2 Stroke Guy/4 Stroke Question

[jsmith811]

Ok guys I have 01 CR250, I love it, but I can't say I'm not VERY interested in the new 450F from Honda, as well as the WR's. BUT WHY DO you need such a HUGE silencer on a 4 -Stroke?? Even my kids XR50 has a bigger silencer than my CR250. Is this something to do with compression? I know Nothing about 4-strokes.

 

[KLX Spode]

On a two stroke, you have an expansion chamber which tends to reduce the noise by using sound waves to scavenge and to reduce scavenge depending on the cycle, and this helps to soften the sound compared to a four stroke which basically has a straight pipe from the exhaust port and needs the additional dampening from a much larger silencer. Not the most technical answer, but hope it helps!

 

[XR650Rider]

4-Stroke=Smaller diameter pipe and larger silencer

2-Stroke=Larger diameter pipe and smaller silencer

General rule of thumb. Some of the new silencers coming out for the 4-strokes are not as large as the stock ones. I could hide inside my stock silencer if it starts raining. I am looking forward to dumping 5 or6 pounds off of the 650 with a new exhaust combo.

KDK

 

[jsmith811]

I still don't understand why the factories can't make the silencers smaller. Seems like they would get damaged easily in a crash.

 

[KLX Spode]

Try sticking a two-stroke silencer on a four stroke and you will immediately know why! It would be absolutley deafening! Since there is no expansion chamber on the four stroke, and none is needed, they have to make up the difference on the silencer. It's no easier to damage a silence on a four stroke than it is to damage an expansion chamber on a two stroke, and if it does get damaged, won't kill the performance like a dented expansion chamber!

 

[DougRoost]

Agreed. In fact at least the silencer is somewhat protected vs. the large expansion chamber of 2 strokes being very vulnerable to logs and things kicked up from the front tire.

Nice to see another KLX spode out there! Sometimes it's not easy being green but I love mine!

 

[smb_racing]

actually I know you might think this is dumb, but a while back me and my friend daniel fabricated a way to throw a DG two stroke silencer on his DR250, being as his DR's exhaust system was stock and had zero baffles in it the two stroke silencer was much improved, it had a strange sound that could only be described as wicked. One main drawback was the two stroke oil that was in the silencer started to burn out as it got warm and thus we had a four stroke that reeked of Klotz :scream:
The custom exhaust would still be on there if it were made of something other than aluminum, the heat generated by the engine basically melted the silencer head tube in half where it met the header pipe, just something for ya'll to laugh about at our expense..