Bump Stick to lumpy???

So I'm having problems with a camshaft that I purchased a few years back for my '69 cb350 twin. I had to rebuild a small engine for a college course and decided my misfiring, oil blowing 16th birthday present would be a great candidate. While going thru the rebuild and correcting the shattered piston rings and re-boring the cylinders I decided to go with a .75mm overbore and found a hopped up cam to go with it on flea-bay. The gentleman I bought it from informed that all he could remember is that it was a hot cam he had bought in the early 70's for a cb350 twin chopper project that never got completed. The cam looked (and still does) to be in great shape with no wear visible on the lobes, so I paid $25 with shipping and then tried to install it with no avail. To pass the class I ended up stuffing the original camshaft in to get the motor running for my final grade.

Fast forward a decade and now I'm tearing into the engine to re-install the kick starter shaft retaining spring and see if I can swap the cams in the process. I've attached some pictures of the original and the "new" cam side by side for reference. It looks like on the first lobe of the points end of the cam it has a 104 stamped into the side of the lobe. My big problem with this cam is that it seems to have so much lift that it's causing the valves to bind up and I can't rotate the engine over, I reinstalled it last night to verify this problem again and somehow broke one of the rubber inserts at the base of the cam chain tensioner.

If anyone can shed some light on what I could do to correct this problem I'd appreciate it. I'm mainly looking to use the bike as a "hot" street bike to run back and forth on errands and pleasure trips thru the canyons of Utah.

The cam at the top of the first pic is the original, as well as the left in the second pic.

Here are a couple of more pics with measurements of the new cam lobes. I tried to get the maximum lobe height on each one. If anything else would help as far as pictures, or measurements let me know. I'm at your mercy :-[.

Try it with just the inner springs to see if that still binds teh spring coils. If it does, get a light spring from the hardware store to test it. What you need to know- before you buy a set of springs and caps is does it lift too far for the guides etc, or does it just need springs with less coils.

It looks like a full drag race cam with lots of lift and will need race valve springs but it may also need shorter guides and taht's what I was talking about above.

There's also the small issue of Late versus Early cams to consider.

Thanks Teazer, I'll see how it acts tonight with just the inner springs and let you know, I'll also try to see if it's hitting on the valve guides at all.

You've got it backwards. Your original cam is the hot one, the early or Type 1 cam. It's also referred to as the fat cam which is a misnomer since the "fat" describes the shaft and not the lobes. Yes, it sounds counterintuitive that the smaller lobes are higher performance but they make the motor spin faster with a higher redline. The later skinny shaft cam binds because the rocker arms are have more offset from the rocker spindle. Early rockers and camchain sprocket are not compatible with later cams and vice versa. Count yourself lucky and stick with your original parts, those are the ones every CB350 owner is after.

DrJ. That may be true in reference to early and late OEM cams, but his cam is reground to a race profile of some sort. You can clearly see the weld where it was built up.

The question still remains which series cam he has and which series bike. If the cam is early and the rockers are late, or vice versa, that could be an issue. His is a 69 and therefore early yes?. And he would need late type rockers to go with a cam with larger base circle.

DRJ, the "hot" cam that I purchased actually mounts up just fine to the stock cam sprocket, it just has so much lift everything binds up, I'm going to try what Teazer suggested and see if I can tell where it's binding with the outer springs removed, I think I'll also see if I can rotate the cam with the head removed to eliminate any stress on the crank sprocket.

On another note is there a clear identifier between the early and later style rocker arms? Do I also need to get the later eccentric shafts for the rockers as well or am I good to run the original eccentric shafts? Thanks again for the help!

Well between kids and other conflicts I didn't get much accomplished on the camshaft tonight. I did how ever verify that my rockers are the early type to match my original cam (no real surprise there), they have a 19 cast into each arm and from what I've found online trolling the web the early arms all have a 1 as the first number on the castings.

I did get the cam re-installed with the head off of the cylinders and no cam chain, however with both springs installed I couldn't tell if it was bottoming on the valve guide or not, hopefully I'll have some time later in the week to remove the spring and look. If anyone has a line on some "late" rocker arms I'm really interested to see if they make any difference. Currently it looks as if the "early" style rockers all line up on the valve stem and cam lobes properly I just can't turn the cam thru even half of a revolution.

Just for kicks, here you can clearly see the build up on the "newer" cam and the "104" stamped into the side of the lobe.

Thanks again for all of the help.

I don't think I'll be getting much done on the cam research this weekend, I had my plans changed for me and had to leave base to rush to the hospital with the wife yesterday. Hopefully I'll get to look at it in the next week or so. On a brighter note though I get to bring home a great present tomorrow! ;D ;D ;D ;D

Congrats dude !!

Well I ended up buy a cam box with the eccentric shafts, rockers, tach & timing end covers off of flea bay for $45. 8) I took the time today to check the difference and was rewarded with being able to completely rotate the cam thru it's rotation with no problems. ;D I did this with cam box and cylinder head removed from the engine just to be safe.

I also decided to take some pictures of the two different style rockers before I send them out to be resurfaced by delta cams (long story involving seller "resurfacing" them for a small fee upon purchase that looks like a die grinder was used ) Enough talk, here's the pics.


"late" on top "early" on bottom


"early" on the left, "late" on the right, notice the 312 cast into this one vs. the 19 cast into the "early" rocker arms.
On the early arms the 19 is cast into the long side of the pivot bore, on the later arms the 312 is cast into the short side of the pivot bore. You can also see a slight indent in the top of the later arm, all 4 of them are like this where as the early arms have no indent/divet.


and last the follower pads (notice the nice ridges in the "late" rocker face )