Hole in the engine case

My cousin's YZ 250f shot what looks like a gear fragment through the case right below the water pump. Lost about 1/2 the oil out on the trail, some while I towed him back, and the rest in the bed of the truck. I have some questions:

He said he noticed a faint, low volume screeching sound coming from the engine right before he shut it off (stopped to wait for other riders). It WAS NOT leaking oil at the previous stop which was about 3 miles before.

1. I'm guessing the sound was because it was low on oil right?

2. Other than that sound the bike was running fine. Should he be worried about catostrophic engine damage? I doubt it

3. What do the outer cases (not the middle case halves) usually run?

4. Now would probably be a good time to go through the clutch and waterpump?

I'll see if I can get him to post pics of the damage. The hole is no bigger than the end of a pencil.

Thanks.

I would have to say it is time to take the motor and do a complete tear down. If it had a failure like that there is more than liklely another problum in that engine. Save your self the trouble and pull the motor down and take the calipers to everything.

AS for case halves if memory serves there about 150 a side.

Yes post pics so we can see. I wouldnt nessesarily say you need to tear the whole engine apart. Take the right side main cover off and see what is damaged and what broke first.

sounds like a bearing or race went dead. and it may be ugly inside. yes, pics would be good.

sounds like that motor is starting to feel the pain of being ridden hard. I'd probably fix the case, get the bike running and sell it. He could get a decent green sticker smoker for whatever he gets for his 250f.

I had exactly the same thing happen to mine. Foreign object inside the case got between the water pump gears and it gets pushed out the side cover. The object also got over on the chain side and chewed up the small cam gear on the crank. My specific advice is: pull the flywheel and check the cam gear, possibly replace the crank AND chain. I did not do that and regretted it because my gear got chewed up and wore down and allowed it to jump time, that took out all the intake valves (ouch). TAKE it off line now before it gets really expensive. $17.00 for a chain is a lot less than the other parts.

I had exactly the same thing happen to mine. Foreign object inside the case got between the water pump gears and it gets pushed out the side cover. The object also got over on the chain side and chewed up the small cam gear on the crank. My specific advice is: pull the flywheel and check the cam gear, possibly replace the crank AND chain. I did not do that and regretted it because my gear got chewed up and wore down and allowed it to jump time, that took out all the intake valves (ouch). TAKE it off line now before it gets really expensive. $17.00 for a chain is a lot less than the other parts.

Great onfo ronbuell. Gas to you. :busted:

I had exactly the same thing happen to mine. Foreign object inside the case got between the water pump gears and it gets pushed out the side cover. The object also got over on the chain side and chewed up the small cam gear on the crank. My specific advice is: pull the flywheel and check the cam gear, possibly replace the crank AND chain. I did not do that and regretted it because my gear got chewed up and wore down and allowed it to jump time, that took out all the intake valves (ouch). TAKE it off line now before it gets really expensive. $17.00 for a chain is a lot less than the other parts.

Awesome post.

Now that I think about it this is likely what happened. Turns out my cousin doesn't have a camera so it'll be about a week before I can get pics of the carnage.

Damn shame this happened. The bike has otherwise been bulletproof in the 4 yrs since the top end was redone.

You might as well take it down and check other items as well. My cylinder was at max and it was making noise. When I checked my small end rod, it was loose and so was the pin on the piston. I got a used cylinder and honed it slightly, then with a new piston, it was right in the middle of the spec. I had to do a new crank, chain, intake and exhaust valves, cut the seats, new stem seals, and other items. Took the opportunity to migrate WR tranny into the YZ and its awesome. Every gear pulls longer and harder and 1st is lower than YZ first, 4th and 5th is higher. I have a much higher top end speed now and crawl ability too. I also know what my time is on the motor for future rebuilds.

My cousin ripped the side case off today and he said the gear behind the water pump impeller broke and thats what cracked the case. He also said there was metallic debris on the clutch basket and other gears up in there. The screeching was likely that broken gear driving the impeller.

He has aluminum welding capabilities at school so hes gonna try to weld the case...he wants to do this on the cheap. I let him know it'd be a good idea to check the stator side for debis and to replace the timing chain too. Now that I think about it'd probably be a good idea to remove the oil feed tubes off the engine to make sure they're clean as well as remove and clean that oil screen in the frame.

Ronbuell was your oil pump OK after your motor went pop?

In terms of the other engine stuff I really don't think it needs it. The valves haven't moved since it was rebuilt in '04 and the kickstart won't budge upon compression unless you hit the decomp lever (Its an '01). I am surprised at how well its held up considering how hard the big boy rides it.

My cousin ripped the side case off today and he said the gear behind the water pump impeller broke and thats what cracked the case. He also said there was metallic debris on the clutch basket and other gears up in there. The screeching was likely that broken gear driving the impeller.

He has aluminum welding capabilities at school so hes gonna try to weld the case...he wants to do this on the cheap. I let him know it'd be a good idea to check the stator side for debis and to replace the timing chain too. Now that I think about it'd probably be a good idea to remove the oil feed tubes off the engine to make sure they're clean as well as remove and clean that oil screen in the frame.

Ronbuell was your oil pump OK after your motor went pop?

In terms of the other engine stuff I really don't think it needs it. The valves haven't moved since it was rebuilt in '04 and the kickstart won't budge upon compression unless you hit the decomp lever (Its an '01). I am surprised at how well its held up considering how hard the big boy rides it.

The one I just built did a big end the oil pump is JUST ok so I ordered a new one both the oil pump and the rotors that run in the case.Pull it part if in doubt its cheap insurance I think.

JSan, On oil pump, no, it was scored, so I replaced it. It also needs sliders for the timing chain, they are on order now for mine. I can do those without too much trouble. I blew out all oil areas with kerosene, then compressed air, then brake cleaner. It was easy since I had it torn down. Also checked all bearings and cleaned them. The only one that was questionable was a shifter bearing that's always bad on Hondas on the shift drum. I left it alone since its not a high speed turn, only turns when I shift, and I didn't have the replacement. It moved, just a little notchy. Bearings can be long leadtime items so keep that in mind. Otherwise buildup went smoothly. CHANGE OIL and FILTER OFTEN !!!!! Good luck

JSan, On oil pump, no, it was scored, so I replaced it. It also needs sliders for the timing chain, they are on order now for mine. I can do those without too much trouble. I blew out all oil areas with kerosene, then compressed air, then brake cleaner. It was easy since I had it torn down. Also checked all bearings and cleaned them. The only one that was questionable was a shifter bearing that's always bad on Hondas on the shift drum. I left it alone since its not a high speed turn, only turns when I shift, and I didn't have the replacement. It moved, just a little notchy. Bearings can be long leadtime items so keep that in mind. Otherwise buildup went smoothly. CHANGE OIL and FILTER OFTEN !!!!! Good luck

LOL I fitted new guides and my oil pump is on order :busted::moon:

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