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DanielHowden

Engine oil on left and right flywheels - 247

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I have my left and right flywheels, not swimming, but there is a lot of oil on them as I turn the crank.  If I wipe the oil off its on there again after one revolution.  I have recently changed the crank seals, so this seems odd to me.

Is this a sign that the crank seal is failing already or is it a possibility that somehow oil is getting through from the gearbox or somewhere else on the primary side?

Thanks, Daniel.

1971 247 Cota

Edited by DanielHowden
Added info

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You may have an overly worn crank shaft,pitting on the crank shaft can stop a new seal creating a good seal, or you  may have forgot to fit the tiny seal springs on the new seals assuming thay are the type that come with seal springs, did you grease the seals before fitting them?. 

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There were no springs when I removed the old seals but just a retaining ring.  I did put a wipe of oil around the seal when I installed it.

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If the crank is really worn that it will no longer give a tight enough fitment on the seal I guess I could have that machined and sleeve it.

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I found that the amount of oil that had come from the primary side as there was next to none of the oil left in the primary casing.
 
I have already changed the crank seals but this is still not working.
 
  1. Do I have the seal in the correct way? It was the same way as the one I took out.
  2. Is the gasket around the seal holder likely to be the culprit?
  3. I couldn't get my mic on the crank where the seal sits due to clearance issues but I did get my digital caliper on there and I measured it at 24.85mm. Seems a little small.

 

IMG_20200413_152620.jpg

IMG_20200413_152602.jpg

Edited by DanielHowden

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Ahhh its oil on the crank, i was under the impression it was in the flywheel stator housing, it could be the seal gasket if you know the seals have been fitted correctly, could d it be pulling oil in between the casing gasket on the induction stroke, did you notice any pressure coming out the gearbox breather pipe when it was running, it could be a pinched crank case gasket or warping on the face of the casing. 

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the bearing face on the little end looks like its seen better days, maybe the crank mains are also worn?

the oil also looks quite contaminated with gritty looking particles?

 

Edited by suzuki250

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If the seal spacer is worn it will have grooves worn in it, not a reduction in diameter.

Have you got the right sort of seal there? It should have two lips in opposition. Looks like a single lip seal in your photo.

It's possible that as suzuki250 says, one or both main (crankshaft) bearings may be shagged which can cause the seal spacer to move up and down enough for the seal to leak past the lips even with a nice new soft seal. You should be able to feel that degree of play in the mains by trying the move the end of the crankshaft up and down by hand.

Another thing is that it is normal to find that much oil in the bottom of a two stroke, but it should look and smell like your brand of two stroke oil.

The definitive symptoms for oil getting sucked into the crankcase from the primary drive are weird smelling exhaust smoke, too much exhaust smoke, weird colour (white) exhaust smoke and having the oil disappear from the primary drive casing. You have only mentioned one of these symptoms.

Edited by feetupfun

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19 hours ago, suzuki250 said:

the bearing face on the little end looks like its seen better days, maybe the crank mains are also worn?

the oil also looks quite contaminated with gritty looking particles?

 

Yes the oil is gritty but its like carbon or similar.  Maybe Im looking at a full rebuild.

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10 hours ago, feetupfun said:

If the seal spacer is worn it will have grooves worn in it, not a reduction in diameter.

Have you got the right sort of seal there? It should have two lips in opposition. Looks like a single lip seal in your photo.

It's possible that as suzuki250 says, one or both main (crankshaft) bearings may be shagged which can cause the seal spacer to move up and down enough for the seal to leak past the lips even with a nice new soft seal. You should be able to feel that degree of play in the mains by trying the move the end of the crankshaft up and down by hand.

Another thing is that it is normal to find that much oil in the bottom of a two stroke, but it should look and smell like your brand of two stroke oil.

The definitive symptoms for oil getting sucked into the crankcase from the primary drive are weird smelling exhaust smoke, too much exhaust smoke, weird colour (white) exhaust smoke and having the oil disappear from the primary drive casing. You have only mentioned one of these symptoms.

Hi, yes it is a single lip seal.  I replaced what was there before but if a double lip seal is the way to go Im happy to do that.  

I did check the main bearings and I could find no noticeable play on either side of the crank.

This oil is definately coming from the primary side, it smells the same and the oil in the primary casing when I took it off was nearly zero and I have no other leaks from there.

Yes, forgive me for not mentioning the exhaust smoke.  It smokes a lot and the smoke is white.  I haven't noticed the smell of it though.

Tricky to know what if I should go for a crank rebuild here.

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6 hours ago, DanielHowden said:

Hi, yes it is a single lip seal.  I replaced what was there before but if a double lip seal is the way to go Im happy to do that.  

I did check the main bearings and I could find no noticeable play on either side of the crank.

This oil is definately coming from the primary side, it smells the same and the oil in the primary casing when I took it off was nearly zero and I have no other leaks from there.

Yes, forgive me for not mentioning the exhaust smoke.  It smokes a lot and the smoke is white.  I haven't noticed the smell of it though.

Tricky to know what if I should go for a crank rebuild here.

No way. It is very likely just the single lip seal causing it.

If the seal diameters are 25 mm ID and 40 mm OD like I suspect they are on your 247, you can use a Yamaha TY175 magneto side crank seal. I discovered that the Cota 348 seals are the same size seal as the left TY175 seal when I changed the crank seals in my Cota 348.

The seal would also be available from a Montesa twinshock-era parts supplier.

The reason you need a double lipped seal is that it has to seal with the high pressure side alternating from crankcase to drive casing every time the motor turns. So if you want to use single lipped seals and can fit two thin ones in the holder, make sure you fit them in opposing directions.

Edited by feetupfun

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8 hours ago, feetupfun said:

 

The reason you need a double lipped seal is that it has to seal with the high pressure side alternating from crankcase to drive casing every time the motor turns. So if you want to use single lipped seals and can fit two thin ones in the holder, make sure you fit them in opposing directions.

Just out of curiosity, would you fit the seals springs out or springs in ?

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3 hours ago, b40rt said:

Just out of curiosity, would you fit the seals springs out or springs in ?

I was thinking about that afterwards. I reckon it would be prudent if using 2 single lip seals to fit them so they were the same setup as a dual lip seal, which I think is springs out, but I haven't looked at a crank seal lately

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