Thump
Senior Member
- Joined
- Aug 14, 2013
- Location
- Nakhon Si, Thailand
- Bikes
- '14 CBR500R; '13 CRF250M; '14 MXS125; '09 Nouvo 135
From the first day I had my CRF250M it was clear that something needed to be done to the exhaust. It doesn't sound like anything and it's too quiet. The easiest choice would be to order a slip-on but since I live in Thailand shipping from the US is a killer on top of the $300 to $500 purchase price.
Also I kind of liked to leave the bike looking stock and to keep the plastic heat shield which looks better than a shiny aluminum or titanium can. The good thing about living in Thailand is that if you find the right people and the right shop you can get some real good work done for very little money.
So I decided to go step by step and see what happens.
There's the exit wall with the end pipe, there are two walls in the muffler which are connected by small pipes and then there's the catalytic converter.
I just wanted a bit more sound and volume, no open, roaring race pipe, so I went to a shop and had the wall close to the exit wall taken out. The other wall and two small pipes stayed in. I cut the end pipe short so that it only stuck out to the outside and then closed everything back up. The result was about a 20% increase in volume but the sound was still crappy, like a stock bike. Can't recommend to do this. This is how it looks when you cut off the end wall:
This is how it looks after taking out the first wall with one pipe:
Okay, so the second wall had to go, then there's only the cat in there, see how that sounds! I had a new end pipe made from a 1,25" steel pipe and some holes drilled into the part inside the muffler. The now empty muffler body had only the cat to slow things down and a bit bigger end pipe. Welded it up and hopefully it sounds acceptable! Well it didn't. It was too loud and sounded like a big hollow steel can which it effectively was. At least now I made some noise, I could hear the sound while wearing my helmet. I was surprised that the bike ran like nothing had happened - no hiccups or backfiring at all, just business as usual. Amazing.
Stock end wall and pipe, 1" (Thai version):
The one I had made, 1,25":
Now I decided to go all the way. Cat out, core with muffler packing in! I read up on how other people had done it, some went with a 1,5" core and 1.5" end pipe and locally available fiberglass muffler packing. Several shops here in Thailand offer the complete package for 1,200 to 1,500 Baht. But I wanted heat-resistant high-quality muffler packing which is not available here so I had to order it which took some time to ship and cost more but it should last longer.
Then about the size of the core: the muffler body is 4" at the end wall and 6" at the widest part, that's quite voluminous! This ain't no light, slim, short aluminum slip-on, this is a heavy, double-walled steel body. A 1.5" core seemed to small because then I'd have to make up for the room around it with packing - 2.25" at the widest part, too much! So I decided to go with a 2" core, still enough space around it and a 1.25" end pipe, a bit smaller, should keep the volume down and provide more back pressure. (I've seen some 2" end pipes!)
So off to the next shop, get the 2" core made; the FMF Racing muffler packing had arrived and we're ready to go.
The perforation of the core seemed a bit coarse so I got some stainless steel moskito netting to wrap around it.
This time we went in from the rear, not from the side (note the catalytic converter):
Only the first time we opened the can from the side which I don't recommend:
Here a picture of the culprit after extraction:
Then we had to cut the core so it fits into the muffler body. Cut at about 10" to 12" and reweld the shorter end in a slight angle:
Here I already wrapped the sucker and tightened things up with wire:
to be continued
Also I kind of liked to leave the bike looking stock and to keep the plastic heat shield which looks better than a shiny aluminum or titanium can. The good thing about living in Thailand is that if you find the right people and the right shop you can get some real good work done for very little money.
So I decided to go step by step and see what happens.
There's the exit wall with the end pipe, there are two walls in the muffler which are connected by small pipes and then there's the catalytic converter.
I just wanted a bit more sound and volume, no open, roaring race pipe, so I went to a shop and had the wall close to the exit wall taken out. The other wall and two small pipes stayed in. I cut the end pipe short so that it only stuck out to the outside and then closed everything back up. The result was about a 20% increase in volume but the sound was still crappy, like a stock bike. Can't recommend to do this. This is how it looks when you cut off the end wall:
This is how it looks after taking out the first wall with one pipe:
Okay, so the second wall had to go, then there's only the cat in there, see how that sounds! I had a new end pipe made from a 1,25" steel pipe and some holes drilled into the part inside the muffler. The now empty muffler body had only the cat to slow things down and a bit bigger end pipe. Welded it up and hopefully it sounds acceptable! Well it didn't. It was too loud and sounded like a big hollow steel can which it effectively was. At least now I made some noise, I could hear the sound while wearing my helmet. I was surprised that the bike ran like nothing had happened - no hiccups or backfiring at all, just business as usual. Amazing.
Stock end wall and pipe, 1" (Thai version):
The one I had made, 1,25":
Now I decided to go all the way. Cat out, core with muffler packing in! I read up on how other people had done it, some went with a 1,5" core and 1.5" end pipe and locally available fiberglass muffler packing. Several shops here in Thailand offer the complete package for 1,200 to 1,500 Baht. But I wanted heat-resistant high-quality muffler packing which is not available here so I had to order it which took some time to ship and cost more but it should last longer.
Then about the size of the core: the muffler body is 4" at the end wall and 6" at the widest part, that's quite voluminous! This ain't no light, slim, short aluminum slip-on, this is a heavy, double-walled steel body. A 1.5" core seemed to small because then I'd have to make up for the room around it with packing - 2.25" at the widest part, too much! So I decided to go with a 2" core, still enough space around it and a 1.25" end pipe, a bit smaller, should keep the volume down and provide more back pressure. (I've seen some 2" end pipes!)
So off to the next shop, get the 2" core made; the FMF Racing muffler packing had arrived and we're ready to go.
The perforation of the core seemed a bit coarse so I got some stainless steel moskito netting to wrap around it.
This time we went in from the rear, not from the side (note the catalytic converter):
Only the first time we opened the can from the side which I don't recommend:
Here a picture of the culprit after extraction:
Then we had to cut the core so it fits into the muffler body. Cut at about 10" to 12" and reweld the shorter end in a slight angle:
Here I already wrapped the sucker and tightened things up with wire:
to be continued
When I close the throttle it sounds great, it pops a bit but not too much. It also pulls a bit better, not much but enough to notice it.
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