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1978 DT400 Left Crankshaft Seal installed backwards?

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I have attached a photo of the left side crankshaft seal that was installed in my 1978 DT400.  
The manufacture's marks or numbers were facing inwards towards the crankshaft. However, according to the DT250D DT400D Service Manual, the seal should be installed with the manufacture's marks or numbers facing outwards. (One page from the service manual is attached.) 
I have seen a number of pictures where the manufacture's marks or numbers were facing the crankshaft.   
Is the service manual wrong?
What is the correct orientation for the left side crankshaft seal?  
 
24 Oct 2021 07:03 #1

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The castle top always goes towards the bearings to act as a stop so you don’t starve the bearings of oil.
1978 DT400E
1976 DT400C
1973 RT3
1971 RT1B
1968 DT1 (Project)
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24 Oct 2021 07:33 #2

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its correctly installed!
if you replace be careful to not buy replacements that do not have a tension spring on both sides (SW type).  I did from an eBay seller with a very catchy name that many have likely heard of who takes pic of seal laying on an old Yamaha envelop and then sells you a transmission seal.

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24 Oct 2021 08:44 #3

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Agreed.  Manual is wrong*.  Your seal is installed correctly. 

Manual is wrong on setting timing too.  So be aware of that when you reinstall your ignition.  Your ignition won't match the manual. 


*what manual is quoting is the "general rule"... for seals, gaskets, and piston rings any writing normally faces "up" or "out".  There are exceptions.  These crank seals are an exception.  The rule does apply to the other engine seals. 

Later model crank seals are still available from Yamaha so get original.  250/360/400 models that are a few years older than yours don't always have this option. 
 
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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24 Oct 2021 09:00 #4

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One more comment on the "general rules" for gaskets, rings, seal, bearings, circlips, etc.... 

That's all they are...  general rules.  And can vary from model to model and maybe year to year.  Sometimes I might say "always" when thinking of a specific part like the numbers "always" facing up on a Yamaha keystone piston ring...  but that might not be true with another type (ie Dykes) or brand of piston ring.  It's a good idea to look carefully at how the parts fit together.  Sometimes you have to ignore the "general rule" to get it right.

Back to this thread, I don't know if I would have ever figured out the "castle turret" bumps on some of the 250/360/400 seals are there to keep from pressing the seal in to far and cutting off oil to the bearing.  (I have far more experience with the smaller bikes).  It's the experts like DEET and Enduronut (one word, not two) that taught me that.  Just passing on the knowledge. 

(I think DEET once posted pictures on how the oil passage can be blocked by pressing in the seal too far and how he indexes a gap in the bumps to line up with the oil passage to be extra safe)

Point is I spend a lot of time of here...  much of it is spent learning from you guys, trying to help others solve problems, and trying to save others from making some of the same mistakes I have.  I've broken a lot of stuff trying to fix it. 

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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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24 Oct 2021 10:41 #5

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Thanks for the clarification on general rules versus reality.  I installed a Yamaha seal, dual lip type with two springs. I got the bike running last night.  I placed the stator plate back in the same place to avoid a timing change.  

Also, thanks for letting me know the manual instructions for timing a DT400 are incorrect.
Just for future reference, what is the correct way to set timing on a 1978 DT400?
25 Oct 2021 18:26 #6

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I put my 78 DT400E together this summer. For timing there is a mark on the top of the engine case, a long line with several small lines on each side of the long one on the stator back plate, and finally a mark on the flywheel. I used a dial gauge and discovered if you line up the mark on case, the long line on the stator plate and the mark on the flywheel you have timing set at 2.9 mm BTDC. Clever Yamaha! The small lines on each side of the long line on the stator back plate give you a reference for advancing or retarding from 2.9. I wanted 2.9 so just lined them all up. 
1978 DT400E
1976 DT400C
1973 RT3
1971 RT1B
1968 DT1 (Project)
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26 Oct 2021 08:22 #7

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Pedalcrazy explained it better than I could!  

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(and in a lot less words)  

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If you need a manual, the monoshock DT175 ignition is timed the same as the DT400.
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
26 Oct 2021 14:49 #8

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