Shorty exhaust/Exhaust options?

[GregEvans]

Hey there...

So, looking for some new exhaust to put on the Ninjette that I am building into a race bike (Build thread HERE).

So what I am thinking about is a couple things...I'd like to know if anyone has done this already (Pretty sure someone has), and what needs to be done if I go with either of these options...

1. Keep stock pipes and add 2 shortys like these
2. Find/Create a 2:1 and use a single shorty (see above link to shorty)

I am assuming, if I do either I will need to do some jetting? Anything else?

[Alex]

Free bump for more views.

[spooph]

Greg,

if you have the ability to bend/weld pipe, you can do whatever you want.

The link you posted looks like just a fancy tip, with no muffling properties what-so-ever. If you were to put something like this on your bike, you might have to rejet the main jet, or not as the muffler only affects the upper 1/3 of RPM range, and the pre-gens weren't jetted as lean as the new-gens...

The only other thing to think about is if the track you will be running this bike at has a noise restriction, and if you'd be above that... That tip you posted, being bent like that, will amplify the sound and actually make it louder...

Ask @racerX about his megaphone exhausts.. His 250 sounds like a Vietnam Era bomber readying for take off... Also, look up the old RC166 Honda GP bikes of the 60's - never would you think a 250 can make that much noise!

Years ago I saw somebody use a 2-stroke mufflers to make some pretty cool looking/light exhausts...

[adouglas]

Something to consider:

Around here some tracks are starting to implement noise restrictions. Stock exhausts are fine as well as a lot of aftermarket, but soon the owners of really loud bikes won't be allowed to run.

As we all know, noise and displacement are not related. Your twoofiddy could easily be as loud or louder than a literbike.

Best check with your race or track day organization to get the scoop before you drop money on a loud pipe.

Edit: Oops. Spooph already said it. Serves me right for not reading the thread. Point still stands.

[Racer x]

My 250 without the convergence cones on the megaphone exhaust is painful. The 250 ninja is stupid loud. At idle and throttle blipping under 5000 rpm it can go above the 120db of my sound meter. At 12000 rpm it could be heard six miles away.

This is a video from the old Monster mile in Maxton North Carolina.

I am filming standing at the starting line. Directly under the loud speaker.

The finish line is a mile away. You can hear the bike hitting bumps at 3/4'mile. People said they could hear the bike the next town over in Lumberton.

The volunteers said it was painful when it went past the shutdown. The tower had to wait till I turned around before they could announce the speed.

http://youtu.be/1R8pQRHTm6w

[rwp]

Wow! That's an impressive bike, Racer X.

I was wondering if anyone as tried the mufflers that are marketed by Blue Collar Bobbers

http://bluecollarbobbers.com/product...t#.VjlGUPmrSUk

I know there's no power increase, but I'm curious about weight compared to stock and noise level. If lighter, then might be worth trying.

[GregEvans]

So the company selling those York Shortys tell me that it's about 90dB with the shortys on...They have cones that increase the backpressure and said that makes it about 81dB...

I'm thinking that's worth it...

Here's what the Rulebook of the Race Organization says:

All motorcycles must have a muffler and must not exceed the
maximum allowable sound limit of 115 dbA.

2. Sound limit of 115 dbA will be determined at 20 inches from, 45
degrees behind, and at the same height as the rear most exhaust
outlet at 1/2 the manufacturer's recommended maximum engine
speed (redline). If no redline is published for the particular
motorcycle, then an engine speed equal to 60% of the engine
speed at which maximum horsepower is developed shall be
used. If neither redline nor maximum horsepower engine speed
is available, then test speed N shall be calculated from the
following formula:
N = 306,000 (Stroke in MM)
(or)
N = 12,000 (Stroke in inches)

3. At all WMRRA events, motorcycles shall not exceed 105
dbA at 50 feet. This measurement will be taken while the
machine is moving on the racing surface. Violators are subject to
being black-flagged from their event.

[Racer x]

The blue collar bobber baffeled exhaust is quiet light probubly OK . 115 do is just below the pain threshold. So it should work.

[adouglas]

Wow. I burned half an hour this morning on the blue collar bobber website. Made me want to go out and pick up a pregen to convert. Nice kit, and the result looks terrific.

[spooph]

If you want a cheap slip-on, I don't think it gets any cheaper than DanMoto - I have their JISU, and really like it!

[Racer x]

I was just about to buy one. But I sold the bike I was going to use. Great people to work with. Very high quality kit.

[VaFish]

Originally Posted by Racer x

I was just about to buy one. But I sold the bike I was going to use. Great people to work with. Very high quality kit.

I'm still thinking about the kit, just not sure I want to spend the money right now, so I'm going cheaper café route with the thought I still may upgrade later.

[Racer x]

I was going that way and then I looked at the video and added up then parts from eBay to make the headlight. Plus a fiberglass seat and tail piece. It saves a ton of work. Otherwise It all has to be custom or maybe just build a different bike.

I was lookin at air tech fairings. There are some cool boxy old Kawasaki two stroke race bikes. I thought of building a replica like my Harly Davison 250rr.

[VaFish]

Originally Posted by adouglas

Wow. I burned half an hour this morning on the blue collar bobber website. Made me want to go out and pick up a pregen to convert. Nice kit, and the result looks terrific.

I have a 10% off discount code if you want to order one.

[FilipinoAviator]

I was thinking of buying a pair of these-

http://www.ebay.com/itm/191482721575...%3AMEBIDX%3AIT

I think with the cone cover off, cutting the stock pipes at the section that is about 2" diameter will make those pretty close to being able to modificate and work.

But, my KDX200 project is eating all available bike funding, so the Ninjette will have to wait.