The metal head gasket on my old trusty MVVS 40 engine has blown out. Anyone know where I can get a replacement? LOVE this motor... outruns my OS SF-46's !!

Brad,


They can be supplied by any MVVS dealer.

They come in sets of 3.


How much nitro are you using? I have never seen one blow, unless the head bolts were not properly and evenly tightened.

You must use 20% oil and no more than 5% nitro. If you add a second head gasket, up to 15% nitro will be tolerated.

Currently using Red Max 18% synthetic oil & 15% nitro blend, though most of its life (approx 10 yrs) castor/syn blends have been used. Only one head gasket was provided with this motor (I believe it was one of the first batch's distributed to USA before Morris Hobbies picked them up). The motor has been in storage for approx 3 yrs & when I mounted & fired it up, the head gasket blew. i'm fairly confident the head screws were snug because I had just taken the head off for inspection as the motor was slightly gummed up from storage (marvel mystery oil). The bearings felt a little rough but after a tank was run they feel smooth again. I've flown the motor about 5 flights recently without any head gasket. It wants to backfire & sling a prop upon start-up if not using an electric starter, otherwise it both screams, transitions, & idles beautifully. One recent change I did make though was to ditch the OEM tuned muffler & replaced with a Macs Muffler, could this have caused the gasket to blow?

Brad!

Before doing anything else, go to 5% nitro, ASAP.
I guess your engine showed you it doesn't like the 15% nitro, in the least expensive way...

The instructions leaflette that came with your engine, says in plain English 20% castor (ricinovi) oil, 80% methyl alcohol.

Nitro is not even mentioned...

Some good commercially available fuels are PowerMaster GMA 5% (it has 22% oil, 50/50 castor/synthetic) and Sig Champion 5% (it has 20% oil, 50/50 castor/synthetic).

Red max synthetic 15% may be pretty good, but only for other, non-ABC/ABN engines...

You need two head shims, if you want to use 15% nitro.

And with any fuel, add oil to 20%, half castor, or more.


After a proper prime (one turn of the prop after fuel has reached the carburettor), this engine will start 95% of the time on the the first back-flip (throw the prop clock-wise against compression).

I cannot understand why some people find an electric starter necessary with these engines.