Mark Barker

Well, here it is - sometimes, the simplest things are best! At my club there are a couple of guys who do not use a pressurised system with 4-strokes (air tube going to the exhaust) or with a high tank. A very successful way is by adjusting the mixture, especially idle jet, as 4-strokes seem to naturally suck in the fuel. I was all prepared today to try the uniflow system. It wasn't too successful, but I didn't spend too much time trying to adjust it. I then tried traditional pipework and just disconnected the pipe from the exhaust which pressurises it. With careful tuning, although it doesn't make sense, it seemed to work fantastically! As there was an awful cross wind today, I didn't fly, but all the ground tests were fantastic. I look forward to good weather for my maiden flight. Once again, thanks for all the input. It is helpful to consider different options. Mark

You are right cuban 8, the ASP four stroke will work with a high tank. The excess fuel from the siphoning effect goes out the exhaust. But it performed so much better on the bench when the tank was in the right position. If Possible I would like to get the same performance in the plane. re. Engine doctor, raising the carb would completely eliminate the problem. I will look into carb extension in the search panel. re. Tony link very interesting one of the problems with the siphoning effect. If you adjust the mixture to take in consideration the siphoning effect, when the plane is inverted for a prolonged period. The fuel would no longer be siphoning into the carb and the engine would not perform the same.I can get it to start ok. It just doesn't perform as it should. I will consider all the inputs and I'm sure, whether I move the carb, or use a regulator I'm sure it be ok. I will post the results once I've worked on the plane .Many thanks

Thanks Martin for the info. If the loop and uniflow don't work, I'll go to Weston and get the regulator.

Thanks again for all the input. I looked for a Cline regulator and an Ironbay. Don't think they sell them in UK, I've seen them on an American site. That would do the job. I think I'll try a big loop as suggested and also use the uniflow system to see if that works. I have seen a regulator for a 2-stroke running from crank case pressure. All sounds very complex. They shouldn't sell ARTF planes clearly showing in the manual a 4-stroke inverted without mentioning you may need a regulator. Very frustrating. Once again, thanks for all your input. I'll let you know how I get on.

Thanks for the ideas. ASP is inverted and I've already cut the cowling. I really want to stick with it! I was going to use a longer tube and loop it to see if that would help, but I've just read on a different site to try using a uniflow tank system. I'd never heard of it. It uses 2 clunks. One clunk goes to the carb and the other to the muffler, with a one way valve so no fuel goes into the exhaust. As soon as you've filled up, block the air inlet. Completely new to me, but it might just work as it's meant to stop the syphoning effect. Unfortunately, the centre of the tank is more than 1 1/4" higher than the carb. It's an ARTF. I'm surprised the tank is in such a daft position, but I can't lower it. Many thanks for your help. I'll come back if it works.

I've got a new Spot On 50 L with a 4-stroke ASP 70. I can't lower the tank any more which means it is too high and it putting the glow fuel straight into the carb. I have heard of Perry Pumps, but I believe that if I just pump it it could make it worse without a regulator. I have seen a Perry Pump with a regulator, but the spec said it was meant to be for a 2-stroke. Any ideas?