primary shaft slack

cba · Post by **cba** » Mon Sep 04, 2006 4:44 pm

How much if any slack should there be on the primary shaft? I've noticed lately that when I take off from a stop there seems to be a little slack between the motor and drive chain. It's just enough to notice, not a big clunk, but noticable. I thought at first, there maybe some wear in the rubbers in the rear wheel. I checked seemed okay. While I had the wheel off I took the drive chain and pulled back and forth while engine was in gear and there was some movement between pulling forward and then backwards. Measuring at the bolt that retains the primary gear, it seems to be about a quarter of an inch. Which when moving the chain seems to be about an inch or so of play. Is this normal or do I have a problem? Thanks, Chet

Tom Neimeyer · Post by **Tom Neimeyer** » Mon Sep 04, 2006 8:02 pm

Chet,

I am far from an expert but I think that "slack" is normal. I say this because the "slack" is just the free space between the transmission gears meshing. If there was a tooth missing, I would suspect, you would hear a lot of gearbox noise and it "jumping" from the extra slack each time it completed a revolution. You may be able to smooth the percieved slack with clutch and chain adjustments.

Good Luck and Cheers, Tom

P.S. Where are you in Texas? I'm in Houston.

5cbxes · Post by **5cbxes** » Mon Sep 04, 2006 8:57 pm

I tend to agree with Mr. Neimeyer. Consider that there are a lot of gears between the rear wheel and the crankshaft. Also, there is the clutch between the engine and tranny and there is a pair of gears to transmit the drive force there also. Plenty of slack before any movement between crank and rear wheel.

alimey4u2 · Post by **alimey4u2** » Tue Sep 05, 2006 12:31 pm

I would think backlash would be more noticable with the engine not running. Isn't the hydraulic primary chain tensioner in the "relaxed" position with no oil pressure..... ?? This would only be noticable with the engine in gear though.

5cbxes · Post by **5cbxes** » Tue Sep 05, 2006 1:43 pm

True. I interpreted cba's slack complaint as one between rear wheel and engine, (i.e.: primary shaft because he recogizes it while the engine is running) And as Tom said, the gears in the tranny would produce most of it.

alimey4u2 · Post by **alimey4u2** » Tue Sep 05, 2006 2:21 pm

I had ommited to read cba's first sentence.....

How much if any slack should there be on the primary shaft? I've noticed lately that when I take off from a stop there seems to be a little slack between the motor and drive chain.

....

My comment was based on the later part of his discription......

While I had the wheel off I took the drive chain and pulled back and forth while engine was in gear and there was some movement between pulling forward and then backwards. Measuring at the bolt that retains the primary gear, it seems to be about a quarter of an inch. Which when moving the chain seems to be about an inch or so of play. Is this normal or do I have a problem ?

What I would do to compare, (engine "initially" off & under compression, in gear) would be to take off up a steep hill (incline) & take off down (decline) a steep hill (holding the bike initially with the rear brake on only,) to see if there is any very noticable difference ?? Kind of a messy description but I think you know what I mean......

PS. I too am in total agreement with the prior distinguished posters....

The International CBX Owners Association

primary shaft slack

primary shaft slack

Slack in Transmission/Primary Shaft