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Best crank for my Polini.

Posted: Mon Feb 06, 2012 1:08 am
by Trafficjamz
Does the polini corsa and a ministroke crank go well together.

Is the SEF crank a better choice?

Or should I just stay with a stock crank.

Re: Best crank for my Polini.

Posted: Mon Feb 06, 2012 1:16 am
by bakaracer
find a stuffer full counter weighted crank. that way it increases case pressure. thats what you want. so a malossi one or sef stock stroke stuffer.

Re: Best crank for my Polini.

Posted: Mon Feb 06, 2012 2:00 am
by Trafficjamz
I have this one that I got from zr50 ghost

Image


Is the scorpion pipe a good match for this crank/bore

Re: Best crank for my Polini.

Posted: Mon Feb 06, 2012 2:02 am
by bakaracer
yeah that will work good. that one has a longer con rod so use a degree wheel to set the duration.

Re: Best crank for my Polini.

Posted: Mon Feb 06, 2012 2:21 am
by Trafficjamz
bakaracer wrote:yeah that will work good. that one has a longer con rod so use a degree wheel to set the duration.

Is the duration is set with extra base gaskets?

Do I need to use polini's metal gaskets.

Re: Best crank for my Polini.

Posted: Mon Feb 06, 2012 2:22 am
by kingkamehameha
Traffic if you use the scorp try polini yellow or blues and a 2k center. It really likes the high revs. Thats a nice crank you got

Re: Best crank for my Polini.

Posted: Mon Feb 06, 2012 2:26 am
by bakaracer
Trafficjamz wrote:
bakaracer wrote:yeah that will work good. that one has a longer con rod so use a degree wheel to set the duration.

Is the duration is set with extra base gaskets?

Do I need to use polini's metal gaskets.
yeah. you will have to get thin gasket paper to make your own. Im not sure if polini has metal base gaskets for the dio. I know they have them for minarelli motors.

Re: Best crank for my Polini.

Posted: Mon Feb 06, 2012 2:34 am
by Trafficjamz
kingkamehameha wrote:....... It really likes the high revs. Thats a nice crank you got
This is the "suicide" crank I got from ZR

http://www.hondaspree.net/phpBB3/viewto ... =2&t=20165

I had to fix it.......I hope my fix works.

Image

Re: Best crank for my Polini.

Posted: Mon Feb 06, 2012 2:45 am
by Trafficjamz
bakaracer wrote: yeah. you will have to get thin gasket paper to make your own. Im not sure if polini has metal base gaskets for the dio. I know they have them for minarelli motors.

A metal gasket came with the polini kit.

I don't know where to get them individually.

Can the metal ones be stacked like the paper ones?

Re: Best crank for my Polini.

Posted: Mon Feb 06, 2012 2:56 am
by bakaracer
yeah. they are very soft aluminum so they crush nice.

Re: Best crank for my Polini.

Posted: Mon Feb 06, 2012 4:04 am
by kingkamehameha
Ive been reading over jennings two stroke articles and the degree wheel s*** has me real confused. I need to see someone do it in person or make a video.

Re: Best crank for my Polini.

Posted: Mon Feb 06, 2012 9:43 am
by Mystic
I think you can get metal gaskets with different thicknesses from japan.webike

Re: Best crank for my Polini.

Posted: Mon Feb 06, 2012 11:36 pm
by Trafficjamz
Mystic wrote:I think you can get metal gaskets with different thicknesses from japan.webike
Yeah, I have seen those.
Those are much thicker than I need, and the boost port on a polini is not that large.

What I don't understand is, How the con rod is longer , but the displacement stays the same? :confused:

why would this crank need extra base gaskets if it is not a ministroke?

Re: Best crank for my Polini.

Posted: Tue Feb 07, 2012 12:10 am
by bakaracer
The stroke is the same but with the longer con rod, it changes the port timing due to rod angle to crank angle.so with a longer rod with the same stroke the port timing will be longer. There is also less stress on the wrist pin and bearing due to less angle on the rod.it also changes blow. Down time because of con rod angle so it stays open a little longer without having to port the cylinder or modifing the ports by adding material

Re: Best crank for my Polini.

Posted: Tue Feb 07, 2012 12:18 am
by Trafficjamz
Will the head or jug need modified the compensate for the jug being raised by extra base gaskets.