Very loud screech then siezure

stampmoney · Post by **stampmoney** » Mon Aug 13, 2012 11:19 am

Hi
I have just started a CB77 305cc engine after a very long time standing, perhaps 15 years. (New oil etc) It ran for about 5 mins then shreeeeeked like mad and stopped. Re started engine and after 10- secs same shreek and siezed.
I removed the alt plate and by spanner turned engine over, very stiff at first then better, getting free but a screech at one place. After 100 turns = no screech and very free. Started up, ran for 30 secs and VERY loud screech and stopped.
Turned crank with spanner and free to turn !!! Compression test = 160 psi on both.
so,
The screech sounded like it comes from the cluch area or the middle of the engine behind and under the cam tensioner. Not from the head. Oil is all over the rocker gear, so assume pump working.
How do I test for oil pressure? Is it possible? Is there any reason for a bearing in the gearbox to sieze up on idle?
PLEASE HELP? Any ideas?
Peter

G-Man · Post by **G-Man** » Mon Aug 13, 2012 11:30 am

Peter

I would drain the oil out and check for anything in there which would give you a clue. Also take a look at the centrifugal oil filter and make sure that it's cleaned out.

The screech may be the starter clutch but, whatever it is, it isn't a good noise. Sometimes the countersunk screws at the back of the starter clutch wind out and snag, so that is a possibility. My CB77 engine had that problem.

It would be worth pulling the rotor and starter clutch off to have a look. I think that the 'extractor thread' in the rotor is M16.

Take care

G

stampmoney · Post by **stampmoney** » Mon Aug 13, 2012 12:16 pm

Hi
Thanks for your reply.
I have removed the oil thrower and I cleaned it out before running. The screech comes more from the cluch side than the starter motor side. It also stalls the engine as a siezure of pistons would, but it "cools" off after a while to free up. That suggests a plain bearing, but it is not a crank bearing. That is why I suspect the gearbox.
Is it possible to run the engine with the primary chain removed??
Peter

G-Man · Post by **G-Man** » Mon Aug 13, 2012 12:42 pm

Peter

If you remove the primary chain, you can still run the engine but will not be able to kick start it, although you will be able to use the electric starter. To get the chain off, you will have to remove the oil spinner and clutch. I would put the spinner and clutch cover back on before you run the engine.

The plain bearings (2) in the gearbox are pretty small and I wouldn't expect them to seize in that way. With the clutch cover off you will be able to see the gearbox shafts on that side.

Let us know what you find.

G

stampmoney · Post by **stampmoney** » Tue Aug 14, 2012 3:21 pm

Hi G
10/10.

The 3 set screws holding the starter clutch to the alternator stator were snapped off (1) worn down to no screw slot left and in contact with the casing and and the last one was loose, just starting to contact the engine case.

Re-fitted starter clutch and it runs with no screeeech.

Great advice.

Peter

G-Man · Post by **G-Man** » Tue Aug 14, 2012 4:49 pm

Peter

Great news. Nasty sounds always appear to come from somewhere else....

Glad you got that sorted.

Send some pics of the bike when you get a moment.

Cheers

G