Topic: Camshaft bearing grease problem?

[Gustlock]

Hi all!

My name is Gus, 21 years old and bought my first bike/project last summer (1976 CB750F).
Couldn't enjoy the bike for a long time because it jammed during a trip with 180 other bikes
After about 50km of driving (countryside so a lot of accelerating en decelerating) the engine was pretty warm. The last 1km was through a town and since I was one of the last bikes it was slow going (10 kph max like a traffic jam). I knew she was pretty warm so drove her easy to the end of the trip. 100 meters before the end of the trip I wanted to accelerate again and the throttle didn't respond First checking it was in gear I realized the engine stalled. I tried the starter but no response, the I tried the Kick-start but it was jammed.
My thought was she was overheated making the pistons expand and jam. After about 20 minutes I was able to rotate the engine using kick-start and could feel compression on all 4.
Just to be sure I brought her home on a trailer

Yesterday I removed the engine. Somebody told me he thought it was an camshaft grease problem. I checked the camshaft and found some wear. This is my first project and I can manage assembling/demounting stuff
The problem is I don't know what is damage and what is normal wear Just don't have any experience

What is your opinion? Please let me know, it would help me a lot

PS the 'scratches' don't seem very deep, I can only feel them very light with my finger nail

[MCRider]

That's on the high side of normal, certainly nothing that would shut down the engine. "grease" is not proper, the cams are lubricated under high pressure with engine oil. If there was a problem there it usually manifests itself quickly and catastrophically by twisting the cam shaft in half.

Keep digging and supplying pictures.

[Gustlock]

Hi MCRider,

Do you mean the wear is still acceptable? I know greas is not proper but I couldn't find the correct translation for oil lubrication

Some more pics 






Just a small bonus


Is there a trick to remove the cooling ribs section (don't know the correct translation ) from the engine? It is attached with a "liquid" gasket and I can't pull it off

[MCRider]

Yes to me that much wear is acceptable and i would continue running those parts.

Didn't realize you were translating, you multi lingual guys blow me away, I have a lot of respect for that.

My two languages are American English and English English, though I struggle with the latter.   

Looking at the valves in the head, the 1 & 2 cylinders were running OK, the 3 & 4 cylinders are all black and were running richer I'd say.

The cooling fin area is the "cylinders". It appears you have all the holding bolts and screws out. If the pistons seized to the cylinders, they may still be holding onto the cylinders interfereing with the removal of the cylinders. You did say you got the engine to turn over after it cooled? If it truly got hot enough to seize the pistons to the cylinders, then the gasket between the cylinders and the cases got cooked too and is resisting the removal of the cylinders.  You mention it was attached with a "liquid gasket"? This is a big NO NO. It could be an adhesive type gasket sealer and you will play heck getting it off. A heat gun may help.

In a good engine (one that had not seized, and had a paper gasket) I would place a small chisel at the point where the cylinder block seams to the crankcases, and tap it, moving it around the seam until the seam lets go. Gotta be careful with this though, don't want permanent damage.

[Jerry Rxman Griffin aka MuthaF'er]

Sometimes by turning the crank the movement of the pistons upward will loosen the cylinder. Best way to do this is by turning the alternator rotor with a wrench on the bolt. A rubber mallet used to carefully tap straight into the fins may help also but do not tap at an angle and break fins.

[MCRider]

Sometimes by turning the crank the movement of the pistons upward will loosen the cylinder. Best way to do this is by turning the alternator rotor with a wrench on the bolt. A rubber mallet used to carefully tap straight into the fins may help also but do not tap at an angle and break fins.

Especially if they're (partly) seized!   

[voxonda]

I am the guy that suggested his oiling problem in the cam area. If I look at his cam, still coinvinced he had a problem there look at that blue colored bearing area. His engine stalled with low revs, and was jammed until it cooled down. Think he was lucky there, If he had ridden at that moment with hogher revs, think he would have broken his cam. Just my opinion.

Rob

[Gustlock]

Thanks all for your respond! I will give the cylinder another go tomorrow
@Voxonda, It's a small world I'm also convinced now. Just have to find a new cam+"cam holder" at a reasonable price...
I will also check the lubrication so it won't happen again

Is this just bad luck or does it happen more often with these engines?

Thanks again!

[voxonda]

Hey there Gustlock,

Yes, small world indeed. Check out the nozzles in the cylinder head, remove them and clean thorough. Is very important.
Change oil in time. Keep your eye on the oil pressure.
It is known to happen to these engines, but they can last forever if treaded allright.

Cheers, Rob

[Gustlock]

What is the most effective way to clean them? Hot water like with the carbs? Ore maybe fuel or alike to solve the oil in the nozzles?
Do you happen to have a camshaft+camholder for sale?

[eastoak]

i agree with MCrider those parts look fine to me if you don't want to use them send them to me

[MCRider]

Hey there Gustlock,

Yes, small world indeed. Check out the nozzles in the cylinder head, remove them and clean thorough. Is very important.
Change oil in time. Keep your eye on the oil pressure.
It is known to happen to these engines, but they can last forever if treaded allright.

Cheers, Rob

I'll definitely defer to you Rob especially if you've seen them first hand vs a picture. To gustlock, losing the pressrue in the cam area usually comes from some debris blocking the oil orifice that Rob has referred too. Usually from a recent rebuild. Otherwise there's rarely debris in the engine unless the cam chain tensioner loses rubber bits or the primary chain tensioner does. You'll want to pull the oil pan and check the pump screen for debris/clues.

[bryanj]

Show us a picture of the pads on the rockers that run on the cam lobes, i suspect the ones from the "blue" side will be worn.

I have one usable cam tower with rockers and a one cam left here in UK if you are interested

[voxonda]

What is the most effective way to clean them? Hot water like with the carbs? Ore maybe fuel or alike to solve the oil in the nozzles?
Do you happen to have a camshaft+camholder for sale?

Got some here, cams and holders.

Rob