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Hondathumper450

XR's Only exhaust & 650R

8 posts in this topic

I have a 2000 XR650R uncorked with the XR's Only competition exhaust. Nice pipe by the way. It has the power disc system on it. I decided to remove all the disc and take it for a ride. HOLY COW WHAT A DIFFERENCE!

The bike was a friggin fighter Jet compared to a cessna prop plane.

Loud as all heck but what a difference. I know this subject has been beat to death over and over but anyone have this exhaust with the 12 disc system on it? I was under the assumption that the disc system would give it plenty of power and still be soemwhat quieter than the stock drilled exhaust. WHat other options have people used with this exhaust pipe? any option from XR's Only other than the disc set that gives it more power? After I rode it with the exhaust disc out of the pipe it would bring the front end up in fourth quite easy but sounded like my crf450 with the fmf titanium 4 exhaust which was just as loud.

I know there are a few bolt on goodies you can get for the competion exhaust. Just want to know who has tried what and their thoughts on it.

one more question with the disc system. which way do you install the disc? with the cup side towards the exhaust pipe or away from it?

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Hey There,

I have used the XR's Only pipe on my XR400 years ago. Found it to be a good pipe, held up well, but was pretty loud.

The disc install with the cup towards the pipe.

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I have had several different supertrap type mufflers and I have alway put the cup side out and the round side towards the pipe.

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I use a similar disk system from a White Bros. Promeg muffler. Hears the thing with the disk system; The disks are supposed to create a vacuum to help scavange additional exhaust. But this is still relative to the flow of what the discs exit surface is. On the Promeg, 12 disks equal a 1.66" diameter exit hole in exit surface. 18 discs equals 2.03". Sound of course increases when using more discs.

I have run usually run 12 discs, usually to keep the sound to a decent level but it is still a bit over 96db, probably somewhere around 98db. Around 7-8 discs will bring the sound level to 96db or use 12 discs and a quite core. The Promeg muffler and discs are 4.75" x 3.5" oval while yours are 4" round I believe but yours may be fairly similar in effect and performance overall.

I have also tried mine without a backplate and yes it did make a very noticable difference in power. This stands to reason since we are roughly comparing a 1.66",(roughly 1 5/8") hole flow to a fully open 2" hole. If you or I were to add 6 more discs, (which I do have now, by the way) to equal a 2" exit tip, we would probably see similar performance to an open pipe. I have yet to try mine with the extra discs to literally feel for myself. It would be louder though of course. The standard use of the 12 disks is supposed to be a good overall power output in relation to the sound output not being atrocious. It's definately a compromise for the big motor that what's to breath.

Mufflers with quiet inserts will have basicly the same effect on power as the use of 12 discs or less. The conventional muffler tips may have 2" exit holes but they are stuffed up inside by the core insert, nontheless.

Yes, the rounded convex side of your backplate should face inwards. This helps bend the exhaust gases outward in a smoother flow to exit the discs faster. There is also a newer "power tip" from XRs Only. It is a backplate with a sharp cone for the XRs Only disc system that directs the gases outward even better to create faster, smoother exit flow. It is supposed to increase power by something like 1 1/2 horsepower. Something to consider if you want a little more from the 12 disks or whatever amount you use at any time.

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you can put more than 12 on i think, from what i can tell on mine, (xr400) you could put on up to 20 or 24 discs. you can always get longer bolts if the need be. The main advantage is the spark arrestor it provides. I run 8 in mine and it gives great torque at a reasonable noise level. yeah the tip is a really trick piece, and it does speed the velocity up also helps give you some good low end torque.

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