Topic: Engine Knock for a Newbie

[coal909]

Hey Guys,

im kinda new to wrenching so im still learning the normal sounds and proper diagnosing so i was wondering if you guys could help me with this or to figure out if this engine knocking is normal to the Cb750 A

video link to it below

https://www.youtube.com/watch?v=4INwbCWJ7CU&list=UUBut_LZ3yhlqg9aSijvXBfg&index=1

[Mr Freeze]

Have you vacuum sync'ed the carbs? These engines tend to get a little rattley if there aren't.

[70CB750]

He is right, you would be surprised what difference properly tuned engine makes.

[Glenn Stauffer]

Take a look at the various tuning guides you can find here: http://forums.sohc4.net/index.php?action=downloads;cat=4

Your best bet is to go through the whole process - valve adjustment, ignition timing, carb balancing.  That should set your engine straight.

[raymond10078]

Idle too low.  Possibly need a carb sync (which should be preceded by a full tune-up). 

[coal909]

Thanks Guys the bike is at the garage getting new tires and points replaced. So when i get it back my next step will to tune and synch the whole thing properly

[TIOMACHY]

THIS IS THE SAME NOISE MY 78 CB750A MAKES ON START UP.  IT ALMOST GOES AWAY WHEN WARM.  I TOOK IT TO A COUPLE OF MECHANICS THAT WORK ONLY ON METRIC BIKES AND THEY BOTH TOLD ME IT'S A CLUTCH COMPONENT THAT MAKES THAT NOISE.  ALTHOUGH A PITA TO HEAR, THEY BOTH TOLD ME IT DOES NOT AFFECT THE BIKES PERFORMANCE AND DURABILITY.   I'M STILL LOOKING FOR THE NECESSARY PARTS TO GET RID OF THAT NOISE.  BUT THE BIKE RUNS REALLY WELL.   IT HAS 37,000 MILES ON IT.

REGARDS.

[coal909]

i got my bike back and after synching the carbs it was much better it still knocks a bit but goes away right away when warm


hope it helps