ADVrider

Go Back   ADVrider > Bikes > Old's Cool > Airheads
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 12-20-2011, 01:50 PM   #16
mattcfish
R90SS/6
 
mattcfish's Avatar
 
Joined: Feb 2008
Location: Bellingham, WA RAIN or shine
Oddometer: 199
Quote:
Originally Posted by oldroadie View Post
I know very little, the whole BMW experience is new to me. I was informed it was a Mac but what do I know? Now it's a 2 into 1 with a Supertrapp disc tuning set up:




Might even get it running again this afternoon once I torque the right head a set the valves.
Not Mac...better, also looks stainless from your picture. Longer primary runners and better collector than a Mac.
mattcfish is offline   Reply With Quote
Old 12-20-2011, 05:05 PM   #17
Hawk Medicine
Coyote's Brother
 
Joined: Jun 2008
Location: NOR CAL
Oddometer: 3,303
Just in case anyone is interested, I found an article in my email today that talks about headers and horsepower. It's very interesting for a novice and at least outlines the things to consider, when designing an exhaust system.

http://www.rodauthority.com/tech/exh...en-performance
__________________
Hawkdude

Hate rots the pocket that carries it.
Hawk Medicine is offline   Reply With Quote
Old 12-21-2011, 04:24 AM   #18
oldroadie
Two wheel addict
 
Joined: Feb 2010
Location: North Alabama mountains
Oddometer: 401
To complete hijacking the OPs thread:



It blocks the shock bolt, otherwise there's plenty of clearance everywhere: it does block any lower adjustment of the footpeg. The Supertrapp end came from Summit Racing, it's an off the shelf item. I cut off maybe 4" of the old flared end (it had a single perforated disc in the end for the only baffle) and had the new opening expanded by a local muffler shop so I could bolt the tunable piece on. I didn't know what to expect when it fired up but I like the way it sounds and I think it'll be easy enough to dial in the A/F with the removable discs.

Quote:
Originally Posted by mymindsok View Post


I've seen a lot of Airheads but I've never seen a Supertrapp that looked like that!

Who built it? The clearance looks very tight. Does it clear the axle bolt and brake lever?

oldroadie screwed with this post 12-22-2011 at 05:29 AM Reason: added clearnace pics
oldroadie is offline   Reply With Quote
Old 12-21-2011, 05:54 AM   #19
craydds
Beastly Adventurer
 
craydds's Avatar
 
Joined: Aug 2010
Location: Las Cruces, NM
Oddometer: 1,108
Quote:
Originally Posted by Voltaire View Post
Hi everyone, I'm building an R90 track bike and I would like to fit a 2 into 1. The guy at the custom exhaust shop seemed to think it didn't matter much if it was equal length of not....
I'm from the world of air cooled VW motors and equal length are the standard....
Spec of the motor is 336 cam, 36 mm Dellortos, 81 clutch, 1 mm off the heads.
The bike is not for road use...its made up of parts I bought locally and off Ebay, the core motor is a 1973 R90.
Cheers in advance, John
I might consider checking with http://www.jemcoexhaust.com/ .
__________________
Ray
ABC #12947
'75 R90S
craydds is offline   Reply With Quote
Old 12-21-2011, 07:56 PM   #20
bereahorn
Beastly Adventurer
 
Joined: Mar 2002
Location: North Coast (Lake Erie)
Oddometer: 1,058
bereahorn is offline   Reply With Quote
Old 12-22-2011, 08:06 AM   #21
mykill
odd
 
mykill's Avatar
 
Joined: Feb 2008
Location: Los Angeles
Oddometer: 1,146
http://www.mez.co.uk/mezporting/exhaust_length.html

An interesting calculator for this application. I have not attempted it.
__________________
Never underestimate the laxative properties of motorcycling.
mykill is offline   Reply With Quote
Old 12-22-2011, 10:06 AM   #22
Voltaire OP
Beastly Adventurer
 
Voltaire's Avatar
 
Joined: Jun 2011
Location: Auckland,New Zealand
Oddometer: 1,063
Quote:
Originally Posted by mykill View Post
http://www.mez.co.uk/mezporting/exhaust_length.html

An interesting calculator for this application. I have not attempted it.
I'll have a look....I've already spent a lot of time reading and re reading your recetech emulator thread comments as I'm starting to assemble my R90 Classic Racer project after Xmas. Your info is very helpful as its actual rider/constructor feedback.
I might even start a build thread as its taken me 5 years to get to this point....4 1/2 years of gathering parts and procrastinating and the big motivator two CSS track lessons and 2 track days
Voltaire is offline   Reply With Quote
Old 12-22-2011, 12:12 PM   #23
Hawk Medicine
Coyote's Brother
 
Joined: Jun 2008
Location: NOR CAL
Oddometer: 3,303
Quote:
Originally Posted by mykill View Post
http://www.mez.co.uk/mezporting/exhaust_length.html

An interesting calculator for this application. I have not attempted it.
Thats a pretty interesting calculator!

I'm looking forward to playing with it.

Thanks,
__________________
Hawkdude

Hate rots the pocket that carries it.
Hawk Medicine is offline   Reply With Quote
Old 12-22-2011, 06:04 PM   #24
mykill
odd
 
mykill's Avatar
 
Joined: Feb 2008
Location: Los Angeles
Oddometer: 1,146
Quote:
Originally Posted by Voltaire View Post
I'll have a look....I've already spent a lot of time reading and re reading your recetech emulator thread comments as I'm starting to assemble my R90 Classic Racer project after Xmas. Your info is very helpful as its actual rider/constructor feedback.
I might even start a build thread as its taken me 5 years to get to this point....4 1/2 years of gathering parts and procrastinating and the big motivator two CSS track lessons and 2 track days
Thanks! happy to try to help. Feel free to PM me if you want/ need specifics on stuff. I had a number of people help me out getting my bike done, so I am happy to pay it forward.
Cheers,
__________________
Never underestimate the laxative properties of motorcycling.
mykill is offline   Reply With Quote
Old 12-22-2011, 06:08 PM   #25
mykill
odd
 
mykill's Avatar
 
Joined: Feb 2008
Location: Los Angeles
Oddometer: 1,146
Quote:
Originally Posted by mymindsok View Post
Thats a pretty interesting calculator!

I'm looking forward to playing with it.

Thanks,
http://www.coneeng.com/

These guys are near my office. I hope to build an exhaust if I ever get some spare time.
__________________
Never underestimate the laxative properties of motorcycling.
mykill is offline   Reply With Quote
Old 12-22-2011, 08:10 PM   #26
bmwrench
Beastly Adventurer
 
Joined: Nov 2006
Oddometer: 1,847
For what it's worth, that looks like a Luftmeister 2:1. Supertrapp's origin was in spark arrestors for industrial stuff, like gasoline powered welders. On bikes they seem to work best with a lot of discs on them.
bmwrench is offline   Reply With Quote
Old 12-23-2011, 04:45 AM   #27
Beemerboff
Beastly Adventurer
 
Joined: May 2005
Oddometer: 2,191
Back to the origonal questions, do unequal length headers work, and the answer is, maybe, sometimes.

I picked up a set of stainless steel 2 in one headers real cheap at swap meet. Fitted them to a 900 cc bored out R75/7

They couldnt be more uneven - one side is twice the length of the other, just comes over like a normal crossover.

IMHO the stock silencer is too restrictive for a 2 in one, but with a less restrictive replica of a Dunstall Decibel fitted it runs just fine.

Up to 4500 revs it doesnt sound or run much differnt to a stock set up, then it all comes together with a delightfull howl.

The carburation now needs sorting as it is too lean on the needle, but that shouldnt be to hard to fix as it is still on the 750 settings.

I dont doubt that a carefully designed and constructed equal length system would produce a couple or more HP at the top end, and if you are racing that can be important, but a unequel length system can be made to work fine for road use.

And if like me you enjoy annoying the BMW owers club memers and other assorted know it alls you will get a lot of pleasure out of it too.
__________________
Adelaide Hills, Australia. 93 R100 GS, 77 R75/7 ,70 BSA B44VS, , 86 R80 G/S PD, 95 BMW Funduro F650 ST
Beemerboff is offline   Reply With Quote
Reply

Share

Thread Tools Search this Thread
Search this Thread:

.
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


Times are GMT -7.   It's 03:23 AM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014