Sunday, January 3, 2016

Big Twin

 I'm of course referring to the 1967 BSA 650cc sitting in my shop. Ok, it's not that big but back in their day this was a decent sized bike engine.
 When I discovered a scored piston in one cylinder and then rust formation on the other cylinder, I figured I'd be seeking the services of an outside party to refurbish the top end. I even spoke with someone that would do the job. As time went on this just wasn't settling well with me. I really like to do my own work when possible and the thought of someone else doing this job bothered me. I'm not even sure why I originally started to seek the advice of someone else. Anyway, they're out and I'll do the work even if it means screwing it up. I already feel better.
 A quick search on the net and I found that pistons are still available. I'll put together a wish list and make an order. First I had to see if the metal transfer and rust formation would come out with my deglazing hone. Like a dumbass I forgot to get a "before" pic.
I really should get a new set of stones but this will be good enough for a garage hack.

 A minute with the hone and things are cleaning up nicely. This is the cylinder that had the rust formation and most of it seems raised rather than pitted.

 The other side that had metal transfer from the piston cleaned up decent. I can't even tell where that big wad of aluminum was stuck to the cylinder. This isn't done yet but it's far enough along that I feel good about being able to save the cylinder.
 I still have to sand blast the outside of the cylinder because it really looks like ass. My brother has a sand blasting cabinet and I think I'll head over there today to get that job done. Then I need to make some decisions about the case halves and paint. I like the blacked out look.

 Regular readers may remember a bad experience I had with J&P Cycles. I'm not gonna go over the details again but it was basically just bad customer service that was corrected. They offered me a gift card for my troubles and I stated I would give them another chance. Recently I had an excuse to use that gift card. I ordered some mounts and such for a GoPro camera and the parts were here in two days. Good service again just like I had before that one bad incident. I just wanted to give credit where credit was due. 


  1. Hi: Had a couple of these 650 Lightnings back in the day. Pretty fast, but vibrated a lot. Had lower end problems with both of them. Fixed the first one and traded the second away. The problem is apparently a design flaw in the crank bearings / oil feed that starves out the rod bearings. It's explained here (scroll down to bottom to "From bad to worse"):

    There's an outfit in Canada that offers a British aftermarket conversion:

    Good luck with the restoration. Jon