Poor Boy Big Bore Kit

Dana01 · Post by **Dana01** » Wed May 04, 2011 5:34 pm

Did you anneal the copper gasket? I'm not sure if stock sheet comes in the right crystal structure.

*For those who are wondering ... heat copper gasket to cherry red with a torch (don't melt it), then dunk it in a bucket of water. This isn't done with new copper gaskets, only used ones to remove any "work hardening" that may have occurred over time.

flathead · Post by **flathead** » Sat Oct 01, 2011 5:41 pm

Hello,

I'm back at the poor boy big bore bike trying to get it ready for Barber next week. I was pretty much finished up this afternoon and ran into too big of a problem to get solved before I load up Wednesday. Anyway I finally got to start the engine up. First kick!! Thanks again Ed for the recipe.
Works every time. This one, even being a twingle, runs smooth as silk. Absolutly no vibration. Idles like an Elgin clock. But I've got one more oil leak at both front corners of the head gasket. So I guess I did way too much thinkin about the drop in compression using the flat top pistons. I should have ordered up a factory gasket and stayed away from the .021 copper with the super thin viton orings. Below is a few pics today. The seat's not attached and probably not going to be a permanent fixture anyway. All the paint is texture powder coat. Platinum for the tank and fender with everything else black. Rims are 2.15" x 18 stainless steel with NOS 3.50 Pirelli 310's. The tailight is from a boat trailer and mounted in a Harley Hummer tailight housing.

Mark

davomoto · Post by **davomoto** » Mon Oct 03, 2011 8:43 am

Looking good Mark! Can't wait to hear how it rides with the po boy big bore kit!

Davo

G-Man · Post by **G-Man** » Mon Oct 03, 2011 10:04 am

It needs the extra cubes to push those handlebars along...... :-)

G

flathead · Post by **flathead** » Mon Oct 03, 2011 2:20 pm

G-Man,

I couldn't resist the bars on this one.

I had a bone stock White CB77 with bicycle ape hangers back in 71'. As a matter of fact, I put ape hangers on everything I rode when I was a kid. We lived in the same town as the Murray Bicycle plant. Used to go to the city dump where you sometimes would find literally thousands of tires, handlebars, wheels, frames, seats, cables, and you name it. I assume, back then they were bringing this stuff in from Asia for pennies and if there was an issue, off to the dump it'd go. It was like Christmas every two weeks when we took off the trash.

Mark

G-Man · Post by **G-Man** » Mon Oct 03, 2011 2:34 pm

Mark

I think that you've done a great job with this project. The bike looks fantastic but I'm afraid that, being vertically challenged, I'd have to stand on the seat to reach the 'bars. I enjoy being in the workshop more nowadays than actually riding the bikes it seems...

When I get some time I'm going to complete my own poor boys big bore kit. I bought a STD bore CB750 barrel for £30 and just need to turn down the top flanges and shorten the lower part to make 'em fit a bored-out 305 barrel. I've got some CB350 pistons to modify but some flat ones like yours might be interesting, too.

Interesting to know how the bike performs on the road.

G

flathead · Post by **flathead** » Mon Oct 03, 2011 3:08 pm

Davo and G

Hope to know how it performs by tomorrow afternoon. I've got a new .05 copper head gasket made up and annealed. Per the Honda flat rate chart .7 hr to remove the engine, 2.8 hr to replace the gasket, and 1.2 hr to re-install the engine. I'm gonna get started at 5PM so I should finish up in time for work , 6AM. It's been a rush to get it finished for the Barber Vintage Festival this weekend.

Mark