Greetings all...... Advice please .

I've just bought a 2nd hand OS MAX 35 - S off the infamous E-Bay. It came from a very reliable chap. It is in really good condition.

Now ..... Not knowing how much running the engine had experienced , I thought it best to first put it through a proper running - in regime , so I used Randy's advice published here . i.e. Smaller prop , 28% fuel [ around 22% castor 6% synthetic ] and starting with several really rich runs with a 5/10 minute cooling off period  etc.

The engine was easy to start but would cut out after about 3 minutes rich running. Installing a new plug appears to have cured that problem.

It's now had around 45 minutes of rich running-in.
It does appear to be running ' hot ' as it does take the full 10 minutes to cool off.

Guys : In your opinion how much running in should this old timer need please ?
Any other tips about this 60's engine would be appreciated.

As an addendum , it's amazing how much has changed since I was a lad as we Brits say ! My two favourite engines , the Magnum XL 36 and Thunder Tiger 36 perform  brilliantly after a sensible running -in procedure and give no problems whatsoever without any internal mods ! I must stop buying 'old' engines !

Much obliged ,

Robin [ ex-pat Brit in the Charente full of ex-pat Brits ]

My "guess"is that the leaning out is due to the fuel level dropping in the tank, which ends up lowering the pressure at the needle. Opening up the needle, as you are doing, fixes it---at least on the bench! How is the tank setup? You want to setup the tank so that the fuel level drop is only an inch or so. You could set it up as a uniflow (vent and pickup oriented at bottom of tank) and avoid any pressure drop.

Hi Robin

You have good advice from Pete  and  Alan, another thing you need do is to put the engine in a fast 4 cycle, pinch the fuel tubing to lean out the engine, if it snapped right back into a 4 cycle it should be ready to fly. Also I too would suggest changing to a less restictive muffler, as not only is the exhaust hole very small, the strap can somtimes bind the piston-sleeve a bit

Randy

Thanks a lot fellas ...... Much obliged you took the trouble to reply to my problem.

Randy has a point , the muffler ' strap ' does need to be pretty tightly fixed and this could affect the liner/piston fit a touch.

Thanks for that Randy ,

Robin .

Robin

It is a good idea to use a thread fastener, such as "Lock Tite"  when using a strap on type such as you have, this way  it will stay without having to crunch it down so tight

Randy