Connecting rod question

[Tim Allman]

I have been looking for a CB77 crankshaft and see one on Ebay (http://www.ebay.com/itm/Honda-305-CB77- ... kB&vxp=mtr) with connecting rods with lubrication slots in the small ends rather than holes. I have never seen the slots before. Is this an early design? A late one? Something to be avoided?

Any comments about the crank or seller in general would be appreciated too.

Tim

[G-Man]

The crank looks clean and shiny but the rods do not. It looks like it has been cleaned up for sale.

The black deposit baked on the rods is an indication of the life the crank (and engine) has had. Bear in mind that the critical parts that wear on the crank are on the inside.

Buying a 50-year-old crank is always going to be a gamble, which is why I like to strip them and clean all of the accumulated dirt from the inside and replace bearing rollers.

The rods are the early type. Another indication of the age of the part.



This one has all new bearings, but can you tell?



G

I have been looking for a CB77 crankshaft and see one on Ebay (http://www.ebay.com/itm/Honda-305-CB77- ... kB&vxp=mtr) with connecting rods with lubrication slots in the small ends rather than holes. I have never seen the slots before. Is this an early design? A late one? Something to be avoided?

Any comments about the crank or seller in general would be appreciated too.

Tim

[Tim Allman]

Thanks for the comments but you are not bringing me happiness. I am now truly wishing I had been nicer to this bike when I was younger.

The main reason I need a new crank is that the right connecting rod small end appears to have suffered lubrication failure and is scorched and worn. It is still smaller than 15.1 mm but is well out of spec to the point of clanking when the engine runs.

The machine shop I deal with (http://www.fast-company.ca/) is well set up for most things and the owner is very competent but he doesn't have the equipment he needs to ream the rod and is unwilling to pay what is needed to get it. It would probably be used once because for anything he sees these days, the rod would just be replaced. (Oh the joy of having a dealer with a supply of parts!)

Perhaps the best thing to do is have the crank pulled apart and assess the situation.

Thanks again.
Tim

[teazer]

Strip teh crank, have a machine shop bore the small ends and press in bronze thin wall bushes and then hand ream them to finished with an adjustable reamer or machine them to finished size.

[Tim Allman]

Strip teh crank, have a machine shop bore the small ends and press in bronze thin wall bushes and then hand ream them to finished with an adjustable reamer or machine them to finished size.

I see that's what G-Man did in the pictures above. That's probably what will happen to mine too.

[G-Man]

Tim

It's impossible to 'know' what you have unless you can inspect it. It will be 50+ years old with an uncertain history.

Regarding your small end bearing you need to ask why there was a lubrication failure. The small end and piston skirt are lubricated by a jet of oil escaping from the big end. If the passageway is restricted then the big end may have suffered too.

The passageway that sends oil up to the small end can be seen at 12 O'clock on these rods. The othe 'slots' form reservoirs to lubricate the side faces of the rod.



You might be lucky with that crank or you might get just as lucky with your own if you strip and clean it.

G

Thanks for the comments but you are not bringing me happiness. I am now truly wishing I had been nicer to this bike when I was younger.

The main reason I need a new crank is that the right connecting rod small end appears to have suffered lubrication failure and is scorched and worn. It is still smaller than 15.1 mm but is well out of spec to the point of clanking when the engine runs.

The machine shop I deal with (http://www.fast-company.ca/) is well set up for most things and the owner is very competent but he doesn't have the equipment he needs to ream the rod and is unwilling to pay what is needed to get it. It would probably be used once because for anything he sees these days, the rod would just be replaced. (Oh the joy of having a dealer with a supply of parts!)

Perhaps the best thing to do is have the crank pulled apart and assess the situation.

Thanks again.
Tim

[Tim Allman]

Thanks. I'm enjoying learning some of the subtleties of the design of these bikes.

I too have been wondering why one side would be so much worse than the other and did a little hunting for a shop with experience with old bikes. I have found a place about an hour away and had a chat with them about my crank. They told me to bring it in, which I will do.

Thanks again.