Topic: 78 750F oil starved head

[strawhouse]

Good Day!
Question for the group... last summer riding my 78 750F I broke the cam... actually sheared the cam off in the cam tower! Luckily it didn't bounce around in the head, the cam tower held it in place!  Even with half a cam I was able to run it!

And yes the valves were bent and very sad.

So Ive torn down the engine, and got a new head and pistons.... Im concerned about oiling and if its still an issue, possibly in the lower half of the engine.

Here is my question, if I use the kickstarter by hand without the head on should I see oil emerge from the two rear studs?  Or does it need the head on?  And yes I have secured the cylinder so it does not come off the block.

[Terry in Australia]

While I've never busted a cam, the top end of my first K1 was destroyed due to a "mechanic" using silicon sealant on my bike, some excess silicon got into my oil and blocked off the oil jets in the head. The cam, cam towers, rockers etc, were all cooked, and the pistons seized in the bores. Uggghhh.

Anyhoo, yep, that should work, why not hook up a battery and use the electric leg? Have you determined the cause of the oil starvation? What's the oil pump like? Before you do much else, pull the pump out and pour some oil in one of the ports and turn the gear, you should be able to see the oil passing from one side to the other. I like to submerse my oil pump in a container of oil and pump it through, the pump should feel smooth in operation.

If you've got access to an air compressor, make sure you blow air through the oilways in the new head to ensure the oil ways and jets aren't blocked. Cheers, Terry.  

[strawhouse]

Thanks Terry
Yes im getting to the point of doing the investigation to see where the problem originated.  Ive cleaned out as much as I can at this point and I am just about to remove and inspect the oil pump.  I was just curious if I could see the oil being pumped out with the head off.... kinda out of interest sake to see if the pump was at fault or not. 

I really have no idea what happened, obviously dirt or something got into the head or oil route and starved the 3+4 cam tower and sheared the cam.  Ill try turning it over with the electric start and see if I get oil on both ports on the cylinder... Ill report back!

[flybox1]

If you think the bottom end is where the blockage is/was, why not give it a good wash if you dont want to separate the cases?  Start your rebuild knowing there's nothing to prevent top end oiling. 

The oil passages in the bottom end are quite large compared to the oil jets @ the head, and into the cam tower.  Pull these tiny jets.  Blow thru them and the passages in the head with carb cleaner, compressed air, as well as the cam tower passages.
Clean and or replace the oil pump screen.  Anything large enough to get thru the screen and pump will back up just below the oil jets.
If the screen is compromised or doesnt seal well, replace it.

 

[Old Scrambler]

All good advice............I have one of those '2-piece' cams..............I tested the oil system with the head on but no valve cover before installing in frame..........just have rags ready

[ekpent]

 Probably a plugged oil jet if just one side of the cam shows major damage upon inspection. Just put one of these back together. Be a good idea to pull out the clutch basket when you are cleaning everything up inside as there are hiding places for metal in that area and unscrew the cap where people mount a pressure gauge and clean out that main oil passage well while you clean and flush everything else. There are also 2 caps on the bottom of the case the same size as the oil passage right under the crank,makes a good drain if you flush out that area if not splitting the cases. Good time to check the valves for leaks and give them a lapping if needed also. Have fun.

[strawhouse]

Thanks guys for the great advice...
I just got in from the shop, I was able to get excellent flow out from the cylinder two rear studs by using the electric start... Glad to see the oil moving!
Next I pulled the oil pump and gave it new seals and reprimed it and reinstalled it. I did find a bunch of hard chunks of something in the bottom of the oil sump.  After washing them off it appears to be some form of sealant....  I'll give the case a good wash and try to find where the sealant was applied....

Looking like sealant was the culprit, a bloody piece must have found its way into the oil jet under the cam tower and clogged it!

[Terry in Australia]

Yeah mate, silicon sealant has killed more CB750's than just about anything else, but "hard chunks of something" could be your cam chain or primary chain rollers falling apart too, so check 'em out while you're at it. Cheers, Terry.

[PeWe]

I'm worried too. I have never been that before nor had the problem. Reading about it here make me alert.
- The problem must start where the cases are joined together over the oil filter. (I used no sealer around the oil channel that has the 183 O-ring.)
all gaskets dry
- Next the base gasket....only O-rings, no sealer....
- head gasket, only O-rings, no sealer
- Cam tower, only 4 o-rings and free orificies. Not too much sealer under the rubber pucks that in theory can float to the inner orificies if used way too much when tighten the cam tower bolts. It can be an idea to tighten the cam towers only after the rubber pucks are sealed, remove cam towers and clean the sealer that has floated out with acetone. (I have always some around the pucks.) Back with towers.

I'll be very concerned when changing oil and oil filter to not let any dirt enter the inside of the filter holder or case which has direct access up to the top....

If having that problem... I should remove head, cylinder and blow the oil channel to filter with compressed air + rinse it with something.
Same with everything else upwards. The cam holders might have old dirt inside.

- Anyone that has checked without tappet covers on at idle?
I'll might take a ride today....I need to go home earlier from my job and not sitting here writing on a forum
Since my engine has minimum of chain and clutch rattle, I hear other sounds I never heard before

[disco]

Hi PeWe,
All good advice there mate! Too much sealer can be a bad thing, especially when it in-advertantly starts floating around inside your engine! Best bet is to not use it at all or to use it extremely sparingly.

[flybox1]

Thanks guys for the great advice...
I just got in from the shop, I was able to get excellent flow out from the cylinder two rear studs by using the electric start... Glad to see the oil moving!
Next I pulled the oil pump and gave it new seals and reprimed it and reinstalled it. I did find a bunch of hard chunks of something in the bottom of the oil sump.  After washing them off it appears to be some form of sealant....  I'll give the case a good wash and try to find where the sealant was applied....

Looking like sealant was the culprit, a bloody piece must have found its way into the oil jet under the cam tower and clogged it!

If you suspect anyone was inside your cases, I think it would be prudent to split them open now, clean off any case sealant boogers, and re-seal it with one of the few non-hardening sealers recommended here.  Its likely the bits of sealant still hanging on will cause additional issues.
Do this while you have the engine out. It might take you 2-3 hours from split to finish.  I'd hate to see you have to pull the engine again to address the issue.