New '77 CB750 but not sure what this noise is.

Dick

Dick

Been Around the Block
Hi guys I got a '77 Honda CB750 a couple of days ago and am going to start cleaning er up!
1194421002_bdDNj-S.jpg

It's going to be a cafe project but it's going to be a 'half assed' version as I have ZERO mechanical skills or fabrication know-how. I figured I'd hit this forum up as it looks to have some SERIOUS bad ass members that I hope I can learn from.


So first up with the bike is that it runs a bit rough:
Here's a short video of the bike clanking a bit. (Pay no attention to the camera placement as I was just more trying to get the mic in there to hear the noise)
Beatrix running rough. :(
So I have no idea what that noise is but it all but goes away once the bike is fully warmed up.


The next thing I want to address is what appears to be a bit of an oil leak as you can see in some of these pics:
Oil underneath (dont mind the corrosion...its just spilled down from the battery compartment)
1194432500_SPtc3-M.jpg



And oil coming from the 'headers'?
1194432510_MGqYU-M.jpg



Like I said guys I know squat about mechanical and this will pretty much be the first bike I have ever 'worked' on so any advice or tips on this stuff will be GREATLY appreciated!
 
my guess is cam chain, but please wait for a educated guess. mine is purely a guess. looks good though!
 
Hey guys, thanks for replying! I think the 'cam chain' is a good start for sure!
 
Cam chain, cam chain, cam chain. Sounds the same on a dohc as it does a sohc. Oil leak could be number of thing. Mine was the tach inlet spewing oil from a faulty o-ring (read: What O-ring??) Not sure of the tach cable inlet on the sohc, but on the dohc, it's directly above the header, which makes it appear to be leaking oil from everywhere.
 
my-79-750-k said:
Cam chain, cam chain, cam chain. Sounds the same on a dohc as it does a sohc. Oil leak could be number of thing. Mine was the tach inlet spewing oil from a faulty o-ring (read: What O-ring??) Not sure of the tach cable inlet on the sohc, but on the dohc, it's directly above the header, which makes it appear to be leaking oil from everywhere.
Click to expand...
So the cam chain clank is pretty normal? Does it need to be tightened maybe?


I still need to scrub this thing down and that way it should be easier to pin point the oil leak. Thanks for the tip on the tach inlet....hopefully that's all it is.
 
Can't really tell from the vid what the noise is. Probably camchain ??


You're on the right track with the oil leak - degrease the engine and watch where the leak is coming from. More than likely the cam cover gasket is leaking and the oil is running down the front of the motor. It can sometimes look like the head gasket is leaking, but that's unlikely.


Put some superbike bars on that bike and just ride it as it is - they're classics ;)
 
no a noise like that is not normal...
it is the sound of metal hitting metal......not good.

No you cant take the valve cover off with the motor in the frame.
If i remember right the cam chain is and endless chain so the crank will have to come out to change it.

I tend to snowball projects but i cant see a reason to get that far into a motor and not do bearings, pistons and rings.
the way i feel is that if the motor is in that bad of shape to start making noise its not just one part that is ready to fail
but with a rebuild you will replace all the gaskets that appear to be leaking.
also it looks like someone have been in the motor already.

also are you sure its a 77 motor and not a 78?
the latter F bikes had a factory "big valve" head. the valve guilds are only good for 30K miles. and thats if the motor was taken care of.

With all that being said i think its the valves that are making alot of noise.
that adjustment is easy to do. and a good place to start

i would not ride or rev the motor untill you fix the noise.

read the manual and adjust the valves and the cam tensioner
you do have the manual right? not a cheap useless aftermarket manual im talking about the factory honda manual
 
also that bike looks like the tins are clean.

DONT TAKE THE DAM THING APART AND RATTLE CAN IT!!!!!!!
get it running well before you thing about "building" it.

just fixing normal running issuses and keeping the bike in good tune will be hard enough for someone that claims to not have any skills.

learn whats normal before you try and see if you can mod the bike.
 
hillsy said:
You're on the right track with the oil leak - degrease the engine and watch where the leak is coming from.

Put some superbike bars on that bike and just ride it as it is - they're classics ;)
Click to expand...
Any good tips on a good degreaser? Or pretty much anything is safe?

Hmmm....was thinking more of the cafe look...but now you got me thinking with that superbike....hmmmm
 
surffly said:
also that bike looks like the tins are clean.

DONT TAKE THE DAM THING APART AND RATTLE CAN IT!!!!!!!
get it running well before you thing about "building" it.

learn whats normal before you try and see if you can mod the bike.
Click to expand...
OK OK!! I won't rattlecan it! Though...that yellow you see....is pretty much all rattlecan already. :-\

But I think you're right on the money...I'm definitely going to take my time and make sure the engine is working at 100% before I go messing with anything else or taking it to the track. ;) Though...can I at least change the bars out sir??
 
Dick said:
OK OK!! I won't rattlecan it! Though...that yellow you see....is pretty much all rattlecan already. :-\

But I think you're right on the money...I'm definitely going to take my time and make sure the engine is working at 100% before I go messing with anything else or taking it to the track. ;) Though...can I at least change the bars out sir??
Click to expand...

LOL please change them and the mirrors too!
 
Cool, nice bike.


Try just adjusting the cam chain first... it's literally just loosening a bolt and then immediately tightening it up again. Look around online for a manual, you need that.
 
Dick said:
Any good tips on a good degreaser? Or pretty much anything is safe?
Click to expand...

I'm not sure what brands you get over there, but here in Oz some of the degreasers are quite harsh on case / frame paint (Kitten from memory...).

I use the spray can stuff form the local cheapo auto shops. Costs about $2 a can, but it's quite mild (IE weak ::) ) and doesn't hurt the paint. You might need to get in there with a nylon brush and scrub the caked on bits.
 
Change the bars to clubmans? Not with the stock pegs.

Superbike bars will give you a lOwer stance and not kill you while riding

But like I said spending any time or money on stuff like bars is a waste untill after you correct the noise
 
hillsy said:
I use the spray can stuff form the local cheapo auto shops. Costs about $2 a can, but it's quite mild (IE weak ::) ) and doesn't hurt the paint. You might need to get in there with a nylon brush and scrub the caked on bits.
Click to expand...
Hey thanks a lot Hillsy!
 
surffly said:
Change the bars to clubmans? Not with the stock pegs.

Superbike bars will give you a lOwer stance and not kill you while riding

But like I said spending any time or money on stuff like bars is a waste untill after you correct the noise
Click to expand...

Yeah, priority number 1 is to get it running 'great'!
 
Dick said:
Yeah, priority number 1 is to get it running 'great'!
Click to expand...

Actually I think you should start with your wardobe first, clubmans then any of that tinkering or "fixin'" you plan on doing ;D
 
You must log in or register to reply here.

DTT Light or Dark

  • DTT Light
    • www.jadusmotorcycleparts.com
    www.lostapostle.ca/
    www.sparckmoto.com

    Spread the Love

    Back
    Top Bottom