Shorty Silencer vs Regular Length

[MyckMcClung]

Yes DirtAddict, what you have been told before coming here is all BS.

[chump6784]

One question, do shortys actually give more bottom/mid and reduce top end or do they just allow the bike the rev out quicker making it FEEL like it changes the power? I have always thought it enabled the bike to rev out quicker resulting in the different feeling power curve

[MyckMcClung]

Well I'll tell you this, the RM85 I bought for my daughter came with a FMF SST pipe and Shorty silencer, the ignition was also advanced to the max. The SST is a topend pipe the Shortly is a bottom end silencer, from open to 1/2 throttle the bike had nothing, then it would just scream with power to about 3/4 throttle and had nothing else. The jetting was also very rich, FMF recommends 48 pilot 125 main stock needle at second clip, this thing has 50 p, 128 m. I moved the clip up to the 4th groove,  installed  a Moose torque spacer between the Vforce 3 and intake tract set the air screw 2 turns out. Now the bike is like a tractor, until half throttle then it friggin rips, up to just about 3/4 throttle and falls flat.
I wish I had the stock silencer or a Powercore to test against the Shorty.

[George]

in my experience, a shorter silencer makes for a sharper, narrower power band. I had a standard pipe on my old kx85 (going back a few years) and 3 silencers, all standard, one normal length, one cut 2 inch shorter and one about 3.5 inches shorter, the shorter ones were better on hard pack/ tacky grippy ground, the longest was best in deep sand/ mud, hope this helps

i wrote this a few days ago, and with standard front pipe a shorter silencer let the engine pick up sooner and go better in the right conditions, if your really serious about racing then its an idea to stock up on a few different lengths, but on my rm250 im not bothering changing lengths because with bigger bikes there is less emphasis on peak power as useable power gives better laps, so i have a full length silencer ont the 250