I just took an old Fox 35 that hasn't been run in many years. I cleaned it up and mounted it on a Twister. When I tried to get it running it would run for about two seconds and quit. I tried two different tanks and the fuel is 10% nitro and synthetic oil. I tried for an hour but it would just run for a second and quit.
As noted by everyone above, not enough fuel it getting in.
But, If it worked before, it should work again, particularly with the very thin fuel you are attempting to use. Take out the needle and spraybar, and put them in a small container (like a 35mm film can), fill it up with lacquer thinner, shake it up, and then let it sit for an hour or so. Then get some wire (like 1/32 music wire) and poke it through, and get absolutely everything out of it. I also use a small bottle brush that comes with the Sullivan Fuel System Cleaning kit, or the ones you can get at the drugstore to clean between teeth.
Also as noted above, if you are using typical RC fuel with all synthetic oil, you need to add a very large amount of castor oil. It may be lucky you couldn't get it going, because if you had, the fuel might have damaged the engine. I would not use any less than 25% oil, mostly castor, and up to 30% wouldn't hurt anything, except for raising your paper towel costs.
Brett