Thread Repair in Oil Filter/Drain Housing - 2004 YZ 250 F

[TurboT]

Alright Gang,

Seems the forums are a little slow at the moment, maybe it's the summer weather and everyone is out riding, but I thought I could help bump start some discussions with a 'concern' I have regarding my YZ.

Late last year, I had purchased the bike and attempted my first motorcycle oil change. Now some of you may know the YZ's have multiple areas to drain oil from, most notably the lower engine bolt, the bolt below the oil filer, and the frame bolt up under the wheel.

After watching a few youtube vids and reading the .pdf manual I managed to find online, I took this job on up country in Pemberton with a bucket of hand tools and some new oil.

Everything was going smoothly, had the oil drained, the oil filter cleaned out etc. I was happy to see that everything looked fairly clean as this was a new/used bike to me and had no idea how well it had been looked after.

As I was installing the bolt under the oil filter, (there are three bolts of course, only one into the crank case the others are blind holes,) I noticed it seemed a bit tight going back in. I removed it, and noticed it must have picked up a little of the thread, as there was minor wear and 'damage' on the bolt thread. Now this was all done by hand so there was no cross threading with a 3 foot bar for leverage. I cleaned it up best I could and as carefully as possible put it back in, it did go in,albeit with a ratchet and with more friction than I'd like, and tightened up like it should.

It is a metric hex bolt, I believe it is an 8mm allen socket that removes it. (might be 6mm don't remember).

So I'm a little frightened that now it's time to do another oil change, that when I remove this bolt the threads are going to come with it. Has anyone had success fixing threads in this area without removing the damn motor ???? I can pilot a timesert install kit, or a helicoil, but damn I'm scared the remants of the tap will go right into the crankcase or oil passages.

Any tips, suggestions, ideas are wonderful. Never removed a motorcycle engine before, and worked on lots of car engines but never motorcycles, and certainly not a 5 titanium valve 40hp 1 cylinder before.

Thanks all!

[Weldangrind]

Hey T,

Some clarification please: is it a blind hole that's in trouble or the crankcase hole?

If it's a blind hole, I wouldn't hesitate in measuring the existing length, drilling out with the appropriate numbered bit and carefully tapping with a bottoming tap (vs. a through tap). This presumes that you have the room to move to the next larger bolt.

If it's a crankcase hole, I'd only use a thread chaser and clean up the threads. I'd hold a Shop Vac hose up to it to hopefully capture the schrapnel.

In either case, you could likely install a stud instead of a bolt. In fact, switching to studs on all three holes wouldn't be a bad idea. From your engine building days, your likely already familiar with how a nut applies load vs. a bolt. Your stripped thread days would be over.

If the existing damaged thread is still somewhat salvageable, you might want to just Loctite a stud in there now. that may reoslve the issue permanently.

[TurboT]

Originally Posted by Weldangrind

Hey T,

Some clarification please: is it a blind hole that's in trouble or the crankcase hole?

If it's a blind hole, I wouldn't hesitate in measuring the existing length, drilling out with the appropriate numbered bit and carefully tapping with a bottoming tap (vs. a through tap). This presumes that you have the room to move to the next larger bolt.

If it's a crankcase hole, I'd only use a thread chaser and clean up the threads. I'd hold a Shop Vac hose up to it to hopefully capture the schrapnel.

In either case, you could likely install a stud instead of a bolt. In fact, switching to studs on all three holes wouldn't be a bad idea. From your engine building days, your likely already familiar with how a nut applies load vs. a bolt. Your stripped thread days would be over.

If the existing damaged thread is still somewhat salvageable, you might want to just Loctite a stud in there now. that may reoslve the issue permanently.

Unfortunately it is an oil feed hole, into the crankcase.

It is the bolt under the internal oil filter. There are three bolts that hold the cap on, two are blind holes, and one goes straight through and 'procedure' is to remove it to allow oil to drain from there, even if you choose not to clean the oil filter. It is also a different bolt than the others, as the other two are regular bolt heads, while this is an allen key style bolt. Not that that matters to the thread pitch.

I do think the oil flow of the engine is forced that way, and into the filter, so any shavings may push up into the filter which would be doing it's job, but this I cannot be sure of. Perhaps I'm splitting hairs, as aluminum is quite soft, and may not do as much damage if they were iron or steel filings, but still makes me a bit nervous.