1970 CL450 engine rebuild

[ducridersantafe]

Hi all, I'm new to this forum and have a few questions about my current project. It's a 1970 K3 CL450 frame number 4000017 engine number 4000035.

It was not running when I bought it and it turned out one piston had a hole in it and an inlet valve was slightly bent.

I am re-assembling the head and the intake camshaft went in very nicely but the exhaust camshaft is binding.

Side note: I found used replacement valve followers and valves on eBay, the original followers were worn and the replacements are in much better shape. Both the original and replacement valves are 96mm long intake and 100mm long exhaust.

The timing mark on the inlet camshaft is a chisel mark, but on the exhaust camshaft, it's a dot.

Is it possible that a previous owner used a different camshaft and valves at some point? The manuals I have don't specify what the correct valve length should be or whether my model should have a hi lift camshaft or not.

Should all four valves be 96mm or is it normal for them to be two different lengths?

Should the timing marks on both camshafts be either a dot or a chisel mark? Which type should be on this bike?

Any help or advice would be greatly appreciated. Thanks, Terry in Santa Fe

 

[Whitey80]

I own and have done dozens of of CB/CL450's

I can answer a couple questions quick, and go out and measure some parts from my bin in a while:

I have only ever seen the hash marks on stock cams, but that doesn't really mean much.

When you say the exhaust cam is binding, what exactly is stopping it? Are you rotating it against the follower and pushing a valve into the piston, is one of end caps or cam end oblonged, is the chain binding from improper routing through the upper chain tunnel?

 

[ducridersantafe]

Hi, thanks for the quick response. The cam doesn't turn easily once it's installed. It's rubbing against the cam followers even when there should be no contact. The cam chain isn't installed yet so that's not it. I'm thinking the valves are too long but I don't know what length they should be.
The camshaft rotates smoothly without the followers in place.
The freshly reground valves seat properly without the camshaft in place.
The A+B torsion bars are installed correctly and the lifters have no play under the valve clips (which makes me think the valves are good, but the camshaft is not correct)
I've checked the camshafts end for possible hash marks, but the only one I can see is a round machined dot.
Thanks again, Terry

 

[Flugtechnik]

This may be a dumb question, but have you tried adjusting the cam followers? Does the cam hit them at all positions of the eccentric adjusting shafts?

Did you have the valve seats recut?


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[ducridersantafe]

Hi, thanks for your response. Yes, even adjusted all the way, they still push up against the cam lobes. Even at this point of the cam rotation, both valves are open. Either the valves are too long or the cam is incorrect. Seems to me at least......
Thanks, Terry

 

[Flugtechnik]

Did you have the valve seats recut? Do you have a picture of the cam?


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[ducridersantafe]

Hi, sorry, yes, the valves and seats were recut, but not by much. The camshaft is still in the head, but here's a couple of pics.

 

[Flugtechnik]

I just did a quick google image search for cb450 cam timing and found a picture of another cam with the punch. I don't think there are any other cams that look like the 450s. I think the later 500s even used the same cam.

So there are two possibilities. Either you have the wrong valves, or recutting the seat changed the geometry too much.

I suspect it is the seats. It doesn't take much depth change to screw up the geometry.

Hopefully someone has a valve they can measure for you to rule that out.

To fix the geometry, you just have to shorten the valve.


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[Flugtechnik]

BTW, I had the exact same problem on mine after I had the seats recut.


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[ducridersantafe]

Thanks Michael. I asked a seller on eBay what lengths his NOS valves are and he told me 96.5 and 100mm, mine are 0.5mm shorter. I'm really leaning towards it being the wrong exhaust cam at this point because of that timing mark, but as I said in my original post, I'm not all that familiar with Hondas, I prefer vintage Ducatis.
I have both a Climbers and Haynes manual and they both mention that at some point, the valve lengths were changed, but they don't specify when and to what length.
Plus, there are three sets of cams on eBay right now and they all show hash marks rather than dots.
I'm really hoping all this work is going to pay off!
Thanks again for your help, Terry