CB72-77 Racer

lloydy1 · Post by **lloydy1** » Sun May 24, 2015 2:58 am

Hi all...New to this site.

Just picked up a new bike as a project to restore. The guy I bought it from described it as a CB72-77. Checking the frame number which is "cb77 102495" I was hoping if someone out there may know anything about it.

This bike has been modified heavily. The crank case breather has been modified to connect to the frame and in turn pipes connect from the top of the frame to the air intakes on the two massive Amal carbs.

The gear box has been modified by a company called JBR in 1985. I have the drawings for all the work that was done to it from them.

So, if anyone can help me out if would be of great help and much appropriated.

Thanks, Dave

G-Man · Post by **G-Man** » Sun May 24, 2015 12:54 pm

Dave

Interesting bike. CB72 was a 250 and CB77 was a 305, but both were pretty much the same other than the barrels & head.

Your bike has yellow racing plates which would suggest that it's larger than 350cc. Normally 305s would be taken out to 64mm bore for a 350 conversion.

There have been some 500s built from these motors using a longer stroke (CB450) crank and bigger pistons.

Do you know what was done to the gearbox? 5-speeds, probably.

G

lloydy1 · Post by **lloydy1** » Sun May 24, 2015 1:48 pm

G-Man wrote:Dave

Interesting bike. CB72 was a 250 and CB77 was a 305, but both were pretty much the same other than the barrels & head.

Your bike has yellow racing plates which would suggest that it's larger than 350cc. Normally 305s would be taken out to 64mm bore for a 350 conversion.

There have been some 500s built from these motors using a longer stroke (CB450) crank and bigger pistons.

Do you know what was done to the gearbox? 5-speeds, probably.

G

Hi G

Ive attached the drawings that came with the bike. Its not 5 speed by the looks of things.

I do have a couple of more drawings, but it wont let me upload them.

The guy did mention it possibly being a 500cc. I have yet to strip it down as I only picked it up yesterday. I will post more pics as I go along with the rebuild.

The guy seem genuine and did mention it had some pedigree. Claimed, although I take it with a pinch of salt, it going around the Isle of Man...not too sure on that one. Nice thought if it did.

Thanks, Dave.

G-Man · Post by **G-Man** » Sun May 24, 2015 2:13 pm

Dave

Thanks for sharing those. The mods look pretty serious. To arrive at a CR 4-speeder? I have one of the 500cc race motors which came with my 350 racer. It looks like you are going to have plenty of fun with that bike.

This one won the CRMC 350cc championship in 1994 and was ridden around the IOM by one of the Honda UK people at the Honda 50th anniversary event.

G

lloydy1 · Post by **lloydy1** » Sun May 24, 2015 2:26 pm

Wow nice looking machine.

My bike has had a right hand gear change modification done to it. The engine is vented into the frame also, with attachments to the carbs. I am guessing that is to enable the carbs to suck warm air?? Have you heard of that before??

Cheers.

G-Man · Post by **G-Man** » Sun May 24, 2015 4:22 pm

Can you post some pics of that?

G

lloydy1 · Post by **lloydy1** » Mon May 25, 2015 2:51 am

G-Man wrote:Can you post some pics of that?

G

Here is some pics of the venting and gear change.

Thanks, Dave.