1974 CB360 Engine Troubles (I think)

Okay so I did some more compression tests today, both with carbs on and off.

With carbs on, compression on both sides was 70 psi.
With carbs off, compression on the left side was 80 psi and on the right side was 70 psi.

I'm a little confused about the readings because I'm able to ride the bike without any problems (besides the smoke and ticking) so what could be causing such low compression?

So I just got done doing the cam chain adjustment, and am waiting for the bike to cool down. Hopefully I can do it by tonight.

Should I retest compression after the valve adjustment?
 
Yes re-test after valve adjustment. And BTW adjusting valves on a 360 is not fun. :p

Post a pic of your compression tester. Does it screw into the spark plug hole w an o-ring on it?

Are you turning the enigne over several times until the gauge needle wont climb any higher?

Pull spark plugs out of both sides when doing test to let engine turn over easier.
 
IMG_0028.JPG


So this is the compression tester I'm using, the only difficulty I've found is that the adapter doesn't screw all the way into the spark plug hole, but I haven't felt any air leaks while doing the test. I have also been doing it with both spark plugs out and turn the engine over for about 10 seconds, carbs off.

What I did find when taking the valve covers off, is that the left intake valve adjustment screw is missing :mad:

IMG_20170529_195250.jpg

IMG_20170529_195314.jpg


I'm going to try to get a magnet pickup tool and try to fish the screw out. Is this something that could have been causing all my issues?
 
You're pics are missing links for me, so I can't see anything, but you should have the compression gauge in one plug hole while a plug is still in the other. Maybe it doesn't matter, since the cylinders are separate. But, having a missing tappet screw will be an issue too. The valves need to be open to suck in air, and you need to suck in air to get compression. Missing tappet screw on the intake side means no air is coming in.
 
+1
I cant see pics either.
The threads on your adapter may not be correct pitch. Just dont try to force it and mess up plug hole threads. Compare adapter to the plug threads. The difference may be miniscule.

Or a plug may have been crossthreaded into the hole at some point in the past. :p

And yes you must find, install and adjust the tappet screw and lock nut. Fingers crossed it didnt jack anything up while bouncing around in there.
Intake or exhaust screw? Im with Irk and assuming intake. If it were exhaust it would build pressure, unless its fucked up.

Just crank it til pressure maxs out on gauge.
 
So I updated my image links, sorry about that.

If I do have the wrong adapters (the one I'm using is the M12 which I read is the same size as the spark plugs), is there any place I can get the correct adapters?
 
Adapters should be right and fine as long as you're threading to the o ring. Regardless, with no tappet screw you're not going to get compression. That valve has to be able to open for the motor to suck in the air that gets compressed. By the looks of that cover, you've had something bouncing around pretty violently in there. Might be time to pull the cover and fully assess the damage. Maybe even pull the head and see what kind of shape the valve seats are in.
 
irk miller said:
Adapters should be right and fine as long as you're threading to the o ring. Regardless, with no tappet screw you're not going to get compression. That valve has to be able to open for the motor to suck in the air that gets compressed. By the looks of that cover, you've had something bouncing around pretty violently in there. Might be time to pull the cover and fully assess the damage. Maybe even pull the head and see what kind of shape the valve seats are in.

YUP.
 
First get a valve adjusting screw and locknut in there and set the valve clearances on all 4.

Next: borrow a compression tester from an Auto supply store and retest compression. Turn it over until teh needle stops rising - maybe 5-10 kicks/seconds on starter button.

Chinese compression testers have a nasty habit of reading low by a long way. I had one that finally read 30 psi on any cylinder...

The gouges in that tappet cover are from the nut and adjuster screw IMHO. You need to find them if you have not already done so. They cannot be left inside in the blind hope that they don't get lose.
 
IMG_20170602_201241.jpg


IMG_20170602_201412.jpg


IMG_20170602_201344.jpg


So I pulled off the cylinder head cover hoping it got caught somewhere in there, but still couldn't find the adjustment screw and nut. The thing is I don't really see any damage to the engine (besides the valve cover) so is it possible the PO just forgot to put back the screw? I also tried sticking a magnetic pickup tool but still didn't find it.

I'm also not sure I have enough time with school and work etc to pull apart the whole engine. If the screw is someone in there, would pulling off the left and right covers possibly get me to it quicker?

Also is it possible that the screw is just stuck to the very strong magnet near the oil drain plug (assuming there is one)?
 
Very doubtful the PO forgot to put the screw back in. There is a screw and lock nut. Most likely, it wasn't torqued well and vibrated out of its threads, fell down through the cam chain opening and into the sump. Only way to the sump is through the side covers, but no clear path to every nook and cranny of the sump through the side covers. You can only hope it's accessible without separating the case.
 
And if you do have to separate the cases, the best way it to flip the engine upside down and just remove the bottom case. All the confusing parts should stay inside the top. :p
 
Hey everyone I'm back again with some bad news. I've been stuck on this bike since when I was doing the oil change on of the bolts broke off and now the bolt minus the head is stuck in the engine. Thankfully my dad helped me get it out and all that's left to do is rethread the hole.

When I was tightening the bolts that attach the engine to the frame (they look like little triangles and have clips for the wires) I heard what I think was a snap from inside the engine. Now I'm freaking out as this doesn't sound good. But it just may also have been some other part on the bike that make a noise, I have no idea what to think anymore.

Anyway, when I was rolling my bike into the garage for the night i started hearing a tick when the bike would roll through one full rotation. Could something have broken inside the engine just by me tightening those frame bolts?

PS I found the tapper screw and nut, got them out with a magnetic pickup tool 8)
 
Good news you were able to fish the tappet screw and nut out. :)

No, I dont believe you can break anything "inside" the engine by simply tightening frame bolts. Unless you somehow cracked the aluminum head cover (engine mount) the bolt is through.

Employ the fastener torque chart in the workshop manual I gave you. Higher # is for dry fitting fasteners, lower # if you use any type of lubrication on fasteners. I recommend using lube, whatever kind suits you. I prefer teflon thread sealant. Some use locktight, others use anti-seize.

Check to make sure drive chain has proper slack.
 
So I looked everywhere for the torque values for the header cover bolts but I couldn't find anything. Not even in the manual.

How do I check to make sure the drive chain has proper slack?
 
I should really start using the manual you sent me I've been using this really torn up old manual but it doesn't seem as detailed as the PDF.

Thanks for the info, hopefully this bike will be working soon, I want to ride so bad
 
rsjudka said:
I should really start using the manual you sent me I've been using this really torn up old manual but it doesn't seem as detailed as the PDF.

Thanks for the info, hopefully this bike will be working soon, I want to ride so bad

Agreed
 
Guys I feel like I'm almost there!

So I did the valve clearance adjustment, and when I started it up there was a loud ticking noise (I'm assuming because my tappet screws were too loose?) but no smoke and sounded much more powerful! Could the ticking be because I didn't do the carb sync yet?

Also, when I was doing the adjustment, I couldn't get it exactly on the LT and T mark, because anytime I tried it shifted like 1 cm over by itself. Is that bad?
 
Back
Top Bottom