1987 Suzuki RM 125 Crank Pitting

therm_1126
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Richland, PA US
therm_1126
Hello, I have an 87 rm 125 and I recently did a rebuild on the entire motor and did some powder coating to fancy it up a little. (Gave the bike more than it deserved). Anyways, I was running the motor during break in and since it started, it had been leaking antifreeze out the weep hole. I replaced all seals so I knew the seal wasn’t bad, so I opened it back up and checked it out. I did it see anything immediately wrong so off I was riding. Next oils change arrived and the oil was milky of course. Noticed the crank was pitted and for whatever stupid reason the crank on this bike also doubles as a water pump shaft. I tried jb weld putty on the crank end and the seal wore through. I’m at a loss, can anybody help? I’d rather not replace the crank since I put a new rod and bearings on it, and I’d need new oem gaskets. Wow Th that being said, can anybody be of assistance? Thanks!
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sandman768
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sandman768 8/1/2020 6:25pm
8/1/2020 6:25pm
Very poor design by Suzuki on these models... you may have to send the crank out to a machine shop that can build up and machine the crank area where it rides on the seal. Other than trying to sand the pitting smooth and just keep trying new seals... I restored an 87 125 last year, Suzuki engineers were definitely mailing it in during these years...
87RM125
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87RM125 8/1/2020 7:24pm
8/1/2020 7:24pm
sandman768 wrote:
Very poor design by Suzuki on these models... you may have to send the crank out to a machine shop that can build up and machine...
Very poor design by Suzuki on these models... you may have to send the crank out to a machine shop that can build up and machine the crank area where it rides on the seal. Other than trying to sand the pitting smooth and just keep trying new seals... I restored an 87 125 last year, Suzuki engineers were definitely mailing it in during these years...
Yeah that seems the best way to go... any other or easier ways? Obviously splitting the cases again is a last resort after the motor was assembled. Also, it really is a great bike in my opinion as far as engine operation goes. They run real nice and produce some decent power
87RM125
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87RM125 8/1/2020 7:24pm
8/1/2020 7:24pm
sandman768 wrote:
Very poor design by Suzuki on these models... you may have to send the crank out to a machine shop that can build up and machine...
Very poor design by Suzuki on these models... you may have to send the crank out to a machine shop that can build up and machine the crank area where it rides on the seal. Other than trying to sand the pitting smooth and just keep trying new seals... I restored an 87 125 last year, Suzuki engineers were definitely mailing it in during these years...
Did you have that issue as well?
sandman768
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sandman768 8/2/2020 4:42am
8/2/2020 4:42am
Mine was not that bad, I had crank rebuilt by Ken O’Conner racing in Conn. he cleaned it up & said it should be fine. If you don’t want to split cases, I would try to clean up the crank end really good & apply a 2 part epoxy liquid metal to the shaft where the seal rides, then sand down the epoxy smooth & try new seal again. I bought my bike blown up, one of the reasons it kept blowing up was the plastic water pump impeller that’s bolts into the crank end was broke, so it was never flowing coolant... the previous owner just kept doing top ends and over heating the bike. My head & cylinder top were warped from overheating so much.

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87RM125
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87RM125 8/2/2020 4:53am
8/2/2020 4:53am
sandman768 wrote:
Mine was not that bad, I had crank rebuilt by Ken O’Conner racing in Conn. he cleaned it up & said it should be fine. If...
Mine was not that bad, I had crank rebuilt by Ken O’Conner racing in Conn. he cleaned it up & said it should be fine. If you don’t want to split cases, I would try to clean up the crank end really good & apply a 2 part epoxy liquid metal to the shaft where the seal rides, then sand down the epoxy smooth & try new seal again. I bought my bike blown up, one of the reasons it kept blowing up was the plastic water pump impeller that’s bolts into the crank end was broke, so it was never flowing coolant... the previous owner just kept doing top ends and over heating the bike. My head & cylinder top were warped from overheating so much.
Jeez, similar issue with mine. Our impeller was totally separated from the bolt and there was evidence of overheating. Thank you for the help, I’ll give it a try! If you have any spare 87 suzuki parts, I’d be interested in purchasing them. My 87 Suzuki is here to say and if I can’t fix the end of the crank, I guess it will leak coolant for a while. I only trail ride, so no big deal

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