engine starting problem

[tc.young]

ok guys, new day new problem.

going to recheck my valves and timing, i go and take off the 8 valve cover bolts. the top right one is free-spinning and there's oil around the rubber.

let's see if you can spot the problem.




here's a reference of what it should look like



did that part really sheer off? stay tuned kids

[tc.young]

well i don't think timing caused all the damage. rather a bit broke off and messed up everything.



broken bit


2 rockers broken


here's some pics of the bike at the shop

[keman]

Looks like a few of the adjustment nuts are gone too. Our did you have those off before you took the pic?

[tc.young]

took them off, i could use them on another project while i worry about this.

[tc.young]

out of curiosity, anyone know what other engines will directly swap in. i'm guessing the 83 750 would. any others? might swap, ride a little, rebuild this engine and then sell the bought engine when done.

[Normk]

That cover mounting boss is, of course, part of the cam bearing cap. The cap is unique to that position on that specific cylinder head so cannot be replaced by another cap. I am sure that everyone knows this but just in case.....


The cylinder head and caps are cast separately and have their mating surfaces ground flat. The caps are screwed in place and then the camshaft bearing bores are bored/machined so that the camshaft is positioned at the correct distance from the head gasket surface and is aligned correctly. This means that the caps are unique for each location as is the case with connecting rod caps and similar installations. While one might find two parts which can be interchanged, I would not bet the deed to the family homestead....

That boss can be repaired by someone who is experienced in repairing such parts which makes it a pity that you are so far from here as my friend Iron John would make an effective repair. I have done similar repairs using a material called "aluminum solder" which is a lower melting temperature alloy used for aluminum work in much the same way as is lead-tin solder or brazing rod for ferrus metal work.

It looks like there may be sufficient remaining thickness in that cap to allow a stud to be inserted with a spacer. We used that strategy in many similar repairs to various aluminum installations with great success.

The stud hole can protrude all the way into the cam bearing bore so long as the bore is deburred and that the stud does not protrude (not rocket science there!).

In this repair the broken surface is milled or dressed flat with a file and a spacer of the correct thickness to replace that of the broken piece is placed. I like to JB Weld or otherwise epoxy the piece but this is likely redundant if a shoulder stud is used. I like the practice of keeping things in place if fasteners are removed.

Take care in assessing your options as you will have a problem if that cap is destroyed. Replacing is not impossible but may prove to be expensive unless you can enlist a machinist who finds the project to be of interest.

In order to substitute another cap, the procedure is to grind the mounting surface of the substitute cap to reduce the radius of the hole. The cap is screwed into place and then the hole is bored back to diameter. When doing connecting rods, this is a much less difficult operation as the position of the resulting hole is not very critical.

In the case of the camshaft bearing bore, however, the bores must all be concentric or the camshaft will bind.