Tuning issues - drag pipes

[Boe Cole]

Friend's grandson bought a 71 Ironhead chopper.  He asked me to help sort out some of the mechanical issues which I am happy to do but found that it has drag pipes on it.  While it sounds nice (too loud for me but......), I'm pushing for him to get some baffles in the pipes as it is my strong belief that the open pipes kill the low speed operation of the engine - the engine needs some back pressure in the exhaust to run well.  He says that it runs well when he gets it going and pulls strong but at low rpm's it does not run well which reinforces my recommendation.

Am I right on this?  Very limited experience on ironheads.

I volunteered to rebuild the carb which is within my mechanical abilities but don't think it will do a lot of good with the open pipes.

[99 EVO Fatboy Rider]

I'll try to spell this correct, krome werks hp plus baffles.

Or the cheap way out. The washer trick. Go to nightrider.com to the v-twin section and read how to make drag pipes work for the washer trick. My brake buzzer went off or I'd post the correct site, no time right now!

[FLTRI]

...Go to nightrider.com to the v-twin section and read how to make drag pipes work for the washer trick.

Here ya go:
http://www.nightrider.com/biketech/exhaust.htm
HTH,
Bob

[garyajaz]

all drag pipes do is make noise, get ticketts and really narrow the power band.
when i was drag racing my 80 inch iron on alky i used them.
all or nothing.  ended up using reverse cone megaphones (open) and got better times.  much more pull mid range.
now run some two inch one peice pipes made for me years ago.
(two inch cause of big inches.  also equal volume and set up with formula with intake tract length in mind.
there are pipes all over catalogs that will have some baffles and do just fine..

[Jlbruggs]

This explains a lot, 5 years ago I bought a 93FXRS-conv with 2 3/4 drag pipes and it felt off in the acceleration at low speeds. I too thought it needed more back pressure n bought cheep 1 3/4 drags with baffles. It helped tremendously, however cheep pipes fit like crap n just looked off and turned blue way faster than they should have. I will try the washer in the other pipes till I can afford the V&H straight shots I want.

[nibroc]

ironheads run very good with drag pipes--that is my prognosis and i'm stickin with it!!!!

[Hillside Motorcycle]

As simple as this;
We've done this since the mid-90's, when Dyno tuning, most drag pipe-equipped bikes, and didn't/couldn't google search it, to figure it out.
Drill a hidden clearence hole for a 1/4" bolt, 3" from the end.
Using a 1/4" X 1 1/2" bolt, stack 3-4 5/16" nuts on the 1/4" bolt, and nut it.
Want more low end?
Drill for a 5/16" bolt, and use 3/8" nuts.
Maintains the sound and look, and costs only pennies.
Scott

[99 EVO Fatboy Rider]

ironheads run very good with drag pipes--that is my prognosis and i'm stickin with it!!!!

And sound awesome!

[Boe Cole]

Thanks All - Seeing as how he is low on bucks (going and paying his way through college), I think I'll sport him to a couple thumb screws as reflected on nightrider.  Guess I'm just last of the big spenders:-)

[99 EVO Fatboy Rider]

Thanks All - Seeing as how he is low on bucks (going and paying his way through college), I think I'll sport him to a couple thumb screws as reflected on nightrider.  Guess I'm just last of the big spenders:-)

I've got local frinds that run like that after me showing them the mod.  it's a cheap way to get something back for less.

[Winston Wolf]

As simple as this;
We've done this since the mid-90's, when Dyno tuning, most drag pipe-equipped bikes, and didn't/couldn't google search it, to figure it out.
Drill a hidden clearence hole for a 1/4" bolt, 3" from the end.
Using a 1/4" X 1 1/2" bolt, stack 3-4 5/16" nuts on the 1/4" bolt, and nut it.
Want more low end?
Drill for a 5/16" bolt, and use 3/8" nuts.
Maintains the sound and look, and costs only pennies.
Scott

Do this, it does work.  Then you will have to lean out the carb just until it will run without breaking up. Don't go much further, or it will get too lean on the top end.  If you put a a/f meter on a bike with drags you will see it go way rich up to about 4000 then get back to normal as it keeps reving. I have drags on my 74 sportie with an adjustable main bendix, I was surprised how lean I had to adjust it to stop the rich break up. Just so you know, if it's breaking up rich, it's in the 10:1 range.