ekker
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Posts: 10
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Post by ekker on Jul 31, 2008 21:06:07 GMT -5
I set out to adjust the valves and timing chain on my 78, SR500 and when I pulled the left side crankcase cover about half a cup of oil poured on the floor. Maybe I'm wrong but I don't think there should be any oil in with the A.C. magneto. The oil is probably coming past the crankshaft oil seal, can this seal be replaced without splitting the engine cases? When I last changed the oil I did over fill it a bit but I don't think this would be the cause.
Any thoughts or suggestions would be appreciated.
Thanks,
Eric
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pcnsd
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Post by pcnsd on Jul 31, 2008 21:43:16 GMT -5
Crankcase seal on the magneto side is from the inside. If I may make a suggestion, clean it up. make sure oil level is correct and monitor for additional leakage. If it continues to leak, lo siento mucho. If not, it may be the oil overfill event.
Good luck
PC
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ekker
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Post by ekker on Aug 1, 2008 6:59:46 GMT -5
I think I'm about to learn more about the internals of this engine than I planned when I started the tuneup.
Thanks for the input,
Eric
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ekker
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Post by ekker on Aug 1, 2008 9:07:36 GMT -5
 Well I cleaned it up, put the oil level to the mid point on the stick and it still leaks. I ran the engine with the cover off, at idle there is no leak but as the revs come up to about 4k a very slow trickle starts to emerge from below the flywheel. I guess as the oil pressure and volume increase with rpm the oil starts to get past the seal. So it looks like I will be pulling the engine apart. I suppose replacing all the seals and gaskets is a good idea, are there any other parts that commonly wear out that I should consider replacing. The engine runs great and seems to have lots of compression and burns no oil. Thanks guys, Eric
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Post by solo2racr on Aug 1, 2008 11:11:08 GMT -5
Before you start tearing down the engine, be sure the crankcase vent isn't clogged. It's possible that it may be clogged and building up pressure inside the engine forcing out the oil. A long shot but, much easier than stripping down a whole engine.
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Post by chew652 on Aug 1, 2008 11:41:33 GMT -5
I am not sure you have to strip the engine to change the seal. If the seal is installed from the outside of the case you may be able to change it by just removing the stator and flywheel(mag rotor). If you carefully thread some small sheet metal screws into the flat portion of the seal so as not to damage any metal surfaces,you can pull it out with vise grips .Then it is a matter of carefully installing the new seal straight. Old 2-stroke stuff again but you wouldn't even have to pull the motor from the frame.
I'm sure some of the old hands around here can tell you if this is possible. I sure hope it is the clogged crankcase vent,that would be easiest to fix. Good luck.
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sven
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Post by sven on Aug 1, 2008 12:37:25 GMT -5
I am not sure you have to strip the engine to change the seal. If the seal is installed from the outside of the case ... It is. Regards Sven |
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ekker
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Post by ekker on Aug 1, 2008 15:30:36 GMT -5
I have just checked the crankcase vent and the oil return line, both are fine.
I just need to find a flywheel puller and have a look at the seal, sure hope I can change it with out pulling the engine.
This forum is a great resource, many thanks guys.
Eric
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pcnsd
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Post by pcnsd on Aug 1, 2008 23:33:56 GMT -5
A service manual is a big help for disassembly. Take photos for later reference if this is your first bottom end. The Yamaha website has down loadable factory exploded part references at www.yamaha-motor.com/sport/myyamaha/prompt/L3Nwb3J0L3BhcnRzL2hvbWUuYXNweA==/Parts%20Catalog/starthere.aspx You will need to navigate to your year and model. Super-size before doing a "Save As" to your computer. You will also need a case splitting tool to separate the case halves. You can build your own from a steering wheel puller and a plate  or purchase one from a company like Works Connection. It mounts to the magneto side. As for the Magneto puller, they should be available from your local Yamaha dealer. What to replace once it is all apart? It just depends on what you find. The Yamaha 500 single is a very tough motor, other than a seal and gasket kit, you may not require much more, if you are not racing. You should clean everything and inspect the following: Small end of the connecting rod (look for the copper to be worn away, if so you need a new rod.) Main bearings (Almost never bad in my experience) Output shaft bearing. Clutch basket for grooving. Others on the forum may suggest other areas for inspection also. Good luck PC |
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Post by solo2racr on Aug 2, 2008 0:08:26 GMT -5
Others on the forum may suggest other areas for inspection also. Good luck PC I would also check the trans gears for chipped/missing teeth. Also check your shift forks for wear and that they are straight. While your in the top, check the exhaust rocker and cam lobe for wear. There is one other trick that is a bit err tricky. Piston rings in a 4 stroke are a finicky lot. They do not like to be disturbed. To that end, when I do a job like this, I will only lift the cylinder off the case just enough to see the wrist pin and leave the rings in the bore. Remove a cir-clip from one side of the wrist pin and slide the pin out. once it is out, set the whole cylinder/piston assembly to the side. One other added benefit to this is not having to compress the rings to get then back in the bore. I have seen engines tore down and the pistons removed from their bore more than once only to take months for the rings to re-seat. Even a light hone to the bore before reassembly didn't do anything to help the rings re-seat. IF the rings SHOULD come out the bottom of the bore, do not rotate them on the piston. At least they will be close to finding their way back to where they were. One other option is to just re-ring. If your compression is a bit low, this is a good time to do this. Also a good time to re-seat/lap the valves to their seats. |
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ekker
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Post by ekker on Aug 2, 2008 7:41:41 GMT -5
I have ordered a flywheel puller and the oil seal from Mark at Thumperstuff. Plan A is to just replace the seal from the outside, hoping to avoid plan B. I,m away with work for a week or so but will update progress latter.
Eric
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pcnsd
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Post by pcnsd on Aug 2, 2008 15:55:33 GMT -5
Crankcase seal on the magneto side is from the inside. My regrets, allow me to correct myself. The magneto side oil seal IS available from the exterior of the case under the magneto. This is what comes of reviewing manuals instead of walking out to the garage. This is from my 79, yours should be the same.  Again sorry for the bad info. PC |
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ekker
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Post by ekker on Aug 2, 2008 22:46:17 GMT -5
Hi PC,
Thanks for the update and the great photo of the oil seal. It looks like a pretty straight forward job.
Cheers,
Eric
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sven
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Post by sven on Aug 5, 2008 10:55:29 GMT -5
The magneto side oil seal IS available from the exterior of the case under the magneto. This is what comes of reviewing manuals instead of walking out to the garage. This is from my 79, yours should be the same. Whatever year of make, either SR or XT or TT, this seal can always be mounted from outside. It fits quite tight, so be careful when you remove it, the bearing cage is just behind. Regards Sven |
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Post by solo2racr on Aug 5, 2008 12:01:30 GMT -5
Also be sure when the new one goes back in that it stays straight. Don't let it cock over to one side. It will tear the rubber off the outside and make the seal useless. Ask me how I know.  |
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Well I cleaned it up, put the oil level to the mid point on the stick and it still leaks. I ran the engine with the cover off, at idle there is no leak but as the revs come up to about 4k a very slow trickle starts to emerge from below the flywheel. I guess as the oil pressure and volume increase with rpm the oil starts to get past the seal.
