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Old 10-13-2014, 08:16 PM   #1 (permalink)
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My 130 mpg 2-stroke Minarelli bike

This is my 1992 49cc bike...
It has a high rev 2-stroke italian Minarelli engine with 3 speed transmission...
It feels sweet until 30mph... After that the engine starts to scream ... but will go to 45-50mph easily... Done the spark plug and transmission oil change myself... Also made the chain adjust, and carb cleaning...
It makes 125-132 us mpg driving normally, with no care for FE, which surprise me a lot...
Don't even shut down the engine downhill!... And the tires are under inflated...
I think with some steady low speed, more tire pressure, and with Engine Off Coast I can easy achieve more than 160mpg...
Can't try now though, has been raining a lot...
Should say I use a 2% Motul oil moisture with 98 octane petrol...


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Old 10-13-2014, 11:17 PM   #2 (permalink)
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The use of a gearbox vs CVT does make a big difference. A streamline body on a bike like this could well yield 200 mpg highway.
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Old 10-14-2014, 08:30 AM   #3 (permalink)
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this won't go highway fast unless the engine is at high revvs, wich will hurt FE...
but I got shocked with the consuption, specially cause 2-stroke tend to be thirsty...
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Old 10-14-2014, 02:42 PM   #4 (permalink)
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Changing the gearing will help that. A larger gear at the engine and a smaller gear at the rear wheel allows higher road speed at a lower engine rpm. A fairing reduces the need for power to overcome air drag. Three to five horsepower may be all that is needed.

The Genuine Stella scooter with a 4 spd gearbox is rated at 140 mpg.
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Old 10-15-2014, 09:42 AM   #5 (permalink)
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I have thought about that, and there are 2 engines with same block, one with 5, other with 6 speeds... but I'm not sure it's compatible, nobody can confirm me 100% sure.
And have to buy a used transmission that may be damaged...
So for the trans issue I decided to stay put for now...

changing tire size isn't an option either, there are no taller tires at that size...

only option is to change the transmission rack at the back, but it won't make a big difference...
The engine has 6.5 hp, but taller gears will loose torq uphill right?
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Old 10-15-2014, 10:41 AM   #6 (permalink)
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Yes, changing the gear ratio would change torque at the tire. With 6.5 hp. available the question is the peak torque rpm and the shape of the curve. If the engine will turn a maximum 10,000 rpm, the cruise speed at 75% throttle would be 6800-7500 rpm. A full fairing, front and rear, will reduce drag by up to 33% so a 15% reduction in gear size such as 60T to 50T would be a good first step. See the latest pictures of streamlined motorcycles at craigvetter.com and the other threads in this forum.
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Old 10-15-2014, 07:10 PM   #7 (permalink)
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thanks, will check it!
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Old 04-18-2015, 03:56 PM   #8 (permalink)
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Performance-wise, sure a small engine like this one would benefit from a few more gears, but would it really justify the cost on the long run?
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Old 04-18-2015, 05:22 PM   #9 (permalink)
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Well, I bought a new front sprocket for 5 bucks, with 15T instead of the original 14...
Received it yesterday so didn't mount it yet...
couldn't go more. first because a bigger 16T sprocket wouldn't fit (not enough space), second cause I didn't find any...
but I was advice not to go more then 1T since the engine is so small and "torqueless".
Since the wheel sprocket only have 34T, the one T on the front is equal to 3T at the wheel, and will gain about 7-8% more top speed, and 600-700 rpms drop at a specific speed like 35-40mph.
I think 15T will fit nicely and won't feel the lack of torque, because my original 1st and 2nd gear are short as hell.
And unfortunately it won't be possible to change much more regarding to drop the rpm and get high speed. bigger tires won't fit, and the original rear sprocket is already hard to find... with smaller teeth only custom made I supposed...
Will try to change it this week and will "put you to speed" (give my feedback)
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Old 04-18-2015, 06:48 PM   #10 (permalink)
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Nice ride.

I am surprised also at your fuel consumption with a 2 stroke with a fairly high output (3 hp is more the norm I believe).

You wouldn't happen to have the wrong speedometer by any chance ?

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