av8tor1977

My Feedback: (6)

I can't say for sure, as I never ran it with the magneto. But I believe it would as you not only do not have the magnet drag of the flywheel, but you also have the ability to optimize the timing.

AV8TOR

NorfolknGood

I have an XYZ CDI unit, maybe I will have to get another driver/flywheel replacement made

RichieN

My Feedback: (5)

What plug are you using in GX31? Is it possible to find the plug for the GX31 to use with Rcexl ignition for the CM-6 10mm plug?

Thanks,

Nosedragger

Use the stock plug, nothing wrong with and it won't give you trouble. No performance increase in an aircrafts low performance application by changing it.

RichieN

My Feedback: (5)

I'm just trying to use the ignition that I have on hand. This is the only reason to search for the different plug.

Nosedragger

The CM-6 plug won't work in the GX31, reach is too short, also the wrong heat range, its hotter, the GX31 is not known for fouling plugs.

av8tor1977

My Feedback: (6)

Well, this project is getting a lot closer guys....

FYI I tried an 18 x 6 prop on this Honda GX31, and it turned it about the same rpms as an 18 x 8, (about 6900 rpms), which leads me to believe that this engine in more or less stock form doesn't like to rev much over 6900. Otherwise it would have turned the lesser load of the 18 x 6 prop at a higher rpm. I am going to test fly it with the 18 x 8.

Here's some pics...

AV8TOR

NorfolknGood

I have flown my Honda GX31 in a 91" Volksplane with several props, best pull was from a 20 x 8 Master nylon jobbie, ran better than with a same size Menz wood!

[youtube]http://www.youtube.com/watch?v=3xsT4tnPZ0k[/youtube]

Nosedragger

Thats it in a nutshell. No load, WOT on the stand, they will self limit to 7500-7800 rpm

av8tor1977

My Feedback: (6)

Yeah, between the ports and the camshaft, it just can't breathe at higher rpms. Gotta use the torque instead.

AV8TOR

tomservo9503

My Feedback: (1)

Is it the ports and cam or is it the valves floating? Or is there a rev limiter built into the ignition (assuming you're using the stock coil of course)? I would expect the stock coil to limit the RPM to prevent damaging valve float. The solution might be as simple as a couple more pounds of spring on the valves, although you might end up needing beefier rockers or hardfacing on the cam, etc for those sort of shenanigans. And a three angle valve job, maybe unshroud them a bit after you open them up and optimize the flow... Right up until the little weed wacker motor blows to pieces.. 

I've got one of those little troy bilt OHV 29cc engines that I'm toying with the spare short block; bored it out about .025" - enough to remove the compression release groove - and cut some compression into the cylinder; brought it up from about 7.16 to about 9.66 - ought to scream if it doesn't explode!

Nosedragger

There is no rev limiter in the coil. Honda limits rpm by using a small carburetor.There is no valve float in a stocker, I know of a high rpm rc boat engine that is running 13,000 rpm on stock springs. No detectible float there either.

av8tor1977

My Feedback: (6)

Well, here's some observations about the SR Batteries giant Eindekker and Honda GX31 combo....

As expected, it flies VERY "scale like". That means it will take off without much fuss, climb ok, and cruise around at less than full throttle. What it WON'T do is loops from level flight, Immelman turns without a substantial dive first, it doesn't do aileron rolls very well, etc. But it sure does look cool, and sound cool with that four stroke "put, put, putting" away, but for me it definitely needs more power.

At this point my personal feeling is that I love the looks of the airplane, but I want more performance. I flew it with a Zinger 18 x 8 prop, and a lot of people "diss" Zinger props, so I am going to try an APC 18 X 6 prop that I have, and also an 18 x 6 Top Flite prop that I have. But I think the real answer is more power from this engine, or a different engine.

Don't get me wrong; it flew just fine and sounded great. I'm just "spoiled" I guess by my airplanes that can go vertical right after take off! I don't expect the Eindekker to do that, but I was hoping for more performance than it has. So, the experimenting continues...

AV8TOR

tkg

My Feedback: (1)

The Eindekker comes with a built in speed brake, you might try an 20x6 to get more low speed thrust.

av8tor1977

My Feedback: (6)

That might help. I don't care about speed with this particular airplane, but it would be cool if it could pull itself over the top of a loop. Even with a dive before hand to grab some extra speed the loops are egg shaped as it is now....

AV8TOR

Bladejunkie

Evening all,I know this is a GX31 thread,but can anyone tell me where I could find a cam pulley for a GX35?I broke mine yesterday(don't ask!!!).If someone could point me in the right direction that would be great.

Thanks Jim.

Twin Star

av8tor, I know this doesn't have anything to do with airplanes but I just wanted to comment on your Homlite blender in the back ground in one of your photos of your Eindeckker. That gives me an idea for yet another project.

Thomas46

Hello Jim,

I guess you tried to remove the "comression lowering mechanismn" (sorry don't know how it is called in English)
Or did you try to change the design of the cam?
If so, please let me know what you have done with which result. I'm interested in, because I lowered the Cam circle (?) 1.5 mm to get more valve hub.
It increases the max rpm from 5700 to 5850 with 20x8 Menz prop.

Anyhow, it might be difficult to get the cam pulley as used part.

If it helps, the Honda Part number for the pulley is 14320-Z0Z-000.

Kind regards and greetings from Germany.
Thomas

NorfolknGood

Try a heavier nylon prop, mine runs better, higher revs and better low end with a cheap heavy prop.

My GX31 is going in a 1/4 scale SE5a I'm in the process of building.

Nosedragger

Your local Honda power equipment dealer should be able to get the part.

or try

Plano Power Equipment
1414 N. Central Expressway
Plano, Texas 75074
(972) 423-5220
FAX (972) 423-5825


FYI GX25 and GX35 cams DO NOT interchange
[hr]

Do you mean Base Circle? did you measure the change in lift at the valve?

Thomas46

Sorry for my poor explanation.

Yes I mean the base circle. And the 1.5mm are the more valve hub.
Next time I will take some more away from the base circle, but before I have to check how much space I have between valves and piston top on TDC.

av8tor1977

My Feedback: (6)

Hi,

How did you make the camshaft base circle smaller? Sanding it?

Yes, I was running it with a Zinger prop; I'm going to try an APC next.

Yes, I did take out the compression release mechanism. It easily starts by hand now.

The blender is a kick. As I was building it I worried a bit that it might need a centrifugal clutch, but that's not a problem. Even full of hard to chop up ice cubes, fruit, etc. it starts easily and blends well at an idle! Revving it up is just for effect...

BTW, if anyone is contemplating the Eindekker and Honda 31, the balance came out perfectly with the rudder and two elevator servos mounted in the rear. No added weight necessary to adjust c.g. It was super simple to cut openings for the servos in the rear of the fuselage.

AV8TOR

Bladejunkie

Thanks for the replys guys,yes Thomas I was trying to remove the compression release mechanism.I did find a new at a local lawnmower shop and it was only $19.00.I'm kind of scared to try and remove the compression release on the new one,because I don't know what I did wrong on the other one?Can one of you guys tell me the best way to remove the compession release?I tried grinding the pivot side side of the little arm,then with a drift punch,I tried to knock the pin out the other side.That didn't work,the cam pulley cracked all around the area of the pin.

Thanks Jim.

Thomas46

Reduction of base circle was done by a friend of mine who has access to an eccentric cam grinding machine.
Perfect surface and cam design. I will go on that further in the next tuning step.
If the result is not what I'm expecting my idea is to design the camgear new, away from the single cam with equal timing for IN and EX. Suitable valve overlapping with 2 cams and reworked "rockerarms" (right word?)

How do you think?


Btw, why all of you remove the comression release mechanism? On GX31, yes I did it too for better hand start, but on GX35 it never disturbs me. Engine starts perfectly and idling rpm is around 1700.

Anyhow, just one idea: If remove of CRM is difficult or with danger to destroy the cam gear, it is may better just to block it.
Clean the area to dry and oilfree condition and use Epoxy to block the mechanism.

Nosedragger

The compression release intereferes with low speed idle sometimes. You have to grind the side of the pin that is swedged over until the arm falls off, the pin will drop out. I've done more than a few of these and never broke one yet.

I happen to know the guy here in the US that made cams for both the GX31 and GX35, grinding more material off the existing cam doesn't work. You need to add material on the nose of the cam.Reducing the base circle can get you more lift but messes up the rocker geometry.More overlap can be had from the single lobe cam as well as lift and duration, no need to redesign the top end of the engine.
When you start changing cam timing you need to commit to making other changes as well to allow it to work as intended. The reason you don't see cams for aircraft is the low speed they operate at, cowling won't accomodate the necessary intake tract length and exhaust length changes needed to work with a cam the will boost torque.
With out an exhaust header of at least 12" more exhaust overlap won't do any good.

sorry to get off topic, maybe another thread should be started by Thomas and he can share his progress.