Best gearing for PK50XL on Polini 115

[kowalski385]

I have a PK50XL (elestart) engine, standard except for:
1. Polini racing cylinder 115ccm
2. Dellorto 19.19 carb on standard three nut manifold (PK50, I think it's 18 mm in diameter-probably should go to larger, 20mm one)
3. Sito exhaust with polished iron exhaust manifold
4. new Newfren reinforced 3-plate clutch with malossi hard spring (no worries there I believe)

I haven't completed it yet (still getting the parts), but I know I'll have to change the primary driven gearing, which is now 15/60 teeth, with 4.00 ratio, helical cut.


What I was wondering is it possible to combine, for example, this primary driven gear with the existing gearing on the clutch? Will it work?
I am trying to find original PK125 gearing, but not sure if I'll make it; I'm aiming for a more comofortable cruising speed (2/3 of power at fourth gear) at about 45 mph, no need for wheelies or top speed over 60...is it possible with my setup?


I believe that this gearing setup won't go over 40 mph at top speed..right?

[Juan]

No, don't go mixing primary gearing unless it's specifically designed to work with a certain basket, DRT do some. I'd suggest you get a set of 24/72 (3.00)although they all tend to be straight cut and are a bit whiney compared to helical.

[bluecati]

I have the same polini 115..with a delorto 19 19..and a leo vince pipe.
With a polini straight cut aluminium 62/21=2.95primary
Excellent balance of torque and top end (easy 60mph).
That up gear kit does not accepts a PK clutch cos the clutch basket is not deep enough...it also requires ali. clutch plates

you may be able to help me

I am having a hell of a time fitting the cylinder cowl to the polini 115. Out of interest what cowl are you using..is it stamped with 50 or 90 or something else...do all the holes line up?

I tried a cowl from the small door 50 and thats even smaller. The screw holes on the 50 cowl wont line up..well one does but no others. I have resorted to fileing the head which doesnt seem right.

your gearing should be in the 2.86 to 3.o range (according to SIP website and heaps of replies on here two weeks ago

Info which cowl ya using on that polini 115 would help me a great deal? (to buy or not buy)

[kowalski385]

Jul 3, 2013 2:06:09 GMT bluecati said:

I am having a hell of a time fitting the cylinder cowl to the polini 115. Out of interest what cowl are you using..is it stamped with 50 or 90 or something else...do all the holes line up?

I tried a cowl from the small door 50 and thats even smaller. The screw holes on the 50 cowl wont line up..well one does but no others. I have resorted to fileing the head which doesnt seem right.

I'm using a original PK50 cowling; all the holes line up, and it fits perfectly, as you can see here (screws are there so you can see it lines up).
I believe it's a 115 barel, because it's 58mm diameter, main screws on the barrel ar short ones (oposing to long studs on original 125 and larger kits), and head is attached with allen screws.