crotch rocket exhaust - DONE

Anyone try putting an exhaust can from a streetbike onto a WR? I'd like to quiet down my bike while still keeping up the exhaust flow; I had an R6 that was ridiculously quiet in stock form and the can still flowed enough for 120 hp so it couldn't have been too restrictive. It was also pretty light since it was aluminum.

Just looking to see if anyone else tried this yet.

Don't think I've ever heard of anyone trying that.

We don't own 4 cylinder sportbikes making over 100hp at the crank displacing 600cc's.

The engineering of a single 250cc engine is quite different. Back-pressure is important.

Love to know what you find out though. Post pictures.

Make sure you have a fuel programmer so you can keep from getting too lean.

motokid wrote:

Don't think I've ever heard of anyone trying that.

We don't own 4 cylinder sportbikes making over 100hp at the crank displacing 600cc's.

The engineering of a single 250cc engine is quite different. Back-pressure is important.

Love to know what you find out though. Post pictures.

Make sure you have a fuel programmer so you can keep from getting too lean.

Be interesting to know if that's true for the WRR or many of the other 4 stroke dirt bikes. But lets look at the design of the WR. It's basically a 1/4 of the R1 with a little less compression ratio and most likely weaker cams. That argument can go on for years and anybody who has knowledge of 2 strokes knows that exhaust back pressure is a must.

http://wikiscootia.wikidot.com/expansion-chamber

http://www.physicsforums.com/showthread.php?t=206232

Now if you look at the modern 4 stroke motorcycle exhaust design, it hasn't changed much since the 60s when we called it a reverse mega-phone. The idea was the airflow traveling over the cone drew the exhaust out of the pipe much like the airflow over a planes wing, and that can be BS too!

I'm of the school of pressure waves over back pressure and I wonder if FMF got that figured out by adding volume in the header pipe before the muffler with the Power Bomb and Mega Bomb? And the then the reverse megaphone design to draw the exhaust gases out quicker after taming that pressure wave?

Just thinking out loud.

I would disagree with motokid on this one - backpressure is not a necessity, certainly not if you believe a Q4 will give you more power. It is a large diameter open pipe - the stock exhaust would generate a LOT more backpressure. An since we're dealing with a slice of an R1 motor, I would think it would work quite well. I have a programmer, but I can't believe the stock R6 can would have any less backpressure than the Q4 - the outlet is much smaller. But all that extra volume is filled with packing to absorb sound.

I can just remember how stupid quiet my R6 was in stock form. The intake made more noise than the exhaust. If I could get the WR to that point I would be a very happy camper.

I'm looking around for some stock exhaust cans. I'll be sure and post up results when I get one.

By all means...I am not an exhaust engineer, or fluid/gas engineer of any sort.


I assume that Yamaha would do their very best to get the most power while still meeting EPA emissions and noise regulations.

I also assume FmF would bypass most of those restrictions and strive for absolute peak performance.


If it was as simple as necking down an R6 canister to fit some aftermarket header....I'd be shocked.

Have at it and take pictures and tell us what you find out.

You might be the next exhaust entrepreneur we all need.

Working on it now. Can is a titanium can from an R1. I have to find a shop to make me up a stainless connecting pipe to hook the can to the header. I put it on as a test before I cut the rest of the pipe off the can. Had to remove the rear wheel to get it in there, but it made me smile. Very quiet. Like, 'wow the intake sure makes a lot of noise' quiet.

That can looks huge on that bike.

Onya for giving it a go, it's good see poeple thinking ouside the box

Let us know how it goes and if you like the results or not

I like your idea toast. More air flow/less noise/no repacking! Here's a link pertaining to putting a GSXR pipe on a DR650. From reading over at ADVrider and TT, sounds like lots of people have done it.

https://docs.google.com/a/mxrob.com/present/view?ndplr=1&id=djwd44j_68fdsm79hf&ncl=true

Wow. I like that Gixxer can a lot better. And with the bolt on exhaust flange fabbing something up will be easier. Time to look on Ebay...

Big score on Craigslist!!!!! Because of all these DR650 riders looking for the gixxer pipes they are really hard to find. I found a guy on craigslist who just posted up the good pipes (2001 1000 with titanium cores) and he was five minutes away. $20!!! It is much smaller and lighter than the R1 can - unfortunately I already started fabbing stuff up and cut the pipe so I can't sell the R1 unit

Spent the weekend doing some fabbing. Wore out a ton of abrasive discs, forgot how hard stainless is.

Stainless 1 7/8" pipe goes over the Megabomb header. Pipe is stepped up to 2" and welded to a 1/4" stainless flange. My TIG welding is a bit rusty, so the welds on the flange are a little ugly...



Here you can see the size difference of the cans



Even with the size difference the titanium core of the Gixxer can winds up making the stainless pipe and can the exact same weight as the FMF it is replacing



Setup is quieter than the FMF, but I'm still not totally happy. The exhaust can has two muffler sections, I can get into the first. I'm going to make a mesh pipe through the first section and pack it with an FMF blanket. I think that will really quiet things down. Acoustical foam is going under the seat and lining the airbox after that - when you yank the throttle the intake snarl is louder than the exhaust. A video will be coming when it is finished.

Mounted on bike





Quick fab of a bracket to hold the stock heat shield in place



This winter the whole pipe and can are going to get sent to JetHot to get coated, not a fan of the heat on my right leg.


Going a different route with the next step to make it quiet. I don't want to have to repack anything, so I'm going to go with a mechanical solution in the form of a dB killer for a Husky TE510. After I put a stainless mesh over it, it will function as a spark arrestor as well. Based on the fact that I've played with my programmer and have wound up with the same settings I would say that I have at least as much flow as a Q4 but quieter. We'll see if that still holds once the dB killer is installed, but from what I've read on the husky forums people are reporting very little loss in power.

How does one post a video clip? Do I need to get an account on Vimeo or some such?

yea or youtube is probably easier.

looks great though

DONE!!!

I had videos with the stock exhaust and the FMF Q4 on my camera but my daughter erased them, so all I have is this: