Doesn't sound good

[MBx2]

Hello

https://photos.app.goo.gl/Lczka93N3cYBWwwa6
*Edit. The clutch handle is held down in the clip so it's not engaged.
I have a 1983 CB 750 F2 RCO4

I have a worrisome sound from my engine that appeared a couple of days ago (or at least it is more pronounced). I've used a screwdriver and also a tube to try and figure out where the sound is coming from and I think I can hear it the clearest on top right where the valve cover is.
I also have a lot of condensations and soot from my exhuast (it's not in particular good condition).
It also vibrates a bit above 4000 rpm (which I thought was because of sync and timing).

What I've done:
Cleaned carbs following MacGregor Carb Cleaning Services "Honda Carb Manual rev G" and plugged the air cutoffs.
Replaced spark plug caps and wires
Cleaned contact surfaces
Measured valve clearance and adjusted it
Compression tests
Adjusted timing
New exhaust gaskets and a new pin bolt (broke one off on cyl #3)
Synced carbs
changed oil
Adjusted cam chain tensioner at idle according to the CB750 manual.
Removed and had a look at and cleaned the starter clutch

Spoiler: The Long story:

After all of that I have taken it for a short test run but I noticed that it was leaking a lot of oil from the tach gasket and only during load. Unfortanetly the oil lamp lit up just as I was in-front of the garage. So I replaced the gasket and changed oil, I didn't notice any metal when I drained the oil though the plug at the bottom. I ran with 10w40 mineral oil and added some zinc.

Later I took it for another test drive and I noticed it was vibrating when I was driving a bit faster. I also heard a ticking sound which I thought was the exhaust. So I ordered new exhaust gaskets and a new pin bolt because I broke one off on cyl #3. After I mounted the exhaust I took it for another test runt and it was still vibrating so i tried adjusting the timing again, Still vibrations so I decided to borrow a sync tool and I balanced the carbs. But I had to bottom out the screw between carb 3 and 4 for it to be ok.

Here's a picture of the exhaust "leakage", it doesn't smell so i suspect water and soot. Still it ain't good, the system is patched and a bit rusty.

This is how my spark plugs looks at the moment. I think I've run at idle for a while and before that I've been driving.

Spoiler: Measurements

Bellow is the valve measurements I've taken and corrected (the ones in bold are shimed) I also added the compression test I've done. I put everything in sequential order

Cylinder	First measurement	Second valve measurement	Compression test cold after new shims	Compression test warm after new shims	Third measurement when the problems were most noticeable	Latest compression test after running the motor for about 800km
1 intake	15mm, 9mm	13mm, 10mm	170	167,5	14mm, 13mm	165 (weaker battery)
1 exhaust	10mm, 11mm	10mm, 10mm			10mm, 10mm
2 intake	14mm, 15mm	14mm, 13mm	172.5	165	17mm, 17mm	170
2 exhaust	Too tight to measure, 8mm	15mm, 13mm			17mm, 16mm
3 intake	12mm, 8mm	12mm, 12mm	167,5	165	15mm, 17mm	175
3 exhaust	10mm, 11mm	12mm, 12mm			10mm, 10mm
4 intake	8mm, 14mm	14mm, 15mm	170	162,5 (weak battery)	16mm, 16mm	185 (started measure with cyl 4)
4 exhaust	13mm, 13mm	14mm, 13mm			16mm, 15mm

My next plan is to adjust the valve clearance, curl up into a ball and rock forward and backwards and hope it helps. Maybe having a look if there's something with the exhaust.

 

[MBx2]

I have given a bit more of thought and I think I need to have a look at the ignition as well (judging by my sparkplugs together with my valve clearance). I will do a spark gap test together with valve clearance and another sync when I have the time and update the thread. But I don't want to do too much of I need to split the engine for a bigger overhaul.

 

[dirtdigger]

If I had to guess the timing chain tensioner or guides broke. The plastic gets brittle and breaks off.

 

[MBx2]

Thanks for the reply. I fill some oil and see how it effects the sound. And after the valve clearance, timing and sync I migh empty the oil and remove the sump to look for evidence.

 

[dirtdigger]

You will be able to see the guides when you have the valve cover off to do the valve clearances.

 

[MBx2]

Ok! Thanks again. I'll update when I've had the time to check. And if I remember I'll take some pictures

 

[kirky]

my 1979 750FZ DOHC vibrates a bit above 4000rpm as well. but the engine is very quiet according to my mate who has owned a few. so this could be normal, anybody know if it is?