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Science experiment on a six CRF 450 exhaust that ended with amazing results

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Hey guys,

So I was looking at the factory exhaust, I'm speaking of the factory 06 CRF 450 slip on, wondering if there was anything I can do to that silencer to give more power. Anyways, a good friend of mine that builds motors for Porsche suggested to take the one spare factory silencer I have and take a bandsaw and make a perfect cut in the front half of the silencer. All he was explaining to do was to do was take the in All, the outside 4 1/2 inches of the silencer with the band Saul, Dremel, whatever you have, as well as the Same amount to the Baffle.

After shortening this exhaust by 4 1/2 inches, and doing various measurements, everything loaded back up perfectly, the only thing that was the mid-pipe bolt that is installed in the flange on the side of the bike right behind your leg if you're sitting on the bike. Obviously this isn't that big of a deal but calls with everything tied down, the factory exhaust is solid.

After taking 4 1/2 inches Al, repacking the exhaust, and also riveting the tail cap back on, The pipe look absolutely great, it looked as if it was a Shorty pie, it didn't stick out at all past the back right number plate which look great. I crank the bike, they crank as easy as ever, and put it straight on the dragstrip. We took the factory own exhaust on and off after timing he run down the dragstrip. After each run, we would put the chopped factory silencer on and do the same exact run at least 10 times per person on the same bike and record the times.

I am very excited to say that this modification has to of been one of the best ideas I have ever had, I had heard about it with two strokes but never did it with a four stroke, but it was so worth it that I took my other factory exhaust and cut the same amount off of it. The best thing is everything fits perfectly, and I actually took my aftermarket exhaust off my bike to put the chopped factory exhaust on.

Just thought I would share my findings with you guys, if anyone would like to try it out it is very very easy, a moron can do it and actually end up with a great looking exhaust. I can post pictures of the factory length exhaust beside the chopped exhaust if anyone would like to see them.

Anyways that's all I was going to inform you guys of, but I can promise you if you do it you will not regret it.

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Hey guys,

So I was looking at the factory exhaust, I'm speaking of the factory 06 CRF 450 slip on, wondering if there was anything I can do to that silencer to give more power. Anyways, a good friend of mine that builds motors for Porsche suggested to take the one spare factory silencer I have and take a bandsaw and make a perfect cut in the front half of the silencer. All he was explaining to do was to do was take the in All, the outside 4 1/2 inches of the silencer with the band Saul, Dremel, whatever you have, as well as the Same amount to the Baffle.

After shortening this exhaust by 4 1/2 inches, and doing various measurements, everything loaded back up perfectly, the only thing that was the mid-pipe bolt that is installed in the flange on the side of the bike right behind your leg if you're sitting on the bike. Obviously this isn't that big of a deal but calls with everything tied down, the factory exhaust is solid.

After taking 4 1/2 inches Al, repacking the exhaust, and also riveting the tail cap back on, The pipe look absolutely great, it looked as if it was a Shorty pie, it didn't stick out at all past the back right number plate which look great. I crank the bike, they crank as easy as ever, and put it straight on the dragstrip. We took the factory own exhaust on and off after timing he run down the dragstrip. After each run, we would put the chopped factory silencer on and do the same exact run at least 10 times per person on the same bike and record the times.

I am very excited to say that this modification has to of been one of the best ideas I have ever had, I had heard about it with two strokes but never did it with a four stroke, but it was so worth it that I took my other factory exhaust and cut the same amount off of it. The best thing is everything fits perfectly, and I actually took my aftermarket exhaust off my bike to put the chopped factory exhaust on.

Just thought I would share my findings with you guys, if anyone would like to try it out it is very very easy, a moron can do it and actually end up with a great looking exhaust. I can post pictures of the factory length exhaust beside the chopped exhaust if anyone would like to see them.

Anyways that's all I was going to inform you guys of, but I can promise you if you do it you will not regret it.

Post the time slips and I assume this was 1/8 mile runs.

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Where's the data?

You could have reduced peak hp while increasing low-mid torque which resulted in the quicker times. Dyno testing both systems is the only way to get real data.

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man that was painful to read....I hope you were using talk to text

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Hey guys,

So I was looking at the factory exhaust, I'm speaking of the factory 06 CRF 450 slip on, wondering if there was anything I can do to that silencer to give more power. Anyways, a good friend of mine that builds motors for Porsche suggested to take the one spare factory silencer I have and take a bandsaw and make a perfect cut in the front half of the silencer. All he was explaining to do was to do was take the in All, the outside 4 1/2 inches of the silencer with the band Saul, Dremel, whatever you have, as well as the Same amount to the Baffle.

After shortening this exhaust by 4 1/2 inches, and doing various measurements, everything loaded back up perfectly, the only thing that was the mid-pipe bolt that is installed in the flange on the side of the bike right behind your leg if you're sitting on the bike. Obviously this isn't that big of a deal but calls with everything tied down, the factory exhaust is solid.

After taking 4 1/2 inches Al, repacking the exhaust, and also riveting the tail cap back on, The pipe look absolutely great, it looked as if it was a Shorty pie, it didn't stick out at all past the back right number plate which look great. I crank the bike, they crank as easy as ever, and put it straight on the dragstrip. We took the factory own exhaust on and off after timing he run down the dragstrip. After each run, we would put the chopped factory silencer on and do the same exact run at least 10 times per person on the same bike and record the times.

I am very excited to say that this modification has to of been one of the best ideas I have ever had, I had heard about it with two strokes but never did it with a four stroke, but it was so worth it that I took my other factory exhaust and cut the same amount off of it. The best thing is everything fits perfectly, and I actually took my aftermarket exhaust off my bike to put the chopped factory exhaust on.

Just thought I would share my findings with you guys, if anyone would like to try it out it is very very easy, a moron can do it and actually end up with a great looking exhaust. I can post pictures of the factory length exhaust beside the chopped exhaust if anyone would like to see them.

Anyways that's all I was going to inform you guys of, but I can promise you if you do it you will not regret it.

Hey,

First of all, way to go in trying something and experimenting!

 

What you ended up doing is change the tuning frequency of your exhaust.  lots of places do this all the time. 

Look at the newer crf450s and you will see that some have long headers while some are short.  this is how you can put the power where you want it.

 

There are ways to calculate this and you should check it out.

you can calculate your tuning and the sound output.  then see how well that matches up to what you actually did.

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Those stock mufflers are still ok after 10yrs of use? Doesn't seem possible that packing is ok.

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Sorry it was a longer post, but yes the stock mufflers are still great, I mean obviously I keep up with servicing mine but other than that yea they are good! And yes it's very interesting how you can change dynamics by simply changing lengths.

Ps talk to text was used haha

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its cool you took the time to try...always fun learning something new!

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