I like it loud

[dave]

This mite sound dumb but here go's can i run my stock pipes with the mufflers cut off or do I need some type of back presure? if so could I just weld a washer in place?

[grizld1]

Why would you open the pipes up then restrict them with washers? You'll wind up with worse flow than the stock system. The issue with open pipes isn't "back pressure," it's achieving correct tuned length and diameter to make power and jetting the carbs for the increased flow. Stock head pipes cut off in front of the mufflers are too short to make good power, particularly at lower rpm. When flow is relieved on intake and/or exhaust the engine pumps more freely, and jetting changes must be made to achieve correct fuel/air mix. Jetting is done by observing engine response to changes, not by cookbook recipes. Just listen to some of the Hardly Ablesons out there with straight pipes and factory-packaged jet kits for them--under engine braking, half of them sound like a string of firecrackers going off because the pilot circuit's lean as a winter coyote. The Hardly boys like to claim that loud pipes save lives. Maybe so, but it's been my observation over the years that the roads are full of cages carrying twerps on the razor's edge of road rage, just hopping around looking for an excuse to let it all loose (accidentally, of course), and that loud pipes can make targets.

[dave]

Anyway I like it loud,to each their own right! I'll see if I canfind somone to help me out with the rejetting when I get to that point as I don't know a hole lot about it!.Thanks for your help. and remenber shhhhhh keep the noise down.

[weekendrider]

The correct length would be?

[grizld1]

ID and length are both variables, and what you pick depends on displacement, intended rpm of power peak, intended rpm of torque peak, and the phase of the moon during operation. In general, a 1 1/2" pipe (~1 3/8" ID) with 34"-36" centerline length is going to work nicely across the range in a stock displacement motor or a 750. Cut filler rings with about 1.5" of pipe attached from the port end of the OEM units, peel the outer pipe away with a chisel, and turn down the weld on the inner till you have a nice tight interference fit with the inside of the 1.5" pipes, then peen 'em in. The restriction off the port will give you some velocity boost and you'll get some antireversion effect as well.

On my 700 conversion I'm using JEMCO 1 5/8" (1.5" ID) low pipes in 35" centerline length, exhaust port and pipe inserts from 650 Central, and Emgo 17" megaphones with glasspack baffles. The megs made a helluva racket till I opened 'em up and found Emgo had put skinny 2" rings of glass around the base of the baffles; properly packed they're a little rowdy but not obnoxious.

[dave]

So the correct lenght would be?? In english this time please!

[grizld1]

What's "correct" depends on the motor and what you want it to do. For general use on a stock engine a pair of cheap MAC pipes with homemade inserts as described will do fine. If you measure a pipe on the inside of the bends you'll get a short measurement, if you measure on the outside you'll get a long one, so pipes are specced on the center line. Does that read like Chinese?

[weekendrider]

Thanks grizld1,
I was thinking I had read 31" on the short measure. And that the older headers "fit the bill" for this? The restriction is similiar in action to the D shaped restriction I've read about?




edit for spelling

[dave]

me no speek chinese!

[grizld1]

Weekendrider, I don't know how 31" on the short side would translate into centerline measure to the valve, but it sounds like a reasonable length. A rule of thumb that Michael Morse offered me awhile back is that long side length of the pipe is approximately equal to centerline measure from outlet to valve. I've seen a lot of things work very well indeed on the street that aren't theoretically optimal, and a look at Craig Weeks' XS650/750 performance manual shows a lot of variation among professional tuners' choices.

The inserts aren't the same thing as "D" porting, which involves welding up and reshaping the exhaust port; there are plenty of things to do that yield more bang for the buck before you get into that modification!

[woodman]

Stock bike with mufflers cut off is going to run like crap no matter what length you make them. The plus side to those who consider it a plus is it will be loud !

[dave]

"YES" I like it loud! Running like crap not so much!

[gdcpony]

I have a pair of pipes you can have if you like it loud. Just give me a quieter set in the same shape. I come home at midnight and the neighbors are going to get annoyed real soon by these pipes (came on the bike). Loud has it's place, but on a commuter bike that has to be authority friendly they are a real hassle at times. Just something to consider.

[dave]

If my nabours have a problem with the noise I envite them over to tell me ,they dont give a sh!# when Im sleeping with their car alarms blowen and all the other cr@# they do. LOUD is good. I dont have to ride with the throtel cracked wide open in the early hours!I try to be as quiet as I can in the nabourhood.But after that LOUD LOUD LOUD!!! HA HA HA!!

[indyjay]

Dude, I'd hate to have you as a neighbor!!!

Are you trolling to get people going or what?!

Grow up and give up on the f*cking loud crap!!!