Polini 4.2 air cooled parts? - Pocket Bike Forum - Mini Bikes
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post #1 of 22 (permalink) Old 11-23-2018 Thread Starter
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Polini 4.2 air cooled parts?

Hello,
I’ve owned a pocket bike (not sure what brand) with an air cooled Polini motor for about 15 yrs. I also have a 8 year old boy who decided to wash this bike and apparently got water in the engine. He washed it and put it away without starting it and it sat for about 2 months. The next time he tried to start it, it wouldn’t even pull over. I disassembled it and the lower rod bearing is stuck and there’s still droplets of water in the engine. I’d really like to be able to fix this. Is there parts available somewhere for these?
Thanks!
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post #2 of 22 (permalink) Old 11-23-2018
Re: Polini 4.2 air cooled parts?

Well if its 15 yrs old and you have a Polini engine its probably a 910 Polini Carena, and I have one. The engine and frame should have Polini markings cast into the parts all over. Does it have 5" or 6.5" rims?? There is also a 911 too.
Sound like you need a new crankshaft, $200 plus dollars, unless you find a shop to split the crank and put a new bearing. I use to get parts at midsouthminimoto.com, from Stoney, don't think he is in business anymore, but you can look at parts for your bike there. Not sure if Polini USA is still here also.

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post #3 of 22 (permalink) Old 11-23-2018
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I whould call around places like hot rods and see if they are willing to attempt to fix it parts are hard to come by for them...

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post #4 of 22 (permalink) Old 11-23-2018
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Re: Polini 4.2 air cooled parts?

It can be fixed...There is a member named Kray15 who has connections in Italy where theyre still racing them...

You can waste your time with Stoney from MSMM aswell as other US retailers or strike a deal with someone over seas then wait for the parts to arrive..

You can go a lil unconventional and bring that thing into the new age with a genuine Polini E-P3 Motor..

https://www.poliniebike.com/en/

Good luck

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Last edited by CAM2; 11-23-2018 at 08:36 PM.
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post #5 of 22 (permalink) Old 11-24-2018
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So there is the small end or the big end damage?
You should change it completly.
Rev. Set from polini is available
https://www.grcmotoshop.com/alberi-m...e-polini-.html

Or change complet crank is not more expensive.
https://www.grcmotoshop.com/alberi-m...re-polini.html

I'm from europ and can help you with parts. Shipping to usa is no problem.
When interestet pn me.

Rgds chrisi

Get your kick with 2 stroke mix

Last edited by Chrisi; 11-24-2018 at 06:02 AM.
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post #6 of 22 (permalink) Old 11-24-2018
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you should replace the bearings as well and check the cylinder and piston for pitting might as well throw in a new set of rings well your in there

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post #7 of 22 (permalink) Old 11-25-2018
Re: Polini 4.2 air cooled parts?

A new ring is only about $30. My 4.2 Polini and 40cc 13hp BZM has the same ring. Need to hone the cylinder if you go with a new ring. Did you try MSMM?? I have not tried to contact Stoney for a year.

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post #8 of 22 (permalink) Old 11-25-2018
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Quote:
Originally Posted by EPR View Post
A new ring is only about $30. My 4.2 Polini and 40cc 13hp BZM has the same ring. Need to hone the cylinder if you go with a new ring. Did you try MSMM?? I have not tried to contact Stoney for a year.
Why should he hone the cylinder with new ring???

Put on a new ring every 25l, a new complet piston/ring set every 50-75l.
Hone an cylinder only when there is no more honestruktur.

A crankshaft repair is not an easy thing to do in the garage, it should be done by a professional.
The shaft must be pressed and balanced so that the engine runs well. I think you are better off with a new crankshaft.

Rgds chrisi

Get your kick with 2 stroke mix
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post #9 of 22 (permalink) Old 11-25-2018
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you should do a few quick passes with a hone then hit it with a bore brush every time you replace rings so they seat in good

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Re: Polini 4.2 air cooled parts?

I use a big 3 long arm stones brake cyld hone and I only hone where the piston ring travels and leave the bottom polished. I would never put a new ring in a used polished cyld.

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I get all my parts from Europe. The French, germans and Austrians are real easy to work with.

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Re: Polini 4.2 air cooled parts?

Anyone know why I can't create a new thread? Im trying to get help with my 40cc 4stroke engine
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Re: Polini 4.2 air cooled parts?

think you need a few more post to post your own. Start a new thread in the Introduction Section, or answer other members posts till you get 6, then try to post a new thread. That 40cc 4 stroke engine 1.5 hp engine is junk. Better to find a 47cc or 49cc 2 stroke bike.

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Race chassis

I'm new here and need to Know how/where to get aluminum frame or something racers use
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Some europe pocketbikes has aluminum frams, polini 910 and 911, grc laser, gp racing, rc 40 dm telai gp1 factory rr.
But you don't ned a full aluminium frame, many blatas, grc's and dm's are steelframe and are good racebikes.

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the problem is there are onley 2 tracks left in the US that I know of where they race pocket bikes

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Thanks for the info guys

Quote:
Originally Posted by MrKitty View Post
the problem is there are onley 2 tracks left in the US that I know of where they race pocket bikes
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Re: Polini 4.2 air cooled parts?

Quote:
Originally Posted by MrKitty View Post
the problem is there are onley 2 tracks left in the US that I know of where they race pocket bikes
And which two tracks are those? I know of a bunch that allow pocket bikes. I race in the seattle area with a supermoto club in their mini class. I know two tracks just within my state that allow pocket bikes. There are about 5 in california and a bunch in the south. Pocket bikes are still used in the US there just isn't really a league anymore. Racers have to ride either on track days or race with a mini club.

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Re: Race chassis

Quote:
Originally Posted by russpalmbones View Post
I'm new here and need to Know how/where to get aluminum frame or something racers use
I know people all around the world selling bikes. If you are fine with paying an extra $200 in shipping on top of a $500 bike (for example) I can hook you up pretty quick. PM me if you are interested. Are you just looking for a frame or an entire bike?

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you must be talking about the Bremerton track? then there is one in Cali. It would be really cool if someone would make a list of the tracks that have mini moto racing the times and classes...

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