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which way does the crankshaft seal go

  • treeves
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which way does the crankshaft seal go was created by treeves

Which way does the crankshaft seal go on my 1974 dt 360 The original seal came out with the spring to the outside, I thought the seal should go like the new seal I show on bike.
27 Jan 2021 13:20 #1

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Replied by msavitt on topic which way does the crankshaft seal go

I am not an expert, but I know a few on this site and the castle thingies should face the bearing,. since your pressing (or pounding) on an edge vs. a surface you got to be careful. I used some PVC fittings to come up with a driver that the first time around (long story) I drove in caveman style with a hammer and the second time around I used same tool under a crank installer tool to nicely draw it in in a more civilized manner
good luck!

ps. proper replacement should have a spring on both lips, not just one
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Last edit: 27 Jan 2021 13:31 by msavitt. Reason: added ps
27 Jan 2021 13:31 #2

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Replied by treeves on topic which way does the crankshaft seal go

Thanks for the quick response
27 Jan 2021 15:01 #3

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Replied by bosco659 on topic which way does the crankshaft seal go

Interesting it goes in this way on this application. On another forum, someone also advised this is the correct direction to put the seal in. I have never done that before. I guess the nubs on the seal face protect the seal in case it comes into contact with the bearing.
27 Jan 2021 17:02 #4

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Replied by MarkT on topic which way does the crankshaft seal go

bosco659 wrote: Interesting it goes in this way on this application. On another forum, someone also advised this is the correct direction to put the seal in. I have never done that before. I guess the nubs on the seal face protect the seal in case it comes into contact with the bearing.


Not exactly. Castle nubs prevent cutting off oil supply to bearing by pressing seal into case too far.
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
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27 Jan 2021 17:11 #5

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Replied by treeves on topic which way does the crankshaft seal go

Put the seal in today and pressure tested and I can see a leak but can turn the crankshaft and not get a leak. Would this be normal or what should I do?
28 Jan 2021 15:31 #6

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Replied by Snglsmkr on topic which way does the crankshaft seal go

If I'm understanding your post correctly and you are saying the replacement seal is leaking at the crankshaft, then it may be the crankshaft/seal contact point is not smooth.

The crankshaft surface could be worn, corroded or damaged.

If the imperfections are minor, they may clean up with fine abrasive paper like 400 grit followed by 600 and even finer. Protecting the bearing from abrasive is important.

If the imperfections can't be cleaned up, then a sleeve over that section of the crankshaft can correct the problem. I have not used that method on my bikes but have on auto engines.
Others on this forum have. If I can find a post I'll put up a link.

Unfortunately, the seal will need to come out to work on the crank. Getting it out undamaged is the challenging part. I have not tried it and I can't recommend it, but raising the pressure in your leakdown tester may work. However, it may pop the oiled side out first.

Others may have additional recommendations on the possible causes of the leak and how to approach it.
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28 Jan 2021 16:18 #7

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Replied by Pedalcrazy on topic which way does the crankshaft seal go

Plus 1 on what Snglsmkr said...pretty much word for word :)
1978 DT400E
1976 DT400C
1973 RT3
1971 RT1B
28 Jan 2021 16:42 #8

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Replied by bosco659 on topic which way does the crankshaft seal go

Does the left side typically fail more frequently than the oiled side? I suppose a leak down test is the only definitive way to check the health of the oiled side’s seal?
28 Jan 2021 17:39 #9

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