I have been trying to start this engine for the last 3-4 days and only got one run of about 3-4 min. Today it started after many flips and ran for about 10-20 seconds and after removing the battery from the glow plug it stopped. This engine was given to me by a friend who has purchased it from ebay. The engine shows no signs of real use or much running. Still looks like it did new back in the day. The needle valve has two holes and are positioned at right angles to the venturi in coming air, otherwise for and aft. Engine has good compression. It pops a lot when flipped and tries to run but wont. I have it on a test stand with a 9-4 prop. Today I removed the front rotor and piston and saw no signs of wear in fact it all looked new. The rod bearings were a nice fit. I'm leaning toward fuel draw as the problem. My starting procedure is fill tank choke until fuel reaches the venture, squirt some fuel in the exhaust bring piston up to starting position attach glow driver hold prop firmly feeling for the bump and the flip prop. At this point it usually pops or maybe to or three pops in a row. Also it has a tendency to run backward a lot while burning out the prime. I'm thinking about trying a different NV assy. I have been running Model airplane engines since 1947 and never have had one give me trouble like this one. My first engine age 12 was a O&R 19 side port on ignition. That engine would start easy and was very predictable. This engine has the restrictor in the venture. Has anyone had this experience with the O&R FRV engine? You can see the engine in the open forum under Dynamic. Richard

I also have a few O&R 29 FRV.  I can't agree about "low power".  Not as strong as a Torp 29 or a Fox, but good enough for the correct size plane.

I suspect your NVA is a replacement.  The O&R NVA has one hole which points down. The venturi insert is also necessary.

I have had good luck using Thunderbolt glo plugs and ordinary Sig 10% nitro fuel.  I think I have used 9-6 wood props, but a 10-5 would also work.

The only problem with these old engines, is the cylinder to case gasket shrinks and leaks. Note if any fuel is coming from that area.  You can fix it with some JB Weld.

Floyd

Floyd

OK.  I missed the part about not running unless battery is connected.  You certainly must try different plugs, and perhaps fuel.  Although I believe this engine will run on almost any fuel that has 20% or more oil.  It is low compression, so maybe a bit more nitro will tend to "boost" the virtual compression.

Floyd

I'd look at the spraybar/NV...would the two holes be offset from CL, like the Fox .35's? If so, turning it 180* might fix it. Sometimes, machined things are not what was intended, due to dull drill or an off day, or whatever.

Next thought would be a vacuum leak at the frontend gasket or cylinder base gasket. The cylinder base gaskets are known to dry out and lose the seal. I would consider soaking the thing in some sort of thin oily stuff to try and moisturize that gasket...ATF or Marvel Mystery Oil might do it. There was a guy that could remove the cylinder and replace the gasket, but I think he's passed away, and don't know if anybody else has taken up the task. Steve

I agree that symptoms point to a leak of crankcase compression.  The front cover gasket is very thin paper, which doesn't seal very well.  Also check for a leak around the needle valve body.  A fiber washer on each side will help.  They often leak around the cylinder to crankcase gasket.  This can't be replaced, so sealing with JB Weld or even bathtub caulk will work.

Floyd

The late George Tallent, who lived on a ranch outside of Tucson, had all the tooling to remove O&R cylinders and replace the gasket.  The real trick was getting a good seal while simultaneously spot welding the cylinder back.
I doubt that anyone will be able to repair these engines in the future.
Floyd