E: Engine Exhaust valve not right

[evcomet]

I always give the upper valve guide more clearance just for this reason. You can do all the work on the lower valve guide, but there is no guarantee that it will put the stem exactly in the center of the top guide. I suspect there was a substantial misalignment to get the top guide to gall. As Greg said, check the lower guide for fit. Check to see that the button on the valve is not to worn. It probably is not too worn, but you can certainly see where it has been working. Get some extra circlips if you do not have a supply.

You can polish the stem. I keep new valves in the shop so I am not tempted to use old ones. I don't know what the free height of the stock springs should be. I have been using Gold Star springs instead.
View attachment 22877
The new spring is on the right. The Vincent spring is considerably longer and owners rarely replace them.

Good luck.

David

David,

So which spring should I buy, the one from Coventry or search for the Gold Star spring?
Should I replace intake spring at the same time?

Jerry

 

[evcomet]

Jerry it is a mixture of mist and splash as the oil passes down from the rocker feed bolts on the oil return pipes across the top of the head. I wonder how tight the cylinder hold down nuts were, when they are done up too tight this can distort the head and cause misalignment of the upper and lower guides, which may explain the top guide seizure. You should be able to refit the upper guide temporarily refit the valve and "Feel" some slight play sideways of the valve head in several directions. If the valve is very snug with no play, then the guides might need reaming slightly. Being air cooled they tend to need some running clearance as the engine temp climbs more so than a modern liquid cooled engine. You might be able to polish the valve stem, lubricate and assemble, and all will be fine. The cylinder head hold down nuts should be torqued to 30 to 32 Ft Lb's in an even opposite manner. Use either some oil, grease, or anti seize on the threads, and be careful to align the pushrod tubes as you lower the head back onto the barrel. Cheers and good luck..............Greg.

Greg,

Thanks for all the great advice. Hope to have it all back together this weekend.

Jerry

 

[Bill Thomas]

Not seen that before, As David said, I would think it was not in alignment, Badly !, The top guide is a bit tight
in the head on some, Which is OK, As long as it's pushed home flat, I wonder if it was not seated flat when fitted, I would check the valve is straight ?.
I wonder if the fault is in the bottom guide, Out of alignment ?.
Well done finding the fault. Bill.

 

[Bill Thomas]

Fit standard springs and check the alignment of the inlet , The valve should be move free, unless the inlet has an oil seal, I would change both top guides, Maybe they where not made of the right stuff ?.
Cheers Bill.

 

[greg brillus]

Jerry, You should change all the springs (all four) just to be safe, they are not expensive, although waiting for parts might hold you up. As David said it is good to have some spares of the small circlips as these disappear forever under the depths of a workbench never to be seen again. I can see your frustration as the bike looks very nice and had some time and money thrown at it. Unfortunately these things can happen to any of us, even those who have been around these bikes a long time still get caught out now and then. Just keep asking away............Cheers............Greg.

 

[chankly bore]

A couple of tips to aid reassembly. Make sure the gland nuts, ET127 are at the top of the tubes when you put the head back on and try to get used to the "feel",height and position of the pushrods in the cam followers at T.D.C. compression as you'll be inserting them down through the rocker eyes after fitting the head. Pen mark the pushrod height against the tube at a known height if it helps. The exhaust pushrod is a particularly devious and recalcitrant animal to position correctly. A good pair of pointy nosed pliers is a big help, as is a dob of heavy oil in the cam follower cup, so you can feel the stickyness when the pushrod is right. I have seen a large tyre-iron shaped tool screwing 3/8" B.S.F. into the rocker feedbolt thread with which old Speedway riders could change valve springs.

 

[timetraveller]

For road use stay with the normal valve springs. If you use the Gold Star ones then you have to change other things as well and there is no benefit at normal revs.

 

[A_HRD]

I think it was Clever Trevor Southwell who advised a simple modification for instances where a warped head was suspected. Simply machine a few thou from the large OD of the upper valve guide. This will allow it to float and allow the valve to find it's own centre taking the stress out of the complete assembly.

Peter B

 

[bmetcalf]

This tool https://www.homedepot.com/p/GearWrench-Valve-Spring-Compressor-912DD/205594537 can be used with the head in place. The end is hooked under a bar with suitable holes that straddles two head studs. To test it, I just reversed a head bracket to be the fulcrum point.

 

[Bill Thomas]

Anybody know what the top guide is made of ?, I know it's a kind of alloy, But it must sort of self oiling,
Even after years of an engine standing, It's not practical to take the upper frame off and lube, Before getting an engine going again.
And I have never seen this before.
Some people seem to put things together, With out lube !.
I was always told to assy' with oil or grease or something !.
Cheers Bill.