Topic: Hawk knocks and lurches when I accelerate

[Rabblerouser]

Hey all...

Greetings from New Orleans...

I've done a number of searches and haven't seen these symptoms described...I'm not so experienced so I need help diagnosing my issue...

My 78 CB400t has recently started acting funny when I accelerate...
It will lurch slightly, as if something slips and it has lost its power momentarily, and catch right away, with an individual (and kinda loud) knocking sound on the left side of the bike. (I can actually feel the knock through my footpegs)

If I accelerate gently, it doesn't happen at all... but if I open the throttle a bit, it happens...It can happen in any gear, but happens more easily in 1st and 2nd than the others (for this to happen in the others, I have to accelerate more aggressively)

It doesn't seem to be coming from the engine, rather the transmission...I thought maybe the clutch was "slipping" but reading a number of posts, it seems that a slipping clutch would mean either slipping out of gear, or rpms which weren't translating into power (engine revs without accelerating normally), and my issue seems different...

Any insights?
Thanks guys...I would feel hopeless without this forum.

[trueblue]

sounds like your drive chain is slipping

[ekpent]

Start out by giving the countershaft sprocket a peek to see how worn it may be.

[Rabblerouser]

The counter-shaft sprocket looks fine...The chain, however, was loose as a goose, many of the rear sprocket teeth were razor sharp, and some looked like waves on the ocean  ... and the chain was kinking in a couple spots...i guess I need to pay more attention to the routine maintenance of the chain (and the rest of the bike)

Luckily I already have an extra sprocket...I just ordered a new chain, and I should be good to go...

I guess now I know what a super-loose chain slipping off the sprocket teeth sounds like...

[coldwave007]

Yup, chain and sprockets will do that.  My 650 was running the original chain and even properly tensioned, at about 100 miles on a ride it'd start slipping and knocking.  One new chain later and life is grand!!!