Large Model Association Forum

Just before Covid my mate had his Moki 215cc (5 cylinder 4 stroke) run up on a test stand, it ran really well. Now 3 years later it's installed in the model and we fired it up for the first time today, E10 petrol with deluxe materials 2T synthetic oil at 32:1, after getting the fuel through it would only start and run on half choke, if you took the choke off it died.

Obviously looks like fuel starvation, but before we go twiddling the mixture screws is there anything else we should check for.

If it was a single, I would be cleaning the carb out, and be inspecting carb diaphragms, but a Moki radial? New territory for me

Maybe you could talk to Stuart McKay , expert with Moki engines ?
Regards Ian Turney-White
ps sorry do not have his contact details

Frank. The problem could be that you are using far too much oil. I have been flying my Moki 150cc for years in my Hawker Tempest using Bell- Ray H1-R 100% synthetic 2T at 50-1, and in hundreds of flights it has never stopped in the air. Give it a try, 32-1 is for running in. Best of luck, Brian.. LMA 42.

Good Morning, Brian is correct regarding the oil content ratio, but It shouldn't really prevent it from running ? I would be checking the pulse pump flexible pipe to check that it is clear ? Other than that, I would be stripping the carb to see if there was any jellified oil/fuel remains within the filter gauze . . . Good luck

Thanks for all the suggestions, we checked the pulse line and it looked clear. Tried it again today with both needles opened 1/8th of a turn but it was just the same. It's definitely fuel starvation so next job is get the engine out and give the carb a service.

Sounds very much like a blocked filter in the carb and while you have the cover plate off to check, make sure the D shaped non return valve flaps in the pump gasket are sitting flat on the machined surface of the carb body as these stop the fuel running back to the tank when running. Also make sure the angled Festo fitting is sealed ok to the carb and clean as a whistle.

Was it stored with fuel in carburettor? If so, most 2 strokes and similar engines using a mix of fuel and oil - of any kind - tend to run into problems as you describe as the volatile petrol evaporates over time, leaving a residue of the oil in the carburettor that can mess with the mixture settings, and also constrict or even block jets or accrete a form of "varnish" around the throttle-slide. Best bet is to get some new petrol, mix up a new batch, and clean the carburettor with acetone or similar to get rid of any oily residues that may be gumming up the works; before fuelling with the new petrol?

Well red faced , after much checking and a carb rebuild, the culprit was a kink in the fuel feed line......................

Now ticks over at 900rpm with clean pick up to 4,000 rpm on a 32 x 14 3 blade prop running on 40:1 synthetic.

Dozy beggar, glad it’s running ok, cracking engine