Bottom End Flush

Hey guys. I'm rebuilding an '06 450 engine for my neighbor. The front/exhaust side cam chain guide/slipper has chunked out pretty good. I found a good amount of the rubber sitting in the flywheel actually.

I was thinking about pouring some kerosene down into the bottom end to flush out any other pieces down there. I have the entire top end, flywheel, and clutch assy. off right now, so it I have clear passages into the case.

My concern is floating rubber chunks or debris up into areas they may get caught in and do damage. Possibly lodging in a bearing or oil passage. I'm not going to fill the thing, just enough to slosh around. I guess I just want some reassurance.

Btw, my advice to the owner was to split the cases and thoroughly clean, but he doesn't want the extra labor.


Isn't kerosene a pretty strong solvent? Wouldn't that essentially wash away grease in the bearings it comes in contact with?

I may be completely wrong, but it seems a little sketchy to me. I think some sort of thin oil would be a better idea.

Yeah, now that you mention it, I do use kerosene to clean all my chassis bearings, but what bottom end components are greased and not lubed by the motor oil?

...what bottom end components are greased and not lubed by the motor oil?

Not a single one of them. The kerosene will work OK, but I would mix in a little ATF (about one part in 4 or 5) to help float debris out. I would also say that you should open up both sides of the engine to do this, remove the oil pump, and back flush the sump screen through the oil pump cavity.

Check the oil filter immediately after the first short ride, and plan on splitting the cases if there's still junk in it.

I will use both the ATF and back flushing the oil pickup ideas. Thanks.

kerosene is light oil. right?

The flush worked well. Although I didn't use the ATF. I had both sides of the engine open, clutch basket/hub removed, flywheel removed. I just poored the kerosene in on top of the crank. Sloshed it around and spun the crank. Then laid the engine, clutch side down, on my 2x4 engine box. Sprayed some contact cleaner in through the flywheel side and lightly blew some air thru there.

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