Exhaust Packing

[gazzaecowarrior]

Gave my 04 Beta 250 a full overhaul two weeks ago. Part of this overaul involved re-packing the silencer. I have allways used the roll type packing but this time decided to try the loose stuff. I have done two competitions on the bike since and the whole charector of the bike has changed. It doesn't seem to have the power in the low gears and seems to rev out too easily. Hills which I would have ridden in second gear I am now riding in third because it would rev out and I wouldn't be able to get to the top. The bike sounds crisp but I am wodering if I have re-packed it too tight. Any advice would be appreciated.

[gazzaecowarrior]

Any ideas guys ?

[firstgear]

I repack my silencer 2 - 3 times a year. I normally use the rolled type but have also used the loose stuff.

From my findings "less is best" If you really pushed it tight I can see where you would notice it in seat of the pants feel test.

Since it is a 5 minute repair remove the end cap and repack with less and see what you think.

[jse]

Gave my 04 Beta 250 a full overhaul two weeks ago. Part of this overaul involved re-packing the silencer. I have allways used the roll type packing but this time decided to try the loose stuff. I have done two competitions on the bike since and the whole charector of the bike has changed. It doesn't seem to have the power in the low gears and seems to rev out too easily. Hills which I would have ridden in second gear I am now riding in third because it would rev out and I wouldn't be able to get to the top. The bike sounds crisp but I am wodering if I have re-packed it too tight. Any advice would be appreciated.

I'll stick my nose in here since nobody answered you, but I may be missing the point, if you can use 3rd instead of 2nd to climb hills, isn't that better, traction-wise? The loose packing, like SilentSport, should probably be packed looser than you think, as the directions say, and not jammed in, like the density of roll packing. I've had good luck with SilentSport as it is much easier to pack the odd-shaped Trials mufflers and you can add to it in a pinch (like the Trial is the next day and all the shops are closed, but the muffler still needs packing). The sound will be different, and maybe you may be mistaking the performance of the bike based on your previous experience with the old packing?

Jon

[gazzaecowarrior]

I repack my silencer 2 - 3 times a year. I normally use the rolled type but have also used the loose stuff.

From my findings "less is best" If you really pushed it tight I can see where you would notice it in seat of the pants feel test.

Since it is a 5 minute repair remove the end cap and repack with less and see what you think.

Thanks for the reponse. I have a day off tommorow so I will re pack it with a lot less and see how it goes.

[gazzaecowarrior]

I'll stick my nose in here since nobody answered you, but I may be missing the point, if you can use 3rd instead of 2nd to climb hills, isn't that better, traction-wise? The loose packing, like SilentSport, should probably be packed looser than you think, as the directions say, and not jammed in, like the density of roll packing. I've had good luck with SilentSport as it is much easier to pack the odd-shaped Trials mufflers and you can add to it in a pinch (like the Trial is the next day and all the shops are closed, but the muffler still needs packing). The sound will be different, and maybe you may be mistaking the performance of the bike based on your previous experience with the old packing?

Jon

Thanks for the response. The point I was making is that the whole feel of the bike has completely changed and I don't like it. I like 2nd gear a lot as it is a good gear to blast up a hill from a standing still start when you don't have space for a run up. If I try it now the bike runs out of revs and my momentum slows down and I end up on my a***. On the same hill before I repacked it would coast up in second with lots of revs left to crest the top of the hill. I am just amazed that over packing a silencer can have such a drastic effect on top end in the low gears.

[jse]

Thanks for the response. The point I was making is that the whole feel of the bike has completely changed and I don't like it. I like 2nd gear a lot as it is a good gear to blast up a hill from a standing still start when you don't have space for a run up. If I try it now the bike runs out of revs and my momentum slows down and I end up on my a***. On the same hill before I repacked it would coast up in second with lots of revs left to crest the top of the hill. I am just amazed that over packing a silencer can have such a drastic effect on top end in the low gears.

You might try re-packing it a little looser. The internal core of the final muffler is part of the "included length" of the designed exhaust system

and you may have reduced the internal volume. MX expansion chambers will be smaller volume for torque values and roadrace chambers will tend to have more volume for higher rev's (that's a gross oversimplification, but may be, in part, what's working here). Did you do anything else to the engine..at all, when you packed the muffler?

Jon

Oh, and you may want to check the core as it may have shifted during re-packing and mis-alignment will kill rev's quickly.

Edited September 2, 2008 by JSE

[rlracer]

On the Beta easiest way I have found is to just buy the stock factory packing it's preformed and takes only seconds to swap out, it may cost a little more but it makes up for it in time & hassel free installation.

[gazzaecowarrior]

You might try re-packing it a little looser. The internal core of the final muffler is part of the "included length" of the designed exhaust system

and you may have reduced the internal volume. MX expansion chambers will be smaller volume for torque values and roadrace chambers will tend to have more volume for higher rev's (that's a gross oversimplification, but may be, in part, what's working here). Did you do anything else to the engine..at all, when you packed the muffler?

Jon

Oh, and you may want to check the core as it may have shifted during re-packing and mis-alignment will kill rev's quickly.

Thanks jon for the advice. Your insight into exhaust design is much appreciated. I am going to repack it again today and give it a blast this afternoon to test whether there is any change.

I didnt do anything else to the engine as it was working fine. I kept the carb set as it was as it was spot on. The only thing I did do was replace the overflow pipes to the carb. I doing this I took some advice from this site and drilled a tiny hole into the oveflow pipes above the height of the float chamber to prevent the syphoning that occurs with mikuni carbs. This seems to have worked.

Gareth

[gazzaecowarrior]

Right then. Re-packed exhaust and had a good spin on the bike. The bike is far better now at high revs. I really had jam packed the packing material in as I have only put back in about half of what I took out. Still sounds good with far less packing. Thanks for everybodies advice.

[razor]

On the Beta easiest way I have found is to just buy the stock factory packing it's preformed and takes only seconds to swap out, it may cost a little more but it makes up for it in time & hassel free installation.

+1