I don't know about GGs yet, this is my first one and haven't messed with any pipes/silencers yet, but my experience is it varies quite a bit from bike to bike. On an 96 KX 250 a short silencer gave much more bottom but lost topend. The 96 KXs had mucho topend , big midrange hit with a long hard pull on top. A longer silencer softened bottom and tamed the hit, but it was slower everywhere.
Jump to a 2001 KX, which had 3 fewer HP than the 96 but had a more balanced power delivery throughout the range, a shorty silencer merely gave a very slight bottom end boost but lost every where else. A longer silencer also lost everywhere but made the bike almost "trials like". It was soft on power but very manageable. No hit anywhere, but no stalling and very good for a really slick track.
On a stock 02 Yamaha YZ 250, the shorty gave a good low end boost, and lost very little on top. Midrange about the same, but less hit in the low to mid transition. Longer silencer did the same as on the 01 KX, made it mellower everywhere but didn't kill as much HP as on the KX. On the stock 02 YZ I liked a longer silencer most of the time except in sand. For me that year YZ was hard to ride in the woods, it had gnarly power everywhere and the longer silencer toned it down everywhere.
Same YZ with a 285 kit? (I later bought a different bike, just got a great deal). Funny thing happened. A shorty silencer tamed the midrange hit, but had much more bottom end so I could ride a gear high and the bike would pull it. More torque. I thought a shorty would be too gnarly but not so, as long as I kept it a gear high and lugged it. On the 285 YZ, a longer silencer also made it easier to ride. It tamed the huge power, tamed the midrange hit, moved the hit higher and softer in delivery. I had to ride it a bit harder, more aggressively but I could get away with that since the overall power delivery was much smoother, and it would pull forever in each gear. Overall with the 285 I liked the long silencer, then even welded on a spark arrestor which tamed the power even more. On the 285 with a flywheel weight and long silencer (with spark arrestor as well), the bike became an easy to ride do it all bike. It felt sleepy but actually I would usually pull away or be even with any other bikes except big bore 4ts. Even a KTM 300 was a bit slower in a drag race.
All of the above was using FMF fatty or gnarly pipes, and I did some rejetting if it seemed necessary but I could have definately changed things even more with more jetting. One strange thing was that the 96 KX benefited in starting from the long silencer, but was harder to start with the shorty and fouled more plugs. The 01 KX was exactly the opposite. But those 2 bikes had vastly different motors and ignitions, I think even different carbs. On the YZs both bikes fouled plugs more with the shorty and less with the longer silencer, even after jetting. I could never get the jetting great on either bike with the short one, but jetting seemed easier with the long one?
Ok, here's the really confusing one. On an 04 KTM 250 EXC, I used a short SX silencer, the shortest one made at the time. It hurt the power everywhere and generally sucked! Then I did all the other SX mods. SX head, piston, ignition, (CDI), red powervalve spring, (KTMs use different PV springs to change power, red is the most aggressive spring). After jetting the bike felt almost exactly like a KTM 300 EXC but with much better jetting and perhaps just a tiny bit less power everywhere. Those who rode it thought I had put a 300 head on it. 04 KTM 2ts were a bit sleepy everywhere stock. With the whole SX kit, but with the stock EXC flywheel, and I think it had a slightly heavier crank than the SX, it was perfect for me off road. It had huge bottom end but was still manageable, would pull on top, midrange, but had no real hit anywhere. Just easy to use "4 stroke like" power but power that pulled long and hard. Again, it took going the entire SX route to get this result. Another funny thing is that top ends lasted longer. I think I wrung it's neck less so it was revving and screaming less? Of all the changes I did to the KTM I think the most significant one by far was the SX CDI. The power delivery was stronger everywhere except the very top end, and it only lost a tiny bit there.
Confused? I am. The only thing I know for sure is changing exhaust in any way varies widely according to each other change, each bike, year of bike, and a whole bunch of factors. The good thing about trying different silencers on a 2 stroke is it is so easy. If you don't like it change it back. I also know that using different pipe/silencer combos can give big results but you can't give up, if you go that route you may have to do some other things such as CDI, and will have to rejet on most bikes.
Keep in mind noise is going way up with a shorty. On some bikes it will be totally obnoxious, and sometimes causes such a sharp bark that it will really hurt people behind you's ears. On my 96 KX and my 04 KTM I only used the shorty silencers on race courses. On the other bikes there was an increase but not so much. On the KTM for instance I even hated riding it with the shorty, it hurt my ears with a helmet on! Riding in sand or deep mud on a closed course race I'd use the shorty, the rest of the time used the stocker. Occasionally would use a longer factory silencer if it was very slick but not a place with deep mud. Occasionally I would use the short silencer but carried an add on spark arrestor which when bolted on basically lengthened the silencer to about the same as the stocker. I lost one of those, they cost nearly a hundred bucks, so then I drilled holes all around the arrestor and silencer and used about 15 small screws with red loctite, and of course the stock muffler clamp, but I bought a better clamp and safety wired it
Last edited by jgas; 11-24-2012 at 09:36 PM.
Reason: Forgot noise.
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11-23-2012, 02:17 PM
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