Back pressure tuning

rocksalt27

rocksalt27

Member
I have recently heard about inserting a bolt into straight pipes in order to adjust the exhaust back pressure in motorcycles. Has anyone ever tried this on a china girl? I think I may try it out myself. Seems like you would be able to tune the engine speed to it's sweet spot with a tach just like your a/f mixture knobs.
 
Don't know about a bolt, But I did buy a battery Terminal cleaner at Harbor Freight this weekend and poked that up into the straight pipe about 3". Certainly did quiet the thing down - which was the objective. Back pressure is good! Couldn't find it @ HF website. This is the exact one I used found at Amazon.

http://www.amazon.com/gp/product/B0...l cleaner&qid=1457968496&ref_=sr_1_17&sr=8-17

Has 2 Different sized Male Ends I used the larger.
 
Last edited:
You could probably get the same effect from pinching the end of the exhaust pipe closed a little bit & doing a GPS test run & then pinching the pipe a little more (& doing another run) until you get the best tuning. ;)
 
I know very little about this (never stopped me from putting my 2 cents in). I was on a long run when my exhaust header came loose. Had no tools to re-attach it. I couldn't believe the loss of power. Another rider caught up with me and had the wrench to re-attach it. Power was restored to normal.

All in all this post will motivate me to experiment.
Thanks for the thread.
 
I didn't go very long with the straight pipe maybe 15mi...I simply wasn't going to ride this bike that loud. After the wire brush insert it quieted considerably. and it runs noticeably well. Still breaking in. As noted above back pressure is required.
 
just took a lighter to the wool I have, then my map gas torch no flames.
I do have some flame wrap for the exterior of the pipe exhaust and I have seen the packing on line for sale.
the tip area where I would be stuffing is about 18" plus away from exhaust port. if anything in time it would get brittle and end up back into the exhaust
port, even though it's forcing exhaust out when running.
just ideas.
I made a baffle out of stainless steel tubing but I have not fired up the engine yet.
this wool is real course.
I remember camping and the adults lighting camp fires being started with real fine SS wool with a battery while we were told ghost stories to mystify us. LOL!
 
You must log in or register to reply here.
Back
Top