Exessive engine noise

daywalker · Post by **daywalker** » Mon Jun 10, 2013 9:38 am

That's weird. I can hear it in person for sure. Maybe my engine sounds different because most of the other dreams I hear on youtube have different pipes. I don't know. You're right though. This video http://www.youtube.com/watch?v=Os2PZ9xf1VE the bike sounds almost just like mine except the exhaust pipes which I may want to switch to. The dealership did say that the noise may be normal for these engines. They weren't sure.

G-Man · Post by **G-Man** » Mon Jun 10, 2013 9:53 am

I concur with the other guys. All I can hear is just normal mechanical clatter. As the boys have said it would be a good idea to check valve clearances and cam chain tension.

G

Hoosier Tom · Post by **Hoosier Tom** » Mon Jun 10, 2013 11:58 am

Definitely check/adjust your valve/tappet clearance and adjust your cam chain tensioner and go from there. While you are getting familiar with your bike you really should route your clutch cable correctly.

HT

48lesco · Post by **48lesco** » Mon Jun 10, 2013 12:53 pm

Does the sound change between cold starting and fully warmed-up? What about under load? If it's quieter when hot, the pistons could be clattering a little. Another thing to check is that the exhaust flanges are tight, exhaust leaks can make a deceptive sound too. +1 on the cam chain and tappet noise, but the dealer should have had that sorted out before he sold it to you.
-48

daywalker · Post by **daywalker** » Mon Jun 10, 2013 1:56 pm

I have my stepdad looking at it right now. He's worked on bikes most of his life including bikes like mine because his dad owned them. He mentioned most of the things you guys mentioned to check. He's taking it for a couple of days and we'll see what happens. He's says the sound is definitely not normal. My camera mic didn't pic up the sound well enough. It's very loud and rattily especially when I rev it up. I'll update as soon as it's done being worked on. Thanks for all the suggestions guys!

This one sounds nice http://www.youtube.com/watch?v=3KesD_N8QBQ

jensey · Post by **jensey** » Tue Jun 11, 2013 12:40 am

Daywalker, your vid is gone.

In general :

I build several NOS engines (out of NOS parts), and I can assure you these engines can be quit, just as quit on the day they left the factory. I think not many mechanics today know, at least not from experience, how these engines sounded in the old days. They think it's old, thus noisy. My modern Africa twin XRV750 '98 is louder (excessive clutch noise) then my C77, and my CB400F (primary chain and clutch noise) is also louder.

But... by the time the odo reads 5000 miles or more, and the engine sat for a long time, the engine becomes noisy.

Why ?

This is a ball / roller bearing engine, cams on ball bearings, crank on roller bearings, transmission on ball / roller bearings etc. There are also two chains in the engine.

Why is this important to realize ?

In most cases the bike had a technical problem in the end of it's active life, so the owner left the bike alone. I bet that on the last ride the engine was quit and smooth as silk.

After 30, 40 years it's been brought to live. If it's lucky, the engine gets fresh oil, new points / spark plugs and a carburetor cleaning. Now the engine is "restored" and driven. But the engine is noisy, and does make a lot of mechanical clattering.

So what happened between the last ride back in the 60's or 70's and the first ride in 2013 ?

Not so much, but enough. If the owner took the time to put new oil in the engine after the last ride, drain the carbs, drain the patrol tank (and oil it) and oil the points before the bike was left alone, the engine would be quit at the first start in 2013.

But in most cases he didn't.

When a bike runs, the oil gets contaminated with aggressive chemicals. The oil itself has become an acid, not strong, but an acid. This acid oil oxidize everything what's in the engine, not badly, but just enough. Especially very clean surfaces like precise tooled bearing surfaces, rollers and balls. The roller surface becoming rough, just like the bearing surfaces. This is the reason for the noise (when everything is else is according to spec's)

Most people who "restore" an engine don't even take the time to look at the bearings at all, the bearings do turn over, so why bother to replace them ?

Like I mentioned, I build several NOS engines and one engine in particular, my CB72 (which is basically the same as a C77 engine) did make a lot of miles, 35000 miles to be precise. The engine is still quit, and you don't hear excessive mechanical clattering.

Jensen

daywalker · Post by **daywalker** » Tue Jun 11, 2013 7:29 am

Yeah, I deleted the video because I'm getting it fixed right now. Everyone was saying they didn't hear the loud engine noise in the video anyway. I knew that these engines didn't sound that loud especially since my step dad who worked on these said they didn't. I could DEFINITELY tell my engine wasn't sounding "normal". I could barely hear myself think. Thanks for your explanation. I think my bike is in good hands. I'll make a video of it after it's been fixed. Then I'll upload the before video again to see the contrast.