Exhaust For Yfz

[CronicArt]

The silencer isn't what makes the differance. Not much hp gained from just changing the can. It's the head pipe that is the important part of the system.

The differance is in the taper of the pipe. How it tapers and where. I believe a long gradual taper will give you more torque on the bottom and gradually pull through the mids to highs as where a shorter taper will give you a harder hitting punch right off the bottom to mids.

My particular head pipe has kind of a pre muffler if you will. Not exactly a muffler but it looks like one on the inside without the fiberglass. The theory behind it is that it cools exhaust gasses there fore compressing the exhaust to allow it to exit the pipe at a faster rate giving me a big bottom end hit. I lose nothing on top but don't gain any either. If I want to change the hit all I have to do is reduce the size of my end cap. Right now I run a 2" diameter end cap and lets my motor breath.

With an exhaust change you also have to compensate with an intake change also. More exhaust moving out requires more fuel and air to come in. It bugs me when guys jump right for a big bore kit. You can get so much out of your engine when it breaths right. Since my motor and the one in the quad are very similar I can tell you exactly what to use to get the most out of what you have without major motor work.

I have never needed any top end a side from long straight roads. Then I have higher gears. For the most part I never get to see anything higher than 3rd. As a matter of fact Tim Ferrys supercross 426 had the 4th and 5th gear blocked off. He ran no higher than 3rd. His sprocket set up was 14/54. They don't even sell a 54T rear. It would be equivalent to a chevy a with 4:10 rear. Using the bottom end to power over the triples. This is what you want for any type of tight course riding where you stay in the lower gears and need short distance hits. I run a 14/51 gear and all I have to do is blip the throttle to get over whoops. No clutch needed.

[rpyfz450]

Originally posted by CronicArt@Oct 24 2004, 03:03 AM
The silencer isn't what makes the differance. Not much hp gained from just changing the can.
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This isn't true for the YFZ. The YFZ and WR share an extra quiet, chambered muffler that includes a sparka arrestor screen. The YZ comes with a a muffler that goes straight through. You're comments were probably comparing the YZ's OEM muffler with aftermarket.

[CronicArt]

Originally posted by rpyfz450+Oct 24 2004, 10:04 AM--><div class='quotetop'>QUOTE (rpyfz450 @ Oct 24 2004, 10:04 AM)</div>

This isn't true for the YFZ. The YFZ and WR share an extra quiet, chambered muffler that includes a sparka arrestor screen. The YZ comes with a a muffler that goes straight through. You're comments were probably comparing the YZ's OEM muffler with aftermarket.
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You are right I was comparing the race ready models. You are absolutle right, once you pull the plug on the stock can you will get a big boost in hp and response.

[05yfz]

thx foR all the information