Inline 4 Exhaust question

[Hammered]

Ok hammered. Looks are looks and are cool, and basic theory that if u give the motor any kind of decent 'drain' (i.e. exhaust), it will work pretty well.

Just sayin' that don't expect anyone on this site to give you good advice on "how sensitive" gs's are to backpressure, etc? C'mon man. Do YOU have sophisticated flow/back-pressure testing eq in ur garage? Neither do we (at least most of us as far as I know/have read).

Actually, yes. The main reason I came here to ask the tech question was because some of the guy and gals here know more about these bikes than the mechanics back in the day. And i understand flow restriction on both ends. knowing if the GS is overly sensitive to different levels of back pressure would tell me to build a smaller or larger header chamber and how many and to what degree all the different angles in the exhaust should roughly be. No, I cant, with the gear in my shop, test the intake to the exhaust CFMs. But I cant build my cold air intake roughly the same volume that my exhaust main header tubing will be. I mean I wasnt asking for a flowchart on the stock numbers these bikes ran 30 years ago, but knowing what others who have owned them experienced helps.


And while on the subject. Anyone ever read about of try running a cold air intake on one of these? Im doing it (A) to hide the intake system a little and fill in some of the open/empty space and (B) cause I havent seen anything on someone else doing it. I did say I was building a custom.

[Steve]

Ok hammered. ... Do YOU have sophisticated flow/back-pressure testing eq in ur garage? Neither do we (at least most of us as far as I know/have read).

You would be surprised to see what he has in his garage.

I've been there, I've seen it.

.

[Hammered]

You would be surprised to see what he has in his garage.

I've been there, I've seen it.

.

You still in Florence or did you finally get to go home?

[Speedo]

wow - talk about being summarily humbled. Genuflection 2 u.

btw, have you seen "World's Fastest Indian"? Seriously. Have you? See it, you'll get all teary eyed and thank me.

anyhoo, see my other posts that may (or not - if not, sorry) be of interest to u...

http://www.thegsresources.com/_forum/showthread.php?t=149740

May I very very humbley ask this question(?): having seen ur basic concept (looks great and really cool btw) which is a leather-british-Brooks saddle-bicycle seat type of thing with an upright riding position, what is the point of obsessing on exhaust flow characteristics etc? Your ride is an aerodynamic brick/dinosaur?

I mean, if I built the coolest looking but Barn-Door-ish hotrod (and there are a LOT of 'em out there), even if I have CFM flow bench (for intakes and the like), and whatever the thehelll they use to flow test exhaust pipes, my "brick" ride (much like a bike) would not be able to take advantage beyond apx maybe 50-60mph.

I guess I'm just asking since I've wasted...err, I mean "invested" SO much $$ in various hotrod projects over the past 25 years.

Ok, fine, assuming you are a hotrodAtheist and won't listen to reason (I never did...well, now i do...):
- so you want "real" flow numbers in CFM off of an official "flow bench" as far as head (combustion chamber), intake, exhaust, etc. Well, may I suggest contacting Vance and Hines or Yoshimura? Their records speak for themselves. These guys know (or used to know).

We average pukes in this forum (again, if I'm off, surprise me y'all...) just want our rides to work, work good/right, and work good/right for the long haul (i.e. not break every other week like drag-racer stuff). Ok and maybe have the rest of us be impressed with your work/ride. Getting something old to look good AND work good is hard. VERY hard and very time consuming. The bikers/rodders who spend all the time and energy to do this deserve a lot of credit.

Rant over.

[GregT]

For what you want - a cruiser type power - the system you suggest will work reasonably well IMO.
The CV carbs are quite sensitive to pipe changes yes, but there's a lot of info here which may help.
Your twin tail pipes & mufflers will act as a pressure bleed resistor which can be tuned - washers with different size holes would be easy.
There will not be any exhaust scavenge/crossover problems unless you're planning on running an ungodly long duration set of cams - a six is the only setup which has problems with a collector this close to the ports.
Be careful with your cold air setup - try not to pressurise the airbox as this will cause more problems than the exhaust.

Greg T

And I met Burt Munro a couple of times - he wouldn't have gone on line to ask, he'd have just tried it !

[reddirtrider]

ps As far as header / exhaust coating. Do not do yourself. Don't D*ck around and send it off to JetHot (or EQ). They have all the powder coat paint booths and ovens and will do it right. My Gs750 JetHot coated Yosh headers have lasted 20 years and counting. No rust. No problems. My Ford 460 truck headers got Jet Coating (silver as opposed to black on Suzi) 5 yrs ago as well....look perfect and brand new. Just an opinion from someone who has spent a buttload of money on various hotrod stuff (and a ton of my own time too) over the yrs and knows what's what and what's worth it....

I'd have to disagree with you on the coating. It's no more difficult than painting your bike, which is 90% prep - same here. If you can do that, you can coat your exhaust. You just need an oven big enough and most are for bike exhausts.

[Hammered]

The reason Im putting as much time into the exhaust design is I plan to ride the hell out of this thing. And ex rodder or not, gas aitn as cheap as it used to be. I live in SC but go home to Northern VA every chance I get and if I can squeze I few extra mile per gallon, then i say why not. Its not as if I plan to finish this build any time soon. As I progress, the concept evolves a little here and there. At one time, I had planned on cutting down the shocks to lower it, but since then, Ive designed a mount to run 2 3" dia air bags. Nothing about this bike will be stock when Im done (whenever that may end up being) So I figure why not step it up every place I can.
As far as Techlines coating,Ill be using Colorgard. Its an air dry coating that cures at about 200 and bakes on harder with the exhaust. A HVLP gun like suggested will do the job great.

[Steve]

You still in Florence or did you finally get to go home?

Finally made it home this past weekend.

Got home for a week near the middle, but was down there for 10 weeks, total.

.

[TheCafeKid]

The reason Im putting as much time into the exhaust design is I plan to ride the hell out of this thing. And ex rodder or not, gas aitn as cheap as it used to be. I live in SC but go home to Northern VA every chance I get and if I can squeze I few extra mile per gallon, then i say why not. Its not as if I plan to finish this build any time soon. As I progress, the concept evolves a little here and there. At one time, I had planned on cutting down the shocks to lower it, but since then, Ive designed a mount to run 2 3" dia air bags. Nothing about this bike will be stock when Im done (whenever that may end up being) So I figure why not step it up every place I can.
As far as Techlines coating,Ill be using Colorgard. Its an air dry coating that cures at about 200 and bakes on harder with the exhaust. A HVLP gun like suggested will do the job great.

How do you figure changing the exhaust will allow you to GAIN HP?? Everything done through the years for performance, or looks, has shown quite the opposite. Sure, you're dumping 40 lbs of weight, but in order to get the bike jetted right, you're expending more fuel. Seems quite contridictory to your idea..

[Hammered]

How do you figure changing the exhaust will allow you to GAIN HP?? Everything done through the years for performance, or looks, has shown quite the opposite. Sure, you're dumping 40 lbs of weight, but in order to get the bike jetted right, you're expending more fuel. Seems quite contridictory to your idea..

I never said I was increasing the HP by doing anything to the exhaust design. But if the design is good and I get a good coating with the Techline, I should see some gain in power. Plus with a change in the gearing, I should see a gain. And as you noted, the weight loss will add tot he MPG even if its a small amount.

[TheCafeKid]

I never said I was increasing the HP by doing anything to the exhaust design. But if the design is good and I get a good coating with the Techline, I should see some gain in power. Plus with a change in the gearing, I should see a gain. And as you noted, the weight loss will add tot he MPG even if its a small amount.

Well....Unless you manage to get the EXACT same amount of backpressure on that exhaust, I am betting it will flow differently (probably a little better) which will require an upjetting. Upjetting means more gas...Im just sayin..

[Speedo]

lovin to see all these posts from you OH guys (being one myself...Cleve/Dayton/Columbus/Mansfield/Lancaster). warms the heart.

Now, to bidness...

Reddirtrider,
You said
I'd have to disagree with you on the coating. It's no more difficult than painting your bike, which is 90% prep Really? I've been a painter (in a past life). How are you painting the INSIDE of that header? Just curious...maybe I'll learn something...

Also, I have to agree with CafeKid in that more power means more fuel (in general)....unless you have some ridiculously awesome plan for max power (and fuel) at full throttle and lean/miserly thing going on at part-throttle and most other driving conditions (Chebby Corvette has done it right/very well in this regard over the yrs).

Do tell...

[Hammered]

My plan for attempting to squeeze all the MPH out of the build I can will come from a change in gearing. I dont need to launch like a bat out of hell on this. If I can drop the overall RPM, I should make up for any, if any jetting over the stock size. I am building an airbox type intake. Now as far as coating the inside of the header with Colorgard. Ive spoken with a REP and Im told that if need be, I could use a ball brush to coat the inside. Im not sure Ill need to coat the inside of the header. Colorgard really doenst need much in the way of prep other than for appearance sake so, a little time with a flap wheel, wire wheel and bastard file should give me all the exterior prep I need.