CB77 Racer

G-Man · Post by **G-Man** » Mon Dec 31, 2012 1:35 pm

Davo

Good stuff. Thanks for sharing those. Great pics from the iPhone!

The liners must be perilously thin with 64mm slugs in there. I'm planning on using some CB750 liners for mine.

Looks like you're al sett for a happy new year but I'll wish you one anyway!

G

davomoto · Post by **davomoto** » Mon Dec 31, 2012 4:57 pm

Thanks Graham! And a happy new year to you and your's as well!

I told the owner about the CB750 liners, but he's not too sure what he's going to do with the bike at this point. He's going back and forth between street hot rod and vintage racer.

CB77GUY · Post by **CB77GUY** » Tue Jan 01, 2013 10:45 pm

Go ahead and run the full advance. I ran almost exactly the same setup back in the late '60's. You're right, the overbored stock liners are not a good choice for racing, I tried that one too. I still have my 305, which I restored to racing trim several years ago. There's a couple of threads on this forum with some pictures of mine. I'm doing a couple or three track days a year with it. If can be of any help, don't hesitate to contact me. Good luck with the project. I hope you will post some pictures of the competed bike.

davomoto · Post by **davomoto** » Wed Jan 02, 2013 10:42 am

Yes, will post pics of completed bike for sure!

Are you still running 64mm pistons? Stock liners?

What are you doing for ignition system?

We're leaning toward total loss with a battery.

CB77GUY · Post by **CB77GUY** » Wed Jan 02, 2013 10:29 pm

I gave up on the overbored liners back in the '60's. They smoked pretty bad when I ran the bike hard. I put a Webco 350 kit in it for a lot of years, which had Forged True pistons and 64mm liners. When I needed a rebore, I went with CB350 pistons and rings. I had to remachine the crowns to get proper squish and clearance for the valves. I also had to modify the skirt to get clearance with the crankshaft. I replaced the Webco liners when I restored the bike because I found a new set of 4th over CB350 pistons and wasn't confident that there was enough left in the Webco liners for a bore that large. I bought a set of 65 mm liners from L.A. Sleeve and machined them to length and rebored the cylinder block to accept them.

I was and am still running a Harmon Collins roller cam. I've upgraded the ignition to a Dyna-S along with Dyna coils. I'm running total loss with the ignition triggers on the right end of the crankshaft. I fabricated a structure to mount the trigger plate that is dowelled to the crankcase so it can be readily removed when I have to split the cases. I bored the taper on the Dyna rotor to fit the crankshaft and hand cut the keyway. I run a Yuasa gel cell battery and it has more than enough reserve to run all day and it is smaller and lighter than the original. The last time out for a track day I rode seven, half hour sessions with no problem. Incidently, I'm running about 53 degrees advance and the engine pulls to a little over 12,000 RPM.

G-Man · Post by **G-Man** » Thu Jan 03, 2013 4:13 am

Interesting set of details.

Thanks for sharing those.

G

davomoto · Post by **davomoto** » Thu Jan 03, 2013 7:59 am

Interesting indeed, and thanks for sharing! I recently aquired a Harmon Collins cam and roller rocker equiped head. I will most likely be bugging you for info on that setup as well in the near future, as I plan to use it with a 3mm overbore kit for my cafe' bike. I was surprised at how well the race bike ran with those large 32mm Mikunis on it!

Davo