modifying an exhaust can-- can it be done?

[3imo]

any suggestions on how to remedy that, considering the modification I plan?

what about rejettin the carbs?

[galahs]

I don't think it would be too much concern.

1, try and have the collector as far back (close to the muffler) as possible.


yeah, you would have to rejet it as a shorter exhaust system would tend to run even leaner than a standard sports exhaust.

[3imo]

yeah, you would have to rejet it as a shorter exhaust system would tend to run even leaner than a standard sports exhaust.

ok, now we are getting somewhere...  would you suggest a stage 3 dynojet kit?  or is that overkill.

my main concern is keeping the engine alive. performance is second.

[galahs]

I'm not sure of the specifics but your heading in the right direction. Especially if your going to add k&n air filters whilst your at it! 

As not many people have done modifications that shorten the length of the system by this much you are treading new ground.

It will all depend on things like how well your muffler flows, design (straight through, dog leg) the size of its internal pipe etc.

An exhaust oxygen sensor might be required to determine what you need. But remember, their is saftey in richness. 

you can always lean it out later on once you learn the characteristics of the mod.

[werase643]

will it hurt...probably not
will it be better performance.....probably not

the only thing that will damage the bike....that i know of... is no exhaust will burn the ex valves and i am not sure why....i never wanted no pipes

there is alot of design going into an ex pipe....go look at some ASME info for books or sites

the issue is going to be very short primaries connected to a chopped up muffy
yes you can get it to work

some times it is better to just do it and see what happens
it might run fine
it might run lean
it might run fat
until you inspect the plugs....you won't know

[3imo]

I'm not sure of the specifics but your heading in the right direction. Especially if your going to add k&n air filters whilst your at it! 

I have to, to hide the battery.  Thats gonna have to be custom too.  I have some Ideas brewing for that.

some times it is better to just do it and see what happens
it might run fine
it might run lean
it might run fat
until you inspect the plugs....you won't know

Thanks! 

[galahs]

Exhaust valves can burn out if no header pipes are fitted or they are extremely short as the exhaust flow from to combustion chamber will be too violent and fast which increases the scavenging effect (due to valve over lap the intake valve open before the exhaust valve closes) allows more air to be drawn into the cylinder.

Now, valve burning occurs as a result of a very lean-burning engine. In order to achieve a theoretical optimal combustion, an engine needs 14.7 parts of oxygen by mass to 1 part of gasoline (again, by mass). This is referred to as a stochiometric (chemically correct) mixture, and is commonly referred to as a 14.7:1 mix. If an engine burns with less oxygen present (13:1, 12:1, etc...), it is said to run rich. Conversely, if the engine runs with more oxygen present (16:1, 17:1, etc...), it is said to run lean. Today's engines are designed to run at 14.7:1 for normally cruising, with rich mixtures on acceleration or warm-up, and lean mixtures while decelerating.

Exhaust valves burn ibecause the engine is burning lean. Normal engines will tolerate lean burning for a little bit, but not for sustained periods of time. The reason why the engine is burning lean to begin with is that the reduction in backpressure is causing more air to be drawn into the combustion chamber than before. Earlier cars (and motorcycles) with carburetion often could not adjust because of the way that backpressure caused air to flow backwards through the carburetor after the air already got loaded down with fuel, and caused the air to receive a second load of fuel. While a bad design, it was nonetheless used in a lot of vehicles. Once these vehicles received performance mods that reduced backpressure, they no longer had that double-loading effect, and then tended to burn valves because of the resulting over-lean condition.

[werase643]

davipu rode cross country 2-3 times with the head pipes only
cut off under the oil pan
with reverse megaphones
the  outlet tip was about as big as my thumb

dit it work...yup
was it f*cking loud and really annoying....yup

did he rejet....i never asked

did it hurt the bike....hard to judge....i think he put 25-35k on it in the first year

[galahs]

lol! 


That would silence the critics that say the GS500 is too quiet.


I'd imagine it would be running lean if he didn't rejet it. But the GS500 is a tough powerplant, I hear it takes alot to kill it.

Still I wouldn;t recommend to abuse it by running it lean.

If your gonna mod it, do it right! 

[werase643]

i know this is old skool
but back in the day.....
we had thes things called books

*SCIENTIFIC DESIGN OF EXHAUST & INTAKE SYSTEMS  ISBN 0-8376-0309-9
  Philip Smith and John Morrison, Robert Bentley Inc.
*THE DESIGN AND TUNING OF COMPETITION ENGINES    ISBN 0-8376-0138-X
     (dated, but good basic info, easy and interesting to
     read)
   Philip H. Smith, Robert Bentley Inc.


you might get from a library

really good technical info is not always on the web.....

[sledge]

My suggestion:
Post the question in this forum.

http://www.eng-tips.com/threadminder.cfm?pid=668

[sledge]

Or you could try this one, I promise you, someone will come back with the info you need,

http://www.eng-tips.com/threadminder.cfm?pid=108

[sledge]

This site will also help you, but you need to be good at maths!!

http://www.headerdesign.com/

[MarkusN]

Even if you have a can lying around, with all the surgery you plan to do on it you are probably not too far off the all custom route. What I'd do: Get some literature on muffler design, then get some stainless sheet, start cutting and folding and create an all custom can with the necessary volume underneath.

Lets you also set the exhaust off center where it wont exit right on your back rubber.

[Jim Knopf]

servus,

a friend from me made this with a ducati exhaust pipe on his gs 500:


very great job!