I have aftermarket yoshis on my VTR, but they are much higher pitched than the Kerker exhaust on my old VTR, which i sold to my mate greg.

I was wondering what the trick is to dropping the pitch? Not aiming to make it louder because the yoshis are loud enough.





see here:
Old bike with kerkers


I rang a custom motorbike exhaust specialist yesterday and he said the muffler core (perforated tube inside) diameter is the major determinate of pitch. Turns out my kerkers are around 57mm diameter and the yoshis are 50mm.
to make yoshis deeper they would need to be re-cored at a cost of $350 for the pair.

So instead, i bought some stock mufflers for greg (kerkers were too loud for him), and he sent me the kerkers back.

So i got the kerkers back from greg. looked like this...





So i shortened by 6cm and painted them hi temp metallic charcoal.
They sound much nicer and bike seems to have more low-rpm power too.











I've recorded some video with yoshis and kerkers, ill see if they are any good for comparison.

I have new Kerker badges which i need to put on still.

I now have a set of yoshis for sale if any one wants them.

 

This is good to know. I'll have to look into this down the road. My current set is the opposite of what I would like as well. They were cheap e-bay ones that I had to get in a pinch, but they are small and high pitched (and a little too loud). I'd like something much deeper and a little quieter.

I wonder what other brands' muffler cores are measuring at (and their corresponding sound).

 

I loved my Moriwaki pipes, they were very low and mellow. I've sold them so I can't measure the inside. Here's a video to hear



I had a set of two bros that were obnoxiously loud, I had to wear earplugs when I was riding.

 

My bike came with carbon Kerkers. Great sound but a bit loud for the apartments I live in. Tried the OEM's and the holes. Worked ok but sounded more like a Harley than a deep V twin. I ent to Autozone and grabbed a 1 7/8 to 1 5/8 and inverted smaller end in first and pounded into place. Wow, deeper and brought torque down 500 RPMs to 2000 with ease. The sound of the kerker and the noise of the DBs of the OEM.

 

The basics are actually pretty easy... You can know a lot about the exhaust note before you buy it and put it on your bike...

The larger the pipe of the core, the deeper the note... 50/55/57/60 mm are the most common sizes... I have seen as big as 75 mm though...

The size of the holes in the perforated core makes a huge difference on sound level, as does the size of the can... Larger can and/or smaller perforated holes makes for a quieter exhaust...

Round cans usually are more "angry" sounding, since they have to be huge in size compared to oval or triangle shaped to kill the frequencies that match the width of the largest part of the oval... Triangle or irregular box shapes are the most quiet, since they effectively kill off part of each frequency that matches the width of the box in each dimension...

The very small bend of the endpipe that some exhaust have making it point slightly down, or at least level, actually makes a bigger difference than you might think... It can effectively cut the percieved sound level in half as it directs the higher frequency noise down towards the ground, away from yours and others ears...

A carbon/kevlar can makes the noise more deep and booming and also louder, where as a metal sleeve is a bit more quiet, and also slightly higher in pitch... Note that many carbon/kevlar tubes are sleeved inside with metal...

Last but not least, the amount of packing material makes a huge difference to the noise level... Some slip-ons only have a couple of layers of material around the core... Some have a thick roll around the core, and some have a roll plus loose material outside the core/roll...