RustyTumbles

Hi all,

I've just purchased a used WM extra 300s 80" for my first gasser. It is about 18months old and in good condition, it is powered by a zenoah G38 (with stock muffler) and a bolly 19x6 carbon prop. It fly really well but is on the heavy side, so verticle is limited. It is currently fitted with a smoke system minus a smoke pump. I want to try and improve it's performance a little bit. So I'm looking for ideas rom you guys to help me out!!!

Now before everyone says change to engine, I want to keep the G38 on it for a while.... I still believe there is a little more power left hidden inside. I plan on removing the stock muffler and replacing it with a slimline pitts muffler. Is this worth doing? I have heard that these engines like to breathe. Is that true? The previous owner was running the engine on premium unleaded and a 32:1 fuel mix. Not sure if he was using mineral or synthetic oil. I was planning on using a high grade synthetic oil (castrol TTS) and leaning the mixture to 40:1. Will I gain anymore power buy doing this? Also should I change the prop size? Not sure what RPMs it was pulling with the 19x6.

I would like to do some weight reduction as well. I want to remove the entire smoke system and possible relocate the fuel tank to over the wing tube. What weight gains if any can I expect? Also if there is any weight in the tail I'd like to remove it if possible by moving things around.

I pick the model up on sunday so I'll post some pics once I get it.

hosam

My Feedback: (121)

you can do a few things to improve the engines perormance such as an electroic ignation and better muffler. However, you can sell the engine and take that extra money you are going to use to improve the engine and buy a good gaser like a DA or BME. I currently fly a WM extra in the Wagstaff trim with a moki 210 and love it, unlimited vertical at 14.5 pounds and no smoke system. the plane is so easy to fly that its better then my previous great planes wagstaff, it has allot to do with the light wing loading.

I have another WM wagstaff that is still in the ARF form that I may put a DA 50 on it for next summer. I want to see the difference but I know that the DA will have way more power.

Good luck

ptgarcia

My Feedback: (36)

Ditching the smoke is a good start. You'll probably loose 6-8 ounces just by doing that. Moving the tank to the C.G. is a good idea also, but it won't shed any weight. Go with NiMH or Li-Ion batteries, and only use the capacity you need. Don't install a 3300 mAh Sub-C pack if you only expect to fly 3-4 times a day (I have used 2700mAh 6-cell NiMH packs in my 50cc class birds with good results). Remove any ballast and move things around to achieve proper balance. I'm sure with a little time and effort you'll be able to drop a noticeable amount of weight. Good luck!

fancman

My Feedback: (16)

I wouldn't spend any money on upgrading a G38. They are what they are and not that powerful. The money you would spend to upgrade that engine would be much better spend, by selling the 38 and getting a BME or DA 50. There is no substitution for cubic inches as they say. And if you upgrade to lipo''s the result is about the same. Take off a couple ounces and you will still have an underpowered airplane.

Stick Jammer

Yep, I agree. It's probably not worth spending more money to lighten it up. Just remove the smoke system. As mentioned, remove any ballast that my be present and shift things around if possible. Fly it for a season and decide where you want to go from there.

RustyTumbles

So you think a good muffler on the G38 will make no difference at all?
Also is it worth replacing the reciever switches and batteries as a precaution as I don't know how long they've been on the plane? I think down the track a new engine will be needed as my flying improves, but at the moment I'd like to see if I can get a little more from whats up front!

Nogyro

My Feedback: (10)

Lose the stock muffler and put on a B&B muffler. You can probably find a used one for $15, and you'll pick up 400 to 500 rpm over the stock muffler. I ran an 18 x 10 Zinger on mine that turned 7300. I didn't know it at the time, but prop the engine so it turns at 7700 to 8000. These Zenoah's like to turn up. DON'T use a Zinger and expect good performance from your plane. They flex way too much. You'll need to go with a Menz, Bolly, etc. wood prop. I would think a Bolly 18 x 8 might be the way to go. No personal experience on that prop. By all means take the smoke system out. For batteries, since you bought it used, be sure to cycle the batteries first and find out there capacity. I don't know how much you fly when you go to the field, but 1-5 cell-1100 mAh- AA nicad pack from Radical RC would be a good/cheap way to go. It weighs 4.5 oz, and should give you 4 or 5 fifteen minute flights. http://radicalrc.secure-mall.com/sho...=234932&cat=1&

RustyTumbles

I was thinking of using a slimline inverted pitts muffler, will that give me more RPMs? I think I'll change the switches just to be sure and test the batteries after a cylce! Will changing the fuel mix help in gaining more power? Not really sure what else I can do untill I get the plane home to work on it..... Can't wait to fly my first gasser!!

Nogyro

My Feedback: (10)

The Slimline Pitts will improve r's over the stock muffler, but they are normally down 100 rpm or so from the B&B. The G38 has rear exhaust to start with, so with the B&B, you actually end up with a pitts. If noise is an issue where you fly, the B&B is quite a bit louder than a Slimline though. Your call. Going to a leaner mixture will gain you very little IMO. Stick with 32:1 with the Lawn Boy for a gallon or so, then go to 50:1 on synthetic. You can stay with 32:1 with Mobil MX2T without any proplems, that's what I'm using in my DA-50.

RustyTumbles

I picked the plane up today!! Got it home and started to strip it down for inspection!!! (AME by trade, so it's a habit) Anyway, the stok muffler has been modified for the smoke system and it looks to be a pretty bad job. It looks as if the case has been split and the oil heater tube soldered in the welded back together and sealed with high temp sealant!! I really think a new one will help alot.....

The kill switch is operated off the throttle servo, as the arm on the servo goes toward idle the arm touches the micro switch, then if you make it over travel it makes the micro and cuts the ignition. Is this a normal way of setting this up? or should I mount a micro servo for this?

Also the power wire for the kill switch was just wrapped around the solder joint at the magneto. Shouldn't it be soldered on properly?

I aslo pulled the spark plug out of the motor and it was really choked up with oily deposits! does this mean leaning of the fuelil mix should be done? Or is the motor just running rich?

Could anyone tell me which needle is what on the carb? There is one with a t-handle on it and one is just a flat bladed screw and a spring. Which one is High and low speed?

Thanks

RustyTumbles

Here are some pics of her front end strip down. I'm going to go right over her from front to back and look for improvements/damage etc

Nogyro

My Feedback: (10)

I've seen them set up like this. It will work ok. If you like, you can change it over to a separate servo, but you are adding more weight.

Yes, it should be soldered.

You'll either have to clean the plug, or get a new one. Make sure the plug is a resistor type plug. You need this to cut down on radio interference. My guess is the carb needles will need adjusted.

The "T" handle needle is the high, and the other one is the low. If you look real close, there should be a small "L" and "H" next to the needles. On all the carbs I have seen, the low needle is closest to the cylinder, farthest out one is the high.

RustyTumbles

Thanks for that. I think I'll leave the kill swith the way it is and just re-wire it to neaten it all up. I'll get a new pug also, the one fitted is an NGK BPMR74 is that the right plug to use? Also what should the plug gap be set at?

Nogyro

My Feedback: (10)

I'm not familiar enough with the plugs to tell you for sure it that's the right one. Maybe Ralph Cunningham will jump in here and let you know for sure. Most plugs used in these engines are set at .025. You might find an answer on the Horizon web site. http://www.horizonhobby.com/

The Ghost

Bigsport,
I changed the stock muffler on a G62 to the slimline pitts muffler from the HSTORE in Sydney and it improved preformance quite a bit. For fuel use premium unleaded only. I mix my fuel with Klotz oil as I have a 25ltr drum. I contacted the Aust rep for Zenoah and I was told that they would only use 25:1 oil mix. If the plug is oiled up I would say that it is running to rich. Have never had any problems with mine on 25:1 with plugs fouling.

Cheers.

RustyTumbles

Excellent thanks guys! I think I'll run the castrol TTS at 32:1 with BP ultimate (98 octane). I will definately get the slimline muffler, after seeing the state of the stock one there is power waiting to be unleashed..... I'm just re-wiring the kill switch today and cleaning down the motor and inpecting everything. It looking good so far!!! Can't wait to fly this thing

RustyTumbles

Well I've finished re-wiring the kill switch, it looks alot better now!! Cleaned the motor up and had a good look at it. Still looks good.. Brought a new plug today also , it was a NGK BPMR7A no a 74. My mistake!! I gapped it a 0.025" or 0.63mm which is what NGK recommends.

Also moved the fuel tank back over the wing tube and re-plumbed it all. Added a fuel filter to the supply line also as there wasn't one on it!

Just waiting on the muffler and prop, then the front end will be complete and ready to run.

RustyTumbles

here are some more pics

flashingred

My Feedback: (2)

BIG SPORT,

ZENOAH HAS A WEB SITE WHERE YOU CAN DOWNLOAD A COPY OF THE MANUAL FREE OF CHARGE.
I AM NOT SURE OF THE SITE ADDRESS BUT YOU CAN DO A SEARCH ON GOOGLE.

I HAVE A G62 WHICH IS MOUNTED ON A CARDEN EL BANDITO. THE PLANE WEIGHS APPROXIMATLEY 23 LBS AND I TURN A BOLLY CARBON FIBER 22X12 PROP AT 7100RPM. I AM USING LAWNBOY ASHLESS OIL MIXED AT 40 TO 1 AND HIGH TEST LEAD FREE GASOLINE. I AM RUNNING A SLIMLINE PITTS MUFFLER. THIS COMBO IS WELL WITH IN NOISE DB REQUIREMENTS.

THE MORE A ZENOAH ENGINE IS RUN WITH PROPER CARE, THE BETTER THEY GET.

IF YOU HAVE A SPRING STARTER YOU MIGHT WANT TO REMOVE IT TO SAVE WEIGHT AND CRANK THE ENGINE BY HAND. USING AN ELECTRONIC IGNITION WILL REDUCE THE POSIBILITIY OF A KICK BACK WHEN STARTING,

I HAVE NOT HAD ANY EXPERIENCE WITH THE WM EXTRA, BUT I HAVE FOUND THEIR KITS TO BE OF HIGH QUALITY.


BEST OF LUCK WITH YOUR AIRPLANE

FLASHINGRED
NEW JERSEY USA

RustyTumbles

Thanks for the info on the manual. I'll try and download it when I find it!

The engine doesn't have the spring starter and from what I've seen the thing is easy to hand start. I think that the engine will perform alot better once the new muffler goes on and it is tuned properly. I may also try leaning the fuel mix to 40:1 also as the castrol TTS says you can mix it up to 50:1. Do you think that would be ok?

ptgarcia

My Feedback: (36)

If it says its okay then it probably is. Keep in mind thinning out the oil will not boost power. Good luck!

RustyTumbles

I do realise that! I'm just after a good clean oil:fuel ratio thats not going to cause any problems!!

Is it ok to run 2x 4 cell 800mah rx batteries into a y lead and then into the reciever? The current setup has 2x 4cell 1700mah batteries which are quite heavy, (4.9Oz each) through two switches. I have replaced the two switches with new ones and I'm not sure if I should use the old RX batteries or get new ones? What do you guys think?

RTK

My Feedback: (1)

Bigsport- You might want to check your fly wheel gap also. It looks like your are rubbing and have some dust there. Might just be the pics thought.

RustyTumbles

Yeah I did see that and I checked it but it doesn't seem to be rubbing at all. It does get pretty close though. I'm going to check it with some feeler gauges just to be sure. Maybe it has been rubbing previously and has been fixed!! Thanks for pointing it out anyway....

ptgarcia

My Feedback: (36)

Yes, it is okay to run 2 800 mAh thru a wye to the receiver. Make sure you have a switch in there. If your going the wye route, you might as well use a single, larger capacity battery, like a 1650 mAh NiMH pack. My 4.8v 1650 mAh NiMH pack weighs just under 4 oz., and my 6.0v 2700 mAh pack weighs just under 7 oz. Hope this helps.