Posts
1720
Joined
8/2/2006
Location
Forest H Ill, MD
US
Edited Date/Time
1/25/2012 10:16pm
Guys, would like your opinions on what to do about this. I recorded some videos to show what is up.
Connecting Rod
Piston and Wrist Pin
Crank
At the end of last season I found some small metal flakes in my oil, 2 rides before the end of the season. I drained the oil, replaced the filer, took off the valve cover and checked the valves. Found the right intake a little out of spec, so I re-shimmed for my last race, planning to do a full rebuild over the winter. My seats are getting re-cut and valves replaced right now. While i was inspecting for crank and bearing play last night, I found gouging in the wrist pin, and some wear in the small end of the connecting rod. The crank has about 70 hours on it, and there is really no play that I can find in the bearings, everything seems normal. The small end of the connecting rod has some scouring, and the bronzing is almost completely gone (or is that burnishing that is showing up from wear?). Note however, there really isn't and up and down play in the connecting rod small end at all. There is some titling movement (which is normal?) but the wrist pin in the rod feels solid vertically. Please take a look at the following videos and offer up your advice.
1: Does this rod's small end look safe to run?
2: Can the surface be polished?
3: What on the bike options are available without splitting the cases and pulling the motor?
4: Is it time for a new crank, just to be sure?
I was planning to keep this bike for another year, and get a 2012 next season. With the $600 I'm putting into new valves, piston, cylinder, etc.. would it be advisable to drop another 500 and replace the crank?
Jason
Connecting Rod
Piston and Wrist Pin
Crank
At the end of last season I found some small metal flakes in my oil, 2 rides before the end of the season. I drained the oil, replaced the filer, took off the valve cover and checked the valves. Found the right intake a little out of spec, so I re-shimmed for my last race, planning to do a full rebuild over the winter. My seats are getting re-cut and valves replaced right now. While i was inspecting for crank and bearing play last night, I found gouging in the wrist pin, and some wear in the small end of the connecting rod. The crank has about 70 hours on it, and there is really no play that I can find in the bearings, everything seems normal. The small end of the connecting rod has some scouring, and the bronzing is almost completely gone (or is that burnishing that is showing up from wear?). Note however, there really isn't and up and down play in the connecting rod small end at all. There is some titling movement (which is normal?) but the wrist pin in the rod feels solid vertically. Please take a look at the following videos and offer up your advice.
1: Does this rod's small end look safe to run?
2: Can the surface be polished?
3: What on the bike options are available without splitting the cases and pulling the motor?
4: Is it time for a new crank, just to be sure?
I was planning to keep this bike for another year, and get a 2012 next season. With the $600 I'm putting into new valves, piston, cylinder, etc.. would it be advisable to drop another 500 and replace the crank?
Jason
given your opinion however, i think i will just replace the crank. At this point ~$500 is alot cheaper than a new KTM250sx.
ether the main bearing is bad, the crank has worn out in the bearing or the bearing is spinning in the case.
The Shop
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