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Creating Custom Exhaust..Inputs?

Old 10-08-2010, 05:23 AM
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Creating Custom Exhaust..Inputs?

With the weather begining to cool off I have decided this winter I am going to create a custom exhaust for my hawk. My goal is to create an undertail exhaust similiar to this.

http://www.youtube.com/watch?v=nWPhj...eature=related

Now what I am contemplating is running a true dual setup rather than a crossover mid-pipe setup. In automotive applications this can be incredibly beneficial..however i am not sure how this would affect the performance of the hawks V-twin. I understand that I will still need to keep some backpressure... just wondering how a true dual setup would affect her.

Thanks!
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Old 10-08-2010, 05:43 AM
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I heard in automotive applications an X-pipe and H-pipe type area helps create negative pressure waves which in turn draw air out of the cylinder head, which are drawn out by the lower pressure (negative pressure waves) areas of the muffler that add on to the head tubes' negative pressure waves. I'm not sure of that here because our bike's exhaust is fairly powerful but you may want to reconsider. Just my .02
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Old 10-08-2010, 06:19 AM
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Well the front exhaust tube is pretty straight forward. Not a whole lot of bending happening which is good.. The rear on the other hand looks pretty restrictive...especially if you remove the right side muffler and see that piece of metal left over from where the two pipes are welded together... Maybe if anything a new crossover pipe would help.. Anyone else notice the "quality" of the welding going on with the hawks exhaust?
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Old 10-08-2010, 06:29 AM
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I've dreamed of creating a custom exhaust for my bike, but I don't have the experience, tools, or the contacts to make that happen.

We've all probably heard that you should try to match the length of the exhaust tubes so that there is equal pressure, but couldn't you just leave some "restrictions" in the rear tube instead of snaking it all over the place to get it the same length as the front? Couldn't that equalize the pressure just as well?

I'm guessing it's not that easy, or else it would have been done already . . .
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Old 10-08-2010, 06:42 AM
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Originally Posted by evines View Post
I've dreamed of creating a custom exhaust for my bike, but I don't have the experience, tools, or the contacts to make that happen.

We've all probably heard that you should try to match the length of the exhaust tubes so that there is equal pressure, but couldn't you just leave some "restrictions" in the rear tube instead of snaking it all over the place to get it the same length as the front? Couldn't that equalize the pressure just as well?

I'm guessing it's not that easy, or else it would have been done already . . .
That is true! I didnt really think that maybe the rear is more restrictive based on the fact of equal length tubes and it needing to be more restricted... However after trying to get some Air Fuel Ratio readings using a wideband I found that there is quite a bit of exhaust turbulence...so much so that it is impossible to achieve and air fuel reading without having an o2 bung actually installed in the headers. Certainly would be nice to be able to test the pressure differentials stock and with a dual setup.
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Old 10-08-2010, 07:14 AM
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Considering some of the best (ie race tested) exhaust systems from yoshi etc still retain some kind of a connector pipe on most motorcycles. I encourage you to go for the design you want but would also say there isn't too much need to reinvent the wheel here. On the hawk I would start my custom work from the "Y" connector back not the header back. Also considering that if you where to rebuild the whole header and decide to use slightly larger diameter tubing you will need to have a seriously hopped up motor cams and all to see the benefits, as well as to get it to run right since the motor is designed to operate withing certain back pressure parameters. When you change one thing a lot it usually means you will have to change other things a lot. If you start at the "Y" though you can get away with a lot more designs.
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Old 10-08-2010, 07:44 AM
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Originally Posted by cornandp View Post
Considering some of the best (ie race tested) exhaust systems from yoshi etc still retain some kind of a connector pipe on most motorcycles. I encourage you to go for the design you want but would also say there isn't too much need to reinvent the wheel here. On the hawk I would start my custom work from the "Y" connector back not the header back. Also considering that if you where to rebuild the whole header and decide to use slightly larger diameter tubing you will need to have a seriously hopped up motor cams and all to see the benefits, as well as to get it to run right since the motor is designed to operate withing certain back pressure parameters. When you change one thing a lot it usually means you will have to change other things a lot. If you start at the "Y" though you can get away with a lot more designs.

Right.. There is no way you can really change the headers on these and no way i would really want to.. Just the "y" is all I am concerned about changing. Ill probably just keep the setup the way it is but maybe attempt a less restrictive undertail setup.. Wont be for about a month but ill keep yall posted with pics.
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Old 10-08-2010, 10:47 AM
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There's another video of that bike that that guy has uploaded:

http://www.youtube.com/watch?v=fkiqnrjXTLY

Looks like it's totally different from the original header. The two cylinders have their own pipes going to their own respective muffler, and right before the mufflers there's a crossover type pipe. It's not a 2-1-2 like the factory header, its 2-2 with a crossover. I might be wrong but that's how the 1098 Duke is.
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Old 10-08-2010, 11:05 AM
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Wow! What a crazy setup.. I wonder if when he got it dynoed what the end result was? Pretty cool setup but way to much for what I had planned. Those mufflers are pretty nice.

I was contemplating running both exhausts around the right side of the swing arm and out from under the tail.. Again though all contemplation. But Im glad you found that video! Going to help me out a lot!
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Old 10-08-2010, 11:15 AM
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Cool man, I'm glad I looked. Good luck and make sure you post pics when you start building.
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Old 10-09-2010, 05:10 PM
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Old 10-09-2010, 10:13 PM
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Take it from a guy who has the skills, the tools, and the means to create an exhaust for his bike, do not do this. If you want one, I would gladly sell you mine, or do a straight up trade for the entire system on your bike including your carbs for mine. here is a list of the things you and I would have to switch:
subframe
battery tray
exhaust mounts
header and pipes
carbs
locking mechanism for seat

I have a lot of time into it, and it isn't worth you spending the time doing. Also, the videos you have shown all show an exhaust system that will not work out with the wheel travel of the vtr. Mine is a small shim above the exhaust away from no problems, but for now I run lots of preload.
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Old 10-10-2010, 10:12 AM
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Some people swap in the R1 rear subframe and tail, and use that exhaust. Then you just need to make your own mid-pipes.
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Old 10-12-2010, 03:30 PM
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Well I am still undecided... Definitely not going to be changing the factory headers and collector.. But I am going to an undertail look... Just not sure what type of mufflers if "any"... :-) Not sure if running straight pipes to the undertail will kill my torque or not... Any thoughts? I think I am just excited to start welding and bending some tubing.
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Old 10-12-2010, 09:12 PM
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Straight pipes are annoyingly loud and If I am correct, a good set of pipes will provide the proper back-pressure to make more torque
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Old 10-13-2010, 01:05 AM
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this set was for sale on here sometime ago,this is the route im thinking of taking,if i could find someone to bend new pipes for a good price.
just change the mids some and i think it could work good for a undertail.
as you can see,the pipes are single for each head.
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Old 10-13-2010, 08:00 AM
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Originally Posted by Just_Nick View Post
Straight pipes are annoyingly loud and If I am correct, a good set of pipes will provide the proper back-pressure to make more torque
Any ideas for a slim line small muffler for the bike? I kinda like the ones in the video but they are still a little big.... http://www.youtube.com/watch?v=fkiqnrjXTLY
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Old 10-13-2010, 03:52 PM
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Why not just use a CBR or ZX6R single undertail exhaust?
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Old 10-13-2010, 05:10 PM
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cbr will not fit with stock tail. The problem is the tire clearance during wheel travel. You cannot put it high enough. Mine are much thinner and there is still a rub. The R1 tail looks neat, but it is not a cake walk.
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Old 10-13-2010, 08:08 PM
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It would fit if you trimmed the wheel well, no?
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Old 10-13-2010, 08:19 PM
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nope, stock subframe, exh. against the bottom of the seat and the tire will hit in full travel. If you dont believe me I can sell you a stock cbr600rr exh. that you can try
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Old 10-14-2010, 06:53 AM
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Ive got something planned... ;-)

Going to take a month or so to complete but its going to be pretty sweet. Ill update when i can and keep all the measurements for future reference. Its going to be an undertail exhaust utilizing the factory downpipes and "y"

Thanks again for everyones inputs...its helped me out a lot.
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Old 10-14-2010, 08:46 PM
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Honestly though, how often is your suspension fully compressed, unless you're fat and you're doing hard wheelies or jumping it. Isn't the chain binding at that point anyways?
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Old 10-14-2010, 08:57 PM
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Originally Posted by Just_Nick View Post
Honestly though, how often is your suspension fully compressed, unless you're fat and you're doing hard wheelies or jumping it. Isn't the chain binding at that point anyways?
If you never get to close to full compression, then your suspension is set too stiff...... and no the chain doesn't bind at that point unless you have it set too tight to begin with.
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Old 10-14-2010, 09:29 PM
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Originally Posted by 8541Hawk View Post
If you never get to close to full compression, then your suspension is set too stiff...... and no the chain doesn't bind at that point unless you have it set too tight to begin with.
Good to know.
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Old 10-19-2010, 05:21 PM
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Well I am having a hard time finding pipe... Does anyone know any local stores that carry thin walled pipe approx. 1 1/2" ID?

I really dont want to purchase online but so far thats all I have found.

Thanks!
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Old 10-19-2010, 06:16 PM
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Originally Posted by 8541Hawk View Post
If you never get to close to full compression, then your suspension is set too stiff...... and no the chain doesn't bind at that point unless you have it set too tight to begin with.
+100

Hit some bumps on the highway like they have in MKE or CHI and you will get full travel no matter what the spring rate or damping. 4" bump at 70mph
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Old 10-21-2010, 05:16 AM
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Well I started bending some pipe last night.. Took me a few days to find the right size pipe but finally found some at midas. Rather pricey but it'll work. Going to start adapting the undertail assembly to accept the pipe and hopefully will be up and running soon.
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Old 11-07-2010, 02:13 PM
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Ok so I finished the exhaust.. Im not going to lie its not really an exhaust.. More as an "test pipe" exhaust. I ran both exhaust tubes up under the tail and out under the tail light. Looks really good and sounds like a something from hell.. I haven't had the privilege of pissing off the neighbors yet but so far it is exactly what I wanted to start with.. Im going to leave it as is for right now and finish up the rest of the fabrication for the heat shielding and undertail.. But i am very pleased with the results. Ill take some pictures as soon as possible and get them on here.

As for tuning well I installed a flo commander which will be a good base line for changing the a/f ratio if needed when i take it out for a ride. The good thing is the amount of restriction that I added to the exhaust assembly while running open pipe hopefully will be about equal to stock.. Only one way to find out though... :-)
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Old 11-10-2010, 05:09 PM
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Here are the pictures of the almost finished product... I still havent decided if I am going to add 2 more pipes to the tail section yet but overall I am very pleased with the results. Had to fabricate the undertail section a bit but came out nicer than factory in my opinion. Was really easy to do also..

I am also going to be doing an exhaust wrap as well... but just wanted to get these pictures up for everyone to see. :-)

Also will be doing a video soon as well... Which should be fun.. :-)
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