Hi,

I finally got around to converting my Honda 31 four stroke. It turns an 18 x 8 prop at almost 7000 rpms. Think that will haul an SR Batteries giant Eindekker around ok?? (About a 100" wingspan, around 17 lbs. weight) My thinking is that it will, but just barely...

BTW, I was able to make a WT carb (two stroke type) work by putting a spring in the diaphragm chamber of the fuel pump, and running an external pulse line tapped into the intake adapter manifold.

Research said that others who tried crankcase pulses had problems with oil getting into the pulse line. So I tried using the intake suction pulse and a sprung diaphragm like the stock (junk) carb, and it works!

AV8TOR

I want to get the 49cc 4 stroke that duro-power has to see what can be done with it, maybe to heavy to use.

Model DP049
Engine type 4-stroke 25°inclined single cylinder
Bore×Stroke 1.65"×1.41"
Compression ratio 7.5:1
Max. power output 1.5HP/7000rpm
Max. torque 2.0N.m/4500rpm
Ignition system Non-contact transistorized ignition(TCI)
Dimensions(L×W×H) 9"×11"×14"
Dry weight 12 lbs.

Ok were did my post go?

The Bit Bucket?????
It was here earlier

What do you think about that combo Terry? You've done some Honda's haven't you?

AV8TOR

We flew the Honda on a 1/3 Space Walker, about all I can say was tha it flew in a scale manner. So you should be alright as long as you don't try any vertical snaps

Ok, Thanks.

We'll see how it does once I build the plane...

AV8TOR

Any update?

Ha! No. I moved to a different city since I made that post. I just this last week got my new workshop set up and operational. Maybe I'll get to that Eindekker soon....

Way too many projects going. I've been trying to get my new rail type dune buggy done before the summer heat sets in, along with other airplane projects, etc.

AV8TOR

An 18x8 at 7000 RPM is about what I get from an OS 160 twin 4-stroke and a Super Tartan. Both fly 17 lb. models well. Not vertical performance but they can do scale-like manuevers and can cruise at @ 2/3 throttle.

J

Yeah, that's what i'm thinking. It is going on a large Eindekker. I am probably going to start out with an 18 x 6. I may sneak a little nitro into the mix as well.</p>

But, the airplane is still in the box, so it's going to be a while....

Acutally Ihave a big closet full of kits and ARF's waiting to be built, but so far, at least in mymind at the moment, the Eindekker is the favorite to be next. The problem is I have been concentrating on my new sandrail project, trying to get as much done as possible before it is just too hot to work outside here. I spent all my "build a garage money" on airplanes and airplane goodies.... </p>

AV8TO</p>

</p>

It never gets to hot to work here in the UK

I'm planning on putting my GX31 in a 1/4 scale SE5a, It will justa bout go in all under cover is I make a carb bend and use just a header pipe on the exhaust. so far I have the engine runing well with a Walbro and seperate impulse pipe, the carb is made up from several I picked up from a garden machinery 2nd hand parts place and I drilled it out to. I'm waiting for my mate to be available to make up the prop driver, since I did the carb it's gone from ole neddy to a race horse .......... oh it hand starts easily to

I cant find any video at all of anyone actually flying a GX31, I would be very interested to see some.

That's a strange thing about my GX 31.....  It runs well, turning an 18 x 8 at 7000, and it is barely broken in.  It was brand new when I converted it.  I put electronic ignition on it.  But it won't hand start.  Won't even "pop".  But with an electric starter it starts so fast you barely hit the "on" button on the starter and it is running.  </p>

AV8TOR</p>

</p>

Did you ever try starting it with the Mag ignition? I find a technique is needed, rather than getting the prop at 12-6 O clock and flip (slap) from there as I do with my Zenoah's I have to get the magnets several degrees before they swipe the coil pick up so the slap has given it enough speed to produce a spark, once you master that it starts very easily.
Once I get my proper prop driver made up I will see if I can borrow a tacho and get some readings with different props, I hope to run it with a 20" X 6" as I will be using it for a SE5a so don't need speed.

Hi AV8TOR,There is a centrifical compression release on the cam that needs to be removed. It will hand start very easy.
motorhd

I agree with motorhd. If you want to hand start with EI, you have to remove the compression relief mech.

J

I was thinking it might have some sort of a compression release, because turning it over by hand it has very little compression, but the motor runs as though the compression is fine.</p>

You don't happen to have a pic of that compression release do you?  Is it located in the cam housing??</p>

Thanks,</p>

AV8TOR</p>

Yes there is compression release. Its mount ON the cam and is easy to remove. You engine will idle better.

Yeah, I found the little bugger, hidden behind the cam gear, and I removed it.  I hope I got the cam/gear back in time properly.  I had the lobe pointed straight down when I took it apart, and I didn't turn over the engine and I put it back together with the lobe pointed down.  I saw that there is a timing mark on the cam gear, but you can't see the timing marks on the crank gear with the seal in place.  I didn't want to remove my prop hub, etc. and take out the seal for fear of damaging it.  (It's tough getting parts here in Mexico.....)</p>

It definitely has more compression hand flipping it now.  I'm anxious to get it on the test stand again.  I bet it will hand start easily now.  Thanks for the info guys.  If anyone has any cam timing info so that I can check mine, let me know.  (As in degrees and cam lift, etc.)</p>

AV8TOR</p>

That's interesting, I didnt realise the 31 had a decompressor! I have not removed one from mine and TBH would not know where to look for it (other than being behind the cam gear) or how to remove it. I can hand start easily with mag ignition, is this decompressor only relavent to CDI and if so why as either type of spark genaration needs fuel and compression to fire.

on the gx31 if the timing is off it will be way off, 24 crankshaft degrees per tooth</p>

all values @ .004" lash and crankshaft degrees</p>

stock gx31 cam .105" both approx.</p>

Intake open 25 btdc close 120 btdc</p>

Exhaust open 118 atdc close 10 atdc</p>

actual timing may vary due to lash settings ,wear on lobeand followers and axle hole.</p>

Because it is a single lobe design you only need to check intake closing point to determine if the timing is correct

btw the spring in the pump chamber does notmake it a four stroke carb, honda used 6 different wy models on the gx31and only half had springs.WOT stumble and acceleration issues <u>may </u>be addressed by cutting one coil at a time off metering lever spring nad using fresh diaphragms, if they are more than a year old they need to be replaced, most of the pumping issues with the honda is due to stiff diaphragms.</p>

Ah, just the info I needed.  Thanks a bunch!</p>

AV8TOR</p>

You are welcome.</p>

oh by the way, you don't need to be afraid of the crank seal by the gear, just  don't try to pull it out, it has a rib in the center that keeps it from going in or blowing out, it can only be removed from crank by splitting cases.</p>

The  key slot in the crank is aligned with tdc and the lines on the face of the cam (one line on each side of lobe) will be level when at tdc. You can insert a piston stop to zero a degree wheel and mark EI trigger for tdc. down load the free tavia wheel print out and glue to a fee cd rom attach to prop adapter etc etc, a piston stop can be made out of wood dowel.</p>

Hi,</p>

Thanks.  I have several degree wheels, and know how to do it all.  Just didn't have the cam timing specs for the Honda.  It seems to be one of those engines that they don't put the technical info on the web; apparently you have to be a dealer to access that data.  I hate it when they do that....</p>

AV8TOR</p>

</p>

Are you guys using the standard plug with 25 thou gap?  What should the valve clearances be? what oil should be in the crankcase? Will be Honda throw a 20" X 6" prop for a 1/4 scale  WW1 biplane and how many sugars should I put in my coffee