Headers Dual v. Single crossover

[pedrocasper]

I have an 84 RT and want to replace the headers (existing ones have some dents in them that just are not nice to look at). Are there any "issues" (other then not being stock ) with replacing with a dual crossover with a single?

Why did BMW change the design? There must have been some benefit...to the dual crossover to necessitate a design change.

Thanks

[pedrocasper]

84 RT obviously means a 1984 R100RT.

[PHMarvin]

Hi, Petey,
I'm not sure, but I believe I read (on the internet, so it HAS to be true) that the second crossover gives the bike a bit more mid-range grunt. I never thought there was a problem with my '76 R90/6 (single crossover) and my '81 R100RT and 2 '84 R100RS's (2 crossovers) ran fine, too. Maybe Tom Cutter, Oak, or Ted Porter can give you better reasons why it is (or isn't) recommended.

[lkchris]

Replacing with a single crossover obviously reduces the volume of your exhaust system.

Kind of like installing a 2->1 system, i.e. bad idea and will reduce performance.

'84 RT could "obviously" mean R100RT OR R80RT, both of which BTW use same exhaust system.

[carockwell]

The cross overs allow more power in the midrange without affecting the top end. Using a set of duals with no cross over will cost a few HP (Like 2HP) at about 3500 rpm.

[BubbaZanetti]

my airhead had both crossovers chopped off and bolts welded into the holes. never knew why the previous owner had done that. never knew what it felt like with crossovers, haha

[pmdave]

Well, 2 HP is a LOT of HP for an airhead, but you can lose 5 - 10 HP through poor carb jetting, tight valves, retarded timing, wrong gearing, etc. None of my airheads have had dual crossovers, and I didn't notice any loss of HP. I'd suggest that keeping the bike tuned, valves set properly, etc. will make more of a difference than the presence or absense of the second crossover. My vote is for headers with single crossover, but let's get stainless steel, eh?

If you're getting beat by your buddy on his similar airhead, slip in a final drive with a higher ratio and let your motor spin. Or slip in an oilhead motor and glue on airhead valve covers and fake carburetors.

pmdave