FOD'd '85 250R

[pismorat]

Foreign Object Damage - My piston and cylinder head were bouncing a piece(s) of magnetic metal back and forth between each other, ultimately closing the plug gap. Once I disassembled the motor, there were about 30 tiny pieces of magnetic metal that would fit on a 50 cent piece in the pipe. I have NO IDEA what it used to be or where it came from. The rings are in tact, though run over by aluminum from the piston, the reeds and screws are all there, and nothing else looks out of place. I'm going to need to do a new crank/rod at this point, bearings and seals, plus a new piston and bore for the third time. I'm even thinking about doing a rad valve or a V-Force reed cage. I'd really like to put it back together and be confident this phenomenon won't happen again, any ideas where to look? PLEASE?!?

[barnett468]

I'm even thinking about doing a rad valve or a V-Force reed cage.

Why?


PREVIOUS KAWASAKI INTERNATIONAL R & D PROJECT ENGINEER AND ATV DEPARTMENT SUPERVISOR AND THE ONLY PERSON ON 3WW WITHOUT AN EDIT BUTTON OR A STAR

[pismorat]

Rad valve because my current reeds are original and not resting in the closed position anymore, and I have a larger carb. that has stretched and torn the stock intake boot. All things considered, I don't want to spend all the money on a fresh rebuild and have an air leak or another piece of metal get sucked through. I still don't know where this piece of metal came from that damaged it this time...

[NeverLift]

Sounds like your connecting rod bearing is coming apart. How much end play is in the rod?

[yaegerb]

Foreign Object Damage - My piston and cylinder head were bouncing a piece(s) of magnetic metal back and forth between each other, ultimately closing the plug gap. Once I disassembled the motor, there were about 30 tiny pieces of magnetic metal that would fit on a 50 cent piece in the pipe. I have NO IDEA what it used to be or where it came from. The rings are in tact, though run over by aluminum from the piston, the reeds and screws are all there, and nothing else looks out of place. I'm going to need to do a new crank/rod at this point, bearings and seals, plus a new piston and bore for the third time. I'm even thinking about doing a rad valve or a V-Force reed cage. I'd really like to put it back together and be confident this phenomenon won't happen again, any ideas where to look? PLEASE?!?

Crack the cases and look for the culprit. No science or magic to it

[pismorat]

I have split the cases. Nothing is too alarming. The rod does have a lot of side-to-side movement, so I bet its bearing is going, or gone. Is it coated steel (magnetic)? The side bearings look OK, but I will press them out in a while and check them better before replacing them.

[oldskool83]

I once bought an xr200 that had a screw sitting in its intake valve slot about ready to fall into motor. If you see somthing missing or broken just rebuilt it. Don't think your the inkynperson to work on it in 3
I can't seem to nail your buddy down. My buddy at work wants to run up in about 2 weeks. Just have him text me on what all is their cuz he said I take all of it but I don't know what all of it is. Kinda going in blind for a 5hr drive. Let me know either way.
32 years lol

[BOB MARLIN]

Last time I had damage like that it was the rod bearing.

[pismorat]

It is definitely the lower rod bearing! I started inspecting it and I can see pieces moving inside the little gap in the rod. I'm starting to gather a parts list and will have here running again before desert season. Besides age, what can cause the rod bearing to tear apart like this? I will get pics soon.

[BOB MARLIN]

I believe mine was caused by a piston that melted or came apart from the previous owner. When I bought mine the owner told me that it had just been rebuilt because the piston died. I think a lot of time when a piston comes apart a lot of crap ends up dropping right down on top of that little slot your looking through where you can see the rod bearing.
A bad oil to gas mixture will starve the rod bearing of lubrication also. The rod, bearing and crank are pretty much a package deal so you have to buy all 3, but they are not too expensive. Now is a good time to go big bore if it was on your list because to do it right you need to machine the cases anyway.

If some of that rod bearing got stuck between the piston crown and one of the ports, like mine did, your cylinder could be jacked also. Being that I needed a new cylinder at that point, I went with a big bore cylinder. Huge increase in H.P, but also a huge pain in the ass. Fitment issues and running hot are some of the trade offs.