CB250G5 Engine rebuild, high pitched noise

[boxie30]

 
 I have finally managed to start the bike with both cylinder firing.

 I now have a new problem, there is a high pitched "squeal" !

 I presume it is the camshaft rotating in the head, as the G5s do not have a bearing to spin on.

 Is there a way to check if the camshaft is getting enough oil without stripping it all down again?

 Or should i let it turn over for a while to make sure the oil pressure is forcing oil up to the camshaft?

[K2-K6]

Eewh, that description doesn't sound good.

 If you think it's the cam, you shouldn't run it at all as it'll very quickly trash itself. Any problems of cam bearings not being lubricated needs correcting before you can run it really. I'd certainly hold off going further towards making it expensive by even turning it over.

I'm not that familiar with specifics of oil route etc on these so would defere to others with more informative knowledge.

[Woodside]

sounds like a lack of oil to the top end..hope not

[AshimotoK0]

See other reply..bad news if top end squealing and cam seizing as it runs directly in the head (achilles heel of that engine). Whole  top end and barrels can be removed from G5 without taking engine out of frame on that model.

[AshimotoK0]

Fairly easy to remove head cover ..That's what  I did on the 2k miler I sold earlier this year..you only need a breather gasket to do this. I do have a spare head,cam cover   and cam but  not sure what state they are in ..no rockers though. Will be week before I can get  to my stash as the owner of the building is away.

[Darkness]

Have you had the clutch cover off by any chance, oil pump drive sits under there and easy to not refit it correctly and it stops the pump working, that was on the CJ250 which I think is the same engine, don't ask me how I know this it gets embarrassing.

Yes, same engine, but with starter motor and 6th gear left off.

If pump drive not engaged properly you can't pull the clutch cover tight on the gasket, which is something I'd prefer not to have discovered!

If you suspect the cam isn't getting enough oil you should pull the cam cover off and turn the engine over by hand until oil appears [Or not] as the cam bearings don't last very long at all if spinning dry.

That wrote off a lot of G5s back in the 70s as repair was prohibitively expensive!

[boxie30]

 
Taken the rocker head off and there is oil all over the cam and  most importantly over the cam ends where they sit in the cylinder head, So i am getting oil!! There is no scoring in the heads where the cam goes it is perfectly smooth.

 A bit of history of this engine. Got it as a non runner, stripped the engine down completely, got it soda blasted and painted and then I reassembled it.

 Run it for about 2 minutes and tried to put it into gear to check it was all working and it died straight away, with a bit of a crunching noise.

 Took the engine out and removed the crank case to get at the gears. Realising that i put the 1st gear cog on the wrong way!!!!!.

 Reassembled it and refitted, got the points sorted and restarted.

 I did not get the noise when it was only running on one cylinder, the Right hand side. Only when i got both cylinders to fire that i got the noise, which is coming from the Right hand side.

 A couple of questions:

 Would a piston ring, put in upside down cause this?

 Would the cam chain tensioner being too loose or too tight cause it?

 Cheers.

[Woodside]

this was the carnage when i had no oil up top on my cb450

http://www.sohc.co.uk/index.php/topic,7681.msg48977.html#msg48977

[Darkness]

Hi Boxie.
Any development on this?
A few questions in my mind are:
You say it only started squeeling when you got it to run on both cylinders. Does it stop squeeling if you take a plug lead off?
Left, right or both?
Does it make the noise in gear (On centre standard), or only in neutral?
Does it stop squeeling when you pull the clutch in?
This may narrow it down to output part of gearbox, or engine.
What did you take off or move to get it to run?  I would repeat the process looking for marks or signs of heat.