Sunday, March 18, 2012

FMF Q4 muffler packing, and pipe polishing

I had been thinking the FMF Q4 muffler on the WR was perhaps a wee bit louder than it should be lately. At idle, it's fine. Rev it up a little in the driveway, and it's not so bad either. But accelerate hard and wind the engine up to the rev-limiter, and the sound carries for a mile.

I suspected the muffler packing may be starting to fall apart. The previous owner installed the FMF muffler and PowerBomb header, and hadn't repacked it at all --- although he really didn't put many miles on it (a thousand miles, tops). Anyway, I figured it was probably time for a re-pack.  Just under $16 including taxes at a local bike shop scored me an FMF4-stroke muffler packing kit. Just a 15" x 18" piece of 1" thick fiberglass.

The stainless steel of the pipe was looking a little stained. Odd how that happens, isn't it?  Since the exhaust system was already off the bike, I decided I would add some elbow grease and make the whole thing look shiny.

FMF PowerBomb header pipe was looking a little cruddy: 
Dirty, rusty, pitted, and discoloured.

The packing that faces up when the muffler is mounted 
on the bike was in very good condition.

But the part that faces the underside was a mess.

Nasty hole blown through. That's where the noise was coming from.

This is the FMF spark arrester screen insert tip. 

I made a slight modification to make it a little quieter. 
Five minutes using tin snips and channel lock pliers.

The opening at the front side of the spark arrestor is now 
partially obstructed. Reduced air flow, should drop the sound level 
a decibel or two, and hopefully won't affect performance too negatively. 

This is what the core looks like when it's naked.

Here's the new fibreglass wrap. 
I used wire to hold it in place.

Look at the shine on that header pipe! Using #00 and #0000 steel wool, 
and also a medium coarse 3M scotchbrite sanding pad, and I went to work. 
I also used a cream polish called BlueMagic Metal Polish --
squeezed a bit onto the steel wool. Followed it up with a buffing wheel
mounted on my high speed 8" bench grinder.  All together, it took a couple 
of hours for the polishing/buffing, and it will probably turn a bronze/brown 
colour after a few rides -- but it looks nice for now. 

There seemed to be plenty of room for the outer muffler sleeve 
as it fits over the inner core -- even after wrapping the new fibreglass.
So, I bought some fireproof $20 kevlar sleeves used for welding. Cut the 
elastic ends off, and wrapped it around the fibreglass. I used only one, 
and saved the other one for the next re-pack. It probably won't serve 
any real purpose, but it takes up some of the excess space inside the 
muffler and it supposedly withstands temps to 500 degrees F.

Some high temp silicone around the lip as it goes back together. 

All ready to go back on the bike. I will let it sit overnight to ensure 
the silicone cures properly.

FWIW, this is the polishing cream I used. The tube of Autosol I had for the pipe on the DR650 was all gone, and the store I went to didn't seem to have any. So, on a whim, I bought this stuff for $8. I'm impressed and will choose this over Autosol the next time. Worked very well.

back on the bike

Here's a before & after video.  It doesn't really sound too 
different for the camera in the driveway, but it's definitely 
quieter while riding (with the engine under load).