A new and very concerning sound from the crankcase...

[Easterntide]

Went on a 300km ride w my better half this weekend. From the very start i was noticing something odd. At low rpms, and in every gear, while doing a gentle acceleration up to speed, or even at a low to moderate steady state speed i was feeling a repetitive knock that was evident in the pegs all the way though to the seat. this was a knock coming from the crankcase. it stopped when i pulled in the clutch and it wasn't there when i was decelerating. Got to the point where i was seriously concerned i'd not be making it home. a sound that was like someone tapping solidly at the bottom of the engine w a hammer over an over.

Although fortunately nothing did happen its now in the garage until tomorrow where i'm taking it to a local cat who does all kinds of work on FJ's (and all others).

He's doing my carbs (as per another thread on here) but obviously i'll task him on this first.

any thoughts?

sigh.

[JCainFJ]

Have him check the rear bolts on the frame down tubes. The bolts that are under the foot peg mount castings. They work loose / break and cause lots of weird problems.

[Easterntide]

thanks for the thought...but could that could cause a perfectly repetitive knock under acceleration?

[JCainFJ]

Yes, the rubber mounted engines in the late FJ's move around quite a bit.

[Easterntide]

Didn't mention that I did adjust the chain and brought I some of the slack. I will back it off tonight and see if that solves anything. Hope it does.

[Pat Conlon]

If you're thinking along the lines of a tight driveline....check the Cush drive bearing.

Remember the motto, a loose chain is a happy chain.

Folks (esp. Folks with the rear raised via shorted dogbones) adjust their chain on the center stand only to find that when the rear wheel is on the ground and bike is loaded with rider/passenger/luggage, the chain to too tight. Cush hub bearings hate tight chains...

[Easterntide]

Everyone is right and i am wrong.
i tightened my chain (what i thought was slightly) and low and behold when i checked it after all the supportive comments from here last night... it was f'n tight. backed it off and went for a ride. problem solved.
so thanks to all and apologies for being so thick!

hopefully it didn't do any further damage. i'll have the gentleman check it for me though when i take it out today.

cheers and thanks,
Don

If you're thinking along the lines of a tight driveline....check the Cush drive bearing.

Remember the motto, a loose chain is a happy chain.

Folks (esp. Folks with the rear raised via shorted dogbones) adjust their chain on the center stand only to find that when the rear wheel is on the ground and bike is loaded with rider/passenger/luggage, the chain to too tight. Cush hub bearings hate tight chains...

[Firehawk068]

Mine did the same thing...............I thought the chain needed a slight adjustment, so I took it in a little. The same thing you described happened.
A slight knock-knock-knock could be felt, and even heard.................So I backed the chain off to where it was before.