DB Killer

[wirespokes]

I recently installed Keihan LaFranconis on the 85 LM. I'd like to make them quieter and the only way appears to be DB killers. My idea is to install them in the outlet of the H pipe.

Has anyone been down this road? What's the best way to go on this?

[Groover]

What do those mufflers look like? I'm not sure how to attenuate the sound other that what you mention, but I believe putting something at the H pipe may hinder performance. I think you would want them towards the the end of the expansion area. I had a Harley for a while and I was always seeking a tone I liked, I ended up liking this brand baffle on a certain set of pipes, but again, they would go towards the rear of the pipes and were meant for more tubular shaped pipes not cone-shaped if that is what those muffler you mention look like, but I think if they fit and are able to fasten them, they should work too.

https://bigcitythunder.com/collections

 

[wirespokes]

The mufflers look like a standard LeMans muffler. They have three channels from front to rear so they barely baffle the sound - it is a nice deep sound, just louder than I'd like.

Since there's very little back pressure from the mufflers I'll have to do something, but there's no way to baffle them from the outlet side. There is room between the end of the H pipe and the inlet of the muffler - an inch or more. I've thought of wadding up some stainless screen and stuffing it in there. It's either that or install a diffuser on the outlet of the H pipe.

[Groover]

I see, maybe you can do a cone shape perforated metal  like those thunder header ones and push up? I think the heat will eventually make it rattle unless you can maybe spot weld it a little or screw it in.

[wirespokes]

My thought too - a cone shape with the small side facing in. A hole on the pointy end and holes around the sides. Create a venturi that produces a high pressure area and along with another low pressure area. Hopefully that could break up the sound waves a little without building much pressure. Bolt it to the H pipe, there should be enough room for a small bolt head.

[Groover]

Worth a try. I was surprised the performance change when I used the baffles that basically just have a washer in the middle of them. You had to mount them at a certain distance from the end, but regardless, it did change the power curve more so than the sound (again, the ones I used weren't really intended as DB killers), but it did change that too.

[Bulldog9]

I recently installed Keihan LaFranconis on the 85 LM. I'd like to make them quieter and the only way appears to be DB killers. My idea is to install them in the outlet of the H pipe.

Has anyone been down this road? What's the best way to go on this?

I'm by no means an exhaust expert, but the DB killer is always added to the exit end of the muffler. The length of the insert changes internal flow of gasses in the muffler and 'kills' or lowers the decibel level. Inserting anything in the H pipe will only restrict flow, not change the tone/sound.