Topic: Found a 750K0 cam, opinions please.

[Alan F.]

So I found this K0 cam, only a few crappy photos are available as usual and the sparse description says it's a 750K0.

What's your opinion, should I pass?

[Don R]

 If you can't measure it, it might be K0 and still worn down.

[BenelliSEI]

Ask for some basic measurements? If can’t provide, pass. Comes back with what you want? Gamble.

[Alan F.]

So I'll ask for diameter of each lobe and bearing surface, and see what the seller can come up with.

I spotted another, in the description it states, "CB750 KO Camshafts can be identified by raised rectangle on left side of shaft" I think that's between cylinders 1 and 2. Picture attached. He's asking a little more than CycleX for his cam but I found another cam with this raised rectangle for half the price but it's got some gold discoloration, maybe it was overheated? It doesn't seem worn from the photos and i'll ask the seller for measurements, but is this coloration a red flag to stay away?

[Alan F.]

No replies yet, found this:

RXman has it right: the only production cams that ever came close to the published 1.415" overall height were found in the sandcast K0 engines. Beginning in the diecast K0 they dropped to less than 1.410 brand-new, and over the years until the F0 engine they became even less. The duration was made to open the intake valves later in the F0 engines (0 degrees instead of 5 degrees BTC), to improve scavenge for emissions reduction reasons, and this pushed the powerband RPM higher.

If the cam has at least 1.350" overall height, it is fine: they start to lose top end if this drops below 1.30" (like mine, at 143,000 miles, 1.29n" intake lobes, 108 MPH top speed instead of 121 like it used to be). They were Parkerized when new, so they immediately wore off 0.002"-0.004" of whatever height they started with while they mated to their rockers, entirely normal.

[corky]

Forgive my ignorance, but do yo want a K0 cam for originality of a rebuild, or is the lift on these cams that much better then K1 and on?

Thank you for the info!

Daniel

[Alan F.]

From my understanding it's the lift. The early bikes had a few attributes that when combined were much more fun than the later bikes. Then government regs to keep them clean and quiet did the rest.

Ignorance fades away if you try, no worries.

[Don R]

 If I could buy one from cyclex for a little less money I would do that. I'm no ko expert but I don't think I've seen the raised square. The K0 that I opened up and built had an incorrect motor. I will check my current stock with a dial indicator though. BRB.

[Don R]

 10 cams, not one with a rectangle on it. An A with 2 rings and two F's with a ring of squares. The one late K0 engine that's apart apparently didn't have one.

[Alan F.]

Well I wonder what the significance is then, more research!  And waiting for the seller to answer back...

Thanks Don I value your help.

[ekpent]

 I've read before but may be an urban legend that another reason besides emissions that Honda changed the cams and maybe some other tuning things was to give the bikes more low and mid-range torque especially when they started to be outfitted with fairings and turning more into cross country tour machines.
  Have you looked over on the Sandcast site yet to see if there is any info on real early cams that may relate to that rectangular casting ?

[Alan F.]

From MarkB's Sandcast #97 Restoration thread on page 34 during the teardown his cam is shown with the raised rectangle between cylinders 1 & 2.

[Jerry Rxman Griffin aka MuthaF'er]

It's been speculated on here that the rectangle cam may be F2/F3 which, if true, would be a good cam

[Alan F.]

I'm hoping to hear back from the seller with measurements, but that might be too much to ask.

[Don R]

  The two F2/3 cams I have here both have a series of rectangles in a ring near the speedo gear.

[Alan F.]

Heard back from the seller, but it was a 10% off offer. So for <$72 shipped I'll have measurements to post soon. I hope I didn't get suckered, the photos looked good.

[Don R]

Good Luck!

[Alan F.]

Thanks, I figured that was going to be all I'd hear from the seller so best to roll the dice.

[Alan F.]

  The two F2/3 cams I have here both have a series of rectangles in a ring near the speedo gear.

I think I found a photo of one. 77-78 K's just have a solid ring with rounded edges there all the way around I think.

This cam is NOS going for $600 Canadian.

[PeWe]

For half that price a new cam from CycleX. CX-1 for stock engines.
The 77-78 cam with a molded ring beside tacho gear was often found cheap used.

I bought one from Canada for $50US when buing other stuff 2 years ago. Look like a low miler. Same seller wanted more for the earlier cams that had been taken from K1-K6 bikes.

My K2 has one 77-78 cam.
It was included in a cam holder deal with rockers and shafts. For around $100US ca: 5 years ago.
Tricky to find good rockers) cam holders today. Often in bad shape with flaking/damaged chrome.
Cmsnl sell a complete set of 8 new for 215 Euro + ev VAT.

CycleX sell welded for $495US.

[Don R]

 My 750A cam has a pair of rounded rings all the way around. I'm told they are a good torque cam. I'm not sure why.

[bryanj]

The A only had 2 gears and needed more torque

[PeWe]

Lower lift on Automatic cam?

[bryanj]

Different duration

[Alan F.]

There was a guy around in the past few years who had a cam oiling failure and needed different parts. He wound up with an A cam and thought it performed quite well.

I'll have a look and add the link here.
Edit: http://forums.sohc4.net/index.php/topic,183386.msg2122394.html#msg2122394

This is the one, according to JerrodR who Frank said the above quote to... The A cam was superior to his previous cam. It's time for me to look at the specs on those. Jerrod hasn't logged in since April '21