How fast does an electric engine starter spin?... Or... hard starting .049

**RknRusty** Fri Oct 14, 2011 9:37 pm

I want to possibly make one if I can do it cheaply enough. I have one engine that's always a pain to start.

The engine I'm having trouble with is an .049 with a new crankcase, brass driveplate, new SPI piston/cyl set and a new killer Bee backplate. It's fed from a 3/8oz wedge tank. I've never used an external tank before, so I assume they make it harder to start. After filling it, I always plug the bottom vent and force fuel to flow to the engine until I see a drop come out of the back, and then prime and flip. Sometimes it floods so I have to close the nv and burn it off and try again.
So, any advice on starting, or making an electric starter would be appreciated.

Thanks,
Rusty

**Admin** Fri Oct 14, 2011 11:45 pm

I sometimes have trouble with engines built from other parts. Try setting the needle to 3.5 turns. If nothing, try 4 turns. Again, if nothing, try 4.5 turns. That usually gets engines started. It very well could be a reed issue, replacing the reed sometimes gets them going. Make sure your glow head is bright. Also make sure it has a good cylinder/piston fit.

nitroairplane Sat Oct 15, 2011 1:15 am

Does it have good gaskets?
I find engines easier to start with external tanks.
Remember if it has a particularly tight parts fit it may be harder to start.
Also maybe it's a little over compressed try messing with head shims.

PV Pilot Sat Oct 15, 2011 2:18 am

A little pre heat with a heat gun or hair dryer helps with a fresh motor. You could probably spin it over with a rubber adapter of your own design using a electric drill, using good judgment.

gcb Sat Oct 15, 2011 3:25 am

When you force fuel into the tube, you are apparently also squirting fuel into the engine intake. With tanked engines, running off a prime is enough time to pull fuel to the spraybar. You should mount the tank as close as possible to the backplate (ie right behind the firewall). The problem was solved on the Sure Start engine by adding a choke tube.

Since you have the Killer Bee backplate, the intake is probably larger than most, which translates to less fuel draw. You should probably be using a pressure or a baloon tank with that engine, rather than a wedge. I do not have a Killer Bee so this is just a guess.

I would suggest using a spring starter because I don't like electric starters on small engines. Some have great success with them, but I prefer a hard flip (or flick). Your choice.

George

Kim Sat Oct 15, 2011 7:32 am

I've got a Sullivan starter for 1/2A's and use it very "gingerly" on my .049's. It's VERY helpful in getting them started in the right direction. I have several, otherwise good engines, that are possessed by the demon that makes them start backwards no matter WHICH way you flip them! The coil starter works best for me if there's room in the plane's nose, but I've got planes whose cowling would be damaged by their use. I somehow never warmed up to the later versions with the plastic plate behind the prop.

I push the starter insert against the prop just firm enough to "bump" it through compression, and never "hammer down" and spin the engine. Usually the engine cranks up (in the right direction) and goes...if not...it's always because of something else that needs attention first anyway.

Anyway, that's my deal...

SuperDave Sat Oct 15, 2011 8:23 am

Plugging the bottom vent of a tank prevents the tank from drawing the air needed to draw fuel properly. thus creating a vacuum.

**RknRusty** Sat Oct 15, 2011 8:23 am

The engine runs great after 15 minutes of flooding drying and flipping. After that it starts fine. It has a new glow head, and it acted this way with its old #1 cylinder too, which also had a new head on it. I think it's just the low vacuum backplate. I guess I need to run it before I leave the shop and walk over to the field and fly it first before the other planes while its still warm. I might look into pressure tapping it. Until then I may get a cheap cordless drill from Lowes, I need one for other things. If I grind it up, I'll replace the crankcase. Being basically a Killer Bee with a Babe crank, it might lunch itself soon anyway.

**RknRusty** Sat Oct 15, 2011 8:25 am

SuperDave wrote:Plugging the bottom vent of a tank prevents the tank from drawing the air needed to draw fuel properly. thus creating a vacuum.

I don't plug it while I'm trying to crank it. I do that only to force fuel through the tube first.

SuperDave Sat Oct 15, 2011 8:47 am

Since that might be creating the problem why do you keep doing it? Try it with both vents open and see what happens.

BTW, I've never had a particular problem starting Coxes. If I do the standard trouble-shooting recommendations serve me well. See Bernie's guide.

SuperDave Sat Oct 15, 2011 10:26 am

One of the purposes of priming is to draw fuel into the engine as well as start it.

My Sure-start will draw fuel on it's own from a tank several inches below the engine. This on prime alone. The fuel may be seen being drawn in when the engine first "pops".

**RknRusty** Sat Oct 15, 2011 11:01 am

SuperDave wrote:One of the purposes of priming is to draw fuel into the engine as well as start it.

My Sure-start will draw fuel on it's own from a tank several inches below the engine. This on prime alone. The fuel may be seen being drawn in when the engine first "pops".

The Surestart has a small enough venturi to pull the vacuum it takes to draw the fuel, the wide venturi on Killer Bee does not.

SuperDave wrote:Since that might be creating the problem why do you keep doing it? Try it with both vents open and see what happens.
BTW, I've never had a particular problem starting Coxes. If I do the standard trouble-shooting recommendations serve me well. See Bernie's guide.

Like I mentioned above, it won't draw the fuel. The line is sealed, no air leaks. I put my finger over the vent and push the syringe until fuel flows to the engine. Then I unblock it and try to start it.
I've never had a problem starting either, but I also never had a backplate with a canyon sized hole in the back. Maybe if I could spin it long enough with an electric starter I could get fuel to it without flooding the crankcase. That's why I was hoping an electric starter would get it there. The spring starter doesn't keep it spinning long enough to pull in the fuel.

I'll try pushing the fuel half way into the line, maybe that will get it there without flooding it. Meanwhile, I was curious if anyone knows how fast an electric starter spins.

SuperDave Sat Oct 15, 2011 11:13 am

Don't know the specific RPM's of an electric starter but it would be assumed that they are sufficent enough to start an angine. I received one from a friend but never have used it except on much larger engines than Coxes.

But I don't believe your problem related to cranking speed. What about the often overlooked venturi gasket? Small but quite significant in drawing fuel.

PV Pilot Sat Oct 15, 2011 11:36 am

SuperDave wrote:But I don't believe your problem related to cranking speed. What about the often overlooked venturi gasket? Small but quite significant in drawing fuel.

It's a backplate motor with external tank I believe, so I dont think it has a induction tube venturi gasket.

SuperDave Sat Oct 15, 2011 12:14 pm

This is the only description of the engin given "hard-starting .049' with no further details.

How are we to know the TYPE of .049?

I'm saying my Sure-start .049 has no problem drawing fuel from a tank located several inches below the engine. Until we know the type of engine having the problems, further speculations are pointless.

**RknRusty** Sat Oct 15, 2011 1:20 pm

RknRusty wrote:The engine I'm having trouble with is an .049 with a new crankcase, brass driveplate, new SPI piston/cyl set and a new killer Bee backplate. It's fed from a 3/8oz wedge tank.

**RknRusty** Sat Oct 15, 2011 1:31 pm

RknRusty wrote:Let's just drop it for now. I'll let y'all know what I figure out.

PV Pilot Sat Oct 15, 2011 7:14 pm

I just now came up from the shop after deciding to do a little investigation with rusty's problem. Granted this is not exactly the same motor that rusty built, but it is a just broke in spi cylinder combo that is similar, the difference is I have the cut crank I believe. Changed out the black back plate for a brand new, right out of the package red killer bee backplate for external tank. It took 6 turns out on the needle to get fuel to flow up the line using a astro flight starter. The fuel bubbles would not move until that was done. Once I hit 6 turns out, the fuel jumped right to the needle infeed, as it should.

I didn't run it or try to start it, I just wanted to see when the fuel would move up the line. I slowly added 1/4 turns till the fuel moved up. Used a 1oz sullivan tank.

**RknRusty** Sat Oct 15, 2011 9:49 pm

Thanks PV, I appreciate it. I'll take another look at mine tomorrow. I've been trying at about 4-1/2 to 5 turns, I lose count after a while. Maybe I'm just not opening it enough. the tank is slightly above the inlet on the engine. Once I get it running, it's fine until the next cold start. I'll let you know how it turns out.

fit90 Sun Oct 16, 2011 8:51 am

The NVA on a Killer Bee backplate is probably fine thread. This is typically128 tpi. You will probably need to at least double the number of turns you use on a normal Cox backplate if you are not using a pressurized fuel system. I will check one later today and post if it is fine thread or not.

**RknRusty** Sun Oct 16, 2011 12:06 pm

fit90 wrote:The NVA on a Killer Bee backplate is probably fine thread. This is typically128 tpi. You will probably need to at least double the number of turns you use on a normal Cox backplate if you are not using a pressurized fuel system. I will check one later today and post if it is fine thread or not.

That had not occurred to me, all I know is it is brass and not aluminum. I'm headed out to the shop right now and I'll check. I might fly it this afternoon. I want to see how the semi-Killer Bee configuration works. A Killer Bee minus the KB crankshaft. If it turns as fast as a KB I'll be waiting for the crankshaft to bust. I think the crank is part of what makes a KB faster though. I need to get one of those for it.
Thanks, Fit.

fit90 Sun Oct 16, 2011 12:52 pm

Rusty,

I took the Killer Bee needle valve out to the garage only to find that my thread gages do not go anywhere near 128tpi. I did try to engage the threads from the Killer Bee needle valve with the threads on a standard Cox backplate needle valve. The Killer Bee threads were much finer than the standard needle valve's threads. I also took the Killer Bee needle valve assembly and compared it to one from Texastimers.com and they looked identical. This was strictly a visual comparison, though.

These are definitely fine threads. I use a Killer Bee backplate with the venturi bored out on a pressure tapped crank case and the needle valve adjusts nicely. Standard needle valves are too coarse to use on pressurized fuel systems. They are too sensative.

If you do decdide to go with any kind of a pressurized fuel system you do not need to change your needle valve assembly.

Good luck and keep us posted,

Bob

**RknRusty** Sun Oct 16, 2011 7:45 pm

PV and Fit, thanks for your help today. Fit, I took the needle out and it looks like the same thread as all the others, which is certainly fine, but apparently not as fine as yours. Mine fits any backplate in my box including the Surestart. It was sold as a KB backplate, but mine must have a standard spraybar and needle. But that suits me now because thanks to PV, I figured out how to reliably get it cranked.

It still takes a lot more tries with the spring starter than a plate with a smaller venturi, but I know where to go with the needle now. Just like yours, PV, mine gets fuel flow at 5-1/2 to 6 turns. If I prime it it will try to start, then sputter out too rich. But once the fuel is there I can close a little and crank and keep doing that until it finally starts and I slowly lean it out to 4-1/2 turns where it runs happily. Very Happy

No more force feeding it like I was doing before. That was just flooding the crankcase.

It doesn't sound like Killer Bee RPM though, more like the sound of a Black Widow. I was hoping for more speed because the plane is a little too heavy for a BW and I was hoping this would wake it up. It will do loops but they are wide and slow.

Thanks all you other guys that took the time to offer up suggestions too.

Rusty

nitroairplane Mon Oct 17, 2011 4:21 am

RknRusty wrote:PV and Fit, thanks for your help today. Fit, I took the needle out and it looks like the same thread as all the others, which is certainly fine, but apparently not as fine as yours. Mine fits any backplate in my box including the Surestart. It was sold as a KB backplate, but mine must have a standard spraybar and needle. But that suits me now because thanks to PV, I figured out how to reliably get it cranked.

It still takes a lot more tries with the spring starter than a plate with a smaller venturi, but I know where to go with the needle now. Just like yours, PV, mine gets fuel flow at 5-1/2 to 6 turns. If I prime it it will try to start, then sputter out too rich. But once the fuel is there I can close a little and crank and keep doing that until it finally starts and I slowly lean it out to 4-1/2 turns where it runs happily. No more force feeding it like I was doing before. That was just flooding the crankcase.

It doesn't sound like Killer Bee RPM though, more like the sound of a Black Widow. I was hoping for more speed because the plane is a little too heavy for a BW and I was hoping this would wake it up. It will do loops but they are wide and slow.

Thanks all you other guys that took the time to offer up suggestions too.

Rusty

So I suppose you'll need a tach to make sure what fuel are you running?
Some engines need high nitro to be properly above the others.

PV Pilot Mon Oct 17, 2011 6:30 am

Yup, add a high comp head, killer bee crank, and run 25%.

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How fast does an electric engine starter spin?... Or... hard starting .049

How fast does an electric engine starter spin?... Or... hard starting .049

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