Valve clearance puzzle

OK, I'm completely stumped by this one - and I'd really like some help, please. I'm restoring my friend's '74 Commando and just installed the cylinder head and torqued it down. I then adjusted the valve clearance as per the manual (and as I've done on mine several times before). Once the correct gap has been set and the nut tightened down, I recheck with the feeler gauge and all looks OK. Then, when I rotate the engine by hand and recheck, the right-sided inlet and exhaust are tight. I've looked inside again, and the tappet and push-rods are in the correct position. I then re-set all four and the same thing happens again! I've done this four times and it happens again. I don't have many hairs left on my head to tear out, but I feel like doing that. Any ideas?

Paul.

You're adjusting the valves by setting the right intake completely open and then adjusting the left intake, etc. and can't repeat the measurents after turning the engine two turns ? I can see why you're frustrated since I don't think it is possible. Let us know what you find.

Greg

Try Rogaine, my wife bought it for my scalp after the hairs fell out. Hair implants are an option but seems to me a waste until you fix the motorcycle issue.

if the cam follower is tight or sticking in the barrel you will not find any play after one revolution of the cam. Try to lift the rocker and thereby pushing the follower down on the cam base - your play should re-appear if this is the cause....

I use elastic bands to keep tension on all the components, push rods in holes and on cups etc etc.

What is the condition of the valve guides? I had this same problem on my Ducati GT back in 76. Drove me nuts trying to figure out what could cause it ! Ducati had a bad batch of soft guides that didn't last, and that's what I got. If the guides are worn oversized, the valve will not seat in the exact same place each and every time. Valve clearances will vary as a result.

Mike

Rubber bands cannot overcome the stiction of a sticky valve or cam follower, sorry.

As I lay in bed thinking over the problem, last night, instead of sleeping, I came to the conclusion that the cam followers were sticking in the tunnel. I then read your posts this morning and see that a couple of you had the same thought. Thanks. The followers were somewhat of a tight fit, but I polished them and they fit in better. I did oil them and the tunnels before installation. I think I should try to push the followers back down as suggested by WEAL Norton and wait until I can run the engine briefly, then re-check them. Hopefully, the pressure they're under while running, as well as higher oil pressure will settle them in.

The head was completely rebuilt, Mike, so the guides are new. I suppose they could be tight, but I'm betting on the followers. Rogaine would have to be miraculous stuff to save me now, Torontonian but, thankfully, my is not bothered by my bald pate - or she doesn't want to spend money on a lost cause.

Thank you all, again, for responding - I'm grateful.

I'm thinking that you are going to have the head off and the barrel too. If the valves won't close, the motor won't run. Why are the lifters so tight ? Any chance that the sides were mixed up ?

Greg

Ran the SS as a 3S @ .016 as was told it wasnt what it was. If you looked real clos it was a S not a 3 .

So leaving clearance out a way initially shouldnt kill it , to let em settle in a bit .Dont give it the big rev though.
Mine was fine , BUT set 5 dg Early too , to get 3S timing . Still wanted to go straight past 7.000 rpm .

One needs the .040 clearance , in that lot . Had shimmed @ .040 off coilbound .A TANGLE wont help in there .

I'm almost positive I installed the followers as I normally would - i.e. with the bevelled edge toward the front. I know I kept them together as paired in the package. However, all this discussion has made me doubt myself, so there's no more to do but pull the head and barrel. Grrr.

Thanks for all your input, nonetheless.

Paul.

As a follow-up to those guys who suggested I take the top end off - I did, and sure enough the followers were extremely tight in the tunnels. They were installed correctly and, in case you were wondering, I did keep them as matched pairs. However, just to be sure that wasn't the problem (i.e. could I have mixed them up, inadvertantly) I swapped the followers and they still were very tight. I then put them aside as the original pairs. The tunnel appeared to be in good condition. I had cleaned up the old followers and tried them in the tunnels - wonderful fit with no play, laterally and they slide up and down freely. The faces were perfectly flat so I went with them. I then replaced the barrel and head and adjusted the valves. I can now turn the engine over several times and the clearances remain as set. I can only assume I received a bad set of followers. Has anyone else come across this, before?

Paul.

phsDommie said:

As a follow-up to those guys who suggested I take the top end off - I did, and sure enough the followers were extremely tight in the tunnels. They were installed correctly and, in case you were wondering, I did keep them as matched pairs. However, just to be sure that wasn't the problem (i.e. could I have mixed them up, inadvertantly) I swapped the followers and they still were very tight. I then put them aside as the original pairs. The tunnel appeared to be in good condition. I had cleaned up the old followers and tried them in the tunnels - wonderful fit with no play, laterally and they slide up and down freely. The faces were perfectly flat so I went with them. I then replaced the barrel and head and adjusted the valves. I can now turn the engine over several times and the clearances remain as set. I can only assume I received a bad set of followers. Has anyone else come across this, before?

Paul.

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I don't think they are bad. I think you simply got a set of .020 overs. If not too late, you may be able to swap them for a std. set depending on who you got then from.

phsDommie wrote,

I can only assume I received a bad set of followers. Has anyone else come across this, before?

Click to expand...

It has been noted before by others including myself on the forum that new camshaft followers often need a bit of dressing. This is done (by me anyway) by getting some fine wet and dry on a thick piece of glass and rubbing in a circular motion the flat sides that run against each other.

In my case it only took about three or four minutes and suddenly from a very tight interference fit, the followers were a perfect fit.

As far as I'm aware, they don't come new deliberately marginally oversize, but these wont be +0.020" if they have gone into a standard (basically unworn ) tunnel.

Just by chance, did you have the barrel sand blasted before painting?
Cash

Just by chance, did you have the barrel sand blasted before painting?
Cash


I don't think it was sandblasted but it's a good thought. I'll check on that. For what it's worth, I did thoroughly clean out the tunnels a couple of times.

Paul