Bonneville America Forums Forums Technical Forums Exhaust what bubs?

Ok, this picture is not a finished product. I was having some ideas about building some slip on pipes and the first thing I did was slide an 18" piece of 1-3/4" over the headers and take it around the block. I didn't notice much drop in my low end torque and I love the sound but I just want to know if this is harmful for my engine? Will it deteriorate any quicker with open exhaust? I had Bubs on it before, so I rejetted (cant remember what too, 45 & 12x?) and i have the cold air intake (K&N's) Any suggestions before I start to actually make a finished set of open pipes?

your going to have to rejet because those will let out more than the bubs with baffles

Frank

I run a similar setup with fishtails. I'd recommend a 4" "beer can" type baffle. They won't take too much sound away and will give you positive back pressure.

Something like this:

+1 on the rejet and baffle. You need some sort of back pressure to get any kind of performance in the low end. Not a lot but you do need some. The baffles like Cowtipper shows are perfect.

The pipe that I have on there now is flared up to 1-3/4" to slip on over the header. I don't want to flare the outlet side to accomodate a baffle. Does anyone know where a straight piece of 1-3/4" ID pipe is manufactured? Muffler shops look at me like I'm crazy. Or are there any baffles made with a smaller OD?

Stick the baffle into the header exit...

just slide it in? flared end pointing in which dirction?(which way to the cups on the baffle face?) and should it be riveted down or welded in? Thanks for all the advice.

Skinny end points at the head. If you just slip them in, they will probably rattle. I'm opposed to drilling holes in my pipes, so I'd try to be creative with the install. Try bending the flanged end out so they fit snug/tight and have to be "tapped" in, JB Weld, or if you have access to a welder, I weld the nuts to the inside of the flange then also put the bolt in from the inside. When you tighten the bolt it acts like a set screw against the exhaust pipe- no holes. that or just weld them in. I mocked up my baffles dozens of times before I got the right combination of sound volume and performance. Once I got it right, I just tacked every thing in.

Mount everything up and try it out before you make anything permanent.

Might try electrical conduit for 1 3/4 pipe. Not sure though. I have always scavenged from old exhaust.

Ok, I pulled my bowls to check jetting. Looks like I had upgraded from 120/42's to 140/42's. Should I still rejet again and if so, what to? I ordered the $3 baffles from JP cycles (2 to slip into headers and two more to cut up and stick in aft end of pipe to finish look/torque cone.

anyone?

If your air box is still completely stock (filter type, all snorkles in, no holes, stock needles, no shims, etc.) and you ate at or near sea level, you are fine where you are at (maybe even a little rich).

Nope, I am running the FREAK Kit, with 18" long open pipes, 4" baffle stuffed in header, 140/42 jetting and stock shimming (if any, have't checked). Dinqua's calculator says I should be at 160 mains if my pilot stays at 42. Do you agree? i'm at sea level.

I would think 45 to maybe 48 on the pilots and about 155 to 160 mains. Just get that impression because I am currently running 48 pilot and 155 main at 1800' above sea level. 48 I think is a tad large for me but it isn't huge,I just haven't taken the few minutes to change it to a 45 since it's been running so good.

Basically sea level here. 155/42, TBS needles, no shims. I'd try the neeles first. They are easier

I'm Fishtails and 160/45/1 shim on stock needles/ open K&N filters/ sea level. Pretty darn close...

Cool, thanks for all the info guys. I'll be sure to take pictures and let you all know how it goes. My next big challenge is dealing with the dissaproving nod from my dealer as I explain why I need jets big enough to stuff a golf ball through because I chopped up my bike....It's worth it though...

Doing a quick peruse of the comments, if I missed it, one thing you should do which is the real story of what is going on in the combustion process of what you do and have to do.

Perform a plug chop to see how the burn is. What happens at the plug is the story being told in reality. Unless you have a dyno then you get the high tech version but I would suspect dial it in with a chop and then dyno to fine tune if necessary.

eddy

What about the old Bubs? Interested in selling? Tried to PM but couldn't get thru.
SteveB

So, I hear you have some BUBS for sale...

If you mean me I don't have anything for sale.I run stock pipes that I removed all the baffles from leaving just the reducer cone for back pressure so I keep my low end torque. I also cut the crossover pipe off and plugged it. Nice and loud and has a nicer sound with no crossover.

I'd like to hear my BuBs without the cross-over.....

It's a subtle change Charlie, it kind of separates the sound of the 2 cyl. With the crossover it's kind of blended. Tone doesn't really change and it isn't louder.