Aluminum vs stainless steel exhaust? Or something else?

Bill Hilly · 07-17-2022, 07:19 PM

I am warming up to my newly aquired TRB7D, and I am considering an aftermarket exhaust. I have been looking at eBay, and they have some stainless, and some aluminum ones. The cheapest ones range from $70.00 to $77.00. I don't want to run into issues like having to bend the clutch arm. I can weld decently, and so I wonder if I would be better off to just get rid of the catalytic converter, and buy an aftermarket muffler? When I had my Brozz 250, I gutted out the cat,and opened the back of the muffler, but I would rather not fool with the stock muffler on this bike. It's not whisper quiet now with it's stock exhaust, like the Brozz was with it's stock exhaust, so I assume it's not as restricted. I have seen claims of 2-5 HP increases . That seems like it's too good to be true on a 15hp bike. What do you think ? Should I just mod my pipe, and replace the muffler, or do full exhaust? Aluminum, or stainless?, Or just leave it be ? The only reason I am thinking about doing something is for a little more usable power. If you don't think I will gain over a half HP, then I probably will leave it be, but if I could add ,say one,and a half HP, then I would think that it would be worth it to gain 10% over current HP.

Thumper · 07-17-2022, 08:22 PM

You can probably get a couple of horsepower, but also a more willing rev and power will develop earlier once the pipe is opened up and the carb is rejet. That is what I experienced on the storm, but I don't have dyno numbers!

The muffler section is a heavy steel part. If anyone has removed/replaced, can you weigh it?

The head pipe, on the other hand, isn't a very heavy section. If you want better flow and less weight without buying a full exhaust, slice out the cat in the headpipe, weld it back up, and buy a lighter and higher flow tailpipe. This might mean cutting/fabricating a modified muffler mount.

Or you can do what I did... just drill a few holes in the tailpipe to relieve the pressure. I guess we are not talking about a high performance conversion either way

Aluminum versus steel might be more about cost or fit, but aluminum should be lighter (and dent more easily).

But it is worth doing. The difference between 14 and 16hp is noticeable!

Bill Hilly · 07-17-2022, 09:30 PM

Quote:

Originally Posted by Thumper

You can probably get a couple of horsepower, but also a more willing rev and power will develop earlier once the pipe is opened up and the carb is rejet. That is what I experienced on the storm, but I don't have dyno numbers!

The muffler section is a heavy steel part. If anyone has removed/replaced, can you weigh it?

The head pipe, on the other hand, isn't a very heavy section. If you want better flow and less weight without buying a full exhaust, slice out the cat in the headpipe, weld it back up, and buy a lighter and higher flow tailpipe. This might mean cutting/fabricating a modified muffler mount.

Or you can do what I did... just drill a few holes in the tailpipe to relieve the pressure. I guess we are not talking about a high performance conversion either way

Aluminum versus steel might be more about cost or fit, but aluminum should be lighter (and dent more easily).

But it is worth doing. The difference between 14 and 16hp is noticeable!

I noticed that the Brozz seemed to be happier at higher RPM after doing the exhaust mods. I had it properly jetted main, and pilot. I was always messing around with different sprocket combos, but I feel sure that it did gain some power, of course as quiet as it was stock,it had to be more restricted than the stock TBR7 ,so I may not gain as much . The cheapest aluminum exhaust I saw was $77 the steel $70. I still may just get rid of the catalytic converter, and replace the muffler, that way I know I wont run into issues getting a proper fit.

Thumper · 07-17-2022, 09:46 PM

Quote:

Originally Posted by Bill Hilly

I noticed that the Brozz seemed to be happier at higher RPM after doing the exhaust mods. I had it properly jetted main, and pilot. I was always messing around with different sprocket combos, but I feel sure that it did gain some power, of course as quiet as it was stock,it had to be more restricted than the stock TBR7 ,so I may not gain as much . The cheapest aluminum exhaust I saw was $77 the steel $70. I still may just get rid of the catalytic converter, and replace the muffler, that way I know I wont run into issues getting a proper fit.

Yep... it isn't good for the exhaust mounting port to have exhaust leakage burning a section of the sealing surface, and it sounds terrible! Stock headpipe fits, and you know it.

Megadan · 07-17-2022, 09:56 PM

Most of the cheap exhaust systems for the crf are a low grade 400 series stainless steel pipe. The muffler body is the part that is aluminum. They are just calling it one or the other depending on how they choose to describe it.

Functionally they are all the same.

Fitment wise. 3 of those exhausts installed on 3 different bikes 2 Hawks and one brozz, I have never had to bend the clutch arm. Ever. I have also never had to use a bracket to hang the muffler down. The only real tweaking I ever needed to do was ping in the pipe ever so slightly on one to clear the clevis on the clutch arm when it was retracted. Didn't hurt performance at all, and wasn't visible either.

The real trick is to not tighten any bolts until the system is installed. This let's you adjust things to get clearances right.

The only fitment issue that is fairly universal is airbox clearance on that back corner. It's so close the radiant heat melts it. We solved it on the Brozz with stick on heat reflective tape and a fiberglass heat sleeve around the pipe

Bill Hilly · 08-01-2022, 06:34 PM

Quote:

Originally Posted by Megadan

Most of the cheap exhaust systems for the crf are a low grade 400 series stainless steel pipe. The muffler body is the part that is aluminum. They are just calling it one or the other depending on how they choose to describe it.

Functionally they are all the same.

Fitment wise. 3 of those exhausts installed on 3 different bikes 2 Hawks and one brozz, I have never had to bend the clutch arm. Ever. I have also never had to use a bracket to hang the muffler down. The only real tweaking I ever needed to do was ping in the pipe ever so slightly on one to clear the clevis on the clutch arm when it was retracted. Didn't hurt performance at all, and wasn't visible either.

The real trick is to not tighten any bolts until the system is installed. This let's you adjust things to get clearances right.

The only fitment issue that is fairly universal is airbox clearance on that back corner. It's so close the radiant heat melts it. We solved it on the Brozz with stick on heat reflective tape and a fiberglass heat sleeve around the pipe

Well the exhaust that I ordered from eBay came today, and I was pleased by the fact that it didn't need drilling of the flange to fit over the studs in the head. It didn't fit really great, but I have plenty of clearance between exhaust, and airbox, and the clutch arm. The pipe is right up against a crossbar, and can't come up any more. I did need to utilize a drop bracket of a hair over an inch, but I
Think it's mainly because the bracket on the muffler is mounted more towards the inlet. It looks ad though it would have probably reached the factory mounting hole if the bracket was on the outlet end of the muffler.. I am a little disappointed that I couldn't use the plastic piece that attached to the stock muffler, and I wish the muffler ran back a hair farther, if it did, I think the bracket on the muffler would fit the factory mounting hole . I may try to get a piece of stainless,and extend it. The power is better, and it runs high rpm more free. I rode it about 25 miles today, and my pipe is already a bronze color.

07-17-2022, 07:19 PM	#1
Bill Hilly Join Date: Feb 2021 Posts: 961	Aluminum vs stainless steel exhaust? Or something else? I am warming up to my newly aquired TRB7D, and I am considering an aftermarket exhaust. I have been looking at eBay, and they have some stainless, and some aluminum ones. The cheapest ones range from $70.00 to $77.00. I don't want to run into issues like having to bend the clutch arm. I can weld decently, and so I wonder if I would be better off to just get rid of the catalytic converter, and buy an aftermarket muffler? When I had my Brozz 250, I gutted out the cat,and opened the back of the muffler, but I would rather not fool with the stock muffler on this bike. It's not whisper quiet now with it's stock exhaust, like the Brozz was with it's stock exhaust, so I assume it's not as restricted. I have seen claims of 2-5 HP increases . That seems like it's too good to be true on a 15hp bike. What do you think ? Should I just mod my pipe, and replace the muffler, or do full exhaust? Aluminum, or stainless?, Or just leave it be ? The only reason I am thinking about doing something is for a little more usable power. If you don't think I will gain over a half HP, then I probably will leave it be, but if I could add ,say one,and a half HP, then I would think that it would be worth it to gain 10% over current HP.
	0

07-17-2022, 09:56 PM	#5
Megadan Join Date: Apr 2017 Location: Omaha, NE Posts: 8,065	Most of the cheap exhaust systems for the crf are a low grade 400 series stainless steel pipe. The muffler body is the part that is aluminum. They are just calling it one or the other depending on how they choose to describe it. Functionally they are all the same. Fitment wise. 3 of those exhausts installed on 3 different bikes 2 Hawks and one brozz, I have never had to bend the clutch arm. Ever. I have also never had to use a bracket to hang the muffler down. The only real tweaking I ever needed to do was ping in the pipe ever so slightly on one to clear the clevis on the clutch arm when it was retracted. Didn't hurt performance at all, and wasn't visible either. The real trick is to not tighten any bolts until the system is installed. This let's you adjust things to get clearances right. The only fitment issue that is fairly universal is airbox clearance on that back corner. It's so close the radiant heat melts it. We solved it on the Brozz with stick on heat reflective tape and a fiberglass heat sleeve around the pipe __________________ Hawk Information and Resource guide: http://www.chinariders.net/showthread.php?t=20331 2018 Hawk 250 - Full Mod list here. http://www.chinariders.net/showpost....62&postcount=1 2024 Royal Enfield Shotgun 650 https://chinariders.net/showthread.php?t=34124
	2

07-17-2022, 08:22 PM	#2
Thumper Join Date: Feb 2021 Location: Kansas City Posts: 2,432	You can probably get a couple of horsepower, but also a more willing rev and power will develop earlier once the pipe is opened up and the carb is rejet. That is what I experienced on the storm, but I don't have dyno numbers! The muffler section is a heavy steel part. If anyone has removed/replaced, can you weigh it? The head pipe, on the other hand, isn't a very heavy section. If you want better flow and less weight without buying a full exhaust, slice out the cat in the headpipe, weld it back up, and buy a lighter and higher flow tailpipe. This might mean cutting/fabricating a modified muffler mount. Or you can do what I did... just drill a few holes in the tailpipe to relieve the pressure. I guess we are not talking about a high performance conversion either way Aluminum versus steel might be more about cost or fit, but aluminum should be lighter (and dent more easily). But it is worth doing. The difference between 14 and 16hp is noticeable!
	1