OK, rod knock?

[buffalobill]

I got my '93 750 project started up and running good today! After good compression test results and valves adjusted everything look very good with this engine.
But, dat sound…I'm afraid to find out it might be rod knock.
Air cooled engines are noisy and it may be from the rockers and it does lessen as the bike warms up.
Is there any test for determining if it's a rod knocking, and if so is it fixable?
Thanks

[scottynoface]

Start the engine up, then pull one plug wire at a time. If it stops when you pull one of them, you at least know what cylinder to be worried about. Sure it's not a tick as opposed to a knock?

[HemiKat]

Other than dropping the pan and wiggling a connecting rod there isnt much more than sound to go by, althought with a rod knocking engines tend to burn more oil. Most rods knocking have a "double knock" when you rev the engine. Its hard to explain. Post a video if you can.

[buffalobill]

Not a double knock!

Other than dropping the pan and wiggling a connecting rod there isnt much more than sound to go by, althought with a rod knocking engines tend to burn more oil. Most rods knocking have a "double knock" when you rev the engine. Its hard to explain. Post a video if you can.

You're right, I'm not getting the double knock sound, as the rod gets knocked up and down. It sounds more like an exhaust leak.
In fact I just ran it again to check the sound and I think it's an exhaust leak at the header to cylinder donut gasket. It seems to be coming from there, not the case. I just had the headers off for cleaning and could be it's not lined up right or I need a new donut.
Thanks

[il_ragazzo]

Start the engine up, then pull one plug wire at a time. If it stops when you pull one of them, you at least know what cylinder to be worried about. Sure it's not a tick as opposed to a knock?

what does it mean if it's a tick?

what sound should it make if the cams are worn with a groove?

[loudnlow7484]

Check the cam chain tensioner as well..... it usually sounds more like a slap than a knock when it gets really out of whack, but it's worth checking anyway since they tend to stop doing their jobs sometimes.

[scottynoface]

Check the cam chain tensioner as well..... it usually sounds more like a slap than a knock when it gets really out of whack, but it's worth checking anyway since they tend to stop doing their jobs sometimes.

I was thinking cam chain noise, as thats usually really distinct, easy to hear, and disappears when you rev high. I would know, I have a Kwacker

[buffalobill]

Worn out that groove?

what does it mean if it's a tick?

what sound should it make if the cams are worn with a groove?

I get worn with a groove sometimes too, but I'm just a hobby bassist.

[Batgirl]

Mine has all those noises

[buffalobill]

OK, update on knock…

I was all wrong that it might be a leaky header.
I started it up again and used a hose for a stethoscope to locate the source of the knock.
It's coming from the location of the #4 exhaust rocker or the end of the camshaft. That's where the sound is loudest.
Could it be the exhaust camshaft walking or knocking sideways?
Thanks.

[scottynoface]

I was all wrong that it might be a leaky header.
I started it up again and used a hose for a stethoscope to locate the source of the knock.
It's coming from the location of the #4 exhaust rocker or the end of the camshaft. That's where the sound is loudest.
Could it be the exhaust camshaft walking or knocking sideways?
Thanks.

Sounds like you might have an issue on #4. Time to pull the head and see what's going on in there. Kinda sounds like it might be a bearing...

[kevin2502000]

Could it just be a very loose tappet?? If it's a bearing you're f-ed, it's machined bearing surfaces.

[loudnlow7484]

I was all wrong that it might be a leaky header.
I started it up again and used a hose for a stethoscope to locate the source of the knock.
It's coming from the location of the #4 exhaust rocker or the end of the camshaft. That's where the sound is loudest.
Could it be the exhaust camshaft walking or knocking sideways?
Thanks.

Pop the valve cover off and recheck the clearances. I know that most of us here never ever make mistakes but it's definitely worth checking to make sure the lock nuts are tightened on the adjusters, and that the clearances didn't change. While you're in there, you can make sure that the rocker isn't sloppy on its shaft, and that the cam isn't sloppy in the end bearing (which would be some work to fix, btw, as those bearing surfaces are line bored as a whole).

[buffalobill]

Bummer…

Is that a worn cam lobe? Looks like the cam, and cam follower will have to be replaced. That's the #4 exhaust cam lobe, knarly.

[scottynoface]

Ewwwww.....