[b]Jan:

I thought you might come in here on that. There have been too many documented problems with the iron piston and steel sleeves running all synthetic to let your comment go. The varnish build up on the piston is an essential part of the sealing, with synthetic this seal will never be achieved.

And the plain bearing crank, with the bearing material being the crank case itself. Even K&B had to change the case on the Sportster 65 befause of people like you. The original design was fine when using castor oil, but people running synthetic oil were having crank bearing failures. In the later production K&B cast a bronze bearing into the case, using synthetic oils the bronze held up better. But better yet with castor oil.

Bill.