I have a new MVVS 1.60 gas engine. Ran real well on the test stand, broke it in carefully and was pleased with its performance. In particular I did not notice the vibration that seems to be a common problem with the gas engines. But when I got it on the plane (Clipped Wing Taylorcraft) it has started to run unevenly anywhere above half throttle. The engine has actually stopped a couple of times in flight which is more than a little uncomfortable. The idle and midrange seem fine and the high throttle settings ran fine on the test stand. So I worked with the low and high speed carb adjustment and checked the fuel lines and tried the engine timing in every possible setting and the same problem persists.

Anyone have any idea what to try next. I have tried several different fuel and oil variations with no help. The one thing that yet occurs to me is that I have been starting it with my regular electric starter instead of starting it by hand flipping. Think I heard somewhere that the electronic ignitions do not like to be spun by an electric starter.

Thanks,

Devdog

Have you got your engine running yet?

I was thinking about one for my dynaflite Chipmunk.

Wayne: this engine has always been easy to start and has run strong. In particular its idle has been superb and the level of vibration matches my glow two-strokes.

The problem is that the high side has run unevenly since the engine has been moved from the test stand to the plane and I can't figure that one out. Going to replace the fuel lines and the gas filter next and see if that helps.

Wylie

I really like the idea of such a light weight gasser in that size range. Have you got that engine sorted yet? I was also looking into converting a Saito to gas. Any thoughts?

Wayne: I have not had a chance to work on this engine yet,. The holidays and etc. have kept my attention in other places. But I do plan to get to work on it soon and I believe that the problem can be solved. I am going to try three or four things at once (like replace all of the fuel lines and install a larger fuel filter and so forth.

Will let you know how all of this works out.

As to converting a four stroke to gas, that one is beyone me-good luck and let me know how it works.

Wylie

I too had an MVVS 160 that gave me fits trying to get it to run. What I found was the wires from the Hall Effect sensor had been burned. Put new ignition on it and it ran fine, so I very carefully reworked the wires on the old ignition and now it runs like a wild monkey. BTW those wires are not just single wires, they are shielded cables so you have to be very careful if you have to repair them.

Another myth...Electronic ignitions don't like electric starters ?
No way.....You don't NEED an electric starter with a electronic ignition, but there is no possible way a starter could do anything to the ignition..Unless the 12 volts from the starter to the ignition...Then you make smoke

You have to determine whether there is really something that has gone wrong with the engine or if it is something to do with the installation. Put the engine back on your test stand. If again it runs perfectly, then it has something to do with the installation. I would suggest that if it does run well on the test stand, one by one use the components of your installation (fuel tubing, tank, battery pack and switch etc.). If it still runs perfectly, then the airflow into the carb and the relative pressure at the inlet vs the pump may be to blame. With the MVVS 160 with its front mounted carb you can be ramming air down the carb throat making the engine go lean. If this is the case, then a richening up of the needles may help or protect the carb inlet from the ram effect.

check your fuel lines .. they may be kinked/pressed thus restricting fuel flow at higher throttle settings(the low end will seem fine).

devdog: I had exactly the same problem with my MVVS1.6 gasser. Finally it turned out that the ignition module failed. I got a replacement by my MVVS dealer and now the engine runs fine. By the way.: I got the latest version which now has 2 magnetos for the sensor.

Staph

In a gas engine carb, the fuel pressure regulator is very important. This regulator is located beneath the zinc plated steel cover of the carb.
Pressure differences near the vent hole in this cover let the engine either go lean, or rich in flicht, depending on the airflow or ram air pressure in the cowl.
It is possible to solder a small brass tube to the vent hole, and add a tube to re-locate the reference pressure to some safe place.
That may very well solve your setup problem.