Driveline Knock - Part Throttle

[pistonbroke]

Heh guys - 1979 CBX, great runner pulls well and now has new 3>1 per side Delkevic replica exhaust. Way queiter exhaust sound, so now can hear a significantly loud "knocking" noise in the drivetrain, when initially accelerating, but really loud, when at speed, and rolling off the throttle (at Part Load)...

Checked and adjusted Drive Chain - all good, lubed. Checked cush drive, chain and both sprockets are in good condition and no play in drive sprocket splines on output shaft.

There is a massive amount of "play" in the final drive shaft (the one the chain sprocket is attached to), when rotating the rear wheel in gear, IE turning the rear wheel back and fro' until the motor compression stops it .....

Seems the same amount of play in all gears, so i'm thinking maybe the Main Primary Chain between Crank and Primary Shaft is the issue ?

Attached picture shows this play - which i'm also assuming is the part throttle Knock i am hearing ? Drive sprocket rotates the transmission output shaft with nearly a chain link of play - i don't think this is normal ?

Output Shaft Play.jpg

Guessing someone here knows what is up - would really like to hear any opinions you guys have out there, before i have to split the Crankcases - bike runs so nice under power, i'm gonna hate to have to do that !!!

Thanks for any and all help guys .... Kev

Here's the bike right now...

[cbxchris]

Kev, before you start whipping the engine out, take the clutch cover off, and check everything out in there !

[daves79x]

Unless the chain is really dry and kinked, it's not coming from there. That 'play' you describe is perfectly normal, I think. Since the bike has an 1100F swingarm and wheels, carefully check chain alignment as there might be a spacer issue with the rear wheel. If everything from the 1100F was used, it should be just fine. As Chris said, the sound is likely from the clutch side. With the help of the shop manual, completely disassemble the clutch, checking for loose or missing parts as you go. Check everything and look for shiny spots anywhere something may be hitting. Is the bike fairly quiet at idle in neutral? You should also drop the sump cover to check for anything foreign in there.

Dave

[pistonbroke]

Chris, Dave, thankyou for the replies and advice. I don’t ever remember having a bike that when in gear allows the drivetrain to wind up that much, but then again I never had a CBX before, or a bike with a “Silent Chain” drive between crank and primary shaft, so I’ll rank myself schooled by more knowledgeable chaps on this subject.

Yep I’ll take the clutch apart and see if anything is up in there. The manual doesn’t say much about the Crank to Primary chain tensioner and the pictures aren’t that clear - is it simply a spring loaded setup or does it use oil pressure in the mechanism do you know ?

Thanks again guys - kev

[daves79x]

Oil pressure tensions the primary chain.

Dave

[pistonbroke]

Thanks Dave, gonna tee in an analog pressure gauge at the sender unit to see how OP looks. Watched a bunch ov Vids on Youtube and all the CBX's i saw have some sought of rattle and knocks ! So maybe i', being too picky !

[EMS]

so now can hear a significantly loud "knocking" noise in the drivetrain, when initially accelerating, but really loud, when at speed, and rolling off the throttle (at Part Load)...

...

Although motorcycles and the CBX in particular have some unique sources for annoying noises, most internal combustion engines exhibit noise under the condition you describe when they suffer a special issue. I don't want to scare you, but I think one of your rod bearings may be on the way out. The typical CBX clutch "rattle" and primary tensioner racket is most prominent at idle and goes basically away under load.

[pistonbroke]

Thanks 'EMS "I don't want to scare you" LoL - i'm a big boy now - not scared, and appreciate your feedback.

I may have punctuated wrong but there is no Noise under hard acceleration, and i've been around ICE's for quite a few years too - this ain't no Rod bearing issue :0

I'll let y'all know what i find when California turns back to the Dry, Sunshine State !!

Thanks and i do appreciate all the notes guys..