I'm gonna jump off a limb here and say that the MVVS 1.6 gas engine looks suspiciously like the new Evolution 26 gas engine.

Right down to that heavy spring loaded choke lever and the adapter plate with crank pressure tube under the carb.

Maybe you can help.

I have had engines that would not keep running, but the EVO 26 won't stop! The throttle plate closes 100% and the carb is as tight as I dare tighten it.

It won't go below about 3500 RPM.

High speed is great. Maybe 7500 RPM with an 18-8, good transition, but it won't stop at idle

Looks to me like the adapter plate is leaking air.

One more thing. I am not running a muffler of any kind. None available here yet, but they promised one in a week.

Any Ideas? Has anyone else had this problem?

Maybe MVVS are indeed better engines?

Thanks

Dick,


How about: The Evolution looks like the MVVS...
The MVVS is the original and it is now also manufactured by MVVS under the Evo name, to be marketed by Horizon Hobbies.

This is possible.

Shutting down a gas engine is supposed to be done by stopping the ignition, but since it will not reduce to idle speed, there might be an air leak there.

MVVS offers the #3270 Pitts style silencer for good performance. But if you want 800-900 RPM more, the #3265/26 header with the #3266 silenced tuned pipe can be optioned for.
Maybe the US dealers don't have then, so shopping around is recommended.

Every gas engine I have ever owned could be shut down by closing the carburetor plate fully.

Except this one.

Don't you think that 3500 is a rather high idle speed?

MVVS can be stopped as well.
Like Dar said, you must have an air leak. so check the intake manifold etc for leaks. Check the back cover rubber seal. It may get damaged when the rear cover is not fitted carefully.
Maybe: did you touch down the engine so hard that you bumped the carburettor? In that case you can fit the manifold using a high temperature resin.

Maybe a little silicone between the gaskets, the carb and the spacer plate?

Never thought of the back plate. I'll check that too.

First time running the engine, right out of the box, on a test stand.

Never been flown.

Thanks for help

Normally, silicone fitting of parts does more harm than good. If gaskets are damaged, they should be replaced.
The only use I find for it is on the exhaust header flange which I always fit without gasket. (partly cured before assembly, thin film of RTV)

I'd have to agree with you on the silicone.

Probably the best thing to do is contact Horizon and ask for a new spacer plate and gaskets.

But I will check the back plate

Thanks

Dick,


3,500 is not an idle. It is climb power....
I wrote that and this engine can idle at less than half that speed.

Just got off the phone with Horizon service. They're sending me everything that goes between the carb and the crankcase.

I had swapped the EVO carb with one from a G-26 (it works just fine on that engine) and the EVO still idles at 3500 and won't stop.

So the Evo carb is OK, as far as I can tell.

I will still check the backplate and its gasket.

The faillure to stop with the carb barrel at full closed is not Unusual for the MDS line of motors, the carb for the MVVS may come from the sam design. Air leaks from any location other than loose componants indicate a bad seal somewhere, probably a bad casting somewhere. YS just sent a 110 back replaceing the crankcase. Unusual for them. Anything can happen in mass production. In any event, send the thing back for replacement or repair. You should not have to fight a new engilne

You're right, especially when I am writing an engine review in a nationally published magazine.

After further investigation, I found that the carburetor throttle plate has a small rounded notch in it just behind one of the fuel passages.

Even with the throttle plate fully closed, air and fuel will be introduced into the engine, allowing it to run at "closed throttle"

I doubt that the MVVS carb has such a notch.

This particular carb must have been designed to be used on a blower or chain saw that needs to idle, but must be turned off using ignition kill, unlike airplanes.

This is 100% different than airplane engines that must be able to be shut off using the transmitter. I use fully closed throttle.

The fix? I took the throttle plate out, soldered the notch closed and filed the plate so it fit the throttle bore again.

Results? It idles at 1400 RPM and will shut off at full throttle closed.

I'm using a Bisson side mounted muffler and APC 18-8 wide blade prop.

Top RPM is 7950, with only half an hour on the engine.

How does this compare to the mVVS 1.60?

The small window is present in the larger MVVS (typo edit) engines as well, because medium revolution performance increases.
All MVVS engines I tested could be shut down with the throttle, including the ones with the cutout aboce the idle jets.
Performance figures should match 100%, because the EVOlution is a re-badged MVVS. Only the ignition is different, but that should not influence performance.

Pettit,
Have you checked the idle stop screw? I remove it completely and depend on the servo for idle speed and shutoff. The carb notch is normal. Also, try the APC 18x6!
Jimnie

Idle stop screw is long gone. One of the first things I remove.

I did use an APC 18-6 and still would not turn off.

Plugged up that notch and it idles at 1500 and cuts off at fully closed throttle, just as it is supposed to do.

With the notch, it would not idle below 3500 RPM.