Simon Jones

Hi, I'm after some help and advice.

I have just bolted an MVVS 160 (glow) onto a GSP/Flair Katana (72") and it is prooving rather difficult to tune. The trouble is there is the added variable of the pump pressure now. I have fited the pump because I've moved the tank back over the CoG.

The MVVS is fitted with the most reent (non walbro) carb. I have managed to get a reasonable top end so far but ile and transition are very hard work.

Any suggesions gratefully recieved.

sj.

Simon Jones

By the way, anyone have any suggestions on fuelfor this motor. Just Engines recoment 0-5% nitro. I just can't get my head aroound using such wimpy fuel.

sj.

jaka

Hi!
Wimpy fuel....Those engines are made to run on low nitro fuel (thanks heaven for that).
What silencer do you use steel, aluminum or pipe??
I woold not bother to mess with apump...just place the tank, 500cc (16 oz) behind the firewall an just fly!
I have a 1.50 MVVS in a SIG CAP 231 EX and it performs really well with the tank in that place. These planes are not F3A peformers...
so the tank doesn't has to be placed on the C of G for the airplane to fly well.

Regards!
Jan K
Sweden
http://hem.passagen.se/airracing

Simon Jones

Hi Jan

Unfortunatly I'm commited to the CofG tank now wih the mods hat I've made so I want to stick with the pump, after all this should help with the tuning.

I think I may have found the problem. Afte afew more hours of trying to get the engine to run right I decided to srip the carb in case here was an air leak or something. On taking out the idle needle I noticed that it does not go to a point. It tapers a bit and then cuts off flat. It looks like it has been boken off from it's shape, but the end is anoised black like he rest of the needle.

So the question is should the needle run to a point or should it have a flat end?

I will be calling the UK supplier on Monday, but it would be good if someone could put me out of my missery before and this way I'll also know if the supplier is telling the truth.

This would make sence as theengine runs quite well at the top end but I cannot seem to lean out he botom end enough. This problem was there before I wen o the pump but isnow worse,I think this is because he engine wasn't drawing as hard at idle without a pump so was naturally leaner and didn' need the needle to do it's job as well. Now the pump is on it's keeping he pressure up and the needle cannot regulate he flow.

What do you think. Do I make sence, or am I talking complete jibberish to make me feel better?

Baphomet

Hi Simon !:w

I am from Germany and i knew someone,who tuned his 1.60 Mvvs GFS
very good.[sm=thumbup.gif]
He uses a Walbrocarb ,the special version for methanol,and a larger tuned pipe,for 45 ccm. He uses 0 % Nitro and 5% Synthetik oil in his mixture.

It turns an 20x12 Menz S at 8300 rpm.

I've bought the same Engine and I will make the same changes,but it will take time.

If you know Denis lyon ,contact him and he can tell you mor about this kind of tuning.I've send him the E-mail of the tuner.

Simon Jones

I've now sold the plane and engine, but thanks anyway.

In the end Igave up on the CoG tank and went back to a non-pumped set up and all was well.

Cheers.

sj.