I have a MDS 148 i have fitted a new carb MOKI purchased from Just engines UK i have tried less nitro i have tried more nitro i have tried cold plug and hot plug
changed props moved tank around ...still this engine will not hold full revs when i hold plane vertical i have tried rich setting leaner settings just dies when i hold almost vertical.

any suggestions?

You have given no background on the engine. Is it broken in, yet?

the engine has run for about 2 hrs aprox 1 gallon of fuel

What prop, what fuel, what plug, which stock carb did it have and most importantly, what muffler, Please

fuel... contest 10%, plug No7 firepower , i have tried different plugs , prop 16/8....i am using MDS 148 standard dustbin silincer .

the carb was the new MDS with logo on carb body.

My 148 will appear to be very rich on the ground especially before it has run at full throttle for several seconds. I set mine to hold full rpm then richen it about 1/4 turn. It then winds up in the air.

I use 5% nitro 2% castor 15% synthetic 18x6W APC. I have had two 148s the early one with the mark 1 carb had a flat spot mid range, the second one with the MDS mk2 carb is great. I set the needle at the beginning of the summer and it runs all year. It is in a 70in span 3 D fun fly and you need a reliable throttle in the hover.

Check your fuel lines esp the clunk line.

I tried 5% and a blend of castor and synth....this has made a big difference my problem has been to much nitro .
Thanks for your help.

I also have this motor. Mine seems to run better with the 18x6 prop. I haven't tried it in the air yet, but it seems instant transition wise on the ground. Many of my mds motors have ran better when over proped.

I started to break in one my 3 MDS 1.48s today, I have been running one that I rebuilt I rebroke it in and run it as a Diesel. This new one as usual had lousy compression at first but after 2 16 oz tanks of Fox 5% fuel it has awsome compression. I deliberately put one of the C1 carbs on it since they are smaller than the C2s at 9mm vs 10mm for the C2. I also used a Davis Diesel in cowl muffler which is very quiet and not restrictive. The plug was the Hangar two stroke SuperPlug that came in it. With the LS needle about 1/16th inch from the end of the spraybar it has a great idle and transition.

I takes a while to break in a MDS 1.48, but once broken in, mine has been a super performer on an UltraSport 1000. I use 15% S&W fuel, an OS #8 plug and a 16X8 prop. It needs to run a click or two rich or it seems to lean out and die. But running a little rich gives me straight up vertical.

bob