Just wondering if anyone knows why the later 600 engines have the thinner oil breather hose take-off located on the crankcases instead of on the rocker cover?

I'm in the process of building a hybrid e-start XT/TT engine and have just noticed that the pipe location was moved between the 89 and 95 model engines, so curious as to why.

Hi
yes they moved it.

It is not a breather but a overflow to prevent the oil tank from pressurizing as the secondary (return) pump is bigger than the primary pump.
The oil tank sitting below the cylinder head level my be a reason for that relocation.

Andy

Thanks for the reply Andy - makes sense that it would be an overflow for the oil tank.

I'm guessing there have also been a number of people who have filled the tank up to the marked level whilst the bike is cold, without realising that the sump may also hold a large quantity of oil. At least that way it has a secondary return path back to the engine.

Anyway, it sounds like it will be safe to block off the extra one in the TT rocker cover, and just use the one on the crankcase as per the later XT motor.

Exactly what I did frankensteining an engine together.
Problems only arise when you combine an early engine case with a late cylinder head - then you are missing a connector :D

Andy