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Old 04-30-2014, 09:28 AM
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Default oil in crank case… bad oil seal?

     

hey everyone! new here figured you guys could help me.

took apart a cr125 2001 that i bought last night that wouldn't run… felt like it had low compression… compression tested it and it was low. took the head off and found a new piston with a bunch of play. Found that the jug was bored .020" over and the last owner tried putting a stock bore piston in. When i removed the jug i saw oil in the bottom of the crank case. Does this mean the oil seals bad??? or could there have been that much oil/gas blow by from the wrong sized piston?

i can post some pictures tonight…but any info is appreciated thanks!

---------- Post added at 08:28 AM ---------- Previous post was at 08:15 AM ----------

by oil seal I mean the crank seal ***
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Old 04-30-2014, 09:41 AM
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IT's not uncommon to find some oil in the crankcase. Any mixed gas that is left in the bottom end when you shut the bike off will leave a bit of oil after the gas evaporates. Given the quality of the work done by the previous owner however, who knows what kind of regular maintenance was done. Might be worth opening up the bottom end and checking things out.
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Old 04-30-2014, 09:54 AM
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bottom end is tight and right… wiseco parts in the bottom end redone by a professional is what i was told. Owner tried to do the top end and must not have know it was bored .020" over
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Old 04-30-2014, 12:18 PM
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Well if it's got a wiseco crank in it, you will be splitting the cases soon enough anyhow when it grenades.
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Old 04-30-2014, 01:17 PM
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Quote:
Originally Posted by JMV View Post
Well if it's got a wiseco crank in it, you will be splitting the cases soon enough anyhow when it grenades.
haha yea i have heard that from a couple people. oh well cross that bridge when i get to it i guess
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Old 04-30-2014, 01:43 PM
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I have heard alot of ppl make those comments about wiseco but everyone where I live runs them and swears by them. Even the shop reccomended them.
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Old 04-30-2014, 07:34 PM
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The only issues i've seen with wiseco cranks is the guys installing them without a crank installer or heating bearings. But I have also had a few that were out of truw straight out of the box. But I always check them on any crank i do.
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Old 04-30-2014, 07:50 PM
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Not sure if the 125s are similar to the 250s crankcase wise..... but oil in your crankcase is either a bad right side crank seal, or pinched centercase gasket. You can tell right away as the bike will smoke like a freight train! Not to mention your expansion chamber will probably have engine oil in it
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