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Question with regards the necessity of changing crank seals. TY250A


johnnyjazz
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Thanks again feetup fun for all the help.  The O ring i meant is not the air screw but rather for the screw that holds the needle jet/main nozzle in place.  i believe this being worn (as it is) can cause running rich, but im pleased to know to diagnose wear on the needle and needle jet too.

Can't find any new needles on  eebs with part #434-14336-00 for the TK, are there any other ones that fit? that said, it seems by the time i replace any TK parts it might be more efficacious to get a new carb altogether?  if that's the case would i go for a mikuni 26mm yeah?  or is the oko carb from mid atlantic trials any good?   thoughts and opinions as always, gratefully received.  :)

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If you do change the crankshaft oil seals and bearings with non Yamaha parts try to get Viton seals as these can withstand the heat far better than the neoprene type. These may be more costly but worth the investment. Be careful with the main bearings and go for a C3 grade type as these bearings are designed to deal with the heat/expansion and contraction within the engine. 

Breathers need hoses/ plastic pipes to prevent water and tiny specs of grit getting in the transmission, ignition cases. I run mine back and up inside the main backbone of the TY frame. Make sure all the carb breather pipes are fitted and routed correctly. Blocked breathers in the transmission can allow gas pressure to build up and force oil out through seals and weak gaskets. It’s the heat generated as the gearbox oil gets hot. I’ve had to clear many a blocked breather to cure oil seal leaks, mainly on 4x4’s where they’ve been up to their axles in mud and the poor breathers let the rubbish in and it then bakes hard in the breather. Same applies to fork breathers. Enjoy your TY they are getting thin on the ground.?

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  • 7 months later...

Had to change my left side crank seal because it was leaking fuel vapors from inside the cases.  the leak was slow, but the points were fouling out and showing white residue after just 5 or 6 rides of 1 hour each.  Not fun to do, but using the sheet metal screw trick on the seal (mine needed two screws) did the trick for removing the seal. RE- lube the crank and the inside of the new seal and tap gently back in with a metal tube of the correct diameter.  I will know this year if the new seal holds, and so far no leaks.  Wish me luck!

 

 

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