Bonneville America Forums Forums Technical Forums Exhaust Bomber Exhaust Question?? Chopping Them??

If I cut 4in. to 5in. off of my british customs bomber exhaust mufflers will it affect the back pressure the mufflers create? Will I have to make some adjustments on the jets and mains? I don't have my air box out yet. I'm hoping to take it out this winter.

It will change the back pressure a little, depending on the baffling. Whether or not you'll have to re-jet is one of those things that you have to determine after you have made the changes depending on how it runs.

Thanks Soren. The pipes aren't completely baffled. You can see straight through them.

I doubt that little bit will make a big enough difference to have to change anything else as long as it is jetted right to start with.

Sweet. I just want to chop enough off to make the rear wheel more visible.
Will it make my mufflers sound a little louder? That would be a bonus.

Probably. But not definitely. You'll have to give it a go and find out. Let us know how it all goes and how it sounds.

Doubt it will be louder but it will probably be a little harsher sound.

curious to see and hear how this goes.

Yes, CHOP IT!

Chop everything, God will sort it out.

Whenever you change exhaust or intake you need to check that what you have done has not made a bad imbalance in air fuel mix. Check plugs before then do a plug chop after the change.

Back pressure should not be affected much unless you remove the baffles and even then with the length it should be enough but again check your burn after no matter what you do, a lean bike runs really nice...for a while.

eddy

New plugs? I saw a set of plugs with no contact point is, that what you mean? Then true...not sure how those even work really.

No Edwin it's a poor man's Dyno.

Run the bike for a mile at highway RPM's (can be done in town at lower speeds, it's getting the bike into the main jets) Once you have done a mile you "Chop" the throttle and power and check the plugs burn the color of the plugs will give you a snap shop of fuel air mixture burn, lean white, black rich..old school was tan was perfection (where mine are at right now)

The reason for checking before is to get an idea of where they are before you start. Stock out of the box are on lean side grayish white with the AI in place etc just to get into the country, This just gives you an idea of what "normal" is.

WHITE is bad, black/sooty bad somewhere in between makes one happy. I have mine at tan and the bike has been running well for 30,000 miles since I started making changes.


I am sure there maybe variations on the Plug Chop but that is what I got from the forum years ago.
eddy

Sweet. Thanks for the insight. That's some great info. This will help big time. Thanks.