Honda Spree and Elite 50 Forums

I've acquired a low mileage 1998 SR 50. I am thinking about building a 120cc methanol drag motor. What kind of power and what kind of brief eight second blasts is the stock crank or replacement stroker cranks good for. Is an extra hearty stroker crank available at any kind of reasonable price. I'm liking a 12,000 rpm power delivery point. Is 40 bhp possible from the Dio reliably for 660 or 1000' drags?

First off there is no way on God's green earth you will ever get 120 cc using the stock crank so your question is moot.

Greetings:

Hmmm, 120cc/1 Liter 40HP makes for roughly 333 HP/liter, air-cooled engine. Maybe, but I suspect not for long. The Crank diameters are designed to be reliable for 5-15 horsepower. Even at that output, even Honda's cranks can break over time. The aftermarket cranks typically are less durable.

Wheelman-111 wrote:Greetings:

Hmmm, 120cc/1 Liter 40HP makes for roughly 333 HP/liter, air-cooled engine. Maybe, but I suspect not for long. The Crank diameters are designed to be reliable for 5-15 horsepower. Even at that output, even Honda's cranks can break over time. The aftermarket cranks typically are less durable.

for a 120cc its more like 20+hp. the corsa kit you have is rated at 11.2hp

Greetings:

Baka-san, is not the 11.2 HP rating estimated by Polini using Honda's carb and pipe? Don't things improve a little with all the OKO and PG goodies added on? I ax this because I'm having difficulty believing that 11.2 HP driven through a slippy-belt tranny is capable of 70+ MPH. Perhaps someone has strapped a built Corsa to a Dyno-Jet for a look-see?

Well, thanks for the responses. Here's the next question. My Piaggio 2t has cranks available that are good for 16,000+ rpm (for a bit anyway). Can such true race cranks such as these be purchased for the Dio?

nope.... ur looking at 12500 being MAX and i don't think that's even under load....only "race" cranks around are stokers and stock stroke.....

stepthrutuner wrote:Well, thanks for the responses. Here's the next question. My Piaggio 2t has cranks available that are good for 16,000+ rpm (for a bit anyway). Can such true race cranks such as these be purchased for the Dio?

For a stock stroke crank. I sell and stock a full circle Malossi crank that is rated up to 16000 rpms. Very nice crank. Though it will take some extensive porting of the cases and the cylinder as well as a high end pipe to turn 12000+ Keith

That's not really a bad price for a Malossi race crank. Is that the stock stroke or are longer stroke cranks from Malossi available?

Can a dio even breathe at revs anywhere near that high? Hard for me to believe it can pull enough air through those tiny intake windows to justify the revs, but i'm not a LEET TUNER .

it can't but the malossi crank supports anyways, its overbuilt, never a bad idea on a 2t crank though...

fastplastic wrote:it can't but the malossi crank supports anyways, its overbuilt, never a bad idea on a 2t crank though...

yes it can. dio motors if done right can rev to 15k. custom exhaust will be needed to match the porting on the engine and case.

Wheelman-111 wrote:Greetings:

Baka-san, is not the 11.2 HP rating estimated by Polini using Honda's carb and pipe? Don't things improve a little with all the OKO and PG goodies added on? I ax this because I'm having difficulty believing that 11.2 HP driven through a slippy-belt tranny is capable of 70+ MPH. Perhaps someone has strapped a built Corsa to a Dyno-Jet for a look-see?

no, its with their intake and exhaust setup. same for malossi.

bakaracer wrote:

fastplastic wrote:it can't but the malossi crank supports anyways, its overbuilt, never a bad idea on a 2t crank though...

yes it can. dio motors if done right can rev to 15k. custom exhaust will be needed to match the porting on the engine and case.

Cool. I have an experienced pipe maker on tap that can build to my timings, etc. With the side feed DIO I'm thinking on a shorty custom intake feeding a straight shot at a right angle to the motor for best high speed effects. Right now every thing is on the table. May even consider a pulse carb. for easy day-to-day tuning.

Im build one a af18 with malossi crank and corsa. 28mm pwk. pg long. and 8.4 gear. for my project honda sky.

strap it on the real dyno test.