200 Cylinder

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Hotdog
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Sat Oct 31, 2020 7:07 pm

Is there a difference between the 200 cylinders (Rally, P2 & PX) ?

gaz_powell
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Mon Nov 02, 2020 10:16 pm

As far as I know genuine Piaggio cylinders and pistons are the same.
They have come with several different heads over the years, early ones suited to leaded petrol.
SIP and BGM did a pattern one that was slightly shorter, allegedly 12HP out of the box, but I'm sceptical of that (happy to be proved wrong with a genuine back to back)
Beware the far East pattern ones, the ports are badly cast as are the pistons.

If you can get a genuine cylinder and use genuine Piaggio, Meteor or better still SIP GS piston (thinner rings) with a tweek

I'm using the latest head now, I've got one of all the genuine stock heads, with various bowl locations and size.

Hotdog
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Tue Nov 03, 2020 7:53 pm

Is there a reason for using the lasted head ? Do you notice any difference compared to the other heads ?

gaz_powell
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Tue Nov 03, 2020 8:37 pm

Earlier heads are (slightly) higher compression.
Harry Barlow tuned me an autisa barrell and advised the later head with the height of the barrell
No packer or head recessing like the standard P2 barrel tune he does.
I've never measured the Autisa against standard overall height.

I'm back using my chiselspeed tuned Autisa, again which was first ran with a slightly higher compression head, after a rebore when it went back on I used the lower (late) head and saw no noticeable difference.

Slightly different set for this year.... But never been anywhere except test centre....SIP road 3 instead of the 2.

I've never measured the bowl size on the different heads but I don't think the ratios are that different on standard heads (I stand to be corrected)
I've never measured squish clearance on a P2 but I know it's generally bigger than the what is considered safe.

MMW do a P2 head with a next to no clearance, they state that the squish is so big on stock P2 that you fit it to standard and gain... I've not tried one. Looking at the pictures on SIP I've got a skimmed one that's not much different.

I happy with my P2 performance and not really wanting to mess with it as it does what it needs to do, very well.

However I'm about to build a spare P2 motor so might just do some head comparison squish checks and measure cc of heads etc

But don't hold your breath...

Gaz

Hotdog
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Thu Nov 05, 2020 7:49 pm

Can anyone pm me Harry Barlow (pro porting) contact details as the number I got doesn’t appear valid.

gaz_powell
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Sat Nov 07, 2020 4:42 pm

Pm sent, hope your not in a rush!!

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