10+ yr old grubee style motor, 39mm bore??? Also, xfer ports are asymmetrical

[taureanirishman]

haven't measured the stroke length, but it is only 39mm wide, and the xfers grow larger on the intake side.

I'll be able to finally get pictures on Tuesday afternoon, but if anyone know anything about this older model of motor I'd love to hear about it.

I had thought I had cracked a piston ring, but turns out the "tinkatinka" sound was my head not being bolted down properly(duh), but was a good thing to take it apart and check it out. Had a bunch of carbon build up on the piston and the combustion chamber in the head so cleaned that out a bit, and some studs came loose.

Got a dremmel with a flexible extension, and was going to do some port work. I think this thing has some higher quality bearings in it as I'd ran it at WOT almost constantly, and I'm a solid 220# with my gear and my bike is a steel Upton Cruiser going all over town and up and down hills...

I'm going to get a non-angle head and stud replacement and loc-tite everything down, but....

I'll get the cylinder mapped onto a piece of paper and upload the measurements and pictures, but does anyone know about this older style engine at all(from this impressively detailed description )

 

[butterbean]

As far as the transer ports being larger near the intake, I've recently read some info that suggests directing the charge rearward is helpful and better for the engine. Perhaps the way your xfer ports are set up might accomplish that? That would be a good thing.

 

[crassius]

can't recall where they come from, but been seeing those ports for a couple years - got a couple old ones lying around - if I'm remembering correctly, those ports sit a bit higher also