GS Exhaust

[mixongw]

Has anyone ever put four straight pipes out the back?

[mark m]

Why do you ask?

Can it be done?

Absolutely. In fact, 4 individual pipes with megaphones on them is the optimum power producing arrangement. Hard to package and heavier than a 4-1, but overall more and smoother power.


Has it been done?

I expect so. Can't imagine it hasn't, anyway. The original Honda 750-4 came with 4 individual pipes when it was first released. Probably others, as well.


Mark

[mixongw]

I'm visualizing the look of Vance & Hines Long Shots on both sides. I'd love to hear that. Custom fab is probably the only way and expensive.

[mark]

Saw the old Honda CBX six cylinder with a 6 into 6 once. Sounded good!

[mark m]

I'm visualizing the look of Vance & Hines Long Shots on both sides. I'd love to hear that. Custom fab is probably the only way and expensive.

I see what you were thinking. That might be pretty cool to see. You are most definitely looking at a custom job for that. Expensive? Depends on your definition. I know of a couple of guys who fab motorcycle stuff and are more than capable of what you are thinking, but it won't be cheap. You can do it yourself with a MIG welder, some mandrel bends and a bit of practice and patience, but it all depends on how bad you want them. I would gladly offer advice and information on the welding and exhaust dimensions you want, but I can't come over to help since we are likely in different countries...


Mark

[LW_Icarus]

Ive almost thought it would be worth it to get all the stuff necessary to make custom motorcycle exhaust. after looking at whats available for alot of bikes these days, being able to build stuff like crossover tubes and things will be a handy thing.

would be cool to do an all equal length supertrapp style megaphone system, theyd be staggered a bit, and Im thinking Id build crossovers into em too. 4 silencers would be heavy and expensive would be the downside.

[mark m]

Ive almost thought it would be worth it to get all the stuff necessary to make custom motorcycle exhaust. after looking at whats available for alot of bikes these days, being able to build stuff like crossover tubes and things will be a handy thing.

It's not that hard, a MIG or TIG welder, a welding course or two, some basic metalworking tools and the willingness to get in there and mess up some stuff will do it. Considering the quality of current aftermarket stuff (especially what's available for our vintage bikes), making your own seems less unreasonable. Doing it yourself lets you pick header sizes and lengths and lets you get exactly what you want instead of having to settle. In my case, I want to do a true megaphone tailpipe (not what Vance and Hines call a megaphone) with the muffler section after the reverse cone to get the maximum performance I can from the bike. This is for my existing Kerker header. Eventually, I want to do a full custom 4-1 with megaphone for max performance and minimum weight.

would be cool to do an all equal length supertrapp style megaphone system, theyd be staggered a bit, and Im thinking Id build crossovers into em too. 4 silencers would be heavy and expensive would be the downside.

If you do a 4-4 system, I wouldn't worry about crossovers. That is a great pipe arrangement and should work very well if properly designed (lengths/tube sizes), without crossovers. Getting crossover pipes to work well takes a LOT of dyno testing and simply adds complications you don't need. The 4 silencer problem is where the weight and packaging issues come into play. Keep in mind, the silencers can be pretty small, as they are only working on one cylinder's output, rather than all 4. That would be a cool pipe to see and hear. Let us know if you ever take a run at it.


Mark

[jhw84]

If you do a 4-4 system, I wouldn't worry about crossovers. That is a great pipe arrangement and should work very well if properly designed (lengths/tube sizes), without crossovers. Mark

My Honda has 4 pipes, with a crossover between 1 and 2, and one between 3 and 4. None between 2 and 3. Helps with scavenging.

Perhaps you could pick up a stock 4 to 4 Honda exhaust on Ebay and modify it to fit?

Glad Im not the only one who likes the 4 to 4 pipes.

[LW_Icarus]

Ive been fortunate enough to get plenty of time on a mig welder, (and a buzzbox for that matter too ) and have notched and bent tubing before.

something to bend the pipes with would be the biggest obstacle for me to manufacture an exhaust, and finding good quality pipe to work with. Ive seen decent benders that use hydraulic jacks, but you end up with the little wrinkles in the pipes bends that way.

I started pondering this before I spent the money on a new crossover and seals for my stock exhaust.

I was also imagining a pair of straight shooter style pipes per side, fat enough to house a universal style baffle. ultimately Im gonna have to do something as the stock exhaust is pretty well thrashed inside, although outside it looks fine.

[mark m]

something to bend the pipes with would be the biggest obstacle for me to manufacture an exhaust

You don't bend the tubing, you cut mandrel bends to the desired angle and weld the pieces up. Check out:

http://www.headersbyed.com/index.htm

for more details and materials. It is virtually impossible to bend bike size exhaust tubing with a die bender without getting the wrinkles or collapsing, it is simply too thin wall to work that way. The prebent pieces are done on a mandrel bender, which has a piece that goes inside the tube (the mandrel) that prevents the tube from collapsing as it is formed. For your bike I would probably use 1-3/8" or 1-1/2" OD tubing with 0.049" wall in mild steel and 0.035" wall in stainless steel. You need a better look at it to determine correct lengths and sizes, but that would be my first guess without crunching any numbers.

was also imagining a pair of straight shooter style pipes per side, fat enough to house a universal style baffle.

Whatever works for your look. I like megaphones, both for style and performance, but everybody is different. Make yourself happy and you will get what you want from it.


Mark

[KARMAN1970]

I'm not sure a 4-4 would make more power but it would sure sound wicked. Four cylinder motors usually make most power (or at least have the best power and torque curves) with a 4-1 header. I cut the mufflers off my GS550L after the 2-3 crossover and right after where the 1-2 and 3-4 pipes merge with just a dremel tool. The tone is a lot deeper and completely changes the bike's sound. All the other guys with crotch rockets comment about how awesome it sounds.
If you are contemplating building a new exhaust, I would just hack the stock pipes right before they join. If you like the sound, just weld on four seperate stright pipes and a few mounting tabs. Then buy whatever mufflers you want and weld them on if you want. With just the straight shorty tubes the motor (at least mine did) leans out at about 6000 rpm though. Just my 2 cents worth.