Beating a dead horse..

[IanDMacDonald]

I can tell you this: between the OEM pipes I have, versus the Mac set I took-off,
I notice little difference in performance. The sound is night and day though. Of course, I'm not a tuner and may not be educated enough on the subject to know either way. I can promise you that my bike still ran like a raped ape in a cage with the Mac's on there . . .

[BA80]

I can tell you this: between the OEM pipes I have, versus the Mac set I took-off,
I notice little difference in performance. The sound is night and day though. Of course, I'm not a tuner and may not be educated enough on the subject to know either way. I can promise you that my bike still ran like a raped ape in a cage with the Mac's on there . . .

So does mine.

[revanoff2]

Well, you guys nailed it. Took a closer look, and sure enough those are not stock at all, with clamp on pipes. No crossover underneath it.

Phooey!

That actually does make things easier, except the part where the pipe for #2 has been beaten in a few spots, so I need a new set for the right side at least.

I can't identify the make of the mufflers unfortunately.

So, this thing runs great already. Would it be safe to assume that since it runs so well, that a PO would've gotten the carbs tuned for the pipes?

At this point, I want to change the sound a bit, and build a crossover pipe for them. My bike doesn't have the center stand under it (though I do have it).

So here's where the conversation gets interesting for me:


I can build an H pipe for simplicity, or I could build a shallow breadth X system.

Which one would work more efficiently? A broader power band would be the top of the priority list, with fuel efficiency a close second.

~Revanoff~

[TopCatGr58]

So, this thing runs great already. Would it be safe to assume that since it runs so well, that a PO would've gotten the carbs tuned for the pipes?

I can build an H pipe for simplicity, or I could build a shallow breadth X system.

Which one would work more efficiently? A broader power band would be the top of the priority list, with fuel efficiency a close second.

~Revanoff~

Hey Revanoff,

When it comes to PO's you can't assume anything! These machines were tuned more leaner in the later years for emissions. My 81 had the OEM pipes, but me being young/dumb/stupid back then took them off and put on a 4-1 pipe, did NOT rejet it, it ran great, full rpm range and fair mileage in the 30+ range.

Aftermarket pipes flow a bit easier than OEM and so that could make things a little leaner with stock jetting. I thought I read that you were getting ~38 MPG...that's near the upper mileage range for these machines. As long as your plugs look good...some color and not bleach white, then it sounds like you have good jetting for the pipes now.

Now as for the power band....it really starts at 3500 up to 7500+. They do have torque in the lower rpms. I'm thinking you are meaning trying to get the most LOW RPM torque/power/throttle response you can get in the 1000-3500 range that folks report they miss or loose some when they put on aftermarket pipes....and/or Pod filters. You have stock airbox, so you still have the velocity stack affect. You do have mufflers, granted they are not stock, not double walled and so also do not have the level of "back pressure" restriction that the convoluted OEM pipes/mufflers have. It's been eluded to this "back pressure" as the reason for the low end grunt/torque. It's also been recently discussed that it's not so much back pressure, as the ability to reduce the "REVERSION WAVES" that cause the carbs to BURP due to improper harmonics in the exhaust system! See this recent thread:
http://www.xs11.com/forum/showpost.p...2&postcount=11

SO....since you already have full length pipes, mufflers with some baffling, that most likely you already have what it takes to neutralize the reversion waves, and adding a crosspipe may not provide any additional performance benefit???

Other ways to increase the low rpm grunt has been to slghtly increase the static timing a few degrees(5), also richen up the pilot jet screws a tad. But just because these bikes can run at 1000 rpm doesn't mean that they will respond to throttle input with the same gusto from that point as they do from the 3500 rpm point!

T.C.

[revanoff2]

Yesterday I pulled off the mufflers and inspected to see if there were any markings. I was unable to find anything.

The way it runs now, I'm OK with what power it has down below, I just wanted a setup (aftermarket) that would be similar to the OEM setup. Now that I know I have an aftermarket setup anyways, I want to emulate the OEM setup for more power/efficiency than what I have currently. Looking into the mufflers yesterday, there seems to be a large restriction in it that worries me a slight amount.

The inside diameter of the actual muffler is smaller than the header pipes on the front of the engine, and it's not a smooth transition from the open part of the muffler to the restricted part. I'm wondering if that is causing some unneeded back pressure and subsequent reversion waves. I like the idea behind having a crossover pipe, the theory behind it seems like it would be benefical.

The only way to know for sure would be to get it on a Dyno and run the numbers.

I'll be doing some more research.

~Revanoff~

[Yahman]

Revanoff,

I sent you a PM, give me a call. I have a couple of different exhaust systems that I might be willing to part with. I'm sure we could fab something up for you.

Ride safe,
Larry

[ViperRon]

Not sure if you have solved your problem yet or not with mufflers. You have Mac pipes so you may able to call Mac and get a set of Flare tip mufflers. The Flare tips have a pretty good sound but also the baffel is easy to remove and you can easily fabricate your own baffel controling the sound. My old tapper tip Mac's were rusted chrome mostly gone so I purchased a complete new set from a guy who had them setting. Flare tips fit right on to the headers you have. The baffel is very simplistic in design and I will say without baffel it will rattle your brain and call all the cops.

[revanoff2]

I won't run without mufflers... I like a little bit of noise, but it gets tiring after about 30 seconds!

I've got a lead on a spaghetti set with cross over, thinking that's the way that I will go.

~Bobby~