True duals on the cheap!
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,078
Likes: 2,150
From: Ohio
96RK
Now, take that MM plenom, cut it in half before the bends, remove the center divider and get it tigged back together, you will gain the Harley idle if you want to further your creativeness.
Now, take that MM plenom, cut it in half before the bends, remove the center divider and get it tigged back together, you will gain the Harley idle if you want to further your creativeness.
Thread Starter
|
Outstanding HDF Member
Joined: Mar 2010
Posts: 2,877
Likes: 2
From: Hallsville, Tx.
Hey '97, 2 questions: Do you have a more detailed description of this process, a link to a previous explanation, perhaps? Does this offer any kind of performance increase?
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,078
Likes: 2,150
From: Ohio
No link, just something I did from from Harley principles and feedback, My MM had the flat non-Harley idle that did nothing for me but I still wanted the EFI. Carbs give that idle because of crosstalk in the manifold and the MM is a individual shotgun barrel type of plenom. Several years ago, forum members were posting pictures of cutting a bottom section of the plenom out and removing a small section of the divider, I went a step further and cut the plenom about a half inch from the bends and removed the divider from behind the butterflies and to the cut, blended it at the bends, fortunately I have access to a tig welder.
I can't say it will help the performance of a slightly modified Evo from experiance, I put a stroker kit/heads in at the time of this mod and knew I needed more air and wanted the different idle. In theory, it should flow more air because of a larger runner volume and open up the channeled air forced into the MM sharp runner bend but no flow benches to prove it, just the backyard american traditon of what founded drag racing and just my labor involved.
Those MM plenoms are getting to be plentyful and cheap, I will gladly make the plenom mod(free) if someone wants to try it as a winter project.
I can't say it will help the performance of a slightly modified Evo from experiance, I put a stroker kit/heads in at the time of this mod and knew I needed more air and wanted the different idle. In theory, it should flow more air because of a larger runner volume and open up the channeled air forced into the MM sharp runner bend but no flow benches to prove it, just the backyard american traditon of what founded drag racing and just my labor involved.
Those MM plenoms are getting to be plentyful and cheap, I will gladly make the plenom mod(free) if someone wants to try it as a winter project.
Thread Starter
|
Outstanding HDF Member
Joined: Mar 2010
Posts: 2,877
Likes: 2
From: Hallsville, Tx.
No link, just something I did from from Harley principles and feedback, My MM had the flat non-Harley idle that did nothing for me but I still wanted the EFI. Carbs give that idle because of crosstalk in the manifold and the MM is a individual shotgun barrel type of plenom. Several years ago, forum members were posting pictures of cutting a bottom section of the plenom out and removing a small section of the divider, I went a step further and cut the plenom about a half inch from the bends and removed the divider from behind the butterflies and to the cut, blended it at the bends, fortunately I have access to a tig welder.
I can't say it will help the performance of a slightly modified Evo from experiance, I put a stroker kit/heads in at the time of this mod and knew I needed more air and wanted the different idle. In theory, it should flow more air because of a larger runner volume and open up the channeled air forced into the MM sharp runner bend but no flow benches to prove it, just the backyard american traditon of what founded drag racing and just my labor involved.
Those MM plenoms are getting to be plentyful and cheap, I will gladly make the plenom mod(free) if someone wants to try it as a winter project.
I can't say it will help the performance of a slightly modified Evo from experiance, I put a stroker kit/heads in at the time of this mod and knew I needed more air and wanted the different idle. In theory, it should flow more air because of a larger runner volume and open up the channeled air forced into the MM sharp runner bend but no flow benches to prove it, just the backyard american traditon of what founded drag racing and just my labor involved.
Those MM plenoms are getting to be plentyful and cheap, I will gladly make the plenom mod(free) if someone wants to try it as a winter project.
Bagger, that's a very generous offer, I may get back to you on that!
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,078
Likes: 2,150
From: Ohio
Road Captain
Joined: Mar 2009
Posts: 734
Likes: 0
From: Southern Missouri ( ozarks)
As for this topic,i've been goin thru this for a long time. Figure if you could get a muffler shop to make you some bends or go online to buy some U bends or J bends, you could copy somebodys left side.Hell you could even copy Bassanis for that matter.AS for heat shields I thought of this....Have the same bends copied for 2 1/2 or larger pipes,cut them down thru the center somewhere,have some brakets welded on them,have a chrome shop chrome those pieces or even powder coat them,attach them with the hose type clamps and you'd have a great set of true duals.Thing is,we're still gonna need a tuner though.....damn if we do,damn if we don't!!
Tourer
Joined: Sep 2010
Posts: 471
Likes: 9
From: Far NorCal
Found it new for $70 from HD Dealer on sale, he had 3 more too!
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
7 Surprising Harley-Davidson Products that Are Not Motorcycles
Verdad Gallardo
8 Best Harley-Davidson Motorcycles Ever
Pouria Savadkouei
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Tourer
Joined: May 2008
Posts: 449
Likes: 1
From: N. MS
Hey Jeff,long time no see......long story,i'll tell ya about it another time.I wasn't able to get to my emails for your address.....
As for this topic,i've been goin thru this for a long time. Figure if you could get a muffler shop to make you some bends or go online to buy some U bends or J bends, you could copy somebodys left side.Hell you could even copy Bassanis for that matter.AS for heat shields I thought of this....Have the same bends copied for 2 1/2 or larger pipes,cut them down thru the center somewhere,have some brakets welded on them,have a chrome shop chrome those pieces or even powder coat them,attach them with the hose type clamps and you'd have a great set of true duals.Thing is,we're still gonna need a tuner though.....damn if we do,damn if we don't!!
As for this topic,i've been goin thru this for a long time. Figure if you could get a muffler shop to make you some bends or go online to buy some U bends or J bends, you could copy somebodys left side.Hell you could even copy Bassanis for that matter.AS for heat shields I thought of this....Have the same bends copied for 2 1/2 or larger pipes,cut them down thru the center somewhere,have some brakets welded on them,have a chrome shop chrome those pieces or even powder coat them,attach them with the hose type clamps and you'd have a great set of true duals.Thing is,we're still gonna need a tuner though.....damn if we do,damn if we don't!!
Yeah, it's just ridiculous the prices they get for these things. There is a muffler shop in the building that my bodyshop is in. I even bend/weld a few pipes myself.
Fullsac gets $178.00 for 2 little pieces of pipe...sheesh, I can get a full set of dual pipes put on a truck for that price, including mufflers...lol.
Club Member
Joined: Jun 2007
Posts: 45,429
Likes: 2,898
From: Bedford UK
It is said that the crossover pipe was introduced by BSA or Triumph (I forget which) on their parallel twins, to deal with loud exhausts back in the 60s. To their surprise they got a couple of more HP. Certainly on the early Evos Harley claimed a little more torque for the dressers with crossover than for the staggered-pipe bikes.
A difference between Harley's cross-over system, compared with the Brit-bikes, is that the system is not symmetrical. So a Harley on true-duals will sound similar out of both mufflers, but with the crossover the right-hand muffler does more work. On later bikes the two mufflers look the same but are different internally, because Harley has tuned them to suit their different load.
I have used true-duals for many years now, initially a Fullsac kit, more recently Samson pipes plus S&S oval mufflers. They certainly sound great! Having said that I have got tired of the left pipe taking a rest on the primary casing, so am about to fit a SuperTrap 2-into-1. I have a dyno sheet for the TDs, and will be interested to see if the 2-into-1 delivers any change in performance.
A difference between Harley's cross-over system, compared with the Brit-bikes, is that the system is not symmetrical. So a Harley on true-duals will sound similar out of both mufflers, but with the crossover the right-hand muffler does more work. On later bikes the two mufflers look the same but are different internally, because Harley has tuned them to suit their different load.
I have used true-duals for many years now, initially a Fullsac kit, more recently Samson pipes plus S&S oval mufflers. They certainly sound great! Having said that I have got tired of the left pipe taking a rest on the primary casing, so am about to fit a SuperTrap 2-into-1. I have a dyno sheet for the TDs, and will be interested to see if the 2-into-1 delivers any change in performance.