Low & Slow's Ninja 250 project

[low&slow]

Thanks !!! I added additional brackets to the lower edge of the front biulkhead and it appears to be very secure and should prevent the tail from tipping downward. Its raining now so I'll have to test it after it stops raining.
I still have to close up the bottom of the tail . I plan to use some sheet metal around the exhaust but so far the coroplast panels are doing well, no melting or scorching. I also need to get a shorter chain so that I can go with a smaller rear sprocket.
I started working part time and my new job will involve a lot of travel so I need to make as much progress as I can before the The Quail Gathering/Vetter Challenge in May.

[low&slow]

I took the Ninja for a good hard ride on Saturday on the local backroads to test the new tail and to test the accuracy of my odometer/tripmeter. The new tail worked great and seems to be very sturdy. My destination was a local motorcycle hangout ( the Livermore Junction ); the brothers and sisters there seemed to like the streamliner. I had some fun and found that my odometer under-reported distance traveled by 9.2 %.

Yesterday, I decided to go ahead and change to the smallest rear sprocket I had: GreenJoe's 33 tooth. I also lubed my swingarm and shock linkage, shimmed the cush drive and shortened my chain by 4 links. I rode the bike to Fremont on some errands and found that the taller gearing was manageable. It starts from a dead stop OK , accelerates at an acceptable pace and brings the rpms way down while cruising. Hills and headwinds now need quick downshifts to maintain speed and often need dropping down 2 gears at a time. We'll see how it goes.
I fueled up on the way home and got ..... 90 mpg !!!
I'm pleased with this and hope to keep the upward trend continuing.

[redyaris]

It looks like you have found a limit with respect to aero gearing interaction, hopefully the 90mpg is a repeatable number. the 15/33 gearing is a very good setup if you can improve the aerodynamics.

[low&slow]

I agree, I think I'm maxed out on gearing for now. The last tankfill only had about 50 miles of 236 traveled with the new 15/33 combo so I'm optimistic that I'll be able to repeat or surpass 90 mpg on my next tank. The Vetter style tail works very well , even in windy conditions. I'm going to clean and adjust my carbs next. They seem to be slightly on the lean side so I won't try to change jets. I have to get some new sparkplugs as I have no clue how old the current ones are.

[jkv357]

Are you running a non-O-ring chain?

If not, it might be worth a try to reduce losses.


Jay

[low&slow]

Hi Jay, Yes, regular old tech roller chain. Are o-ring chains supposed to be more efficient ? I'll check it out, thanks.

[jkv357]

Originally Posted by low&slow

Hi Jay, Yes, regular old tech roller chain. Are o-ring chains supposed to be more efficient ? I'll check it out, thanks.

A regular old non-O-ring is more efficient because it doesn't have the seals creating friction.

An O-ring chain will live longer because it's sealed - keeping grease in and dirt out.

If you keep a standard one adjusted and lubed and it will be fine, plus reduce rolling resistance from friction. I would think you would want to run the tension on the loose side, but still reasonable.


Jay

[sendler]

Originally Posted by jkv357

Are you running a non-O-ring chain?

If not, it might be worth a try to reduce losses.


Jay

How many miles does a non O ring chain last in the rain?

[beatr911]

Great numbers!
A couple of questions to get some perspective though:

1) What would you say are your average speeds for the 90mpg tank?

2) What is the engine speed at say 70 mph?

3) What is the hp produced at say 70 mph?

4) How did you verify the accuracy of your odometer?


90 mpg at normal California freeway speeds on California gasoline would be darn good. This homegrown recipe is putting another wrinkle in to the equation of how much time and effort to spend on an aerodynamic shell.

In your tune up, consider iridium plugs and opening up the gap .005" from stock to expose more mixture to the spark. Not dyno proven to me anyway, it seemed to help the lean mixture power on my bike.

[jkv357]

Originally Posted by sendler

How many miles does a non O ring chain last in the rain?

"How many licks does it take to get to the center of a Tootsie pop? - one...two...three... - three".

Couldn't resist. I know you're old enough to know that one.

Definitely not as many as an O-ring chain I'm sure, but if you had it well-lubed I would think it would do OK. Obviously a regular chain wouldn't keep the elements out as well as an O-ring chain, but overall it's not being worked very hard.


Jay