Topic: R numbers on cams - 78 CB750K

[cookindaddy]

I just got a nice looking new (old) cam with "R-2" embossed on the shaft. I haven't torn down the engine it is meant for, but I think that the last time that I was in there, that cam had "R-9" on it. What do these numbers mean? Both cams are stock (or believed to be stock). Thanks

[Whaleman]

Long post about this in the last 3 weeks. Dan

[cookindaddy]

Thanks. Can you give me a link? I did search on cam and number with no hits.

[shizzomynizzo]

Lower the numbers, the earlier the motor it's from and the hotter the cam. An R1 is best, but R2 is not bad. R8 and R10 are the weakest cams for the 750.

At least that's what I remember. R1 - R3 are getting kind of rare now and will definitely bring over a hundred, where as an R8 will bring 35 or so. 



No just kidding, I remember now. The R1 and R2 are the bad ones. They make your motor leak oil. You should send it to me and I will get rid of it properly 

I'll look to see if I can find a link.

[shizzomynizzo]

Just found the thread...Disregard everything I told you!

R1, R2, etc are just casting numbers and mean nothing more. I guess I should have followed up the next day or so. Glad I didn't run and buy any cams thinking they would be worth more money!


http://forums.sohc4.net/index.php?topic=62266.0

[cookindaddy]

Thanks! I should have searched "camshaft". I guess the search here only checks subject, not message body.

An interesting, informative and funny read!

Thanks again.

[Bodi]

"search" searches content as well as subject for me, just typing "castrol" in the box and hitting "search" brings up more old (help!) oil thread posts than I ever would want.

[MCRider]

Just found the thread...Disregard everything I told you!

R1, R2, etc are just casting numbers and mean nothing more. I guess I should have followed up the next day or so. Glad I didn't run and buy any cams thinking they would be worth more money!


http://forums.sohc4.net/index.php?topic=62266.0

I thought the way you did about the early numbers. what we've found in that thread is that at some point (mid-70s) Honda started to repeat the casting numbers.

So I think there is still some truth to the idea that lower numbers are hotter, but only if one is sure they came from an early engine, and its not as linear as I had been led to believe.

So you can have a red hot R1 if it came from an early engine, or a dud R1 if it came from a later engine. And you may have an R3 that's hotter than an R2, again depending on the engine date it came from. That's what i came away from that thread with.

And almost for sure any early cam is hotter than an R9. But you could have an R1-3 that's deader than the R9 if the R1-3 is from a later engine.

One thing is for sure there are hotter cams but the only way to be sure is to measure them. Its obvious to the naked eye if one has a micrometer eye. Mine aren't as good as they used to be.  

[Inigo Montoya]

Actually the 77//78 K bikes used the 75/76 F motor. They also had larger carbs then the earlier K bikes and contrary to what some might want to believe, were only a couple hundreths of a second slower than the 69. I know people want to talk smack about the 77/78 but everything they base it on is all because they do not like the looks of the bike and because it is heavier. Pretty short sighted if you ask me as the f3 weighs more than the f2 and yet is faster. Or they will try to quote personal experience but isnt it funny how most of these experiences were decades ago and how time dims those memories?

Otherwise, I guess stock cams do not interest me. If I am doing any work on the bike and need a cam, I am not going to buy a 30+ year old cam from a questionable engine that I dont know the history of. But if you like old engine parts, go for it.