I was wanting to replace my exhaust since its starting to rust through. Was wondering which one would flow the best as i would like to get some more power out of the bike. Plan on redoing the jets and putting som foamies on with it
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Exhaust
- Thread starter Oprahands
- Start date
I think the 2-1 exhausts or crossovers will produce the best flow over the broadest range. If you are drag racing and turning very high RPM then shorter pipes are recommended but usually the XS needs about 31 to 32 inches plus some sort of muffler.
If you use large diameter pipes you will need to add those restrictors that fit next to the head and narrow the first 3" or so.
I'm currently running a MAC 2-1 small diameter pipes while experimenting with my own design of tunable muffler.
I'm sure others will be able to suggest some tried and true mufflers.
If you use large diameter pipes you will need to add those restrictors that fit next to the head and narrow the first 3" or so.
I'm currently running a MAC 2-1 small diameter pipes while experimenting with my own design of tunable muffler.
I'm sure others will be able to suggest some tried and true mufflers.
Without engine work, you'll do good to keep the power the stock exhaust makes with aftermarket. You might lose about 10 pounds of weight. Louder is easy. 
Hmmmm. Even with correct jetting for the pipes, and sensible header diameter and lengths? And a muffler that actually muffles ?Without engine work, you'll do good to keep the power the stock exhaust makes with aftermarket. You might lose about 10 pounds of weight. Louder is easy.
Well these hardly ever get before and after dynos and the ole butt meter is often influenced by throaty brrm brrm noises.
Maybe the specials that were getting pretty quiet but standards through 79 had pretty decent pipes.
Maybe the specials that were getting pretty quiet but standards through 79 had pretty decent pipes.
I don't know the optimum pipe diameter for an XS650 operated on the street. I got a very respected opinion that the Mac head-pipes were very close. Currently, the Mac pipe is 1.75 inches. I hope the size hasn't changed since I got that opinion. You want all the exhaust gas to escape as fast as possible. To small and the gas doesn't escape. Too big is too slow. It's like your garden hose. At regulated pressure, the water just flows out. Put your thumb over the end or decrease hose diameter to speed the escaping water. I know that's pretty simple, but I don't have much understanding beyond that.
Mac has an X-pipe that theoretically should speed things up pretty well. Is anyone reading this running it?
Mac has an X-pipe that theoretically should speed things up pretty well. Is anyone reading this running it?
I believe the general consensus is that 1 1/2" or 38 mm OD, with 1 3/8" or 35 mm ID is as big as you want to go on an internally stock 650. Any larger will most likely hurt bottom end and mid range.
1 3/4" or 44.5 mm OD pipes may work on a 750 or larger with a hotter than stock cam.
For comparison, the stock headpipes are not much more than 30 or 32 mm ID.
All old carburetted Ducati 900 Monsters and SS models had 40 mm OD/ 38 mm ID pipes, and have 70-80 hp in stock form, and have been souped up to 95 rwhp or more without any increase in header size. The Ducatis are aircooled, sohc 2 valve engines, much like the XS, so should be a valid reference even if their cam profiles may be a bit more radical.
I have drooled over the Mac pipes myself, and would have bought them years ago if they had been in the 38-40 mm OD range. Not any larger than that.
1 3/4" or 44.5 mm OD pipes may work on a 750 or larger with a hotter than stock cam.
For comparison, the stock headpipes are not much more than 30 or 32 mm ID.
All old carburetted Ducati 900 Monsters and SS models had 40 mm OD/ 38 mm ID pipes, and have 70-80 hp in stock form, and have been souped up to 95 rwhp or more without any increase in header size. The Ducatis are aircooled, sohc 2 valve engines, much like the XS, so should be a valid reference even if their cam profiles may be a bit more radical.
I have drooled over the Mac pipes myself, and would have bought them years ago if they had been in the 38-40 mm OD range. Not any larger than that.
I thought I had always read that 1.5" pipes is what the 650 liked. I did see on the MAC web site that they're making theirs 1.75" now. They didn't used to. I have older MAC headpipes and they are 1.5". The big issue I had with them is the sealing lip is very small and they didn't seal up well at all. The O.D. of the sealing lip was smaller than the port which allowed the pipe to slide side to side and easily come off the seal ring. I had to make inserts from the ends of old stock headpipes to get the MACs to seal up right. This worked very well and while it wasn't my intent, I may have made myself some AR inserts in the process. Here, you can see how skinny the sealing lip on the MAC pipe is .....
The inserts stick into the headpipe, holding it perfectly centered on the seal ring. Like I said, they seal up great now. The insert is stuck into my head with some Yamabond. I also added a filler ring to fill the step in the head .....
The inserts stick into the headpipe, holding it perfectly centered on the seal ring. Like I said, they seal up great now. The insert is stuck into my head with some Yamabond. I also added a filler ring to fill the step in the head .....
When I read between the lines on the Mac website, it appears to me that using 1 3/4" headpipes is a marketing decision, not a technical one.
They keep using the term "Big" with a capital B. And talk a lot about flow. But as exhaust systems also involve pressure waves, unlike for example sewage pipes, "bigger" and "more flow" is not neccessarily a good thing.
In addition to my favorite Ducatis, have a look at some other modern twins, like the Yamaha 700s, Kawasaki Ninja/ ER 600/650, Suzuki SV650, BMW F800/850/900. Those bikes output somewhere between 65 and 100 hp, and they all have fairly small headpipes, I'd guess around 35 mm or 1 3/8" OD.
They keep using the term "Big" with a capital B. And talk a lot about flow. But as exhaust systems also involve pressure waves, unlike for example sewage pipes, "bigger" and "more flow" is not neccessarily a good thing.
In addition to my favorite Ducatis, have a look at some other modern twins, like the Yamaha 700s, Kawasaki Ninja/ ER 600/650, Suzuki SV650, BMW F800/850/900. Those bikes output somewhere between 65 and 100 hp, and they all have fairly small headpipes, I'd guess around 35 mm or 1 3/8" OD.
Thanks for that! That certainly clarifies it.
There is good info on Michael "Mercury" Morse site 650 Central. Click on Exhaust in the left column.
2 into 2 pipes made by XS Performance.
The ID is 1.410" , the OD is 1 1/2", they are 35" long with a slight kick up at the end.
They have complimentary Theoretical Horsepower and Torque Peaks, so TPOs are not necessary.
EPOs recommended. These come with a stock-style removable finned clamp.
(Gaskets are available below).
#LMXS07-0757 ..... $162.95 each pair
Torque Peak Optimizers are to compensate for large diameter pipes like the nozzle on the end of a hose. Exhaust Port Optimizers are similar to what 5twins showed in the previous post. I don't understand it well enough to explain it, so I'll leave it to someone else to do.
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This is part of the point to the AR inserts. Besides their "anti-reversion" effect, they also reduce the pipe I.D. for the first few inches up by the head. This promotes flow out of the engine, but once down in the pipe, a slightly larger I.D. would flow better. So, with the insert, you get the best of both worlds - better flow up top out of the head, then better flow down farther through the larger I.D. rest of the pipe. I'm not sure exactly when a TPO on the muffler end of the pipe is needed. In other words, how big the pipe needs be before a TPO is needed.
According to Mr. Morse, the 1 3/4" pipe requires a TPO. I remember someone installing these on his bike and it coming "alive". I seem to remember him having 2" pipes. That was on the Micapeak email group several years back. It speeds exhaust flow at the end of the headpipe.
So, I believe the consensus is the a 1 3/8" ID works best.
That Mac X-pipe throws a curve into it. Does the crossover speed, or slow the exhaust gases? I agree that marketing isn't always to be trusted.
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I guess the better solution would be stepped or tapered headpipes. Something like the pipes on this Mule build:
https://www.bikeexif.com/mule-yamaha-xs-street-tracker
Which also happens to be maybe one of the top 3 of all XS builds I have ever seen pictures of.
I happen to have the "XS Performance"/ MikesXS/ Heiden Tuning pipes, and the first version of the "Commando" mufflers (the type with a removable M10 socket head cap screw in the centre of the baffle)
The bike runs ok, and is not too loud.
But I think the lower bend is too sharp to look right, and my set are nit symmetrical when looking from the front. One pipe angles a bit outwards, the other runs straight down. Which bugs me quite a bit. On the positive side, the mufflers sit at the same height and angle without
The bike runs ok, and is not too loud.
But I think the lower bend is too sharp to look right, and my set are nit symmetrical when looking from the front. One pipe angles a bit outwards, the other runs straight down. Which bugs me quite a bit. On the positive side, the mufflers sit at the same height and angle without
The old style Commando mufflers were very nice. The new ones they sell now are not so good. They only look the same. The baffling inside is totally different. They are the EMGO brand now and are nothing more than one of their other mufflers with a new "skin". They also only come with a 1.75" inlet, requiring the use of those reducer sleeves to fit on a 1.5" pipe. Those things suck, very hard to get sealed up properly.
At one time, I think that old Commando was one of the nicest mufflers available for this bike. Not any more. So, the hunt is on for the next good replacement. I really wish the Chinese would knock off some Conti replicas. God knows they copy everything else, lol.
At one time, I think that old Commando was one of the nicest mufflers available for this bike. Not any more. So, the hunt is on for the next good replacement. I really wish the Chinese would knock off some Conti replicas. God knows they copy everything else, lol.
So, maybe the Mac exhaust is good if you use the AR inserts in the front and TPO inserts at the back? There are nice mufflers out there, but they can get very pricey.
I thought I had always read that 1.5" pipes is what the 650 liked. I did see on the MAC web site that they're making theirs 1.75" now. They didn't used to. I have older MAC headpipes and they are 1.5". The big issue I had with them is the sealing lip is very small and they didn't seal up well at all. The O.D. of the sealing lip was smaller than the port which allowed the pipe to slide side to side and easily come off the seal ring. I had to make inserts from the ends of old stock headpipes to get the MACs to seal up right. This worked very well and while it wasn't my intent, I may have made myself some AR inserts in the process. Here, you can see how skinny the sealing lip on the MAC pipe is .....
The inserts stick into the headpipe, holding it perfectly centered on the seal ring. Like I said, they seal up great now. The insert is stuck into my head with some Yamabond. I also added a filler ring to fill the step in the head .....
My Mac 2-1 pipes are 1.5" but they are no less than 15 years old. They were on the bike when I bought it and were the best pipes I've had to date. Thus the reason I just put them back on after all these years.
My own experience with larger diameter pipes is that you will need the inserts like 5twins shows in his photos.
I think you'll do well with the new Mac 2-1 if you add the inserts but I have to ask, will you have to remove the pipes to do oil changes as those are nothing like my Mac 2-1 pipes which are made more like this one: http://www.macperformance.com/mac-21-y650.html
