enduro/cross kit

[kc57]

Looking thru some pics. And I saw this Enduro/Cross Kit. Reading the description on the box, it says it has a hand ported and polished cylinder. And it shows RV after the part #s for the Cylinder, Head and Piston. Im guessing that's for reed valve. How would I know if I have one of these kits or just the reed valve on a Combat engine ? Thanks

[Bullfrog]

Hmmm, my memory of the Enduro/Cross Kit may be faulty on some of the details -- but here is a bit of information anyway.

First of all, I'm thinking there might have been a bit of marketing, um, "sweetener" in the text on the box. As I recall, the major work on the porting was done on a milling machine . . . though there almost certainly was some hand work for de-burring and general clean up of the cylinder. "Polishing" is a bit of a stretch (at least in my memory of the kits) . . . but there was enough hand clean up to (mostly or partly) justify the claim of hand porting.

As I recall, the cylinder head was re-machined to provide a better combustion chamber shape and more effective squish band than the stock CW head - compression was very nearly the same between the two.

Depending on the expertise of the individual doing the porting, there ought to be very little difference between an "Enduro/Cross" cylinder and "just a reed valved cylinder".

Adding the reed valve to a CW cylinder (with appropriate porting, and leaving the exhaust port height at stock) with the stock 28mm carb would require several steps richer jetting. Somewhere in the neighborhood of 240 main jet, probably a 40 pilot jet and a richer slide (2.0?) and at least a richer needle clip position (possibly a richer needle). I just can't remember the slide and needle stuff.

The CW engine with proper reed mods and properly tuned carb is a dandy engine!!

Ed

[kc57]

Thank you Ed !

It is really nice to have both a technical and historical perspective. And its always good to be reminded of the power of marketing. Ported and Polished ? sounds good, wrap it up !