Is there any truth to this?

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#1
Hey,
I was at the local yamaha dealer and they were riding a banshee around, noticing how loud it was i went to the back side of it and looked at the silencers. They were gutted, no packing. Once inside the dealer i asked him about it and he said if your not riding on the trails and only on the race track then its a very good mod to do, but it is loud so if you ride on the trails its not good.

So, is there any performance benefit to gutting silencers on 2 strokes?

The other thing he told me about was cutting down my stock silencer on my bike, cut as far back as possible is what he told me to do, im kind of iffy about that though. is there any performance benifit to that?

BTW, i ride a 1999 suzuki RM 125, fmf fatty pipe, stock silencer, boyesen reeds. Blew the motor going down a dirt road chasing after another guy, lower rod bearing sort of melted/dissapeared. I just got the crank back yesturday so im happy!

Sorry for the lengthly post, and thanks in advance for your answeres!

Andy
 

Rich Rohrich

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#2
Originally posted by indy650

So, is there any performance benefit to gutting silencers on 2 strokes?

Only if you think losing horsepower is a benefit. You need to find a dealer that isn't a complete idiot. :thumb:
 
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#3
Yeah, i figured as much but that quad was very very very loud hurt my ears pulling into the place!
 
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rickyd

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#4
Not too mention that even private tracks can get shut down due too moise.. I'd visit another dealership..
 
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#5
Thanks for the info, but is there any benefit to shortening the silencer or is that just bs too?

I do coop (work there for free, well i get 2 credits) at the local polaris dealer, so i dont know why i went to the yama dealer.

Thanks,
Andy
 

Rich Rohrich

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#6
Shortening the silencer will change the pressure bleed characteristics of the pipe and can change the power. Whether or not it will change things in a postive way can only really be determined by testing on your bike.

The problem with this approach is twofold. For starters shortening the silencer will make the bike MUCH louder, and secondly, if the change isn't a positive one there is no easy way to un-shorten your silencer.

You'd be better served by learning to jet your bike really sharp and keeping the current silencer clean and packed on a regular basis.
 
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#7
Is it like in physics, what is it like open air column resonance length or something, is that what the ideal length would be? but other then that all the pressure and sound crap is way over my head
 

Rich Rohrich

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#8
As you shorten the length of the silencer or increase inner core diameter it tends to decrease the bleed-down pressure and will usually move power to a higher rpm. Lengthing the silencer or decreasing the inner core diameter will usually move power to a lower rpm.

Too much bleed down pressure can increase piston crown temps at sustained high rpm, and lead to detonation and even seizure in serious cases.

These are basic rules of thumb, not a hard and fast rules, so testing is gthe only way to know for sure.

Here's something you should read to better understand two-stroke tuning : http://www.eric-gorr.com/techarticles/basic_two_stroke.html
 
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#9
do you think going from a stock silencer to a spark arrester silencer would add a little torque anywhere on a 250?
 

Rich Rohrich

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#10
Originally posted by Nevada Sixx
do you think going from a stock silencer to a spark arrester silencer would add a little torque anywhere on a 250?
It would depend on the design differences between the stock silencer and the SA.
 
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#11
If my bike has no low end, i mean none, could that be because i need to repack my silencer? i just did it this this summer, haddent ridden it scince mid september.

It mabye has 5 rides on it and its already all hard and some of it is blown out! i mean i packed the entire contents of the FMF stuff in it and its already about 60% blown out.