Board index Flathead Power-Technical Questions, Answers, and Suggestions Knuckles Knocking sound after adding 60w oil

Knocking sound after adding 60w oil

Post Thu Apr 15, 2021 7:01 pm

Posts: 5
I hadn't ridden my knucklehead for months and my brother and I decided to try to get it started up. I checked the oil and it was about a quart low. There was a quart of 60w Valvoline on the shelf in my brother's garage so I dumped it in the tank.
After removing the carburetor and cleaning it we finally got it started there was a very noticeable knock sound when I was riding it around the neighborhood. Later after coming across several quarts of 50w at my house I remembered that I had always ran 50w Valvoline so what may be going on after adding the quart of 60w to the mix? Nothing else was changed other than cleaning the carburetor so I know that is the root of the problem.


Post Fri Apr 16, 2021 8:23 am

Posts: 3526
Location: Central Illinois, USA
It could be, Wreakhavoc,...

If you didn't see that quart of oil that disappeared on the floor, then you probably have a sprocket shaft seal (like for a belt drive), and that quart stayed in the bottom of your cases.

Now you've added a fifth quart with no place to go, and its knocking at the door... maybe.

I'm just conjuring of course.


Post Wed Apr 21, 2021 8:25 am

Posts: 1786
I would always drain the crankcases on any older bike, after it had been sitting for a long period of time. Check what’s in the tank plus what came out of the drain plug. If the engine has oil, start it and warm it up gently, watching for circulation; THEN check the oil level in the tank.
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Wed Apr 21, 2021 9:37 am

Posts: 3526
Location: Central Illinois, USA
Don't pull your case drainplug, Wreakhavoc!

There often isn't enough room to the frame member to get it out, damn easy to get crooked going back in, and even if you don't, its gonna seep once the inside sealer is broken.

Once again, if there is a modern seal on the sprocket shaft, then the natural, factory-designed escape for static sumping is blocked, and the cases can fill completely.


Post Fri Apr 23, 2021 12:47 pm

Posts: 1786
Oh ok, I don’t know knuckleheads. 45s have the drain plug in a relatively accessible spot, with a cut-out in the frame ... you still need the right spanner, and it is easy to cross-thread. Better to just kick the engine over a few times, maybe once a month. I wasn’t aware the drive side main bearing was a factory-designed relief for static dumping, it certainly doesn’t work that way on the 45 - or at least, there’s quite a lot in the cases by the time it comes out THERE.

One of my 45s has a hydraulic hose joint in the feed line, so I just uncouple it when the bike is stood for any length of time... and a BIG orange tag on the handlebars to remind me to couple it up.

Best thing is to start the bike, gently warm it up, THEN check the oil level.
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Fri Apr 23, 2021 3:23 pm

Posts: 3526
Location: Central Illinois, USA
I don't know why they put a drain on the carbureter bowls either, 45Brit!

Neither should be used.

Please leave them alone, Folks.

Pandora Plugs.


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