Hawk 250 Enduro Exhaust.

[Weldangrind]

Originally Posted by Entropy

So in theory what does the expansion chamber do? Help scavenge the gases?

There could be some merit to the theory of adding an expansion chamber to a four stroke, but it is unlikely to show any gains at this power level. FMF also says that it will reduce sound volume a bit.

[SeerAtlas]

Originally Posted by pcspecialist

On a 4-stroke, not a thing. And on a 2-stroke, you need a much, much, much larger expansion chamber to do much good.

hmm, i think there's a difference between "not much" and "not a thing". On the old harley race 750's the engineers/tuners spent years tuning the pipes trying to find any little bump or shape that would create a reverse exhaust pressure wave pulse that would sync with the valve timing to gain that last small increment of power out of the engine.
hell, look at the work the top racing bikes have done one their respective exhaust systems. only the "look at me" posers run straight pipes and that seems to be for volume

[pcspecialist]

I can believe reduced sound level.

[ughmas]

Motocheez just put up a new video for the install of this exhaust! good stuff

[2LZ]

Excellent! Unless I missed it, did he say what setup he got for what bike and what year?

[pcspecialist]

Just removing the cat on the stock exhaust makes a HUGE difference, I'm still getting the carb dialed in so I can't say just how huge yet. With the stock carb, proper jetting was 110 main (and shimmed up needle) before removing the cat. After removing the cat, even a 115 main is too small. Significant increase in power, but, when at high altitude, the bike does even better.

[Wolftrax]

Originally Posted by pcspecialist

Just removing the cat on the stock exhaust makes a HUGE difference, I'm still getting the carb dialed in so I can't say just how huge yet. With the stock carb, proper jetting was 110 main (and shimmed up needle) before removing the cat. After removing the cat, even a 115 main is too small. Significant increase in power, but, when at high altitude, the bike does even better.

I agree killing the cat is as dramatic a change as installing the Mikuni. Motocheez's video pushed me over the edge though and I went ahead and ordered the aluminum exhaust. Love the look as well as the fit on the Hawk.

[fitze]

Originally Posted by Weldangrind

There could be some merit to the theory of adding an expansion chamber to a four stroke, but it is unlikely to show any gains at this power level. FMF also says that it will reduce sound volume a bit.

No on the expansion chamber for a 4 stroke, it's all about how you handle the back pressure.

Entropy said So in theory what does the expansion chamber do? Help scavenge the gases?

No

4 stroke engines, in which intake and exhaust valves retain fuel in the combustion chamber the 2 stroke engine depends on the expansion chamber to retain fuel in the combustion chamber. You change the size and shape of the expansion chamber for what you want the bike to do. Quick Acceleration or Broad RPM range or maybe Broad to Lower power range.

It can be endless and frustrating building the pipe you are looking for.

[hertz9753]

Originally Posted by 2LZ

Excellent! Unless I missed it, did he say what setup he got for what bike and what year?

http://www.ebay.com/sch/Silencers-Mu...&_ssn=rch-2012

I have the red one.

[pcspecialist]

Originally Posted by Wolftrax

I agree killing the cat is as dramatic a change as installing the Mikuni. Motocheez's video pushed me over the edge though and I went ahead and ordered the aluminum exhaust. Love the look as well as the fit on the Hawk.

I cut past the welds and just barely squeezed the cat out, you must have had a real fun time getting it out of the opening you cut.

I see your's was a slip over, those don't have as free flowing mufflers as the current ones that use a flange. I probably would have gone with the aluminum exhaust too.

[Wolftrax]

Originally Posted by pcspecialist

I cut past the welds and just barely squeezed the cat out, you must have had a real fun time getting it out of the opening you cut.

I see your's was a slip over, those don't have as free flowing mufflers as the current ones that use a flange. I probably would have gone with the aluminum exhaust too.

It popped out fairly easily, I wedged a flat screwdriver behind the cat and pryed it right out. My bike never reved freely above 6000 rpm, now it bounces off the rev limiter in the first three gears easily.

[pcspecialist]

Final product after decatating:

[BlackBike]

Pcspec...

[Weldangrind]

Originally Posted by Wolftrax

It popped out fairly easily, I wedged a flat screwdriver behind the cat and pryed it right out. My bike never reved freely above 6000 rpm, now it bounces off the rev limiter in the first three gears easily.

Nice job, Mark. Do you have a pic of the header after you welded it back together?