Project Polini

Discussion in 'Performance Mods' started by Simon_A, Aug 27, 2008.

  1. Simon_A

    Simon_A Member

    Hey all, with the happy completion of my last motored bike, I have decided to kick off "project Polini"

    I have mentioned it a couple of times before, but it has always been on the back burner.

    This will be the motoredbike equivalent of a drag bike.

    I had a stint a few years ago with pocket bikes (CAGs, etc.). Built a air cooled bike as far as you could go, and then stepped up to a watercooled 911 dreambike. In standard guise it was bloody quick. But me being me I couldnt leave it standard.

    So I got from Italy a top end racing package. This was the head, cylinder, piston with rings, gaskets etc. Also got all the suggested upgrades to match, polini race exhaust. 19mm Dell ' Orto Carb (black version, factory set up for racing) , 2 shoe BZM race clutch, Polini carbon fibre reeds, etc..

    Its a watercooled setup as I said as an air cooled motor cant put out the power of this thing without cooking itself.

    To give you an idea, with the 3 port top end and everything stock these things put out 7.2hp. With the setup I have its rated to 13Hp+. On a pocketbike that means a top speed of in excess of 60mph, and brutal acceleration ( you have to lean all the way over the handlebars to take off unless you want to suddenly be on your back with a bike on top of you). Trust me that hurts, mine flipped me once, rather embarassing really.

    So the pocketbikes are long gone, kids, curiosity and those things arent something I wanted to think about, but I kept the polini and its running gear.

    This setup with Haggard's excellent rackmount conversion in my mind I had a excellent but truely scary idea.

    And we all know what that is, but once its finished am I crazy enough to ride it?

    Everything on the setup will be built with thick angle steel. I have a length of 40x40x5mm angleiron. All the bolts for the sprockets will be of M8 high tensile bolts. Motor mount bolts are M10.

    Anyway, I have added some piccies so all can see what I have to play with.

    Laying everything out, the rear rack will have to be about 18 inches long, so its gonna hang out the back a fair bit, but it should be okay.

    I havent a clue as to what speed it is capable of, but its gonna be a lot more than I am comfortable with. But hey, I have the motor, what else would a mad motoredbike mechanic do???????????

    I will keep you lot informed of its progress. Its not gonna be a overnight build, but I will add to this thread as I get to stages of the build.

    Attached Files:

  2. SirJakesus

    SirJakesus Guest

    Wicked nice looking engine. I like how it has the rubberized engine mounts like a car has to absorb vibrations. It may look a little funny rackmounted with that tuned pipe sticking way out the back of your bike but you'll probably figure something out. My 2.2hp stock mitsu has a nice amount of power behind it I couldn't imagine 13hp! It'll be a great ride if the bicycle doesn't eat itself. Keep us informed I'd love to see this thing in action.
  3. Simon_A

    Simon_A Member

    Well figured out today where everything will go. If it was a air cooled bike it would be a lot easier.

    Got the sprockets figured out with their order and got it ready for the M8 hi tensile bolts.

    I have the radiator rear mounted, I figured if it was front mounted it wouldnt get great air flow as it would be right behind my back. I also will mount it low as that will allow greater air flow through it.

    Also I rear mounted the sprockets as I want the chains the furthest away from my body just in case. These things rev to 12,000 rpm ( 15,000 if I change the crankshaft ;) ), so I can live without the concern. I will fit guards where I can but its better to be safe than sorry.

    It took me a good hour to mock up the arangement, but the attached picture shows the layout.

    Long rack, but theres more than just a engine to mount and the exhaust is fairly long as well, so it will work.

    Attached Files:

  4. SirJakesus

    SirJakesus Guest

    Are you going to do any further gear reduction to accommodate for the fact that a bicycle wheel is much larger than a pocket bike wheel?
  5. Simon_A

    Simon_A Member

    Im gonna "suck it and see". See if it has a usable torque curve in the usable speed range, the output sprocket is a BMX front sprocket, so it can be changed, I will also run the chain down to the HT spoke setup, which can also be changed.

    If the torque curve is usable, I will leave it as is, I mean we drive normally at less than half the top speed when we drive a car, so I can have the same luxury, hopefully.
  6. SirJakesus

    SirJakesus Guest

    /me pictures simon tucked into his handlebars with the engine screaming as he keeps up with cars on the state highways :)
  7. isoxazole

    isoxazole Member

    Hows the ride?

    My Polini clole will kick itself out of a vice at high throttle.
    Is your bicycle rack sufficent to handle the forces .
    I intend to use the mounting brackets and angle iron welded to the swing arm.
  8. fastboy9

    fastboy9 Member

    this project looks pretty exciting! a watercooled polini engine sounds amazing, u shud giv kawasaki999 a race, his top speed is 55! i wouldnt be surprised if with the right gearing you will get that.

  9. isoxazole

    isoxazole Member

    Hey Simon, your layout picture helps me.

    We have almost the same hardware. I just got started though.
    I really can't wait to see yours and mine passing traffic!
    I am not using a staton or anything, just a chain to the rear wheel using a hardly pedaling sproket that is designed for this purpose.It is about 8-10 inches across.There will be a tension pully on the chain. donno how many teeth that is. That size should accomidate for the higher revs from the engine and give more torque.
    The engine will be mounted to a custom angle iron frame.
    I want to see how you mount the water pump.
    I have a raleigh bike computer already on the bike.
    I can post results in km/h
    Should be built in next month or so.
  10. Simon_A

    Simon_A Member

    All metalwork will be/is 40mm x 40mm x 5mm steel. I hope its sufficient, if not then there is something seriously wrong.

    Also I am gonna change the clutch to one that engauges a lot lower that normal, so the clutch cant kick too hard. Will mean clutch wear is something to be concerned about, but saves the bike becoming airborn at 8000rpm when the clutch engauges. The clutch can engauge and then it can hit the powerband, unlink both things happening at once.

    Dude, you do realise these things rev to 12,000 rpm + dont you. Direct drive would make me a lot nervious. It will need to be well geared down.

    But yeah it will be able to pass traffic. Dont think I will rev it out more than once, bikes arent meant to be able to do that. But I know I will do a top speed run, once.
  11. isoxazole

    isoxazole Member

    I called a local pocket bike store to see if they had a gearbox for Polini.
    They do. Still wondering how or where to where to mount the liquid pump but that should be obvious when I go to get parts.

    Attached Files:

  12. isoxazole

    isoxazole Member

    Yes I am using a gerbox now. donno the ratio. stock from polini
    I like your idea of using a different clutch.
  13. Simon_A

    Simon_A Member

    Dude, the image is of a stock clutch bell housing. That bit on the end is just the sprocket cover. Its not a reduction gearbox. Just housing, cluthc bell, sprocket, cover and 2 bolts.

    Thats it.
  14. isoxazole

    isoxazole Member

    OIC TY
    didn't know exactly
  15. wavygravy

    wavygravy Guest

    i hope the cars you pass with the polini are only doin 25, remember unlawful operation reflects on mb.c as a whole! its all in the wrist , & do use good common sence when ya decide to really open it up! a time & a place for everything!!
  16. isoxazole

    isoxazole Member

    Yes, I will be a proper ambassador so that noone is treated unfairly because I decided to trench someone's property. I'm moving into the country where I'll have a lot of space.
    Think I'll put lead in the forks to help keep them down. I'm riding the bicycle now to get used to the different turnning radius before putting the motor on.
  17. isoxazole

    isoxazole Member

    Just wondering how your bild has been going. I see you don't really have the time - which most people don't. My project seen a bike change to a chopper from the rack mont on a mountain bike idea. Good one too cause this centers the gravity and the bike is very stable and don't want to wellie. Someone else built it with me, but I get to fix all the problems.
    I don't mind. I get the looks for it.
    Need to adjust the clutch to engage sooner. I am getting advice from the local pocket bike store and they are very helpful.
    My build took about a day and a half then about a week to discover problems. As soon as I get brakes, a helmet and spedometor I'll take it out and see what it can do.
    Does figure 8's in the parking lot fine. Just have to roll to a stop. Don't flintstone it at 40... it will almost take your foot off.
  18. jg767

    jg767 Member

    I'm thinking of getting a 6.2 hp air cooled polini, just need to know if it will match uo to a staton gear box. Does it have a 76mm clutch?
    I'm also hoping that it's quieter than the gp460, which everyone says is very loud, I'm trying to keep the sound at a manageable level.
  19. datsun610

    datsun610 Member

    Hi mate im bulding a bmx with a 18 hp blata water cool motor have u finishd urs yet any more pics or vids how dose it go
  20. robin bird

    robin bird Member

    Morini has a 16 hp --50cc engine with 6 gears ! would that ever be wild on a bike ! The only problem the engine alone is about 1200 dollars shipped then theres the radiator !
    The other problem is i dont have the courage to ride it ! but id love to watch someone !