Another TY250 crank seal story

[David Lahey]

This story is about the mag side crank seal on a TY250D motor. I bought a TY250D in about 1998 and ride with the brother of the person who owned the bike in the early 1980s so know some of the history of the bike.
Back then it suffered quite a bit of neglect and was put into a local bike shop for a motor rebuild. I'm guessing the odd thing that happened to the LH crank seal was when it was worked on at that time.
I rode this bike for a few years and always had the feeling there was something wrong with the jetting just off closed throttle and it took ages to run well when warming up. It was the only TY250D I hade ever ridden so for a while I just thought that because it had quite different jetting to the TY250B, that maybe they were all like that.
Anyway I eventually decided in about 2006 to see if there was a cause for the odd way it ran. The reeds seemed OK and I couldn't find anything wrong with the induction tract or base gasket, so took the ignition stator off for a good look in there. No oil visible, but when I sprayed WD40 on the seal and kicked it over, some WD40 got sucked in through the seal.
When the new seal turned up, I pulled the old one out and saw that the inner lip had been tucked under for a long time as can be seen in the photos.
Photos after tea

[Mark K]

So now I just have to ask.... Before you fixed it there was obviously air being sucked in and ruining the fuel / air ratio, so after you fixed it did it need to be re-tuned, or re-jetted, or did it just run properly with no further ajustment?

[David Lahey]

From then on it ran like a flippin dream - and its the motor that went into the Majesty in 2007
No I didn't make any changes except the new crank seal
The setup for that bike is:
Carby is standard jetting and float height Yamaha-Mikuni from a TY250D
Airbox is standard TY250D (breathes through lid)
Exhaust is home-made header of standard diameter, main chamber standard TY250 and WES end muffler
Ignition is standard points/coil set to standard timing
Sparkplug is B6ES

[Stu]

David, was this the TY you rode this year at Denman? I want a WES exhaust sytem! It looks just right and sounded much better than my TY250a...

[David Lahey]

Stu there are WES mufflers on the TY250A, the 250 Majesty, and on the TY175B I rode at Cowan's property in June this year. They transform the sound (quieter and more pleasant at the same time) of both the TY175 and the TY250s, as well as that the motors seem to run better but that may just be my imagination.
David