Hole in Crankcase Cover

Hey everyone,

Don't know if anyone has experienced this problem; A rock punched a hole in my crankcase cover during an Enduro this past Saturday. The hole is located just forward of the straight plug. I was 45 miles into the 75 mile enduro when I discovered oil on my boots and left side of the bike. It was still running and oil loss was minimal. I figured on running it 'til it died or I finished the race. My bike ran great for 25 hard miles before it finally quit on a long uphill. It did not seize, the oil level was still adequate, it just stalled. Tried every method and trick to start it for an hour, but not even a pop. Finally, after a PBJ sandwich break, I gave the throttle 3 twists and it started for about 2 seconds. There was oil mist and forced air coming out of the hole. Long story short is that I was able to keep it running by constantly pumping the throttle to keep gas feeding the cylinder and got out. My questions are: 1. Any thoughts on why it would die after that many miles. 2. Is there normally pressure in the crankase to blow air and oil through a hole in the crankcase cover. 3. Anyone think of other problems that may result from the punched cover?

Thanx for your answers and the awesome forum!

I recon the amount of crap that would have gone in that motor is guna cost you big bucks so get your wallet out. good luck :)

Jeez...you just kept on riding it. :) Were you planning to get a new bike soon?

BTW, where is the "straight plug"?

Thanx for responding guys, but I'm looking for some specifics. Why would it suck anything up and cost money? Why should I be looking for a new bike? Do you really know what the problems of the hole in the leftside crankcase cover could be? Or just guessing. I know running it when there is a potential problem can cause bigger probs, but that's racing. The crankcase cover (left) on my '99 WR has 2 screw in plugs. One is smaller on top, that is the timing plug; the second, the straight plug, is for access to the rotor and nut that holds it on. The timing plug is meant to be removed to time the bike w/ a timing light. So my question remains... Does anyone know of a specific problem I should look for or why it would stall the bike?

There is definitely pumping presure in the crankcase caused by the piston going up and down. I assume since there is oil in the magcover there would be presure there as well.

So I guess it was sucking and blowing all the dirt in and oil out for 45 miles or so. That can't be good.

Anyway, I guess if the hole was small and there was still a 1/2 Qt or so of oil in the motor after you stopped, Yr motor could be okay. The fact that the bike won't restart is not a good sign though. Low oil level sometimes results in the clutch going south before the motor seizes

At this point I'd:

Change the oil (whatever is left)

Pop a new plug in.

Cover the hole with some epoxy.

Try to start it and see what happens.

If the motor is lunched, running it a little more won't matter, after what you did to it already.

Good luck.

This may indirectly answer your questions. I had a stick punch thru one of the rubber half moon shaped gaskets on the head during a race this summer, I did not notice till the race was over that my leg was covered with oil. I drained the oil from the frame and engined and measured it, to see how much was left and to calculate how much I lost. I lost almost half my oil and found the bike was hard to start after I stopped at the finish and needed to ride another mile to the car, it was hard to kick thru even with the comp lever in, so I figured I screwed the engine as this was before I measured the oil. My local dealer said it shouldnt have done any damage, unless it was really really low on oil, and that It would cost bucks to tear it apart to look. I changed the oil and have had no problems, with many a race since then.

Also the crank case is under pressure and can suck in stuff, as evidenced by Yamahas excellent routing of the crank breather tube just under the shift lever, many a rider has ridden thru deep water or stalled and restarted the bike in water only to suck water into the engine.

I was unclear if the hole was from a rock or if you lost a plug. Either way I would measure how much oil is left and make a determination from there whether to flush it out really good with oil, strain it to check for debris, or tear into it to check for engine damage. JB weld can make it all better.

Good luck.

Thanx T.O.P.

I did just as you suggested today. Plugged the hole (more like a 1/2" tear) with JB weld and drained the oil. I lost < 1/2 a quart and the oil looked good; no water, dirt, metal, etc. Changed the filter while I was at it. I'm going to let the JB weld set up for ~ 24hrs to ensure a good bond. I've got my fingers crossed until tomorrows trial run. Thanx to everyone for your help and input.

You might want to consider a magnetic drain plug just for insurance, as there might be some stray metal in the engine, plus its a good idea anyway. I bought a moose and it seems like the threads dont match so I didnt put it in. I think Ty Davis company makes one.

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