Starting hot Fox

I'm entered in the sport race in the upcoming northwest regionals. The engine runs fine although it is quite a problem is getting it started again after running the first tank through it. Any advice on starting a hot Fox 35 would be greatly appreciated.
Thanks in advance -
Doug

Well Doug - This stunt guy does it a little different than most racers. We have the privilage of Bob Whitney & Dave Hallas in my club, with Wayne Trivin not far away either. They laugh at me with my nice neat syringe and twist lock glo starter when we do our club Fox racing. But hey, I'm just there to support the event.

I guess it depends how serious you are. The serious guys rig up a hot glove. Usually a battery in your pocket, with leads running down your fore arm to a set of contacts stitched into the thumb and forefinger. So you grasp the profile, and engine in one hand while lighting the glo. The other hand usually has a fuel bulb, for shooting into the quick fill tank.

OK, now to your actual question, restarting a hot Fox. The best answer is not to let it get too hot in the first place. Most races are won in the pits. The motor must be well broken in, as that is the first and biggest source of heat, friction. Then, find a prop combo and RPM that that lets your Fox unload to a respectable lap time without OVER heating it. Sure, you may find that tweaking the needle gives you a better little lap time for that first tank full, but that one may also cook the engine.

Depsite your best efforts, If you can't get the engine to run cool, Some guys dowse their engines with fuel from the bulb to quench it before flipping. I personally don't like this, it bakes on crud that makes it eventually run hotter. I wear a soft protective silicon sleave on my thumb (or a bandaid will do in a pinch, if you don't, you WILL need one later) and suction flip prime my Foxes with my thumb in the pits. The Fox will usually take 3 or 4 fast flip primes when hot, as long as it's not super heated. Lots of others prefer to exhaust prime, but I've always felt my way is faster for what I am comfortable with.

Oh, one other neat trick if the Fox is really sizzling hot, it usually cooks the fuel faster than you can prime it. So...if the side of the tank flexes, like a clunk or thin metal tank, squeezing the side of the tank with your thumb while flipping can get lots of fuel moving fast.

Lets see, what else, oh yeah, keep the outboard wing tip down while flipping, especially if you are short tanking a larger tank, so as to get the pickup into the fuel.

That's hot Fox starting from someone who hate's to do it's perspective. You will no doubt get lot's of other opinions. I have no visions of being a pro racer, so take it for what it's worth.

Have fun!

Eric V.

Choke er" till the cows come home!! cuz a hot motor evaporates the prime. BTW my methods aint written" in stone.< Paul

Buy an L & J ?

The key to restarting a hot Fox is to not let it cool off! In Fox racing, you want to fuel as fast as possible, and also get the fuel up to the spraybar. Don't choke! You should hit the prop hard and if you are lucky (or good), it will go. Sometimes you can spray the head with some fuel (but be careful, it might ignite). The worse case scenario is to let the engine cool off somewhere between running temperatures and completely cool. Those are really tough to start.

This is one of the "charms" of Fox racing. You not only want a fast run, but a fast start. I think more races are lost by fast engines which don't restart. This is an event where your finish depends more on the pitman's skill than your own flying.

You could be flooding it on the second refill. Put a predetermined amount of fuel on the refill without overflowing, then try it.

I see some guys use a clip in the overflow vent. When they refill the tank one hand holds the clip down. Sometimes, if you are too quick and release the clip too early while refilling the tank, it will easily cause the engine to flood.

Here's the technique that has worked for me in about 24 years of racing Fox .35 stunt engines in Northwest Sport Race. Should get a one-or two-flip start in most instances:
I'm talking about pit stops here, presuming you have the initial start down to one flip.
On the catch, immediately splash some fuel on the head. Do this first, before fueling, and it will cool the engine a bit. *
Pinch your overflow cap device and fuel. DO NOT PRIME!!!! A hot Fox does not want a prime. That's a way to guarantee that it won't start. **
Attach battery clip, lift plane for a good angle of attack, and whack the prop hard, forward through compression. HARD. ***
Most of the time, it will go. If it doesn't go on the first flip, usually a few more quick flips will get it started, if it's anywhere close. Resist the temptation to prime unless it has totally cooled off. If it doesn't go pretty quickly, one choke might be in order, but usually it's not necessary.

* Don't worry about fuel baking on the head; I've never had any problem with that and we have engines that have dozens of races on them.
** You will get a bit of a prime, of a sort, through the fuel line as you fill. Practice with your particular setup may give you an idea what sequence to use in letting the overflow cap close. What I mean is, not every setup is the same. The question is whether you keep squeezing fuel for an instant after the tank is full, before letting the overflow cap reset -- or whether you stop squeezing before resetting the cap, etc. The difference will be whether you seem to get too much or too little fuel to the engine. Practice will tell you.
***Another thing that practice may reveal is that maybe your engine likes to be whacked hard AWAY from compression, like the backflip method mentioned elsewhere on this board. No substitute for practice. We've had engines that liked it one way, and some that liked it the other way.

Hope this helps.
--jt

One addition to John's excellent advice-
when flipping the prop, practice flipping with your finger as close to the prop nut as possible, and practice getting the most grunt into the flip just as it hits compression. With this technique a good pitman can start many engines that even a high speed electric starter won't coax a burp from. The trick is to get it to hit compression as hard and fast as possible. Just banging the prop out near the tip won't do it.

Hold an ice cube on the engine until it melts about 10 seconds or so. After that it will start.

In a race event, in ten seconds, you have lost three laps. You have just lost the race!!

Bigiron