Biggest diameter Commando headers?

What is the biggest diameter headers that are off the shelf?
Who has them?

Is there a maker of 1 5/8" or 1 3/4" pipes?

hobot

All I'm aware of is Commando Specialties 1 1/2" pipes.

Thanks, 1.5" size is what was on the 750 bike prior.
That may be enough, just can know w/o testing which size
a 920 with boost likes the best.

hobot

Gday Hobot,
and may I ask what sort of boost are you talking????
regards Foxy

The best (performance-wise) exhaust I've ever seen was a custom-built-job for my buddy Cliff's 1974 Commando, it was a kinda "S" high pipe thing with VERY big, smooth bends in the pipes (but it was not especially large in diameter). those coupled with LONG intakes (he took out the battery-box to fit them) made the bike the fastest and quickest Commando in Houston, Texas for YEARS! (he had done a lot of other work to the bike).

Unclviny

Viking Exhaust can make about anything.

Foxy, the rear rod plus its top and front minor helpers allowed Ms Peel with
an accidental hot rod engine set up, whip up on everything else I've
ever ridden or ridden against. Was fast enough to keep up with
900's to 130's mph, and way way ahead of them up to 100 mph
where some actual leaning required. Good enough I was just gonna
stick the ancient deadly Drouin centrigugal blower on the
750 Combat engine, then darn old Ducati came out with the 1198
so I horse traded up to a Steve Maney 920 Hi CR engine.

I've the original magazine reports of editor and Tom Drouin
having a go at it. Tom's and TC Christensen ads calim 10 PSI
on 750's but the editor only had balls to touch 8 lb while
Tom could load engine to 12+ PSI. So a belt drive snail blower's
boost is a relative quantity and ratio, not like positive
displacement blower with set boost ratio no mater the rpm
and throttle opening. BTW TC about spits when hearing
Tom Drouin name as feels Tom dropped the ball and cost
TC a bunch.

920cc/56 cid engine is ~20% bigger than a 750, so I figure
in general Drouin will deliver 20% less boost ~8 PSI in general.
Yet the idenical mate to my re-engineered Drouin
is on a stock 850 and pilot now used to it can load his
to 12 PSI, which means at will wheelie in 4th by just
a faster throttle roll on. All depends on how fast you
snap open throttle and still traction to load engine.

Here's photo of the Drouin before spiffed up & re-done and refinished
in rough black to smooth shiny. The Drouin suppled
Lake Injector had bad tendency to slick slide open d/t
the suction and has killed daddies of riders telling me what
to beware of. QuickSilver carbs are like Lack Injectors
with a fuel bowl idea circuit and mechanical cam push/pull
dual carb flat slide throttle. I'm starting with a 38 mm for
the low down help but figure as a draw through carb can
flow well over 200 cfm miture. 150 cfm is average per 100 hp.

Also a teaser special install. I've hand fulls of various blown Commando
as many ways to skin that cat. Though not all up to my needs
> one to one throttle to tire rpm, nothing at all to do with
regular traction concepts, extra throttle at Ms Peels rates
causes hesitation in acceleration or fast changes in lean
angle or aim around the CoG, gotta back off to hook up out of there,
usually right at point of least traction suddenly an insane sling shot.
http://rides.webshots.com/photo/2604371 ... 1179uosHfe


http://rides.webshots.com/photo/2609216 ... 1179QBWGRq


hobot

Geez Hobot, you dont believe in doing it by the half measure! You might aswell slot in a can of NOS while youre at it! your threads make an interesting read to say the least. I checked out the photo links and couldnt help see the results where youve thrown the bike away and went surfing down the road removing a bit of bark (ouch)!! Been there done that too after hitting a roo, not much fun. But he come off second best as the sheep dogs turned him into crap.
I look forward to seeing the build when its complete and of course the test ride results.
Rgds FOXY

1 5/8 are just like the Atlas pipes and what I run on my bike. Be aware that these have a very thin ring that the exhaust flange bolt presses against that is prone to braking away. There have been many welded repairs on the two sets I have got from Viking in NZ. These Black chrome sets were not cheap but needed repair after just 50 hrs on the machine. They were nice to look at and fit well but not sturdy enough to hold up under use. I am not the only one who has found this out.

Ugh on the Viking Exhaust. I was an mid stream customer of his
and paid his price and waited a while, then on install found
the LH flange so over size would not fit in head nor pass
the ring bolt over. Took some swearing and grinding on both
the pipe and the new brass ring bots to get them useful.

Wesly and I know real well about fractured pipes up front.
I expect to lose Viking bodged pipe in a few 1000 miles.

Foxy, I've crashed a whole bunch this last decade, almost
all of it on THE Gravel paths, most of that by sudden
hazards deer, tree falls, wash outs tractors school buses
and big dump dogs, some braking on slow 5 mph turns
and loose its worse than ice as unpredictable, bigger rock jerk tire out.
I've found if I'm a bit aggressive on THE Gravel and
in traffic I ballistically have more upright chance and tend
to scar away surrounding traffic. I've yet to crash
attacking turns, entirely possible, but I'm rather
careful not to ever depend on front tire traction
when really going at it. Takes good power to turn
safe at speed also any braking leaned into entry is a big
no no to me, better be going slowing enough upright that you
can be oh hi throttle going into and out of them.

I've had a number of crashes just strolling along 35ish
and hit series of sloped pot holes that lifted both
ends up a few inches but added a torque that leveled
bike sideways before landing and sliding on me.

hobot

Off subject, but I believe the racers use a combo of rear brake and power in corners. Apparently this lowers the CofG and can go faster. Not the done thing on gravel, all you can there is sit on the tank, steer with the power and hang on!!

FOXY

THE Gravel is a Harsh Teacher but Teaches Everything You Need To Know
including blow out saving.

Anyone who is on brake while leaning or turning is not at max
turning or accelerating loads while leaned. On Gravel paths it will slap
you down on THE Gravel so fast you don't know what went wrong.
My ONLY way to brake when not creeping, is straight up straight
ahead.

There is a fad out last couple years to drag front break
while cranking in power, very very dangerous and may
add a few mph to already corner crippled moderns
but it barely significant increase for the risk involved.
I've had instructor explain the process and tried it.
I'm sticking with my taboo to ever enter corners I
am still braking while lean, uh uh, no way Jose.

Racers brake to try to load front more, which is counter
productive to me as takes load off rear so can't hook up
as much power. But if on such corner cripples that
can't hook up much power leaned, might as well
go for the little extra the wimpy front can add.

The racers who use brake to slide rear around sharper
are doing than mainly because the bike they are on does
not have power enough to trust it to break free as long
as needed and not hi side. Supermotard is common
to use brake to slide rear side ways to travel to
both help slow shooting off road as well as face
rear more in line with next throttle up into next line.
But supermotard ain't usually got the power of a
sports bike.

Ms Peel had the torque on tap to power rear around
to almost 90 mph, need blown big block to do it over the ton.
Thats the point of me seeking bigger headers.
Best 920's pump about 160 cfm in and out, ~100+ hp.
Peel could exceed 200 cfm.

Peel has pulled side ways wheelie lain over past 45' in
some decreasing corners to drop front down way
sharper than could be turned, all the while
planted like crazy with all the mass on rear smashed
down patch, That when real torque needed right Now
not to hi side.

Fat tires laid this far over just grease right out on that
kind of power application. Pashaw.

hobot