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| CR250M air leak https://vintagedirtbikeforums.alp-sys.com/viewtopic.php?f=21&t=927 |
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| Author: | FirePig [ Mon Feb 27, 2006 6:21 pm ] |
| Post subject: | CR250M air leak |
Howdy all, ('73-'74 CR250M) I just put my engine back together after having a new main bearing insert machined into the left center case. Had the center cases, barrel and head back togther and went to pressure test it and it's dropping about 3-4 lbs per minute. Not good. I'm used to dropping less than a pound per five minutes. Squirted soapy water, found one leak at the base gasket and fixed it and then pressure tested again. Still sinking like the Titanic. More soapy water and while spraying the left main seal some overspray lands on part of the case and a big bubble appears, in fact I soon have three areas on the case bubbling. On the left center case in where the ignition is mounted there are three "plugs" (I don't know if that's what they are but at the moment it's the best I can come up with) that have some hard brown expoxy or something covering them. Never paid these any attention until today. They are about on the outside of the area that's built up to hold the main bearing. I don't know if these are holes left over from casting or what? Not sure if it's just a simple matter of digging out the expoxy or whatever is currently covering them and putting some fresh stuff in there? Any help appreciated as always. Loren |
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| Author: | FirePig [ Tue Feb 28, 2006 5:14 pm ] |
| Post subject: | |
May have answered my own question. Took my Dremel and started to grind off the expoxy cap on these plugs with the intention of smearing some more epoxy on and seeing if that would work. Wanted to grind out these plugs a little to get better bite. Went into them like cutting butter with a hot knife. Noticed that one of them was loose so I took a dentists pick and easily popped it out. Turns out these plugs are made of what I think is aluminum putty. Popped all three out as they were all loose anyway. Went to a buddies house who has a full machine shop and just about every metal working compound known to man. He had some "industrial grade" aluminum epoxy. Mixed up a batch and filled the holes. Now I have the engine in a warm place and waiting 24 hours for the epoxy to fully cure and see if that does the trick. I think this all started by heating up the left center case to get the new main bearing in and the temperature differential between the aluminum case and these epoxy plugs caused the holes in the aluminum to expand open and break the seal that had existed for 30 years thus leading to the air leak. I had heated the case several times in the past when replacing main bearings but I must have got it to hot this time. So one of the things others might learn from this is when you have a lower end air leak that you just can't trace down to left main seal or base gasket or intake gasket you might look at these three plugs a bit to the outside of the left main seal as the culprits. |
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