Convert a 2T 49cc from 10mm to 12 mm

[skuttadawg]

I know obviously 12 is larger diameter and do not want to drill out the rod . So if I have a 10mm wristpin , can I swap out the crank to use a 12mm wrist pin BBK with another crank that is of size ? I heard that the variator is larger on the 12mms too as a way to know or get an idea of what size the engine has with out taking it apart .

Any suggestions for a forged racing crank are welcome .

650 to 700 budget for BBK , crank , racing pipe and CVT upgrade

Or just buy a Hoca Powerkit ?

[skuttadawg]

Also does Polini require case boring for some of their BBKS ? I know a 49 can use most 72 and would need to be bored for a 90 piston and crank . That may be an option much later but for now its 72cc like here for example www.scooterdynasty.com/50cc2tminarellijoghp.aspx

[reveeen]

So if I have a 10mm wrist pin , can I swap out the crank to use a 12mm wrist pin

You can, but doing so is coming at the thing arse about face. Why would you not buy a kit that has a 10mm wrist pin? Or, if the 12mm kit came at the "right price", why not buy a piston to fit?

If I was buying a crankshaft it would likely be an Athena stroker. (the Athena stroker crank for a Zuma, has a 12mm wrist pin, accepts the small flywheel/variator, and requires no case machining)

Typically, you would not expect to bore (or open up the case), for cylinders with a 47mm bore, it's only when the cylinder bore size is bigger than 48mm do you expect to have to open up the cases.

[lshigham]

Apr 25, 2012 2:41:09 GMT -5 reveeen said:

So if I have a 10mm wrist pin , can I swap out the crank to use a 12mm wrist pin

You can, but doing so is coming at the thing arse about face. Why would you not buy a kit that has a 10mm wrist pin? Or, if the 12mm kit came at the "right price", why not buy a piston to fit?

If I was buying a crankshaft it would likely be an Athena stroker. (the Athena stroker crank for a Zuma, has a 12mm wrist pin, accepts the small flywheel/variator, and requires no case machining)

Typically, you would not expect to bore (or open up the case), for cylinders with a 47mm bore, it's only when the cylinder bore size is bigger than 48mm do you expect to have to open up the cases.

The higher end kits only come with 12mm rods, as the 10mm small end bearings tend to pack in more easily (seen it on a friends scooter).

[jmkjr72]

i have not had to bore the case for a 70cc kit if you get into the 77cc kits then you will need to bore the case
but if you are spliting the case for a crank replacement then you might as well flow and trench the case
700 bucks thats a small budget if you want good stuff
your looking at least 200 for a good crank
www.spmotostore.com/CRANKSHAFT_STAGE6_p/s6-8016600_12.htm
then dont forget good bearings and seals

[jmkjr72]

also dont forget that if you have a 10mm small taper crank on the scoot right now to make sure you order a 12mm crank for a scooter that came with the small taper otherwise you will need to spend more money
so look at yamaha zuma or vino cranks

[skuttadawg]

I like that crank but I did not see ifits 10 or 12mm . I thinking 200 crank , 200 BBK and 200 too 300 for a good pipe and upjet my 19mm carb with EFI this summer

[inuyasha]

Apr 25, 2012 13:54:57 GMT -5 skuttadawg said:

I like that crank but I did not see ifits 10 or 12mm . I thinking 200 crank , 200 BBK and 200 too 300 for a good pipe and upjet my 19mm carb with EFI this summer

Hi
www.spmotostore.com/category_s/3025.htm
Take care and ride safely dear friend
Yours Hank

[jmkjr72]

Apr 25, 2012 13:54:57 GMT -5 skuttadawg said:

I like that crank but I did not see ifits 10 or 12mm . I thinking 200 crank , 200 BBK and 200 too 300 for a good pipe and upjet my 19mm carb with EFI this summer

did you not read the part title
Crankshaft Stage6 HPC Minarelli horizontal 12mm. incl. conrod bearing

yeah at 700 you are not going to get any cvt parts
then you also have to figure in more for your bearings seals jets needles springs and rollers

[skuttadawg]

Ooops . Well I already set aside money for a Dr Pulley variator and clutch . So with 700 or so I want a 47.6mm BBK and racing crank and pipe . I have a 19mm carb to rejet unsure of brand it only says Japan on it . Looks like a billet head and cast block and maybe the piston is too or its the ceramic coating on it . In the link above .

My question on it is why only one compression ring instead of two ?

Suggested pipes ?

[jmkjr72]

what kit are you looking at
the kits in the link that inuyasha posted are all for vertical engines do you have a vertical or a horizontal
a link to the kit you are thinking about would help in pipe selection

there isnt a race kit out there that has 2 rings
it will rev faster but it also wears out faster