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1970 CB350 Rocker Arm Clearance issues after rebuild

hoffdahobo

Member
Joined
Jul 29, 2021
Total Posts
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Location
valdosta, ga, usa
Hello!

I've been working on a 1970 CB350 that is my father-in-laws. He told me that he got some head work done previously and that he is suspecting that it was done incorrectly. I validate this by trying to install the head and having zero valve clearance, couldn't get the side covers on with the valves in place. So I send the head off to be reworked and finally have it back. Installed the cam gear and cam which is the skinny cam and tried to install the rocker arms and pins in and now there is another issue. The covers go on smooth when its just the rocker arm pins and cam but to get the covers to slide on with the rocker arms in place i have to set the pins to be facing up (the little tick mark faces up). I can then successfully put the covers on easily but have almost no valve adjustment. I'm assuming that the shop I sent the head out to did the job correctly but I'm beginning to get really frustrated with this whole thing. The rocker arms have .8 marked on them and no other visual indicator. All these parts came out of the engine and was in the engine when it ran (almost 20 years ago) so unless he mixed and matched stuff i'm assuming everything is correct. I have put the left cylinder at TDC as well with both valves closed per the book and i can move the intake pins a very very small amount and the exhaust pins move but with some force. None of the valves are loose enough to make a ticking noise when trying to adjust. I can attach pictures of the valves/pins/cam/and cam gear if needed to help out. Thanks!

Other side note: The engine does turn over fairly easily when the rocker arms are in with the two side covers attached. No binding
 
You may have the wrong rockers to match the cam. The "fat" cam rockers have no identification marks on them. The "skinny" cam rocker have 312 cast into them. You can't mix and match these parts.
The fat cam rockers (286 middle number) have to go with that cam because they have longer ends to make up for the smaller base circle.
 
Here are some photos of what I'm working with right now. The only stamp number on the cam is shown as well as the rocker arms. The engine serial number is also attached. It's been quite confusing figuring out what is what and unfortunately my father-in-law doesn't know as well. Any guidance would be amazing
 

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You definitely have 286, fat cam, rockers.
Here's a comparison photo. 286 is top, bottom 2 are 312, skinny cam.
350 rockers.jpg
Note on the right side, besides the lack of a number, there's a large bump on top that's not present on the 312 rockers
 
So with that being said, my father-in-law told me today that the cam I have is not the original cam. He said he got my current cam from Honda and insisted he ran the bike with the skinny cam for awhile. I don't see how that's even possible. I guess I'll be on the hunt for a fat cam and sprocket
 
There's only one 312 rocker, we ID them by the middle 3 numbers, and those are the correct ones for the skinny cam.
You need 4, intake and exhaust are identical.
 
Thanks! I'm becoming paranoid with all this so the reassurance helps. I don't wanna spend money on parts I can't use yea know
 
LongDistanceRider said:
I understand completely on the paranoia and buying unneeded parts. We'll get you running
Click to expand...

So I got the rocker arms in and everything is finally lining up for the first time. I was able to get the valves adjusted and the engine mounted in the frame tonight. Now I'm thinking about the Boyer kit 00293 CDI to replace the ignition system that I'm actually missing. I don't have the mechanical timing advancer or really any component of the ignition system. Seeing that the CDI kit comes with an electronic advancer it sounds like it will save me money from trying to find an ebay one. I am in search of the advancer bolt if you know a good place to grab one? I have the washer for it. I thought i ordered the correct bolt earlier but it doesn't seem wide enough (the bolt just slides in the end of the cam and doesn't grab the threads).


https://www.britishbikebits.com/boyer-micro-power-igntion-kit-honda-cl-cb-250-350

here is a link to the CDI kit that i've been looking at.
 
The bolt for the end of the cam isn't special other than the dimple in the centre so a mechanical tach can be used. Its a M6x14.
The washer is hardened to work with the advance unit.
 
a m6x14 bolt is too small in diameter. Apparently a m8 bolt is the right size for the cam end. Something doesn't feel right about that but it fits.
 
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