Hi Av8tor.

As before, thanks for the insight and observations - i agree totally that it helps focus the experimentation into a more coherent effort.

As regards Walbro carbs, I had a look at their website. I think the two types with Butterfly valves most suitable for our purposes are the WA/WT series and the HD series for larger engines. I note the only main difference in the blurb seems to be the WA/WT series has a prime/purge function which isn't mentioned on the HD's.

In Rotary valve carbs, the WY series has a plethora of choices, too complicated for me to see which would be best.

Does anyone have any experience with these types? they are obviously the lates versions - perhaps people have been using s/h versions?

All very interesting.

Thanks,

Roger.

PS Just seen you have been using the Walbro WT499