exhaust compression and tuning? Short Pipes?

[jjwithers]

It has been a few years since my last airhead assembly. I seem to remember when i was doing one of my bikes that i was advised against shortened exhaust pipes or 2 into 1 pipes because it makes the carbs harder to tune, or keep in tune. I seem to remember being told that the exhaust compression was part of the design of these bikes.

Am i imagining all this or does this hold some truth?

i will want a reliable (low maintenance) bike over cool pipes.

The plan is to make a /5 with 32mm bings and the Sienbrock kit on there (to give it a supposed 35% gain), electronic ignition, 5 speed, and a fancy paint job.

[Garnet]

I am no expert, but it seems that BMW designed the headers and air filter box very well compared to their contemporaries. Nothing is gained by messing with them unless other MAJOR engine mods are done.

[jjwithers]

that is what i was told... and i don't want to break what already works for the sake of looks.

[mattcfish]

It has been a few years since my last airhead assembly. I seem to remember when i was doing one of my bikes that i was advised against shortened exhaust pipes or 2 into 1 pipes because it makes the carbs harder to tune, or keep in tune. I seem to remember being told that the exhaust compression was part of the design of these bikes.

Am i imagining all this or does this hold some truth?

i will want a reliable (low maintenance) bike over cool pipes.

The plan is to make a /5 with 32mm bings and the Sienbrock kit on there (to give it a supposed 35% gain), electronic ignition, 5 speed, and a fancy paint job.

I've always liked my 2 into 1 better than stock pipes. When I was using Bings there was a noticeable improvement in how smooth the bike ran, especially in the higher RPM's when extraction came into play. They also seemed to stay in tune longer. The Dellortos I use now are a bit more fussy, but they like the pipes.
Pros:
Lower cost than new stock pipes
Perform better (in my opinion)
Durable (mine have lasted over 18 years and are still going strong)
Sound nice. Not too loud, but a noticable haul ass sound (addictive).
Look great

Cons:
Die hard airhead conservatives don't like them. ....Hmmm maybe that's a pro

[Major Softie]

A well designed intake and exhaust is making use of pressure waves to get the most torque, especially in the mid-range. BMW seems to have done a very good job of this. Even in a fairly stock motor, you may be able to make some improvements in peak power over stock by playing with the intake and exhaust length/volumes, but you usually lose more in the middle than you gain on the top.

In a heavily modified motor, it is, really, a different motor, and the best intake and exhaust will be different than for a stock motor. It's not hard to come up with something that works, but finding the perfect combination that develops the best overall power is not easy at all. The guys who are really good at figuring such things out are very valuable individuals, especially those who can do it with a minimum of experimentation and dyno time.

Of course, if you just put a blower on the damn thing, it makes the plumbing questions so much easier.

[Deleted User 62]

It has been a few years since my last airhead assembly. I seem to remember when i was doing one of my bikes that i was advised against shortened exhaust pipes or 2 into 1 pipes because it makes the carbs harder to tune, or keep in tune. I seem to remember being told that the exhaust compression was part of the design of these bikes.

Am i imagining all this or does this hold some truth?

i will want a reliable (low maintenance) bike over cool pipes.

The plan is to make a /5 with 32mm bings and the Sienbrock kit on there (to give it a supposed 35% gain), electronic ignition, 5 speed, and a fancy paint job.

I've always liked my 2 into 1 better than stock pipes. When I was using Bings there was a noticeable improvement in how smooth the bike ran, especially in the higher RPM's when extraction came into play. They also seemed to stay in tune longer. The Dellortos I use now are a bit more fussy, but they like the pipes.
Pros:
Lower cost than new stock pipes
Perform better (in my opinion)
Durable (mine have lasted over 18 years and are still going strong)
Sound nice. Not too loud, but a noticable haul ass sound (addictive).
Look great

Cons:
Die hard airhead conservatives don't like them. ....Hmmm maybe that's a pro

Matt, yours is a Mac, is it not?

[mattcfish]

Matt, yours is a Mac, is it not?

Yes.... I had Luftmeisters on order for about 2 months. This must have been when the company was going under. I had to cancel the order, my original BMW system was crumbling away. I found these for a bargain price back in the early 90's. Did I say anything about how you can also repack the muffler.
Love these pipes. My bike is a joy to ride.