Wednesday, April 14, 2010


Monday I was riding to the Mars Bar and cruising down 8th st in Ballard which is pretty much a slight downward incline for a couple of miles.

I was enjoying my new derbi, and just kind of blissfully riding when I thought, "You know, Phil is right, I shouldn't kit this thing. It goes plenty fast on 50cc and this way it will be more dependable." SQUELCH! The back tire locked up and I skidded for about 50 feet.

My initial thought was that I hard seized the motor... but how could that be? I pulled the plug and it looked perfect, I didn't notice any loud blats right before it seized that would indicate an exhaust leak or a massive case seal blowout...

Well, this morning I took the head off and the piston and cylinder look... spotless. Pristine. I removed the jug and have come to the preliminary conclusion that the crankcase bearings kicked the bucket. I'll post some pictures later, in the meantime, any derbi gurus know what size bearings and seals I need to get to rebuild this engine?

I read up in the Variant Manual and it looks like these are the bearing sizes:
Crankshaft - 6203/ 17.40.12 and 6204/ 20.47.14
Main Gear - 6301/ 12.37.12 and 6302/ 15.42.13

Now, the diagram in the manual shows a case inducted engine and I'll be rebuilding a piston port, but we'll see if the bearings are the same size.

1 comment:

  1. bummer! piston port and pyramid reeds are pretty much identical. some piston port cases even have all the casting setup to be pyramid reed, there's already channels for the pyramid reed block, they just have it blocked off in the crankcase. so you should be golden.