Buying a bike for MPG/Vetter Challenge, what would be your favorite?

[user removed]

I don't think the 2008 Eliminator (US version) is 250 CC. Not sure about the earlier models as they were available up to 1000 cc if memory still serves me correctly.

The 2011 CBR250R is steel frame and swing arm. I just checked them with a magnet.
The rear suspension monoshock is located just behind the engine and the whole rear of the frame could be removed and modified fairly easy. While it may not be significant also consider that the CBR produces about 10-20% of the emissions of the Kawa.

The fixed headlight (doesn't move with the front forks) helps with streamlining. Ninja is probably the same.

Another factor is the cooling fan for the radiator. If you reduce airflow too much the the fan will come one (temp controlled), something that you could monitor to optimise your aerodynamics.

The CBR is optimised for torque, while the Ninja has greater power and engine speeds over 8500 RPM that is not really ideal for mileage. Also the larger single cylinder looses less heat to the cylinder head and walls.

Mine has just hit 3000 miles and the difference now compared to brand new is significant. Also much longer service intervals, like 6 k oil changes.

Disadvantages of the CBR is the speedo reads off the rear wheel, so sprocket changes can not easily be re calibrated in the speedometer and odometer.

The Kawa as well as all motorcycles will soon have to pass emission control standards that will require fuel injection almost certainly. The carbs are old tech and not very green
if that is important to you. Since you are already going to toss the fairings, you might find a naked CBR cheap without frame damage. I'll be looking for one in my area for the same purpose.

regards
Mech

[user removed]

http://www.salvagetitlecars.info/aut...s/HONDA/CBR250

here are a few.
regards
Mech

[jkv357]

Originally Posted by FXSTi

Good catch. Those didn't show up on allofcraigslist.com. I must not have used the right search term. Does anyone know if the 2008 was revamped at the same time as the Ninja?

Kirk

Good question - they don't look the same from those photos. I'm familiar with the older style, but not the '08 version.

Prices are right for a project!


Jay

[BHarvey]

Originally Posted by jkv357

That is a pretty decent list IMO.

The Ninja 250 is the clear winner when price is a factor. The engine has proven to be pretty efficient, even though it makes its peak power and torque WAY up there.

As far as the Ninja mods BHarvey suggested - I have to disagree. I don't think you'd want to go that direction from a mileage perspective. From what I have heard about flat-slide carbs, they don't like small throttle opening. I would think you'd want to drop down in carb size to increase the velocity at smaller opening while sacrificing some (unneeded) top-end power. Pod filters would kill any positive intake pulses (and your throttle response and mid-range power). Ducting in warm air to the airbox would be better IMO. You want small exhaust pipe dia and some amount of backpressure, so I wouldn't mod the exhaust system.



Jay

When tuned, small throttle openings are good. FCR's atomize fuel very well allowing a little leaner AFR than other carbs, without running hot.
The small pod filters give the carb the 'impression' that it is smaller and a smaller filter 'requires' smaller jets. Pod filters have a weaker pulse at low rpm, but midrange is not affected. Back pressure is a myth. With a proper exhaust, you have just as much low end as with a smaller diameter exhaust, but better flow and more power everywhere else.

Here's the difference-
Open velocity stack on carb- 165 main
Big air filter attached to carb (no airbox)- 148 main
Very small pod filter- 135 main

The horsepower loss is 7 from largest to smallest main setup.
Peak torque is the same for all three, but happens earlier with smaller main setups.

[jkv357]

Originally Posted by BHarvey

When tuned, small throttle openings are good. FCR's atomize fuel very well allowing a little leaner AFR than other carbs, without running hot.
The small pod filters give the carb the 'impression' that it is smaller and a smaller filter 'requires' smaller jets. Pod filters have a weaker pulse at low rpm, but midrange is not affected. Back pressure is a myth. With a proper exhaust, you have just as much low end as with a smaller diameter exhaust, but better flow and more power everywhere else.

Here's the difference-
Open velocity stack on carb- 165 main
Big air filter attached to carb (no airbox)- 148 main
Very small pod filter- 135 main

The horsepower loss is 7 from largest to smallest main setup.
Peak torque is the same for all three, but happens earlier with smaller main setups.

Interesting. Was this done on a Ninja 250 engine? Are you sure the "very small pod filter" wasn't just restricting air flow? What was the main jet with the stock air box, and how did you determine you had the correct jet size for the modded filters - especially if it lost 7 HP?

How is backpressure a myth? Have you ever altered a muffler and noticed a negative change in throttle response? Gaining top-end power but losing mid-range? As you increase the header dia you will lose velocity but gain max flow. That's fine if you want peak power, but it's not going to help cruising MPG. Why do most engines run better with a muffler than just a straight pipe?

Your turn...

[alvaro84]

Originally Posted by Old Mechanic

Disadvantages of the CBR is the speedo reads off the rear wheel, so sprocket changes can not easily be re calibrated in the speedometer and odometer.

If it really reads the wheel itself, why do sprocket changes count at all? If you don't change tire size, wheel rotations over the same distance shouldn't change.

[user removed]

The pickup for the speedo is in the tranny output shaft. Most bikes read off the front wheel and sprocket changes do not change the speedo reading. The CBR speedo "reads off the rear wheel" but not directly off the wheel itself. The output shaft of the trany which drives the front sprocket depends on the rear wheel for information realtive to vehicle motion.

Guess I oculd have been more specific in my description. It works a lot like the speedo in cars. Speedo reading is digital.

regards
Mech

[BHarvey]

Originally Posted by jkv357

Interesting. Was this done on a Ninja 250 engine? Are you sure the "very small pod filter" wasn't just restricting air flow? What was the main jet with the stock air box, and how did you determine you had the correct jet size for the modded filters [COLOR="Red"[/COLOR] - especially if it lost 7 HP?

How is backpressure a myth? Have you ever altered a muffler and noticed a negative change in throttle response? Gaining top-end power but losing mid-range? As you increase the header dia you will lose velocity but gain max flow. That's fine if you want peak power, but it's not going to help cruising MPG. Why do most engines run better with a muffler than just a straight pipe?

Your turn...

All jetting was on Dynojet dyno with exhaust sniffer.

Stock airbox main was 155.

Small filters DO restrict flow due to pressure change.

Going larger on exhaust only affects response badly if you are already on the large side, and going larger. If you are on the small side to start, you will not loose throttle response even at low revs.

Most people don't want to spend the money on dyno tuning, which is why alot of bikes DO run better with a muffler. It IS all in the jetting to get the best performance out of the mods you make.

Lots of motorcycle intake ports are very large, too large and you can gain big response in reducing the size of the ports, but big carbs, cams and open exhaust make this MORE of a problem, ESP on the bottom end performance.

Combine this with the fact that most motorcycles have poor ignition setups, that are computer controlled, and need to be advanced a good deal to bring bottom end performance to where it should be.

Example, my bike from idle to 3k rpm's fires at 5 degrees before TDC.
Above 3k , it is 31 degrees before TDC.

Now, with E-ZERO and proper jetting, the bottom end response is much better, AND it makes more power up top.

With E10 and proper jetting, below 3k is only usable in the first 3 gears, but only at light throttle in 3rd. Makes less power up top as well.

Now, if I could advance the timing the E10 should work as well as the E0 in power and response.

[euromodder]

Honda CBR125i or CBF125i (both chain driven) or maybe even a Honda Innova, using the same engine with an automatic scooter drive.

The 125i should be powerful enough to propel a streamliner beyond 70 mph - the stock chain drive versions will top out around 70 mph.

[low&slow]

I found a Ninja 250 on CL this afternoon that was for sale at Fremont Cycle Salvage for a good price and decided to go immediately to check it out. Its a 1999 Ninja 250 that had some cosmetic damage with 23K miles on it but seemed to run strong with a straight frame and forks. I negotiated a price and settled on $799. They had already received 5 calls about it but I was the first person to show up. While I was there another prospective buyer came in looking for the Ninja 250 I had just left a deposit on. whew!!! I will pick it up the bike tomorrow.
I was starting to get a little disappointed that I had missed out on 2 other bikes this past week but I'm glad I stuck to my plans and was able to get this bike well under budget. Attached is a picture of it. I can hardly wait to start working on it.
all the best, Vic