OldCoot

My Feedback: (47)

With the amount of drag on the biplane the 18X8 gave me the best thrust vs speed for the performance I wanted.
I think you will need to try different props, 18X8 or an 18X6-10 or a 20X6 or a 20X8 or an 18X10.
It will all depend on how you want the edge to act.
Props perform differently on different airplanes. It's trail and error until you find the prop and RPM combination that makes the plane fly the way you want it to.
You will also find that there is a slight performance difference between different brands of props of the same pitch and diameter.
For the most thrust (pulling power) you will want higher RPM, large diameter, low pitch such as the 20X6.

cantw8tofly

My Feedback: (3)

Hey coot just one more question.... Can you run this engine without the air horn on the carb? If i could take it off it will same me having tobutcher my cowl even more.

Have you tried it without it?

OldCoot

My Feedback: (47)

I cut the length on mine in half for the same reason. But I left just a little sticking outside the cowl.
Removing the velocity stack will not adversely affect the engine, but, it will probably increase the amount of blow back through the carb.
If you take it off be sure that the carb mounting screws do not penetrate too deep. You may need to use slightly shorter screws.
Only draw back is that with it removed, all of the blow back will be inside your cowl if the carb intake is inside the cowl.

cantw8tofly

My Feedback: (3)

Oldcoot....... I am having a very bad glitch problem with this engine running. have you had any trouble with this?


Is the plug that came with the engine a resistor type? Also have you found a spark plug that matches the one that came with engine?

I know that champion makes alot of resistor plugs but i dont know what one to get.


Let me know what you think

OldCoot

My Feedback: (47)

The Champion resistor plug is RCJ7J. The plug that comes with the engine is not resistor.
I have no interference problems because I am using 2.4Ghz. Are you using PCM. FM does not work well with gas engines.
Also you can try securing the plug cap to the plug with a hose clamp. On occassion the spring on the plug cap will not be tight enough and let the cap vibrate against the plug.
Also make sure that your receiver, receiver battery, servo wires, switch wires, etc. are at least 10 to 12 inches away from the engine and ignition module or ignition battery.
You should also be using a plastic or non conductive pushrod for the throttle servo.

cantw8tofly

My Feedback: (3)

Coot. Where did you find that champion plug at. I am having trouble finding one, almost like it is not a good number?

cantw8tofly

My Feedback: (3)

Oldcoot, yes i think that number may be wrong. I called several pl;aces and no one has a listing for that number.

Are you sure its not an rcj7y ? 3 of the places asked me if that number might be what im lookin for.


Just checkin........thanks

lamar389

My Feedback: (2)

I’m using an rdj7y found at an auto parts store. Since it is a resister plug, the insulator part is longer so I had to cut out part of the rubber boot (inside the plug cap) to make it fit. I’m using and FM radio with no glitching problems, with the receiver about 12� from the ignition module. A clamp on the plug cap is a good idea for extra security.

OldCoot

My Feedback: (47)

The only difference between the RDJ7J and the RDJ7Y is that the Y has a projected tip. You should not have had to alter the rubber boot.
Be careful with the projected tip plug as it puts the ground electrode extremely close to the top of the piston.
I checked the RDJ7Y when I was assembling the engine and the ground electrode is only about 1/2 mm from the piston top. Of course, this is OK as long as nothing hits. I decided to use the RDJ7J just to be safe.

http://www.sparkplugs.com/results_cross.asp?pid=rdj7j

http://www.sparkplugs.com/results_cross.asp?pid=rdj7y

cantw8tofly

My Feedback: (3)

Ok guys thanks alot. i am goin to try and find one of those plugs locally right now.


If i can find on ill post later to let ya know if it worked or not.

cantw8tofly

My Feedback: (3)

O.K. I think i got this thing figured out.

Here is what i did:

Moved the throttle servo back next to the rudder and elevator servo's
installed an rdj7j resistor plug.
Solderd a ground wire from the cap to the engine block. [ read that one in the forums ]
Installed a hose clamp on the cap to hold it on securely . Also after reading your post the other night i checked and found that i had not been pushing the plug cap on far enough. I just didnt think that i would have to use much force to put it on. But when i checked it i was able to push it on another 1/4" futher than before.


I ranged checked it as best i could in the yard with the plane tied down. Next is to find an open spot so i can really range check it.

I will try and do this tomorrow and let ya know how it goes.

Also i wanted to thank you guys for all your help.


cantw8tofly

OldCoot

My Feedback: (47)

Maybe you have it.
Let us know how it does.

batchelc

My Feedback: (7)

cantw8tofly,
I bet being able to push the cap on another 1/4" was the big culprit....cantw8 to see it fly this weekend. Maybe I need to order one for my Pitts.
Batch

cantw8tofly

My Feedback: (3)

Ya man that pitts i sold you can handle it. You get the engine installed and ill test fly it for ya up in missippi.

cantw8tofly

My Feedback: (3)

BUMP!!!!

bipeman-RCU

My Feedback: (16)

Hey Oldcoot,

I am not familiar with liquid bearing retainer. What do I want to use? Where do I get it?

I just ordered one of these from Abell R/C for $210. Going in my 1/4 scale Ercoupe project (old Jim Messer kit).

OldCoot

My Feedback: (47)

I use Loctite 603 available at most auto parts or bearing stores.

I lightly rough the bearing and casting with 200 grit sandpaper and clean with brake cleaner.
The surfaces must be completely oil free to get a good bond.

http://www.rshughes.com/products/079...&refcp=froogle

bipeman-RCU

My Feedback: (16)

Thanks OldCoot! Any problems removing the bearings then? Or splitting the case, in the case of the engine we are discussing?

The Loctite spec sheet says to apply 482 degrees F to remove. I guess that can be done to the engine case if needed.

OldCoot

My Feedback: (47)

Since the case is split, removal is not nearly as difficult as if the bearing pressed in.

You don't need a lot of the retaining compound. Just a couple of small drops on the top and bottom case halves.

bipeman-RCU

My Feedback: (16)

Very well then. Thanks for the great tip. I hate spinning bearings! Had to deal with that problem on the old A&M's (pre - Brison) a bit.

I'm really looking forward to getting this motor and will likely order more.

Antique

My Feedback: (4)

Not true, all dual conversion FM receivers, both PPM and PCM work well with ignition gas engines. Hundreds of us have used them for many years. Some are still using AM radios. Just need to do a good clean radio installation.

SRimer

more performance, prop/rpm etc.

jedijody

My Feedback: (1)

Swings a JXF 20x8 prop at 6900+, idles about 1600. Super easy to start. 3lb 2oz engine,muffler, and ignition. Get them assembled, test ran, and adjusted with a 1yr. warranty from Valley View RC $279.95

Jody

SRimer

I have puchased one and put it together, however I was a little disturbed by the way the piston looked on top, it looked like it was machined only at the center section and the skirt was left the way it came from custing, it didn't have a nice dome shaped top, is it normal?

bipeman-RCU

My Feedback: (16)

I received my kit a few days ago but have not had time to put it together yet. I have my piston here in front of me.

"Skirt" normally refers to the sides of a piston, the part that contacts the cylinder wall (not really, as there is oil between them). The skirt of my piston is machined nicely.

What I think you are referring to is the top of the piston which seems to be un-machined except for a 3/4" circle in the middle. I too wondered about this but decided that it really does not matter. Carbon will quickly collect and fill in the roughness.

I think the top of the pistons are left this way intentionally. Note that the machined area is actually higher (raised) than the rough area. The chinese probably think that the roughness will cause better mixing of air and fuel, or better distribution in the combustion chamber.

Flat top pistons are pretty common. I have not seen a domed piston in a model engine, gas or glow.