EXUP Worldwide was born from the ashes of the original EXUP Brotherhood – the definitive forum for all those who have interest in Yamaha FZ, FZR, and YZF motorcycles.
Lately my bike would spit/sputter on cold start, blow soot out the exhaust, labor during revs, not a crisp/responsive throttle, sluggish, increasing vibration, etc ... generally degrading performance. I just figured since it was approaching 26K miles on the odometer it was due to valve clearance. Exhaust was not acting like it was free-flowing very well either so I decided to repack the exhaust muffler. Old fiberglass packing was loaded with soot. Repacked with new fiberglass packing and the results are outstanding.
Bike starts without hesitation. Idles smooth. Revs cleanly from idle all the way to the top. Crisp throttle response. Feels like a new motor. Took it for a ride today and it feels like I gained a bunch of horsepower. Vibration is gone too. I think the old packing was so packed with soot that it was blocking the free-flow of the exhaust. Now with the proper free-flow of the exhaust the engine is able to perform like it's suppose to.
Smooth, responsive, and fast.
So what do you know about what should be packed in there? I picked up a beauty of a race exhaust off Ebay but so far as I can tell, there's no packing in there at all and various internals are rattling around. I thought I'd open it up, see what's up and pack it. But I don't know what with...
I do know that when my car muffler last died it pushed what looked like hair out of the tailpipe.
The article illustrates a Two Brothers Racing muffler. Other manufacturers mufflers are similar. My Yoshimura muffler had screws rather than rivets and did not have any steel wool wrapped around the inner core (just fiberglass). I bought an FMF muffler repacking kit and used it in my Yoshimura. The link does not show the inner core without the wrapping ... but basically it's a metal (steel) cylinder with holes and perforations in it. Just pay attention to how it's assembled as you take it apart. You want the fiberglass to be wrapped snug (but too tight) around the inner core. You want enough fiberglass wrapped around the inner core that it all fits snug within the muffler (outer casing) when you slide it back in.
Some articles recommend using high-temp silicone sealer on the end caps when you reassemble the muffler. I didn't need to on the Yoshimura because of the way it's constructed. The inner core fit into sleeves on the end caps and the fiberglass wrap extended past the sleeves to eliminate and blow-by of gases out the end caps. That's why I recommend you pay attention to how it's assembled as you take it apart.
There are different repack kits for two cycle (two stroke) and four cycle (four stroke) engines. Make sure you get the correct type.
Wow. Everything you always wanted to know about packing exhausts.
It makes me think I'm definitely in the wrong business. The prices these sports exhausts cost - then you look inside and it's a two-bit perforated tube inside an old baked bean can (ok, a big one), packed with fibreglass. And the less stuff you have in there, the more you can charge!
Thanks, anyway. And, come to think of it, I haven't seen the neighbour's cat for a while now...
I've got the standard can. 50,000km. Definately full of soot. Doesn't appear to be anything I can do about it. Is there some magic way of cutting/rewelding it.
It's just that if I put a non standard one in its place it won't pass its yearly government test.
John
If you're going to take a shot at me let me know so I can duck...!
You can easily get road-legal aftermarket exhausts - unless there's something about the Spanish laws that I don't know. Or you can do what everyone else does - run whatever you like normally, then just pop the original on at testing time. It seems unwelding a welded exhaust is a pretty specialised job.
Yoniboi wrote:Is there some magic way of cutting/rewelding it.
The answer is yes. Welding aluminum or stainless steel takes experience and equipment. Problem with the welded exhaust is that it's not contructed to cut apart and weld back together. The result may be a ruined exhaust can (muffler). A reputable welding shop should be able to give you an estimate.
How about ftang's suggestion of a road-legal aftermarket exhaust or switching the exhaust from aftermarket to OEM for inspection?
