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Old February 17th, 2011, 01:42 PM   #41
afbarr
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Quote:
Originally Posted by VeX View Post
So yeah, as for the double edged sword: What are you trying to do? Racer X needs maximum horsepower (so high RPM) and hence would need a large diameter or short intake runner. If you want a little more "umpff" getting out of the hole for stop-light to stop-light riding, you might extend your runners.
At the moment I am more interested in a street bike with good low and midrange torque. So I guess I sabotaged myself by removing the airbox. It sounds like I should add back the runners (or fab longer ones). But I'm going to run them without them for awhile to be able to compare later on when I add them back (plus I'm tired of my bike being in pieces and last night I finally put the carburetors back in. I need to adjust the throttle cables and put the gas tank back on before the weekend as I hope to be installing steel braided galfer brake lines if they arrive!). Then next week I should be ready to test the jetting assuming the weather is fine.

Before I put the carbs back in, I did replace put in a dynojet needle and a Keihin 108 main jet (I have Keihin sizes 105-115 to work with). I also replaced all 8 screws on the float bowls and all 8 screws on the vacuum covers with hex-head screws. And I have the offset screw driver adapter and the 3mm hex bit so I am set to "easily" change jets and needle height going forward. I'll also be installing carb sync tubes and already have the Carbmate vacuum tester. So I'm ready

So how do you know all this stuff? All this stuff is fascinating to me and I want to learn more about it.
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Old February 17th, 2011, 02:45 PM   #42
Racer x
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Quote:
Originally Posted by afbarr View Post
nitrous? that's sounds fiendishly evil what sort of setup do you have for this? for how long can you run with nitrous boost? how much engine wear does it cause? why nitrous though? seems impractical for street and illegal for racing. but maybe not for drag racing?

What 32mm CR are you using? How does it compare to the Sudco "special" CR's? If I recall they come in odd mm sizes such as 31, 33, etc. They recommend their 31mm for the ninja 250.
Sorry I meant 31mm cr from sudco.
I use Boss Noss for Land speed racing. 121.8 so far.I spray for 1/2 or so .mostly OK clutch won't hold. Check my blog for 2011 details.
Sorry for the thread jacking.
I have some longer manifolds fabed up . I will post up photos soon
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Old February 17th, 2011, 08:49 PM   #43
afbarr
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yoshi full exhaust vs two brothers slip-on

Quote:
Originally Posted by Racer x View Post
Sorry I meant 31mm cr from sudco.
I use Boss Noss for Land speed racing. 121.8 so far.I spray for 1/2 or so .mostly OK clutch won't hold. Check my blog for 2011 details.
Sorry for the thread jacking.
I have some longer manifolds fabed up . I will post up photos soon
That's cool that you have figured a lot of these things out. In some ways its surprising that all the mods you put in is "only" giving you 33hp at best. But I guess that's a pretty healthy boost in terms of percentage over stock.

Is the Yoshi full exhaust much better than a slip-on Two Brothers M2 exhaust? That's what my bike came with when I bought it of the original owner. It was too loud! So I put a Two Brothers P1X powertip on it so it's probably even less impressive.
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Old January 11th, 2019, 12:31 PM   #44
Mohawk
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I appreciate this is an old thread but I noticed something missing from the details here. Adjusting the runner length can move the peak torque higher or lower in the rpm range but has very little effect on the area under the curve & itís a trade off lower rpm torque traded for higher rpm hp or vice versa.

The total runner length is measured form the entrance to the runner which includes the velocity stack, carb or throttle body, the isolator & the head port to the back of the intake valve. Easily measured with a flexible steel rod with the throttle held open.

Pods usually destroy the air feed to the intake. All I takes should begin with a velocity stack this can be just a rolled lip to the carb or TB intake, it should a minimum radius of 6mm (1/4Ē) to ensure smooth flow in to the intake. Any pods should be mounted forward of this lip & be significantly wider, to ensure clean air flow.

Tapered velocity stacks produce a wide pulse response in rpm terms, straight ones produce the highest pulse tuning effect, but itís only at a very specific rpm, and produces less effect than a tapered one outside that sweet spot rpm.

As always YMMV
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Old January 11th, 2019, 04:27 PM   #45
Mohawk
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You can always try this calculator
http://www.timeinthegarage.com/exhaust-calculator/

For the ZZR the numbers are Exhaust 66BBDC 26ATDC @14000rpm for a 125cc cylinder

For the Ninja 250R - 61BBDC 31ATDC @12000rpm for a 125cc cylinder
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