Topic: Noisy tappets or exhaust leak?

[greddm]

1977 cb750, bike seems to run great after a full rebuild, but seems noisy. I've attached a video of the sound the bike is making. Seems to be the valves, but I had the timing pretty dialed in before I put the engine back.

I also tightened the exhaust nuts. The number 3 header on this pipe was slightly bent. It made the install tough but it seemed to go on fine.



1977 CB750

[Gordon]

Did you remove the old exhaust port crush gaskets and install new ones? 

[greddm]

Yep


1977 CB750

[setdog]

I'm still quite the amateur, there are others far more experienced than I.
Its very difficult to diagnose by noise alone precisely what the problem is, even more so through a video.  At least that seems to be the case..
I have an engine making very similar sounds, I've adjusted all the usual things
Numerous times but the noise has persisted.   I'm just going to
Pull motor and make sure I'm getting enough oil up top.  Unlike you though,
 I've never Pulled this bikes engine and I put about 700 miles since I got it after it
Sat for many many years in a warehouse.   Here is my engine at
Around 2200-2500 RpMs or so, well above idle.

[greddm]

Setdog, it was actually your video that made me think I had a problem. They seemed noisy but I didn't have anything to compare it to. I don't care, but wanted to make sure it's not causing damage.


1977 CB750

[greddm]

Ok, just pulled my exhaust and I can see that the crush rings on 2 and 3 only have contact on 1 side. I bought these pipes from Carpy when they were on sale. Starting to think the reason they were on sale is because they were a crap batch. The face of the headers are not perpendicular to the exhaust ports.

Is there such a thing as extra thick crush washers?


1977 CB750

[Stev-o]

I've heard of guys using 2 gaskets, I would suggest getting all new and doubling 2&3. 
Your idle sounds a little high, what is it at?

[greddm]

I had the idle set high so the sounds was a little more pronounced


1977 CB750

[greddm]

I'll try the double gasket trick


1977 CB750

[setdog]

I'll try the double gasket trick


1977 CB750

I'm very interested to hear the outcome, my pipes are aftermarket 4-2, I've tried snugging them  up and in my case it didn't really change anything noticeably so I've ordered a set of
Intake boots and replacement stock style air filter from vintagecb750

[greddm]

I think I'm going to pull the engine too, got a head gasket leak that's getting worse, going to get all this crap taken care of!


1977 CB750

[TwoTired]

Why doesn't oil splash out when you remove the tappet cover?


Exhaust gasket leaks are easily found with aquarium tubing.  Get a a two or three foot length and put one end in you ear canal.  Use the other end to probe for the noise source.

[greddm]

Two Tired, there was just some small drops flying out. How much should be splashing out?


1977 CB750

[greddm]

It was also leaning away from that side because of the kick stand. That may have contributed to less oil splashing out?


1977 CB750

[TwoTired]

My Cb550's make a huge mess when removing the exhaust side tappet covers.  One can't get the covers back on fast enough.  I don't remember if I tried that on my 750s though.

[MCRider]

My Cb550's make a huge mess when removing the exhaust side tappet covers.  One can't get the covers back on fast enough.  I don't remember if I tried that on my 750s though.

IIRC, same with a CB750. Makes a mess real quick.

[greddm]

Yet another reason to pull the engine...


1977 CB750

[greddm]

I wanted to post a follow up in this thread:
I pulled the engine and removed the head. I found that one of the tappet adjust screws was loose so the rocker arm was just slapping around.
I also found that my leaky head gasket was due to the cylinder stud nuts loosening up. I torqued them twice so I'm not sure why they had loosened up. Anyway, glad I pulled the engine. It sounds great now.


1977 CB750