I have the following engines and would prefer to have one jug of fuel for them all.

2 Strokes
OS 46 FX, GMS 47, Irvine 53, Sport Jett 50

4 Strokes
YS 63 FZ, Saito 100

I was using 10% nitro fuel and ran out so I bought 2/4 cycle with 15% nitro. The only engines currently in planes are the GMS and the Irvine. The GMS took a little adjustment, as did the Irvine (both ran great on 10% but I was told the 4 strokes would need more than 10%). But when I was doing final adjustments on the Irvine, it stopped and would not start. Worked on it at the field and gave up. Got it home and removed the cowl on the plane to find I had blown the head gasket. Could this have been caused by flooding the engine or the 15% fuel? The manual says the Irvine can take up to 20%, but many posters here say no more than 10% without a head shim. I would prefer one jug of fuel for them all but understand if I cannot get away with that. Will all be fine with 10, 15, more, less? Any help is greatly appreciated.

Well, after posting this, I did some more searching. It seems like I will need to carry to gallons to the field. One 30% heli for the 4 strokes, and I am thinking of sticking with 15% for the 2 strokes. If I stay with 15%, will I need to do anything to the Irvine to help it handle the extra nitro?

YS recommends 20% nitro and 20% synthetic oil.
Most major fuel companies market a YS 20/20 fuel.
I'd think his would also work fine in your Saito.

I guess I'm just cheap, but I see no reason to run high nitro fuels in two stroke sport engines. The 10% stuff runs great and is cheaper.

YS 20/20 will work well in all of them.

ditto what warren says. I run Powermaster YS 20/20 in all my 2 and 4 stroke engines.

Jett says they test on 15% and there is a lot of talk here about the Irvines needing a head shim for anything over 10. Any ideas as to what could have blown the head gasket on the Irvine?

Engines don't just blow head shims, not even on 15% fuel... are you sure your head bolts were tight and if they were, were they torqued evenly?

10 or 15% fuel will work fine in all these engines... some, like the YS may be able to handle more, but will run fine on 15%

Winibald,

The YS will not run well on 10%-15% nitro; power, idle and response will suffer. It is even likely to overheat.
If this 10%-15% nitro fuel contains Castor oil, it will also clog up its pump. Only all synthetic oil for YS.

Dean,

Irvines may need 10%, or less nitro and could overheat from any more. They actually run very well (better) on 0-5% nitro.

Bob, Warren, Dean,

For the OS, GMS and Irvine, fuel containing some Castor oil is recommended; I believe all synthetic will void the warranty on OS engines. Although the GMS manual is inconclusive, ALL engine experts (Clarence Lee, David Gierke, Harry Higley, the late George Aldrich) said that in ABC/AAC/ABN engines, the fuel MUST contain some Castor oil (5%).
The YS 20/20 doesn't fit the bill.

Dean,

You will have to carry more than one jug, if you plan on having all your engines for a long time. Sorry.
Not too much of a hassle for your car, is it?

The Saito is the least of your problems, as it will accept any drink.

Rudeboy - the engine was new and I had not touched the head bolts. I would think a new engine would not have those loose so soon. I ran 2 small tanks through it on the bench and then flew it a total of 3 times on 2 different days. Once I switched fuel, it needed some adjustments and that is what I was doing. Could it have overheated?

Always tighten the screws on new engines. Assembly line workers work fast with air powered drivers. They don't really check them, except maybe on a random basis.

I tend to agree with "sport pilot" here... always check all the screws on new engine... especially the head bolts.
I have found them unevenly torqued and even partially loose on more than one of my engines when they were new. Unevenly torqued head bolts are not a good thing, as they can deform the top of the engine case and the liner with it.

In fact, I take every new engine completely apart and clean it thouroughly before I attemp to start it. I have found metal shavings in several engines. Last example was a new MVVS 1.44 twin... its piston pins are closed on one side... there were A LOT of steel chips in both piston pins! Imagine what this would do to the liners and pistons if they start coming out during operation...

After the cleaning I put everything together and tighten all the screws evenly. I also put some synthetic oil on the threads prior to assembly... that saves the threads and helps in getting the screws loose again later.