Rejetting for straight pipes?

[mmattockx]

You're saying going back to stock pipes would be best?

I wouldn't say best, but almost certainly they would be better than untuned straight pipes. Defining what you mean by 'best' would help some. If you want smooth running with minimal noise and moderate power then stock is likely best. If you want more power and want or don't mind a louder exhaust then an aftermarket pipe will be best.

Definitely

Stock is always best.

Nonsense. Aftermarket pipes are just fine and will work just as well as stock if done properly.

Makes perfect sense to me. Is there any black exhaust systems you would recommend that would fit this make/model whilst still achieving a throaty sound? I've been attempting to dig but don't know the first thing.

As noted, take off H-D mufflers are all over the place for cheap and would be a good first try. If you don't like the chrome some sandpaper and header paint can make them black in an afternoon. I doubt you are going to get anything that sounds throaty, the engine is small at 650cc and just doesn't have the displacement to sound very big and deep.


Mark

[GSCafe]

"Throaty" is different on a smaller cc bike. I would describe my exhaust as such at lower rpm. To get to that sound, you are going to let a lot of noise out on hard acceleration. I'm using a 4-1 with megaphone muffler. I had mine powdercoated (ceramic) instead of painted. Header wrap helped accent the rumble and tame a bit of the sound volume.

[tkent02]

I doubt you are going to get anything that sounds throaty, the engine is small at 650cc and just doesn't have the displacement to sound very big and deep.


Mark

You should hear my 550/675. Throaty it has, at least when it isn't at 10,000 RPM.

[bohisboh]

"Throaty" is different on a smaller cc bike. I would describe my exhaust as such at lower rpm. To get to that sound, you are going to let a lot of noise out on hard acceleration. I'm using a 4-1 with megaphone muffler. I had mine powdercoated (ceramic) instead of painted. Header wrap helped accent the rumble and tame a bit of the sound volume.

What specific system did you get, if you don't mind me asking?

[bohisboh]

I wouldn't say best, but almost certainly they would be better than untuned straight pipes. Defining what you mean by 'best' would help some.

By best I mean optimally rideable including freeway speeds. And I wouldn't mind a little more 'oomph' and some noise, while not being obnoxious.

[mmattockx]

By best I mean optimally rideable including freeway speeds. And I wouldn't mind a little more 'oomph' and some noise, while not being obnoxious.

Optimally rideable really is a jetting issue more than the pipe, but some pipes can be extremely hard to tune for. It sounds like you want an aftermarket exhaust system in that case. It will still require rejetting, but shouldn't be goofy like your straight pipes likely are. Do you have some pics of the bike showing the exhaust system so we can maybe see what we are dealing with?


Mark

[bohisboh]

Yes I found an older one. Apparently I can only have one file per post? No idea I'm on my phone.
20160518_145824.jpg

[Rob S.]

...the engine is small at 650cc and just doesn't have the displacement to sound very big and deep.
Mark

An old Brit 650 twin with open pipes sounds pretty mean. Although the one I'm recalling may have been modified, at first I thought it was a Harley.

[GSCafe]

What specific system did you get, if you don't mind me asking?

Kerker full 4-1 header with megaphone muffler was on the bike when I bought it. The original exhaust is rusted out. I've really come to appreciate the sound of the Kerker. I don't think it is sold anymore. (for '79 GS550)

[mmattockx]

Yes I found an older one. Apparently I can only have one file per post? No idea I'm on my phone.
[ATTACH=CONFIG]45653[/ATTACH]

Ouch. That looks like someone cut the stock pipes and then just tack welded on the extra pipe. In that case your easiest first try may be the Harley take off mufflers if they fit the head pipes where they were cut. That would get you closer to being right with the stock jetting. No matter what you do you are going to have to open the carbs up and see what you have and adjust to suit the exhaust you end up with.

An old Brit 650 twin with open pipes sounds pretty mean. Although the one I'm recalling may have been modified, at first I thought it was a Harley.

Yeah, but that has 325cc cylinders whereas OP's 650 has 162.5cc cylinders. Not nearly as much oomph from the smaller cylinders.


Mark

[Steve]

Yeah, but that has 325cc cylinders whereas OP's 650 has 162.5cc cylinders. Not nearly as much oomph from the smaller cylinders.

Actually, they are 168.25cc, but who's counting?

AND, ... since two of them come together, they are pushing 336.5cc through each of the mufflers, which is pretty darn close to the 325cc that you quoted.

.