Dear ATVC: I ended up purchasing a used bottom end on eBay for my 1994 Yamaha Timberwolf 4×4 since my engine needed a new crankshaft and I wasn’t feeling up to splitting the case. What I received today was different than the pictures in the listing – the connecting rod, crankshaft, balancing shaft and bearing have quite a bit of rust on them; none of this was apparent in the pics. The gears appear fine but there also appears to be some “gunk” in there. My question is, is there any way to remove this rust without splitting the case? I was thinking of spraying a corrosion inhibitor spray in there over the next several days and then trying to figure out a safe way to flush all the crap out. What would be a good “flushing” chemical? The crank does spin very smoothly so I am really hoping to avoid splitting the case.
Not to worry, surface rust of this nature takes very little time to appear in an open engine but rarely is severe enough to cause issues.
We’re with you, though – give it a thorough cleaning/ de-rusting before installation.
Get yourself a good de-ruster (we use Evapo-Rust from Harbor Freight for $10 but there are many reputable brands out there).
Fill the entire lower end and let it sit for 2-3 days. Dump.
You’ll be surprised how much of that corrosion will already have been removed. However, sometimes spots can prove stubborn so what we typically do is get a spray engine degreaser and a couple of long wire brushes.
Spray down the trouble spots, get yourself a good work lamp and do your best impression of a chimney sweep.
After you’ve got it all sparkling, we typically mix up a weaker batch of the Evapo-Rust by mixing it 60/40 with warm water – fill, soak and dump out. Repeat if necessary.
Let it dry thoroughly and you should be ready to roll, no case splitting required.
