So I'm wondering if this could work: Leave the stock headers and just remove and plug the left side output under the bike and drill out the right side can to get back to the same approximate back pressure to avoid performance issues or the need to rejet.

First: Will this work at all?

Second: If so, how many and what sized holes should be drilled in the remaining stock can?

Third: What can I use to plug the hole where the left side can was removed?

I don't see why this couldn't work, but then, I don't know much.

If it will work, I was thinking to painting the remaining can and cover gloss black so it would look integrated, modern and blend.

This isn't for my bike, but for my son's 91. He wants it to look more modern.

 

The exhaust leaves the system through the hole in the muffler only after it passes through some baffles. By drilling out the one side and plugging the other, you would have to drill enough holes to get the proper spent gas release. In doing so you would be releasing to much un-baffled exhaust and the bike would be to loud. What you have been reading in regards to people drilling holes in the muffler is, letting some un-baffled exhaust pass making the bike louder. With my TB slip-on, one side is plugged while all the spent gasses pass through a baffle in the slip-on. How much baffling you use determines how quiet it is and how much back pressure you may have.

In other words- it's not a good idea.

 

Joe, you can get the single sided exhaust can pretty cheap. In fact it's the cheaper option if you need to replace the entire system. You may be able to buy just an end-can that will fit the OEM system collector box , maybe $120 , not as cheap as I would like, but then I am really Cheap!

Otherwise a potato would act as a good exhaust plug and pull the innards out of the other side , but it's gonna be loud, though you will get a nice aroma of French Fries after about 10 minutes of riding

 

Here's a setup I came across from the UK

LINK not too expensive imo, might have to
smuggle one back in a suitcase

 

Would it be possible to remove the left can and drill inside the INTAKE side (maybe with a long bit at an angle) in order to run all the exhaust through the baffles, and then just drill at the rear for sonic purposes?

Also, Since single side conversions do work, I suppose I am safe in concluding that blocking the output to one can is not the kind of bottleneck that significantly effects back pressure? (Even though it reduces the path for exhaust by 50%)

 

I wonder why this isn't listed on the Scorpion site? Irritating.

 

The one small hole would not be large enough after low to low/mid range. My TB single hole has more area than the two factory holes combined. That's why it breaths better now. You do need back pressure for low and mid range rpm's but to get a bike to scream at the higher revs you want an open pipe. Manufacturers are now following Yamaha's way of thinking with the ExUP valve. The Exup (Exhaust Ultimate Power) valve is regulated buy a servo and cables and controlled by the computer in the EFI bikes. It closes a butterfly, just after the collector, at low and mid range RPMs and opens at the higher revs.

Without back-pressure, you get some leakage of air/fuel mixture past the open exhaust valve,at low RPM, and into the head pipe. If there is enough present, it will be ignited by the next wave of hot spent gas. This causes a high pressure and blocks the next wave. This makes for a weak burn and you need to open the throttle more to clear the system. The back-pressure holds the mixture in the cylinder for burning. But....at high revs with the throttle wide open, you really don't care that some is leaking because even more is being rammed into the jug by the flow. The air/fuel mixture has mass and rams up against the closed intake valve. This creates a high pressure and when the valve opens again the mixture rushes in under pressure. You need to get rid of the old to make way for the new with an open pipe at high RPM and keep the waves moving down the pipe.

When you have an improper exhaust system or leaking system, spent hot exhaust enters the outside world and expands the outside air. This air blocks more exhaust from leaving the pipe. A properly designed muffler or exhaust system eliminates problems and can help performance in the RPM range desired. What you want is a steady flow of burnt gasses without high and low pressure waves at the end opening of the system. You just don't build a system without trial and error. The HD guys take a hacksaws to their pipes and they have popping and blatting pipes.

 

So THAT'S what causes that. Thanks for the info. I'm going to keep reading it until I really get it digested. Thanks for the effort.

 

Hi I have a Scorpion end can coversion on mine and it sounds great. The baffless are removable with 1 screw. Cant tell you about the performance difference cos it was on when I bought the bike. if you what to see it check the pictures of my bike. Looks good and with the baffle removed it sound amazing with out being to bad. For English laws the baffle has to be in for M.O.T but hay that only takes an hour with the ride to and from the station.

 

Here's a little more to think about. My TB is a glass pack. A glass pack uses a can with an insert. The insert is more like a tube and can be plugged on one end and has holes along it's length. The tube is then wrapped with a fiberglass material and then inserted into the can. The spent exhaust gasses fill the can and pass through the fiberglass and into the insert and expelled out the open end. When you think about it you can see how the pressure waves tend to even out as they enter the tube at different lengths and create a more even steady flow out the open end. This tones and mellows the sound.

The more packing the more quiet it gets but the more back-pressure is obtained. Glass packs can get louder over time as the packing material breaks down and is expelled along with the exhaust.

The popping you get with an open pipe as mentioned before also help to explain why Miles Per Gallon also drops a little as they become less fuel efficient. You don't make HP with out being a little wasteful. Drag cars use a super charger to pump so much fuel into the cylinders that they actually over charge the cylinder to a point that raw fuel is pushed past the cylinder and into the (open) head pipe where it is burnt. That's why on these cars you can see flames shooting out of the exhaust pipes.

Edit: adding more stuff.

HD pipes do the flame thing and popping due to lack of back-pressure and a rich mixture. They can even small rich as raw fuel is expelled. Actually on any engine, I am just picking on HD's as they are more common with open pipes.

My Stratoliner has an ExUP valve. From what I have read, Yamaha and others have tried to get more HP out of the bike but they claim that the factory pipe is best for max HP. You can make it louder by putting shotguns on it but you loose the valve. Best way to make it loud and not loose power is installing a slip-on after the valve.

Two strokes are a whole new ball of wax. Very confusing so here is the link.

Two Stroke Link for more reading.

Her's a great action shot of a 2-stroke pipe.