Cut off the end of my muffler

[RockyIII]

Hello fellow captains.

Yesterday I decided to take a hacksaw and cut off the end of my muffler as the previous owner had soldered a thick heavy piece of metal into the end of the can to reduce the exit diameter for noise purposes.

I decided to do this because I did a lot of reading on the net about reducing back pressure and that most HP gains are to be had with the least restrictive exhaust system. Also I figured that the bodge job mod was really backing up exhaust gases and I didn't like the idea of that.

Anyway, by cutting off that restriction, I now have the originally designed exhaust back and now the the exit hole is 3 inches wide as opposed to 1 inch wide. The exhaust "muffler" is basically just a 3 inch wide foot long "CAN". So "free flowing" is now an understatement and it's loud as you know what.

Now, I still have the 20050pods_ign_retard tune and that worked great when I had more back pressure in the exhaust, but now, the idle is a bit hesitant on start up and also has a hesitant/lumpy low throttle pick up response. I believe it's running quite a bit leaner now as there is a much better scavenging effect in the exhaust. A lot more decel popping and cracking.

I'd like to know if I'd do better downloading the triples/Jars tune or any other suggestions would be welcome. I still have all stock air plumbing in place with OEM filter.

A thousand thanks in advance.

 

[Aivmid]

You took a hacksaw to it?

How's it look?

 

[RockyIII]

Well, it was very difficult to cut it dead straight, so I'm going to file it down to a nice flat round surface. The whole exhaust system itself, is nothing really fancy. It's all covered up with stainless heatshielding which discolours very quickly after cleaning. Turns to dark golden with the heat. It does it was designed to do very well I believe.

I know I should have some K&N to go with it, just haven't got round to it. Think I'm gonna download the Jarstripp tune and see how the engine/exhaust deal with that combo.

Will be interesting.

 

[CanberraR3]

Got any pictures you can post. This I gotta see.

 

[RockyIII]

I'll get one in a mo. It's quite hilarious!!! I'm laughing as I type. Stay tuned.

 

[RockyIII]

Here are the pics.

http://www.r3owners.net/attachment.php?attachmentid=4283&stc=1&d=1346018350

 

[RockyIII]

more pics

http://www.r3owners.net/attachment.php?attachmentid=4284&stc=1&d=1346018771

 

[RockyIII]

I'm thinking a nice stainless db killer should look good in there. It's a 3.5" opening now.

It's louder than before but not by a long way. It pulled much more freely and smoothly than before, especially in the power range, quite liked it actually.

 

[CanberraR3]

It's a very interesting looking bike you have there. Unfortunately none of the pics are very clear but I can tell that it's not your ordinary looking RIII. And I bet it's bloody loud. You're going to want some restriction in there for the back pressure and improved torque. Let us know what you decide and some clearer pics would be great too.

 

[RockyIII]

I think you could be right. The idle sorted itself out very quickly and idles great. It's definately breathing better as I said. In a way, the small reduction in torque almost helps as it's now mellowed out a bit down low and throttle control is easier. I almost don't care that much for tons of low down torque as my driving style is more laid back upto 3000rpm which is where I like to start ripping it, and I can definately feel a pleasing airy forward surge but not less powerful. I always felt that the crappy soldered on piece of metal before with a 1" hole was restricting the engine as when high revs came the engine seemed to be all pressured up and it was just bugging me. So I had to cut it to be honest, thinking that I could buy an insert baffle later with a bigger than 1" exit hole. But like I said, I can feel a pleasing difference in the way the engine breathes at high revs especially which is where I like it.

Bye the way, is there an ideal exit hole size, or is it too complicated to say, suppose it depends on the whole exhaust design, don't know.