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Cylinder stud dowel pin missing? YZ125

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I am rebuilding the top end for the first time on a very low hour 2005 YZ125. I noticed after I got the cylinder pulled off and over to my workbench that one of the stainless steel dowel pins that goes over the two left side cylinder studs was stuck in the cylinder hole (thats another story, I can't get it out of there). I went over to the bike and did not see the other one around the cylinder stud.

In case my description of the part is vague, the part number is 99590-10114-00.

I also noticed corrosion around the stud that was 'missing' the dowel whereas all the other studs were clean as a whistle. Is it possible that only one was installed at the factory?

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Here are a couple pictures:

The first one shows the one dowel that is stuck in the cylinder.

The second one shows the cylinder stud (corroded) that was 'missing' a dowel.

IMG_20110426_165923.jpg

IMG_20110426_165953.jpg

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The more I think about/google/read about this, the less I am thinking the odds are very low that it was left off at the factory. I read that one guy left one off during his rebuild and it resulted in the cylinder shifting and damaging the cylinder. I do not have any cylinder damage. I'm guessing right now that it is either:

1. Somewhere on the garage floor/stand/etc. I need to comb the garage and look for it.

2. In the crankcase. Is this possible? Is this dowel too large to have dropped down there? I figured I would have heard it hit somewhere after dropping it did go down there. I moved the connecting rod up and down and it moved freely and smoothly without any abnormal noise.

Is it possible it would fit down in the case, and if so is it retrievable without splitting the cases. Any ideas/suggestions are much appreciated.

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I had this happen on a 250f. I didn't know that it was down there for sure, but I thought I would be safe. I wound up taking the motor out(without top end) and shaking it around. I heard it in bottom bouncing around. After about an hour of shaking and putzing I got it in view of my flashlight. My dad has one if those flexible grabers with the fingers, and I got it out.

I hope this helps, there may be a better way. But either way you should make sure it's not down there.

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OK thanks a lot for the information. I think I'm going to try the same if I it doesn't turn up after combing the garage. I was going to pick up one of the flexible magnetic retrieving tools, but perhaps I should get one that grabs with fingers.

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buy another oem one, there cheap, and put it in, easy, they just slide in there tight though especially if theve been in there for a long time, i just reaplaced mine when i did my rebuild just because lol.

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I ordered two more today, but I just wanted the peace of mind knowing the old one wasn't down in the bottom end.

Tonight, I looked very closely with a light and saw nothing. I then turned the bike upside down, turned the connecting rod up and down a lot and heard nothing. I then shook the bike upside down and heard and saw nothing.

After looking down there with a light, I do not think its even possible for it to get beneath the crank assembly. This in addtion to the corrosion around just the one stud that I think did not have a dowel pin makes me feel it wasn't on there. I guess I wonder what you guys would do at this point. After all of this, I think I'm confident it's not in there and am going finish the rebuild.

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Glue in in with loctite stud and bearing mount. I forget the number, but my bottle is full of red stuff. I've had it so long I can't read the label on it. If you ever need it removed, you can use a heat gun, and like all loctite agents, it will come right out.

I always wondered about people saying to use loctite on spark plug inserts on air cooled four strokes: it loosens every time you run the engine.

If it were me, I'd prove it wasn't down those cases. If it is, and you start it, well, draw your own conclusions. I dropped a bolt down the cam chain cavity of my Daughter's FZ a few years ago. Pulled the engine and went spelunking. Lucky for me, it was sitting where I could see and get it without pulling the head and cylinder, but I would have done that had I needed to. Time consuming, but cheaper and faster than the whole engine being rebuilt.

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I agree, but after doing what I've done so far to find out if its down there what other option is left other than to split the cases?

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Great post. That would be costly if it happened to fall down there. If you can, blow some compressed air down there. It will often spit everything back up. This includes gas and oil, so be careful.

Glue in in with loctite stud and bearing mount. I forget the number, but my bottle is full of red stuff. I've had it so long I can't read the label on it. If you ever need it removed, you can use a heat gun, and like all loctite agents, it will come right out.

I always wondered about people saying to use loctite on spark plug inserts on air cooled four strokes: it loosens every time you run the engine.

If it were me, I'd prove it wasn't down those cases. If it is, and you start it, well, draw your own conclusions. I dropped a bolt down the cam chain cavity of my Daughter's FZ a few years ago. Pulled the engine and went spelunking. Lucky for me, it was sitting where I could see and get it without pulling the head and cylinder, but I would have done that had I needed to. Time consuming, but cheaper and faster than the whole engine being rebuilt.

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i,m pretty sure it won,t fit down there.if you didn,t hear rattle around ,i wouldn,t sweat it.

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That's easy enough to prove with the other one.

I actually thought about doing that! I said, if I put this other one down there and it disappears and cant be heard or seen then the other one might very well be down there, but if it doesn't disappear then the other one probably isnt down there. I would then have to deal with retrieving the other one, but that shouldn't be too hard if it's within sight.

Pretty disconcerting thought though to purposely try to see if I can lose a part in the motor. lol

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I actually thought about doing that! I said, if I put this other one down there and it disappears and cant be heard or seen then the other one might very well be down there, but if it doesn't disappear then the other one probably isnt down there. I would then have to deal with retrieving the other one, but that shouldn't be too hard if it's within sight.

Pretty disconcerting thought though to purposely try to see if I can lose a part in the motor. lol

I agree with rc and would use some air. there aren't any nooks or crannies in that side of case for that thing to hide, and you will hear or see it easily.

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I agree with rc and would use some air. there aren't any nooks or crannies in that side of case for that thing to hide, and you will hear or see it easily.

I'm definitely going to get a can of compressed air and try that out. Thanks for the suggestion guys.

When you say that side of the case, where are you referring to? I apologize for being ignorant of the bottom end on these bikes since I've never been into one personally, but from looking at the schematic as well as down between the crank assembly I'm guessing there is no way for something to get down there other than between the crank assembly either in front or behind the connecting rod. Is this is correct, and if so, do you mean that that is the only place it could be because it would be unable to clear the gap beneath the crank assembly and bottom of the case?

I apologize for belaboring this and I'm feeling 98% confident it isn't in there, but I appreciate any and all outside opinions and viewpoints before going ahead and buttoning this thing up and starting it.

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The crank flywheels are a very close fit to the inside of the cases, so it couldn't be there, but between the flywheels is an area where a surprising number of things can hide. If for some reason it was still in there and you started it, you would certainly know it. It most likely would do in your engine.

If you're going to use air, you need a lot of it at high pressure, not those cans for computers. Go buy a 300 dollar compressor at Sears, you'll find lots of use for it. Use a blow nozzle and blow out at full pressure.

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I've been thinking about getting a compressor anyways, so I'm glad you suggested that over the can of compressed air.

Just to be clear, when you say between the flywheels you are referring to the two wheels that make up the crankshaft assembly, correct?

If so, that would mean I would definitely see it between there with a light, and would use the air to blow it out?

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I've been thinking about getting a compressor anyways, so I'm glad you suggested that over the can of compressed air.

Just to be clear, when you say between the flywheels you are referring to the two wheels that make up the crankshaft assembly, correct?

If so, that would mean I would definitely see it between there with a light, and would use the air to blow it out?

yeah , flywheels/crankwheels. If you don't have air I would use a magnet-on-flexible-rod thing to check if it's there.The only place in the case to hide would be between the crankwheels at bottom of case.

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Great! I actually had someone on another forum just say the exact same thing. Thanks a lot for all the information guys. I can breathe easy now. I'll try report back after I have it all put back together and up and running.

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