MVVS 58cc problem
 

Hello!

Just bought an MVVS 58 from a friend and decided to try it yesterday.
The engine is about 3 years old but it had never been started and it´s equipped with an aftermarket canister and a 24x10 propeller.
After running it at 1/2 - 3/4 throttle for about 15 minutes I took it up to full throttle and I only got 4900 rpm.
I understand that the engine needs running in a bit more, but I was really disappointed that it seems to have about the same power as my old crrc 45cc engine.

Should the engine really be this powerless or do you guys have any suggestion what to do with it?

Best regards,
Johan

RE: MVVS 58cc problem
 

You should get around 6000-6500 rpm depending how the canister works. You just have to adjust the needles right. Check manual from mvvs.cz for factory settings, but basic settings are highly dependable of the muffler used.

RE: MVVS 58cc problem
 

The needles are adjusted, but I still can´t get it over 4900 rpm...

RE: MVVS 58cc problem
 

You should check battery voltage versus ignition requirements. The Vlach EZM ignition goes to low rpm setting on low voltage so the pilot can still bring his plane in. I believe it is 4.2V (check battery, leads, switches) It is the ignition voltage that counts, not the voltage at the battery.
If voltage is OK and steady, look the seller of the engine deep in the eyes and ask the truth about this engine. He may have had this problem before he sold it to you.
The Vlach ignitions are no longer available.

PS
If the engine has the Vlach ignition, it is older than three years

RE: MVVS 58cc problem
 

Then I have to suspect air leak. Check that carb bolts are tight enough and change the hose that runs from carb foot to engine chamber. If that doesn't help I would open the carb and check diaphragms.

RE: MVVS 58cc problem
 

I realize the MVVS is a strong motor, but 58cc is 58cc, a 24x10 wouldn't be my choice for a break-in prop. I'd try a 22x8 for breaking it in then switch to a 23x8 and go from there.

RE: MVVS 58cc problem
 

24x10 is perfectly OK for the MVVS, so is 22x10x3 or Mejzlik 26x10N

RE: MVVS 58cc problem
 

Pe I put a 22x10x3 on a MT57 and got 4800rpm. The plane took off, but was a dog, I then put a 23x8 back on it and it turned 7100 and flew great.

RE: MVVS 58cc problem
 

Yes, the engine has the Vlach EZM ignigion.
I know my friend bought the engine about three years ago, but I have no idea how long it had been lying at the dealer, so it could very well be alot older then three years.
The only reason he bought it was to have a bigger plane then me , but he soon realized that after hurting his back just after he´d bought it and only having one and a half leg after an accident several years ago he was unable to get such a large plane out of his house, so unless he´s started the engine in his livingroom I´m sure he had no idea about this.
When I tried the engine yesterday I used a 4,8v pattery pack, but my intention is to use a 7,4v Lipo and a regulator that can be switched between 5 and 6 volts. Any Idea what the correct voltage would be for this ignition?

Could be... At this moment I´m hoping that "pe reivers" is right about the ignition not getting enough power...

Yes, it might be a bit large, but it was the only propeller I had at the moment...


Thanks for your replies.
//Johan

RE: MVVS 58cc problem
 

I am sorry for your friend. Been very close to that myself after a car accident.
OK, I'll tell you what the ignition realy needs. Be careful with what you do, because these ignitions are out of their warranty period.
It needs a resistor type plug, set to 0.5mm gap
It needs a 4-cell NiMH, with 6V max. Having said that, some have had good success using 5 cells. I cannot recommend that, but if you want to try, bleed off some of the peak charge before you disconnect from the charger.
At the time, Vlach advised against using regulators. (The voltage ripple or whatever.). An extra capacitor to reduce the voltage ripple might make it safe to use though, and allows you to go up in voltage until the engine reacts.
I used an earth wire soldered to the ignition tin box and bolted to the engine, just to be sure of an earth connection all the time.

If all this fails, the cirquit inside the ignition box that causes the ignition advance may have failed, so the ignition is retarded all the time.
If you are handy, you can fit the sensor to a hose clamp and time it for 26° advance fixed. The engine will tell if that is the solution by running like a champ. This will be the last resort to save the Vlach ignition and make it work.

As final solution, MVVS makes replacement modern ICU ignitions that have the VLACH plug boot available, or use RCexcl or CH ignition modules. (PM me)

RE: MVVS 58cc problem
 

Here we go again...

Checked the engine for air leaks and found none.

Started the engine and I still only got 4900 rpm.
Moved the ignition sensor to 26° but still only 4900 rpm.

Any ideas? Could the ignition still be faulty?

Maybe I should just take this czech piece of crap and use it as an anchor for my boat and get myself a chinese 100cc engine instead...

//Johan

RE: MVVS 58cc problem
 

How much you want from it or do you change it to boat anchor :)

RE: MVVS 58cc problem
 

Hi!
24x10 is OK!
Possibly a little too small if you fly att sea-level and use a cannister silencer. MVVS says a Mejzlik 26x6 carbonfiber prop turns 6100/6200 rpm using the MVVS No 3204 cannister silencer and a 24x10 Mejzlik turns 6400rpm with the MVVS 3207 silencer.

For comparence I use the first variant of the MVVS 45cc engine with the aluminium case (100 g heavier than the newer one with magnesium case) and use the small MVVS cannister (No 3206)
I get 6600rpm both with with a Mentz 24x8" and Graupner wooden props and 7200rpm with a top-Flite 24x8" prop. A 22x8 prop is way way too small for the MVVS 45cc gas engine and should be for the 58cc engine as well.
I run my engine on 2,5% all synthetic oil and 95oktan lead free fuel. Running in was done on what MVVS recommended; 4% all synthetic oil.

No lenghty running in time is needed on any MVVS engine, be it gas or glow!! This must be a severe miss understanding!
The engine should turn top rpm after just a tank or two.

MVVS uses the Brisk UR-17 plug for these early gas engines. The new one uses the much smaller NGK CM-6 plug.
4,8V-6v, 2000-2800 mAh NiMH cells is used for ignition. I use 4,8V , 2500mAh AA GP cells soldered together.


Check the spark plug function by removing the spark plug and hold it against the crankcase ...as you turn the prop (Hold it with a pair of rubber glows) you should get a spark as soon as you turn the prop.

RE: MVVS 58cc problem
 

[quote]ORIGINAL: jaka

Hi!
24x10 is OK!
Possibly a little too small if you fly att sea-level and use a cannister silencer. MVVS says a Mejzlik 26x6 carbonfiber prop turns 6100/6200 rpm using the MVVS No 3204 cannister silencer and a 24x10 Mejzlik turns 6400rpm with the MVVS 3207 silencer.






That sounds about right. I've got an Evolution58( US version of the MVVS) with stock pitts muffler that spins a Mejzlik 24X10 @ 6500rpm and the motor is still new about 1.5 gallons thru it. Very good running engine.

RE: MVVS 58cc problem
 

Not all 24x10 props load equally, I have seen many hundred rpm difference between two different brands, but I doubt that accounts for all of your difference.

RE: MVVS 58cc problem
 

I lost my anchor, can you help me out?

RE: MVVS 58cc problem
 

you might call it a boat anchor of an engine, but show me another 58 that will spin a prop like it.:D 7450 on a Vess 24-a with a MTW re2 pipe.

RE: MVVS 58cc problem
 

Looks like your ignition is locked in low voltage mode, and does not advance anymore. In order to test this, you have to turn the sensor about 22 degrees clockwise. Because now the ignition is fully advanced, the engine may kick back if you are careless.
If this fails, you can fit an RCexcl ignition as an alternative.
Many folks will gladly accept your "boat anchor" and make it run like it should. Just push the right buttons and that "Czech piece of crap" kicks butt.

RE: MVVS 58cc problem
 

How is your Hall-sensor installed? Both washers usually have to be on the topside to make the gap small as possible.

Just came out of field flying MVVS 58, Xoar 24x10, MTW RE2 pipe and DIY MTW header kit in EF Extra 88". Could not be happier how the motor is working. It's still under break-in, but I have had zero deadsticks, automatic choke is working fine and vibration is minimal. Few liters more and I can switch to 2% fuel.

RE: MVVS 58cc problem
 

Tried turning the sensor about 22 degrees, but still only 4900rpm...
Could it still be the ignition that´s causing this problem?

RE: MVVS 58cc problem
 

Did you just turn the sensor, or moved the sensor + bracket to 22 degrees more advanced firing position?

RE: MVVS 58cc problem
 

I fixed the sensor to a hose clamp and moved it somewhere around 22 degrees. As I suspected ( and like you said ) the engine kicked back so there´s no doubt that the ignition was advanced, but still it just doesn´t wanna go past 4900rpm...

RE: MVVS 58cc problem
 

I think that's the end of the road with the current ignition. There seems nothing wrong with the engine, but the ignition will not go past the low rpm treshold and thus limits engine rpm
It will be wise to invest in a CH (RCexcl) ignition suitable for the short reach taper seat spark plugs like NGK BMR6F.

btw,
flat gasket seat plugs also will fit the engine.