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Thread: Push most power out of 50cc barrel

  1. #16
    apriliaforum Member Satanic's Avatar
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    Quote Originally Posted by ToraTora View Post
    If you aren't matching the top end to the bottom end, how can you expect proper results? In Malossi's case have you weighed the pistons? I haven't used their cranks, or cylinders so I couldn't say if the crank is designed for all of their kits, or not. You could try asking one of their techs.
    I don't have digital weighing scales.

    Engine mounts didn't fracture with the Airsal 80.

    Fractured within less than 300 miles using the MHR 80.

    Malossi's crank is more expensive than their cylinder kit.

    Airsal's pistons are probably lighter (speculation). Exhaust manifold on Airsal's aluminium kits is pathetic. Needs dremeling for correct fitment, unlike their iron range.

  2. #17
    apriliaforum expert ToraTora's Avatar
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    Quote Originally Posted by Satanic View Post
    I don't have digital weighing scales.

    Engine mounts didn't fracture with the Airsal 80.

    Fractured within less than 300 miles using the MHR 80.

    Malossi's crank is more expensive than their cylinder kit.

    Airsal's pistons are probably lighter (speculation). Exhaust manifold on Airsal's aluminium kits is pathetic. Needs dremeling for correct fitment, unlike their iron range.
    How do you know that the time with the Airsal didn't weaken the mounts to the point that within another 300 miles they would fail? It's not something that you would necessarily see with the necked eye. Also, maybe the MHR was designed for the engines with the balancer. Again, I'm not very familiar with the Malossi product line. When I've looked at them at Treats they seemed nicely made.

    The thing here is that if your engine is vibrating a lot there's probably something that should be checked out, because they shouldn't vibrate as much as you are suggesting.

  3. #18
    apriliaforum Member Satanic's Avatar
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    Quote Originally Posted by ToraTora View Post
    How do you know that the time with the Airsal didn't weaken the mounts to the point that within another 300 miles they would fail? It's not something that you would necessarily see with the necked eye. Also, maybe the MHR was designed for the engines with the balancer.

    The thing here is that if your engine is vibrating a lot there's probably something that should be checked out, because they shouldn't vibrate as much as you are suggesting.
    Malossi's brochure lists their 80 kit for the RX / SX.

    Click image for larger version. 

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    Valenti sell Athena 80 kits for RME 50's http://store.valentiracing.it/index....y&path=182_186

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    Look at the reinforced bottom frame rail mount..

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    Thick chunk of sturdy metal (^)

  4. #19
    apriliaforum newb Kimmo kekki's Avatar
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    Malossi and Athena are quality products !
    These Airsal and all other cheap brand stuff are usually made of cast iron, and those are soft like cheese ...


    sent with OnePlus 5T

  5. #20
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    Is jasil racing evolution crank any good?

  6. #21
    apriliaforum expert emX50's Avatar
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    Quote Originally Posted by Gvidas View Post
    Is jasil racing evolution crank any good?
    You are probably approaching this project from the wrong angle.
    The very first response by Rj got the perspective correct.

    That said, define 'power'. Do you ride between stop signs, and want acceleration, or do you ride freeways and need top speed ?
    These two ends of the spectrum may be better balanced by changing gearing.

    Remember that it is a SYSTEM, with all parts working together.

    So... standing on shoulders etc... and never one to use just a sentence when ten will do

    You need to think about your riding style.
    This is everything.

    So you want performance and fuel economy?

    That sounds like a noob statement, but the two can go hand in hand - so it's fine (within reason).
    By increasing the fuel burn efficiency, you will get more power per litre of fuel.
    ... only that, if you are taking advantage of that extra power (which you will), you will likely burn more fuel.

    Again, referring to Rj's advice... where do you need the economy?
    Is it around town?

    Then you'll need the stock pipe, to gain a broad power band.
    You can then keep the carb lean for town conditions.

    A larger atomiser diameter, a small idle jet, and push the taper further into the throttle range.
    If you are using a PHBN 17.5 you could go with an A7 on notch 4 or even 5 (with testing) - GA212 atomiser for 50cc will likely be fine.

    If PHBG I know both Xero and spudgun had/have their tapers hitting very late... around 40% throttle.

    The engine simply sucks what it needs through the atomiser... which has proved ideal for many people.
    So you gain a Jekyll & Hyde bike, that can function fine in stop start conditions, and yet when you hit the taper... boom... you fly.

    But with a stock pipe (de-restricted) there is no point in fitting a high compression crank.
    Such a crank is only valid, when the engine lives at very high RPM.
    The higher crankcase pressure increases the speed of the gas transfer to cope with the mind blowing requirements of an engine that lives in the 10k - 13k region.

    If you fit a high pressure crank into an engine that lives in the 6k to 10k region.... the additional pressure will simply push fuel down the pipe.
    If memory serves me right (I can't be arsed to confirm so don't quote me)... at 10k and 20mm bore, the airspeed is 24m/s so at 13k it is 32m/s
    You can see why additional pressure might be useful, to get all the gas in place, in time.

    So forget fuel economy

    My advice would be to take the project in stages.
    De-restrict everything, and fit a 17,5 carb, and a twin air filter (or similar) to help breathing.
    Then (repeating Rj again)... concentrate on the air path through the read valves.

    When you've got it running nice, and your money saved... or at least spent wisely
    ... you can move ahead from an informed position.
    You'll better know what you want to achieve.

    74cc would be the next typical step.
    74cc seems to provide the extra grunt and acceleration that makes the bike like a full blown motorbike.
    At least, that's what I have found.

    Good luck!

  7. #22
    apriliaforum Member Satanic's Avatar
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    Quote Originally Posted by emX50 View Post
    keep the carb lean for town conditions.

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