CarnageZ28
Member
- Mar 25, 2008
- 109
- 0
So at this point I dont know where to begin.
So I happened to come across a 1991 RM 125. Really clean, but needed a top end. Kid said he rode it home after it let loose, still ran, but rough. He tore it down, saw it needed sleeved, and sold it to me.
I get an iron sleave pressed in, port matched, bored and honed. New Wiseco Pro-Lite piston, ring, wristpin, bearing. Since he rode it home, we assumed the crankcase was clean, but split it anyways to be sure. Tore it down, split the case, cleaned everything thoroughly. There was absolutly ZERO metal in the motor. Rod bearings WERE good. Slight side to side play, but ZERO up and down play. Reassembled, using plenty of oil on all parts. All fresh fluids. New premium gas, mixed at 20:1, just as the owners manual calls for. I know, its rich, but its what Suzuki calls for, even for my 89 Quadracer . Used SuperM oil.
Fire it up, fires on 2nd kick, idles great. Let it warm up for several minutes. Turned the choke off, good idle, took it out. Made several light-throttle (Less than 1/2) rides up and down the street, not going near redline on it yet, and it started to die on me. Had 50psi compression.
Tear it back down, looks like foriegn material got lodged between the piston and cylinder head. Took out the head, piston, and required cylinder boring. There were pieces of some type of magnetic metal jammed into both the head and aluminum piston. We assumed somehow a piece of metal was wedged somewhere that I missed, but I was 100% positive I was clean with it.
So I tear it all back down, split the cases again, this time there WAS metal in there from it blowing up. Last time there wasn't. I clean it all out, reassemble, get a .060 over Wiseco piston, bored, honed, cut powervalves, etc. Reassemble again, using plenty of oil on assembly. Ring was seated correctly, circlips were put in properly. Reassemble the top end. Get it together. Again, bike fires on the 3rd or 4th kick. Idles nicely with the choke on. I let it warm up for a few minutes, cut it to half choke, let it run a little longer, and then turned it off. Ride the bike a few light passes up and down the street, making passes in 3rd gear running it up to 60%redline, let it compression brake back down, run it up a little higher to say 65% redline, let it compression brake back down, to help seat the rings properly. Did this proceedure for several passes. Never took it up to what would be redline. Just enough to come into the powerband of the motor, then let it compression brake back down. All of the sudden, same old thing ... It starts sputtering coming up the hill, I downshift it, and it siezes up..
Pulled the engine out, took the head off, and the new cylinder head, and new forged piston are mangled, just like last time. Foreign material wedged between the piston and the head. It is magnetic, and is NOT Rings, Circlip, or Wristpin material. Light scores on the cylinder. Will need bored, piston, cut powervalves, honed, and head on the top end. However, this time, the big-end rod bearings are shot. I assume from the piston hitting the head? There is TONS of play vertically in the connecting rod, that wasn't there before. I am 100% absolutly positive there was no foriegn metal left in the crankcase from when I split it last time. I was VERY clean, and have done literally 30-40 of these types of motors before in tech/shop classes/for friends.
Any ideas WHAT is causing this? I know, FOR SURE, there was no metal down there on the last rebuild. And I have no way of contacting the previous owner. I am open to any/all suggestions. Its late, I'm frustrated. Im going to bed on this one.
So I happened to come across a 1991 RM 125. Really clean, but needed a top end. Kid said he rode it home after it let loose, still ran, but rough. He tore it down, saw it needed sleeved, and sold it to me.
I get an iron sleave pressed in, port matched, bored and honed. New Wiseco Pro-Lite piston, ring, wristpin, bearing. Since he rode it home, we assumed the crankcase was clean, but split it anyways to be sure. Tore it down, split the case, cleaned everything thoroughly. There was absolutly ZERO metal in the motor. Rod bearings WERE good. Slight side to side play, but ZERO up and down play. Reassembled, using plenty of oil on all parts. All fresh fluids. New premium gas, mixed at 20:1, just as the owners manual calls for. I know, its rich, but its what Suzuki calls for, even for my 89 Quadracer . Used SuperM oil.
Fire it up, fires on 2nd kick, idles great. Let it warm up for several minutes. Turned the choke off, good idle, took it out. Made several light-throttle (Less than 1/2) rides up and down the street, not going near redline on it yet, and it started to die on me. Had 50psi compression.
Tear it back down, looks like foriegn material got lodged between the piston and cylinder head. Took out the head, piston, and required cylinder boring. There were pieces of some type of magnetic metal jammed into both the head and aluminum piston. We assumed somehow a piece of metal was wedged somewhere that I missed, but I was 100% positive I was clean with it.
So I tear it all back down, split the cases again, this time there WAS metal in there from it blowing up. Last time there wasn't. I clean it all out, reassemble, get a .060 over Wiseco piston, bored, honed, cut powervalves, etc. Reassemble again, using plenty of oil on assembly. Ring was seated correctly, circlips were put in properly. Reassemble the top end. Get it together. Again, bike fires on the 3rd or 4th kick. Idles nicely with the choke on. I let it warm up for a few minutes, cut it to half choke, let it run a little longer, and then turned it off. Ride the bike a few light passes up and down the street, making passes in 3rd gear running it up to 60%redline, let it compression brake back down, run it up a little higher to say 65% redline, let it compression brake back down, to help seat the rings properly. Did this proceedure for several passes. Never took it up to what would be redline. Just enough to come into the powerband of the motor, then let it compression brake back down. All of the sudden, same old thing ... It starts sputtering coming up the hill, I downshift it, and it siezes up..
Pulled the engine out, took the head off, and the new cylinder head, and new forged piston are mangled, just like last time. Foreign material wedged between the piston and the head. It is magnetic, and is NOT Rings, Circlip, or Wristpin material. Light scores on the cylinder. Will need bored, piston, cut powervalves, honed, and head on the top end. However, this time, the big-end rod bearings are shot. I assume from the piston hitting the head? There is TONS of play vertically in the connecting rod, that wasn't there before. I am 100% absolutly positive there was no foriegn metal left in the crankcase from when I split it last time. I was VERY clean, and have done literally 30-40 of these types of motors before in tech/shop classes/for friends.
Any ideas WHAT is causing this? I know, FOR SURE, there was no metal down there on the last rebuild. And I have no way of contacting the previous owner. I am open to any/all suggestions. Its late, I'm frustrated. Im going to bed on this one.