Topic: Another knocking sound, loud this time and with vibrations.

[vetec]

I have been searching for answer to my engine problem with this loud knocking sound in back part of Honda CB650C RC05 engine, here is video.

Carburators synchronized. Today I opened bottom of engine (oil pan) and I try to remove and inspect primary chain tensioner. I couldn't take it out. I noticed that it got some tension but primary chain is loose (sideways and tension loose)

On last shot on video you can see also loose sprocket next to primary chain tensioner.
I have visually inspected sprocket gears and what I could peep at, while turning engine - looks ok.

Knocking is very loud and whole bike vibrates. It disappears on higher revs.

Looking for good advice before I take engine apart.

Thank you!

[fizzlebottom]

Since you had the oil pan off, did you make sure the cam chain tensioner was sitting in it's correct spot at the bottom? If the top end was rebuilt, some folks don't reinstall the tensioner correctly and it makes contact with the primary chain.

[vetec]

I dont think is cam chain tensioner, its in its correct place and I can tension cam chain ok.

[newday777]

Have you had this motor apart?
That knocking is saying the cam timing is off a tooth (or 2-3) and the valves are tagging the pistons.
(Looking back through your few posts on here since you joined, to see what you've done on your bike, welcome aboard BTW, I'm surprised you didn't mention the knocking to begin with )

[vetec]

Thanks for welcome!

Well sound comes from back/bottom of engine. I think that primary chain is stretched.
Sound and vibrations disappear when engine runs above 2500 rpms.

Although I could see on cam shaft some wear (where valves contact camshaft) - scratches, surface has different color, yellowish.

I was hoping that this will be cure by correct service: timing, carbs synchro, spark plugs etc.

   

[tshrey]

That sounds like solid troubleshooting, the individual power pulses smooth out above 2500 rpm.  If it was anything else having interference it wouldn't go away like you describe.

[vetec]

ok, I sorted out my knocking problem. It was carburetors with wrong timing chain set up, 2 notches in wrong place.

I have installed new set of carbs, synchronized it and I set up correct timing.

thanks!

[fizzlebottom]

ok, I sorted out my knocking problem. It was carburetors with wrong timing chain set up, 2 notches in wrong place.

I have installed new set of carbs, synchronized it and I set up correct timing.

thanks!

Why did you install new carbs? Were they damaged somehow?

I was going to say this sounds like both a timing issue and wildly out-of-sync carbs at the same time.

[vetec]

Carbs were bad. Someone tamper with this motorcycle before me. Changing carbs took all noizes away, engine is running smoothly now.