I have a new MVVS 58 and would like some help -

I have put about 4 litres of fuel through - at 30:1,
After practically every run I have had to richen the bottom and top (maybe 1/8 turn)

Is this normal ?

When will it be "RUN IN" ?

Please also confirm - If the motor starts BACKWARDS - it is a sign of being lean at the bottom end

Best regards
Dominic Stevens

Dominic,


From the amount of fuel used I can calculate that you have so far opened both needles over two turns from your starting position...
This doesn't look right to me and I am sure not to you either...

Are you sure some strange-order vibration is not causing the needles to creep-closed while the engine is running?


If your engine is starting backward, it is nearly always a sign of an over-advanced pick-up, causing an initial kick-back, that causes a reversed start... Readjust the position of the ignition pick-up.

This engine has a reed-valve to control induction, so it can run well in both directions.


And about running-in, some schools will tell you that the engine must be run gently, while using about 12 litres, before break-in is complete.

...But from race shops and some full-size aero-engine manufacturers, break-in is best achieved by running the engine hard; high load and high RPM, for the ring(s) to become seated onto the cylinder-bore finish, that will be 95% complete within 10 minutes.

They say a 'gentle break-in' treatment just causes the cylinder to become glazed... So it is anything but that and will require 12 litres.


I sent you a link in the PM system.


Your Nikasil cylinder is manufactured, so hardly any time and fuel need to be wasted on break-in.

Thanks for the info -
I agree from my post - the richening has prob been about 1/2 a turn in total, certainly not 2 turns - but the positions are not changing in flight.

First to check will be the pickup - Is there much adjustment there ? as the magnet (1) and mounting screws for the sensor are fixed ?

It has certainly picked up RPM - now pulling 7000 on a 24x10 Menz

Which leads to my 2nd problem of noise - over 100db at 3 metres - which is a problem with my new airfield having noise restriction at 95db
I hope to fix with a different prop, and will be trying a 24x12 3w and 26x10 Menx next

Would you class the MVVS canister a muffler or as a pipe, as I have plenty of horses - I may have to change ..

Have you any thoughts on my predicament

Model - Composite ARF 2.3 Extra

Best regards
Dominic

Dominic,


There are a few millimeters of adjustment span in the pickup, the plate has oval holes.
In terms of degrees of advance, the amount is more substantial than you may think.

Move the pick up a bit, in the direction of the rotation of the crankshaft.

The #3204 canister exhaust is mildly tuned.
Substituting a lesser exhaust system will reduce the RPM you are seeing, which is commendable, by 600-800 RPM.

This engine is stated by MVVS, to be able to spin a Mejzlik prop of the same size (which offers less load), at this RPM.

About noise, adding a silicone tube of the suitable diameter and some length, will reduce the magnitude of the sound.

Noise reduction calls for slower props and freedom of vibration. which can be achieved by:
1) larger props for reduced rpm.
2) balance the prop (mass, blade surface, blade angle)
3) mount the engine pod on vibration isolators.
4) check plane resonance and reduce it using appropriate damping.

Steps 1-4 will gain you up to 6 db total.

I have had a request for information on the pipe install. here are a couple of photos

Please note - that both ends had to be shortened to fit ... and the angle of the motor is down from 90,degrees (see CARF world - germany)

Dom

Dom,
The installation looks good, especially the way you hung it in silicone covered cables and the way to prevent it slipping back.
How are you going to cool the pipe?

Cooling - I have used some ceramic cloth (from BVM) to protect the wing tube and the UC,
And the are big holes in the bootom of the fuse - aft for the pipe to suck the heat out

Dom

Sounds good. I was expecting to see a tunnel to force the air along the muffler walls.

I have run this motor now for more than 10 litres - and still working out a few bugs - which I list here for comments and for others to try when troubleshooting.

1. Problems on the tune - for me this was dirt in the carb pre filter - solution run a fuel line filter and keep it clean.
2. Needles should be around 1.5 turns - more than 2 turns, or very sensitive - clean the carb.
3. Support the plug lead - and don't let it move / vibrate - the outer braided sheath will break where it is soldered to the plug cap, if stressed - recommend tape ?
I got servo jitter, when turning the ignition switch on, and no starting with this problem.

And todays BIG one -

4. If impossible to start - and does not appear to be flooded, when you check the plug. And there is no sign of fuel line problem,
Have a check of the reed valves.

Comments here please - I was surprised to see a problem with the reeds.
I found the carbon reeds were open about 2-3mm and look warped,
My solution - for now - was to take the reeds off and put back on - up the other way -
This reduced the gap to maybe 0.5mm - 1 mm and closed easy.

Another check of the reeds - without disassembly - seems to be - take the crackcase pressure line off the carb - and turn the motor over - if you can hear it sucking and blowing hard - the the reeds are sealing when the pistion is going up and down ?

My starting process involves
Choke on, ignition off, throttle low - Bounce prop from compression to compression 5 or so times.
Choke on, ignition on, low throttle - With a couple flips - Starts and stops
Choke off, ignition on, low throttle - Then 3 - 4 flips - Running and flying

Any suggestions to these problems - and comments are welcome, especially if I am doing it wrong !!!

Cheers
Dom

dom

I am sure I read somewhere that if the engine starts backwards you are in fear of damaging the reed valves this may explain your bent ones as you seem to "Bounce prop from compression to compression 5 or 6 times" that seems likely to have given the reed valves a back pressure I think.

Nuje

The reeds are not damaged from running backwards, but probably from too much choke.
procedure:
turn on choke and ignition, Throttle at fast idle
start engine. It will stop
open choke
start again
Let warm up a bit, reduce idle and check throttle response
ready

No related to backwards running, but do you know if MVVS 45 and 58 have a check valve high speed jet?

Most Walbros have a check valve to prevent air flow to the idle jets at idle. The HDA189 as used on the 58cc however has none listed on the walbro site. (item 19, nozzle assembly check valve). It has the screen check valve instead (item 50)

Hallo there,
I have a problem on my new MVVS 58.
I Installed 22x10 3 blade prop from mejzlick.
Everythings it'ok at start. Engine starts normal - sometimes backward - RPM is 6600 -
After few minutes - maybe when it come hot - engine has a tendency to cut off starting from minimum to max.
I open needle L until 2/half turns.
The needle H is at basic setting eg. 1 turn and ten minutes.
I tried to fly but engines cut off after few minutes.
At this setting seems to improve but I am not sure.
Please Help me.

Danilo

Are you cross-posting? I just answered this question at http://www.rcuniverse.com/forum/m_44...tm.htm#4497485