wood duck
New Member
After reading all the talk on muffler modifcation, I am getting the itch to modify the muffler on my Jonny 520SP. It has the older style muffler on it, with an internal baffle. It is made with a front and rear half crimped together.
The baffle is a square C-section with the opening down, center aligned with the cylinder port. This also prevents the muffler from crushing when the attach bolts are tightned down. The baffle has a .785 diameter hole in the top part of the C, through which most of the exhaust gases must pass. The .510 diameter outlet is a pipe on the upper left as you face the muffler and points toward the bar at a 45º angle. The pipe protudes into the mufler and ends just above the hole in the baffle.
The bottom half of the muffler appears to be just an expansion chamber. It has double layer in front to act as a heat shield.
The down facing opening in the C baffle is about .539 wide by .937 deep, the balance being blocked off by a hat section in side of the C.
Looking at areas:
The cylinder port is about .547 sq. in.
The baffle hole is about .484 sq. in.
The outlet pipe is about .204 sq. in.
The lower baffle opening is .539 sq. in. but exits in to the lower half of the muffler.
So my question is this:
Should I add an outlet to the lower part of the muffler or is this space required for exhaust dynamics. By adding a port to the lower half, I can point it towards the bar like the original.
Or I could open up the upper baffle hole and add the second outlet to the top, leaving the "expansion chamber" intact but having to point the outlet towards the side handle.
If you have read this far, you are patient and I am verbose.
Thanks,
Jeff Borning
The baffle is a square C-section with the opening down, center aligned with the cylinder port. This also prevents the muffler from crushing when the attach bolts are tightned down. The baffle has a .785 diameter hole in the top part of the C, through which most of the exhaust gases must pass. The .510 diameter outlet is a pipe on the upper left as you face the muffler and points toward the bar at a 45º angle. The pipe protudes into the mufler and ends just above the hole in the baffle.
The bottom half of the muffler appears to be just an expansion chamber. It has double layer in front to act as a heat shield.
The down facing opening in the C baffle is about .539 wide by .937 deep, the balance being blocked off by a hat section in side of the C.
Looking at areas:
The cylinder port is about .547 sq. in.
The baffle hole is about .484 sq. in.
The outlet pipe is about .204 sq. in.
The lower baffle opening is .539 sq. in. but exits in to the lower half of the muffler.
So my question is this:
Should I add an outlet to the lower part of the muffler or is this space required for exhaust dynamics. By adding a port to the lower half, I can point it towards the bar like the original.
Or I could open up the upper baffle hole and add the second outlet to the top, leaving the "expansion chamber" intact but having to point the outlet towards the side handle.
If you have read this far, you are patient and I am verbose.
Thanks,
Jeff Borning
