Hey Rick,
yup, thats the WT 540 carb with a 13.49 mm venturi. The new zenoah's come with the wt 338 (which is also a 13.49 mm, as was mentioned earlier in the thread by Buck) and the aluminum prop hub, so yours seems to be a weird hybrid if you bought it retail! Otherwise someone might have upgraded it with the new prop hub. Thanks for the article - I read it some time ago and it gave me some fresh ideas. I guess I have been spending way too much time online looking at anything gas engine related. I was also trying to decide as in the article, whether to put the pick up sensor in the back or up front - both are viable options and my prop hub already has a magnet in it - its just a little far in front on the crankshaft and I was concerned, with the vibration of the sensor bracket extending that far. I guess Ill have try it out one way or the other.

by the way what plane is your G-38 going into - mine will eventually end up on a 72" giles 202