Shim for Cylinder By sking3111 (Read 378 times)

[sking3111]

Hello, just bought a 70cc big bore kit for 2 stroke scooter, it offers a shim to raise the Cylinder. My question is is the shim only if I have a performance crankshaft? My crankshaft is stock. Thanks for Suggestions.

[clonedrone]

No. and Yes, is also to raise the cylinder for Stroked applications, you did not mention the thickness.
The MFG's cylinders height varies, You want the timing or outside edge of the piston at what is called "Zero Deck".
The piston should ideally at Top Dead Center (TDC) not stick out of the bore or be down in the bore.
Minimum Squish clearance should be No tighter than .039 or 1mm with the Stock Con Rod.
Use some type of straight edge to check, + or - .010 ( Ten Thousands) can and will effect the Static Compression Ratio.
You don't want the engine firing with the piston down in the whole and out of the whole may get dangerously close to hitting the cylinder head.
Jump over to the Tech area of this board and read the Squish Clearance Thread.
If you need to custom the thickness of the base gasket Cometic Gasket can custom one up in a couple days for cheap.
Cometic offers for Two Smokers what they call a compression stack of base gaskets, consists of three to four different thickness base gaskets, typically .005,
.010, .015, .020 etc.
Do the same for setting up ol KZ and GS Big Bores back in those days, offered in several different materials.
Ride On!
Clone
Snit, a little to much information. sorry

[sking3111]

Thank you much

[rapidjim]

Good read