Flat Tracker Conversion

[Gary E]

Originally Posted by 45Brit

I didn’t follow the thread through yet, but I have a similar exhaust on my XL883 and I have 16-18 discs and a closed end cap. Seems to suit the bike just fine.

I imagine it is fairly loud. I have since gone to using 12 discs. Spark plugs still look good color wise with stock carb and jetting.

[45Brit]

It’s not particularly loud, passed MoT with no advisories. The closed end cap makes a BIG difference. I had 6, then 12 discs and an open end cap on my flat track bike and they were much louder.

I have a Stage 1 jet kit, which came with the bike. It originally had SE slip ons, which were offensively loud (I can’t understand how it ever passed MoT like that; it probably didn’t). I fitted a 2:1 high level exhaust with a short reverse cone megaphone which was quite loud, sounded very much like a Norton Commando.

Now I’ve got the Supertrapp 2:1 and it is much the best exhaust I’ve had on this bike. It had a megaphone which was LOUD, but the disc muffler is much better

[84rzv500r]

I have 12 disks and used both open and closed endcaps on my homebrew XR-1000 system and the open endcaps perform much better while the closed are quiet and forestry service approved.

Its gonna be fun if i get off my lazy ass and finish it...

[Steve9]

I've got looks like the same pipes on my '03

I took all the caps off. Think there was about ten on each pipe

Yeh, lazy............

[Gary E]

Originally Posted by 45Brit

It’s not particularly loud, passed MoT with no advisories. The closed end cap makes a BIG difference. I had 6, then 12 discs and an open end cap on my flat track bike and they were much louder.

I have a Stage 1 jet kit, which came with the bike. It originally had SE slip ons, which were offensively loud (I can’t understand how it ever passed MoT like that; it probably didn’t). I fitted a 2:1 high level exhaust with a short reverse cone megaphone which was quite loud, sounded very much like a Norton Commando.

Now I’ve got the Supertrapp 2:1 and it is much the best exhaust I’ve had on this bike. It had a megaphone which was LOUD, but the disc muffler is much better

Yes, the open end cap would be louder. And having a different jet set explains running the high number of discs without it going lean. My carb is total stock for '89

[45Brit]

Originally Posted by Steve9

I've got looks like the same pipes on my '03

I took all the caps off. Think there was about ten on each pipe

Yeh, lazy............

My flat tracker came to me with twin Supertrapps and no discs or caps. It was loud and for small British tracks, it’s better with 12 discs and open end caps. The small increase in back pressure improves the pickup. It probably costs at the top end but on 1/4 mile and 1/2 mile, you don’t notice

[sportsterpaul]

My understanding is that the open cap is the equivalent to 10 additional discs so it’s possible that 10 disc and open cap would be similar to 20 discs and closed cap....

[45Brit]

Originally Posted by sportsterpaul

My understanding is that the open cap is the equivalent to 10 additional discs so it’s possible that 10 disc and open cap would be similar to 20 discs and closed cap....

I’ve found from experiment, that the numbers of discs are in that range. They vary from bike to bike, not least because not all end caps are the same, and not all mufflers are the same.

There seems to be a maximum useful number of discs, and looking at the Hooligan bikes in the pits, it’s around 20 or 22 (Hooligan Race Bikes are a good guide to this because quite a few riders use Supertrapps, for whatever reason). My 883 seems to be happy at 18 and a closed cap. The flat track bike wants all the discs it can get, I go with 12 and an open cap on that but it came to me with no discs or caps at all.