Topic: Cam difference

[Doum]

I'm wondering if there is a year with a better cam for the cb750? There is a year that give better performance? Supersport model?

[ekpent]

Been discussed quite a bit. Grab a K0 or K1 cam if you can,little peppier.

[MCRider]

Been discussed quite a bit. Grab a K0 or K1 cam if you can,little peppier.

Agreed. But they likely won't be cheap. And they will be used.

The simplest way might be to just buy a WebCam #41.

Can be used without changing anything, springs, pistons, etc.

http://www.dynoman.net/bikepages/sohc/cams_web2.html

[Doum]

Nice!
I have already a webcam #41 for my turbo setup,but I was looking at a good cam for the 836 rickman....and I have a NOS K1 cam in stock,so I think I will be ok!

[Hinomaru]

Just curious here ...

How do you know that your NOS cam is for a K1?

Is there any identifying markings or other clues to go by? 

Honda shows the same cam part number for the KO thru K6: 14101-300-000 

[MCRider]

Just curious here ...

How do you know that your NOS cam is for a K1?

Is there any identifying markings or other clues to go by? 

Honda shows the same cam part number for the KO thru K6: 14101-300-000

Good question. There are "R" numbers on the cams which are casting mold numbers. For along time I thought these were indentifiers, but after a long thread here a few years ago, we discovered that an R1, which I thought was an early cam, was always an early cam. But some forum members had R1s out of later bikes. So those numbers are not to be trusted.  You have to know what motor it came out of and that it had never been replaced before. In other words, the complete history

The part number issue is a frustrating thing. You cannot order a K0 cam. When you order a cam you get whatever is the most recent. We had this issue in the shops I worked at. If someone came in with a K0 and needed a cam, they would get a K2 cam, for example. There was no way to get the K0 cam, and they would suffer the performance drop. Luckily, this was a rare event. cams virtually never failed on engines that had never been rebuilt. The rebuilding opened them up for getting debris in the oil holes which would then cause cam failures. And rebuilt bikes were often upgrading the cams anyway.

[Doum]

I said it because someone write cb750k1 on the tag beside the part number.It's from a old dealer from the 70's so I would presume it's correct.But I will check for the part number on the tag.

[MCRider]

I said it because someone write cb750k1 on the tag beside the part number.It's from a old dealer from the 70's so I would presume it's correct.But I will check for the part number on the tag.

As Hinomaru mentioned, the part numbers for all K series cams are all the same. You'd be better off with a date of stock. If you (or that dealer) ordered a K1 cam in 1974, it would really be a K4 or K5 cam, same part number. It needs to have been bought from Honda no later than mid to late 1971. Later than that and you've got a K2 cam.

Once Honda stopped making a cam, they never looked back. They looked forward, with the same part number.

If you don't know the date of manufacture, you don't really know anything.

[Doum]

Stamped R10....any idea for the year?
I have also a used R12 and R1

[MCRider]

Stamped R10....any idea for the year?
I have also a used R12 and R1

As i mentioned in previous post, while we would like for the R numbers to be sequential, it was proven to me in a thread from a few years ago that they are not. R1 was an early cam, for a while. But then Honda used the R1 mold for later cams and threw the whole thing off kilter. They R10 is almost certainly a dog.

I will say that with a good eye, you can tell which is a hotter cam by looking at the profile of the lobes. The bike in my avatar, having been built in 1972, in a shop, there was a totalled K0 and we pulled the cam out of it and put it in my K1. It was marked R1. With an 836, ported head, shimmed up valve springs, and pipe, it ran really well.

[Hinomaru]

Those cam R numbers are interesting for sure and here‘s another clue for the CB750 cam detectives. One way to visually distinguish a desirable early production R1 cam from the later R1 cams is the orientation of the R1 mark. Note the differences between the vertical and horizontal placement of the R1 mark next to the cam sprocket in the examples below.

Early CB750 R1:




Late CB750 R1:



Disclaimer: This is from my own observations and not to be taken as gospel. 

[MCRider]

That is interesting! 

[ekpent]

Dang it now we all have to go back and look at all our cams again !! Good observation on that John.