Again guys, MANY thanks for all your very valuable input.

I have used the Orbit clunk with complete success but only on smaller engines such as the RAM 500 and PST 600 but you have convinced me that its not suitable for larger engines so out it comes as the first stage . In fact I will keep the clunk but remove its screen and try again. Even if that is not causing the fuel vapour bubbles I see it as a potential source of problems so thats another reason for its removal.

This clunk problem makes sense as I having been using an Orbit type clunk for the pickup in my refuelling can and on close inspection it is getting gummed up with algae. The Kavan pumps have worked fine for refuelling but now I know why they sometimes change speed abruptly for no apparent reason.

It may interest some to know that on my BVM F4 with an AMTNL Pegasus HPES I use TWO header tanks in series (a flameout on the heavy F4 could be fatal) and the main feed header never gets ANY air, or vapour, in it, consequently never a flameout (just one in flight shut down, finger trouble on my part). My JetCat 160 powered models all use standard clunks with added lead weights and simple geometrically centered pickups in old JPX oil tanks, never a flameout. BVM UATS also give me first class service with the JetCat p70 and PST 600r in my BobCats, again, never a flameout.

My particular thanks to Craig B for his PM which described the Orbit clunk problem in detail, I'm now fully convinced it has no part in the Hawk's fuel system.

Thank you all again, RCU at its very best.

Regards,

David.