle jet. Floats at 18.5 mm

On the dyno it ran well ( on full throttle) good power and better mid range than the old 36mm Amals, but on the track, by the time it's warmed up for a race, the plugs are black and fouled and missfiring.

John, what fuel are you using ?

graeme

GRM 450 said:

John, what fuel are you using ?

graeme

Click to expand...

50/50 mix of Shell racing 100 ( essentially avgas) and 98 octane unleaded. Works OK with the Amals.

Maybe it's the pumps squirting too much at off to on throttle when you are warming it up ? A squirt every throttle blip and no full throttle to clear it ?
Maybe try turning the pump down or disconnecting them, or different slide/pump ramps ?

graeme