Pinasco 225: checking cylinder clearance

Checking the clearance between cylinder skirt and crankcase on the Pinasco 225 I'm currently fitting. These new kits have tighter clearances there as well as between piston and cylinder. These should perform remarkably well once run in, but beware run-in time is longer on this kit than on the classic, older Pinasco, or the other aluminum kits, for that matter.
UPDATE (may 15, 2015): this seemed like the perfect touring kit, but I found out while setting it up that it's in fact made to be plug and play NOT with a 60mm (110 rod) crank (225cc), but with the 62mm eccentric version (235).
In its 225 form, the exhaust port doesn't open completely, and the squish is akin to the values found on Piaggio 200cc cylinders, evidently not the most performance-oriented. The extra 1 mm up-and-down stroke on the 62mm crank (actually the 60 stroke crank fitted with a 1mm eccentric crank pin) would allow to completely uncover the exhaust port, and bring the squish under the 2mm mark.
This is unfortunate for a kit advertised as the ultimate touring kit MADE FOR THE 60mm crank. Basically, you would need to adapt this kit by installing a 1mm base gasket to get the piston and ports to align, and skimming the top of the cylinder AND the cylinder head by 2-3 mm to get back into the realm of acceptable squish values. the only problem with this option, is that the compression ratio would be through the roof, and aggravate among other things, the pinking already associated with the kit.
Best (easily attainable) solution: install an adequate thickness packing plate to get piston and ports to align, and leave the head as is. At this point, raising the squish a little more won't adversely affect performance in a noticeable way, but with help decompress the engine, and reduce pinking.
NB: the purpose of this video was to show that it's necessary (or at least it was on the first kits released) to check clearances, and to "lathe" the surfaces when necessary. I checked everything except the exhaust stud, which turned out to be a PITA. It was tight with every exhaust tried, and I had to spend quite some time getting the exhaust to fit on the stud. That seems to be sorted out on the more recent kits delivered by Pinasco, but it would be wise to check before fitting anyway.

[@stephenashmore6815]

Does the 1mm base packer mess up the port timings, particularly the transfers? I ran this kit with a 60mm stroke all last year and loved the power. However there was a lot of pinking at high speed. During a rebuild, I noticed the piston wasn't clearing the bottom of the exhaust port and I'm considering raising the barrel as per your description.

[@frankeenstein]

I originally purposely left out the packing plate, to avoid adding on to the already outrageous squish. Given that in this configuration, the piston doesn't completely clear the ports, compression is very (too?) high (I blew a flywheel side seal inside out), and it DOES tend to pink at high revs, it appears a better option would be to concentrate on aligning piston and ports with the help of the adequate packing plate (0.8 to 1.5, likely), and not worry about raising the squish. For touring purposes, the kit could do with a little less compression to reduce or eliminate pinking; and the squish being already out there, an extra mil won't noticeably affect performance. It should actually make it less peaky while compensating with better port usage.... This will be the next order of business when I feel like using the wrench again...

[@tadficuscactus]

On the website they say there is also a 235cc version of this kit. Does it just have a spacer plate under the barrel?

[@frankeenstein]

Oskar Henning-Tapley
No, it achieves the extra 10cc with an excentric con rod, but it's the same kit as this (which actually attains the 225cc mark with a 60mm rod). To be honest, the 235 configuration should be the one best suited for this kit: in the current 60mm cranshaft/225cc displacement configuration, the exhaust port isn't completely uncovered, and the squish is around 2.5 . The extra piston movement allowed in the 235 setup should both reduce the squish to a more reasonable value, and completely open the exhaust port.

[@tadficuscactus]

thanks for that info. By excentric con rod do you mean it is shorter than on standard cranks?

[@frankeenstein]

Oskar Henning-Tapley
Nope. It's still a 60mm con rod, but the pin is machined so that the rod is actually placed 1 mm outward, meaning that it goes up 1 mm higher towards the head, and 1mm lower into the barrel,