I oil starved my bike and now it runs awful. Now I'm finally getting the courage up to pull the engine and see if I can assess the damage, people have suggested that it might be confined to the top end.

I had it in my head that if there was any cylinder damage, I'd replace the cylinder with one of those 299cc units for the YF300 from Aliexpress. So I looked them up to see how much they're selling for these days, and I came across this: Loncin CR6 YF300 KLX250 KLX300 Engine Motorcycle Cylinder Head Assembly Assy With Valves Camshaft Crankshaft

I'm not at the point where I know if I need it yet anyways, but is this advisable? It's half the cost of a used head from a KLX250S, and it comes with gaskets and everything. But I'm worried because the 299cc cylinder wasn't a direct fit without modifying a part, and this is my first time digging into an engine.

 

IMO, your cylinders/piston/crank are going to be ok unless you really ran it way low on oil. Usually the cam journals go 1st, they are very sensitive to oil pressure, all those other parts, not so much except for the rod bearing. Not sure on the rod if it has bearing caps or not. If it does, you could just replace them.

 

It's not nearly as bad as the other oil starvation stories I've heard around here.

It's harder to start, lower top speed, and once it's warmed up it's really hard to start. And it seems to be slowly getting worse. The metal flakes in the oil filter were pretty small. I have some hope I can get this going again, but still on the lookout for a used engine to pop up in Canada.

 

If you ran it out of oil and you are still riding it? Get a whole new engine.

 

I ran it out of oil and noticed the hard startups. Then I thought the problem went away. Then I did a thousand mile road trip, making sure the oil didn't run low again. On the way home I noticed the top speed had definitely dropped on the highway, and my last rest stop before home I had to bump start the motorcycle.

It started slightly hard but seemed fine in the morning, but had to be bump started again at the post office.

I drained the oil and there were maybe thirty small metal flakes in the oil filter.

I've been looking for a new engine but no luck. There's one for sale in USA right now but between exchange rate and going to the border to get the engine, I'd be better off parting the bike out.

I figure it's borked anyways and has to come out of the bike, so I might as well tear it apart at least and have a look inside. You think it's unsalvageable?

 

My '12 hammered out the rod bearing about 7 years ago, so I'm pretty familiar with the internals of this engine.
The only bearing surface that depends on pressurized oil is the camshaft.
It'll see increased piston skirt wear with some possible galling.
The remainder of the bearings are ball or roller bearings.
If the meral flakes are new, it definitely did some internal damage.

 

The hard starting and loss of power could be from cam bushing wear as others have said. A check of valve clearances should be done. The symptoms are indicative of no valve clearance, especially the intakes. Worn cam bushings could cause that.

Ride on
Brewster

 

.... and metal throughout the engine & transmission.

 

I got the valve cover off. All the valve clearances are to spec except one exhaust valve has too large a gap. I couldn't figure out what the cam bushings were.

Once I got the cam cap off, all the bearings looked good too (so far as I know, the cam lobes and bearing surfaces all looked like normal wear, and felt completely smooth). So I'm still not sure what's going on there. I'll get the valve cover back on and keep working on getting the engine out.

More details, if it matters:
The hard starts were accompanied by a high pitched sound. A bit scrapey, or maybe high pitched motor-ish?
My oil level was roughly 250ml below the window. That's how much I put in before I could see any in the window with a level bike.

 

Doesn't sound like you have any cam damage. I would open up the oil pump and inspect that. The metal is coming from somewhere. The metal in the oil might be clutch plating, you use a lot of 'clutching' while riding?
With the exhaust valve too loose, that negates the valves causing hard starting. The starting problem starts with 'tight' valves.
Your statement about cam bushings & cam cap's, is confusing and you may want to consider taking it to a motor guy. The cam cap is the cam bushing, one and the same. There is no 'bushing' insert or piece.