IMAG0074

…You what what? Part 2

It has been brought to my attention that it wasn’t clear as to why Matt and I milled down the Jobbit 2.0 case and new cylinder. Its really pretty simple, because of the similar stroke length. The Honda Hobbit / Camino / PA50 have a stroke length 39.6mm and the Yamaha Aerox has a stroke length of 39.2mm. I know, I know that’s a difference of 0.4mm! It will surely be too big a difference to work!  But in reality 0.4mm is about the size of a gasket. Get on with it! where does them milling come in?! Well that’s the next part. At bottom dead center you want transfer and exhaust ports to be fully open right? Right. And at top dead center it shouldn’t hit the cylinder head right? Right. So at BDC the hobbit cases do not achieve this and at TDC the piston doesn’t get anywhere near close enough to the cylinder head for good compression. So lets…

mill them down!

Oh wait, you want the case bolts to still hold the case together? I guess we can mill the cases as far as we can and take the rest off the cylinder.

Hope this helps clear things up. Here is a stroke length diagram for the hell of it, I found some place on the net.img76-bmp

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>