Main shaft seals

[Puffs]

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[nice2day]

Hi Puffs A 2 stroke is more likely to draw oil through the crankshaft-seals when the engine is on the "over-run" where the engine is being driven by the movement of the bike but the throttle is shut. This condition is more likely to create a very low pressure (vacuum) in the crankcase area and thus sucks in the oil...Obviously some oil can get in at any time but I am describing the most likely scenario....

As regards the violin and sound: There is not an actual flow of air. Sound is a high frequency vibration that is transmitted through the media to the ear but there is no actual gas flow occurring. You can have a room with deafening noise inside but there is no air escaping from that room.

Les

[Puffs]

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[nice2day]

You are giving examples of instruments and noise generators in free open air....Not moving air and reversing it at a rate of 25 times a second with a wavelength of 14 metres, though an air gap that is in the order of square micrometres... maybe the diameter of a hair....I contest that in trying to do the above task, it is near physically impossible and has no correlation with sound generation. It is a matter of simple physics as the massive energy that would be required to override this resistance is not available in the engine set up. This resistance is caused by the air's inertia and it's flow resistance, something I did not mention earlier. IE: It does not happen

Les

[Puffs]

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[AlanJ]

Hi Guys,
Just to add to the mix, I have a TS 250/1 and 2 Saxon 301's and the seals on all three are clutch side facing out against the gearbox oil and the right side
against crankcase pressure facing in. Could it be that it was found by the MZ engineers that this was the best solution and maybe, and I can only guess at this,
that the pressure build-up in the clutch side requires the lip against the oil in the gearbox. If this was the case then I can understand and as Puffs has said, put
the new ones as the original. You may have read my post, way back, when I got the Saxon 301 going, after buying it the clutch side seal (after standing 13 yrs)
was stuck to the crankshaft and was spinning in the housing. The Saxon started but you have never seen so much smoke in all your life, my wife and next door came running, thinking I was on fire, to be honest, I couldn't stop laughing.
Wish you well guys Alan

[dave47]

If Alanj is right about the TS250/1 seals facing the same way as on the ETZ, and I think he is, either MZ changed them at some point in the production run, or the published drawings were in error. I will edit my earlier posts to reflect the uncertainty.

[Puffs]

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[AlanJ]

Hi Guys,
As I said earlier, I have changed all my main seals with a 251 to go but it always is a surprise to me when you read posts of guys buying bikes that have
been standing (often in adverse conditions and not checking) and as you know the clutch is often the worse for the amount of rust either from condensation or water running
down the clutch cable. All my 3 bikes have had something similar to sort out and to be honest while one is looking at the clutch you might as well do the seals
after all they don't cost a bomb and (if you use anaerobic multi gasket you can take your time with the cover) I thought I wuld get that one in.
Anyway guys wish you well Alan.