What oil and mix?

[stewart clifford]

I've got an Mvvs 40cc which I've not run for a couple if years since a crash. I'm just about to re fit it into the repaired model but noticed the piston is covered in black oil which implies to me it was over oiled. I think it was recommended to run it on either 25 or 30-1, which I did but it used to run very hot and I had a few dead sticks with it.
I would be very grateful for any advice on a type and ratio of oil to make it run properly.

Stewart.

[Paul Williams]

http://www.mvvs.cz/docMVVS/40en.pdf
From the manual
Fuel
Always use unleaded 95-octane petrol mixed in the proportion 40 volume units of petrol to 1 unit of Mobil Racing 2T oil. If necessary, quality brand-name synthetic oil intended for racing two-stroke engines can be used too. Mix it in the proportion 30:1. Never use inexpensive oil developed for garden appliances or synthetic oils intended for the operation of methanol
model engines. The manufacturer declines all responsibility for all engine damages arising from the use of low-quality fuel.
Store fuel in containers designed for this purpose. Do not use mixed fuel older than 90 days.

[Clive Hall]

I have an MVVS 26cc which came new out of the box with a black coating on the piston skirt. This is normal for this engine, so I suspect that this may be what you are seeing on your engine rather than burned-on oil. If so, be glad, it's a sample of MVVS quality construction and attention to detail.

I run the engine on a 50:1 mix of petrol and Silkolene Pro 2 and it runs like a sewing machine. I am told that this oil will still give adequate lubrication up to a 100:1 mix, though this seldom works because engines run out of piston ring seal with so little oil in the fuel. Pro 2 is also inclined to leave a brown stain build-up on light coloured cellulose finishes; if left exposed to light in clear containers it darkens markedly, though this does not seem to affect performance. I have run a Zenoah 38 on this oil at 60:1 with completely satisfactory results.

Clive Hall

[Ken Roddham]

Stewart - I can confirm that the black coating you see on the piston is a Teflon coating applied to assist running in.
I repaired an MVVS 58 for one of our LMA members last year - it had been subject to damage from a heavy crash. On completion of repairs I test ran it on 40:1 oil mix and it ran nicely.
MVVS state :-
"Always use unleaded 95-octane petrol mixed in the proportion 40 volume units of petrol to 1
unit of Mobil Racing 2T oil. If necessary, quality brand-name synthetic oil intended for
racing two-stroke engines can be used too.
Running the engine in, use MVVS Racing 2T oil, which comes with the engine. Mix it in the
proportion 30:1"

Quite a few of our member use either Halfords Synthetic of Stihl Semi synthetic with good results.
Over the past couple of years I've done quite a few repairs on various types/makes of engine, and I can say that in my opinion the MVVS and ZDZ, although a little heavy, are up there with the best of them.
Hope this is of help to you.
Regards, Ken

[stewart clifford]

Thank you everyone. The common response seems to be to use less oil. Having taken in all the suggestions I've now flown the model very successfully 4 times using 40-1. I use that mix in my other engines, finally I think I've cracked it. Did also back off the high needle just a touch.

Cheers
Stewart.