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Makotosun

78 it. 250 crankshaft seal

  • jtb605
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78 it. 250 crankshaft seal was created by jtb605

Hi everyone , needing to replace my clutch side crankshaft seal, can't find a manual, the seal has small tabs about 1/4" wide and spaced all the way around it. Does this side go in or out. It was in on the one that came out  all help appreciated. Thanks 
17 Jul 2026 17:26 #1

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Replied by RT325 on topic 78 it. 250 crankshaft seal

Goes in towards the bearing.
Think it's to leave a gap so fuel mix can get to the bearing via the hole leading down from the transfers.
Don't push it in any further than flush & should be good.
Try to fit it so the gap between steps leaves the hole an open path to the bearing.
If by chance & if my memory is correct, the steps have a very slight--step down--so in the event of a tab going past the feed hole all wouldn't be lost & could still get mix past there.
Anyway, fuel mix could get behind the bearing at the crank wheels so not gonna starve.
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17 Jul 2026 22:49 #2

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Replied by MarkT on topic 78 it. 250 crankshaft seal

Yes, "castle turret" bumps go in towards the bearing.  
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
18 Jul 2026 08:17 #3

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Replied by jtb605 on topic 78 it. 250 crankshaft seal

Thanks, could you tell me if I'm correct to slip the oring up next to the bearing ? As I was tapping the other bearing in the little spring came out and had a small kink in it. Could I use a couple of large washers and a piece of PVC to press the seal in with the nut on the shaft ? Just don't want to ruin another seal. 
18 Jul 2026 15:36 #4

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Replied by jtb605 on topic 78 it. 250 crankshaft seal

Thanks, should that seal be lubed on the top and bottom ? I've been told several different things. Also To prevent damaging another seal, could I use a big washer against the seal,a piece of PVC and another washer, then press it in by tightening the nut on the crankshaft against them ? Thanks for your help. 
18 Jul 2026 17:01 #5

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Replied by Schu on topic 78 it. 250 crankshaft seal

I’ve used a similar method of stacked washers and drawing the seal in with the nut,

youtube.com/shorts/JDq0PwSc9AY?feature=shared

youtube.com/shorts/4USk-V55UWw?feature=shared
Schu

CT1B, CT1C, JT1, JT2, CT2, RT3, DT360A (2), GT80B, DT100B, DT125B, DT175B, DT175C, DT250B (2), DT400B, Z50

Someday, you'll own some Yamahas
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19 Jul 2026 04:13 #6

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Replied by jtb605 on topic 78 it. 250 crankshaft seal

Lube or not ?
19 Jul 2026 07:36 #7

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Replied by Schu on topic 78 it. 250 crankshaft seal

I simply dip my finger into Yamalube and swipe it around the inside diameter of the hole.

I am no expert, but I’ve done it this way successfully many times.
Schu

CT1B, CT1C, JT1, JT2, CT2, RT3, DT360A (2), GT80B, DT100B, DT125B, DT175B, DT175C, DT250B (2), DT400B, Z50

Someday, you'll own some Yamahas
Last edit: 19 Jul 2026 08:54 by Schu.
19 Jul 2026 08:51 #8

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