DaveR

My Feedback: (7)

I have a Midwest AT-6 that I'd like to use a converted engine in. I have had glow reliability probs with this bird so I wanna go gas. Any suggestions for engine choice? Currently weighs about 15.5 lbs with Webra 120 and around 1.5 lbs of lead in the nose. Oh, its 1000 sq in. I figure I can go w/o the ballast with the gas motor with little weight gain. It seems right now the Homie 33cc is popular, but I'm open to suggestions.

bdtsr

My Feedback: (5)

28cc Mac's are available for about $45 shipped. I'm getting a hub and muffler from Ken Lambert. This might be a good candidate for the AT-6. I have an OS 1.08 in my AT-6 right now and it's overpowered considering they say a 1.2 to 1.4 2 cycle for it. I'll look at my AT-6 and Mac engine to see if it looks like a possibility.

SNIGGEMANN

My Feedback: (10)

Boy I'm glad you guys came along! I'm in the process of setting up my Midwest AT-6 with a 25 or 30cc homelite conversion. I have a 25cc with a CH ignition that I have been running on a test stand but I am having some problems with getting it to produce any more than 6200 rpm's with a 16X8 prop. I had talked to someone at CH who seemed to indicate the Homelites and Macs are good conversion engines. The Mac is probably more powerful but also weighs a little more than than the Homelites but for this application that might not be a bad thing. I have not flown this plane yet so any input you guys could give me on characteristics would be greatly appreciated.

av8tor1977

My Feedback: (6)

Careful here. Get some rpm numbers before you make a choice. My Homelite 25cc, which has the base gasket left out for more compression, and a larger carb and opened up exhaust turns a 16 x 8 at 8200 rpms here at 7000' density altitude. According to RCIGN1, the McCulloch 32cc engines are not as powerful. They are however, a little easier to convert. I have a couple of Mac 32's, but I haven't converted them yet so I can't help with comparison numbers; only quote what I've heard.

I think the 33cc Homelite would be a better choice for your airplane.

Good luck,
AV8TORE

Antique

My Feedback: (4)

The Homelite 25 I converted ran 8400 with a Mejzlik 18-6...Didn't try a 16-8, should run about the same....I had a Mac28, changed it to a 32, didn't get good results..Maybe it was just too old...That said, I liked the Homie 25 way better...

bdtsr

My Feedback: (5)

Well I eyed up the mac 28 and a G23 and a Kalt 22 bare no carb or muff (ok G23). The G23(s) look like a better fit. I was thinking about the Kalt (needs a cylinder) and rotating the cylinder 180deg and running the exhaust out in a scale location. How about your opinions on this one Ralph? What would it take ($) to add an ignition system to the Kalt?

SNIGGEMANN

My Feedback: (10)

Looks like I need to do some more adjusting to get mine to turn as fast as you guys. av8tor1977 & RCIGN1, what kind of carbs do you have on your engines? Same for the mufflers? Any suggestions for me on how to get mine to run faster? I am currently having problems getting mine to run with a Walbro 324 wide bore carb when I open up the choke all the way. I have a velocity stack installed but I am still using the stock muffler. I have yet another Walbro carb to try but the bore is not as big as the 324. I also do not know a good starting point for the needles as I've had them all over the place. Any help would be greatly appreciated.

Thanks

av8tor1977

My Feedback: (6)

The weedeater engines really like bigger carbs than they came with, and the exhaust opened up. The chainsaw engines are designed for more power to begin with and usually have bigger carbs.

I take all the baffles, screens, etc. out of the muffler, close off the original outlet, and install two outlets of 7/16" or 1/2" i.d. As for a carb, I'm running a 10mm venturi (smallest internal diameter) on my 25cc Homelite. When you go to a larger carb, check your carb adapter to see if it needs opened up to match the carb size.

I don't know what prop you are running, but the APC props work very well for me, and are considerably better than the Master Airscrew or other low end props. I changed one engine from a Master Airscrew to an APC prop, and gained almost 1000 rpms and 2 lbs. of thrust.

Good luck,
AV8TOR

SNIGGEMANN

My Feedback: (10)

av8tor1977,

Thanks for the advice. I'll check to see if the carb adapter needs to be opened up to accommodate the larger carb. I was planning on modifying the muffler as you described so I'll go ahead and do it. Also, I am running a Master AirScrew so I'll pick up an APC to replace it. One thing I didn't understand was what you said about the carb.........(smallest internal diameter).....I don't know what you mean. The WT-324 I have has a venturi of 11.11 mm but I'm not sure about the internal diameter?

Thanks

Antique

My Feedback: (4)

Big enough...I tested 2 or 3 different carbs, from 3/8 to 1/2, not much difference..Walbro has a new small carb that seems to work really well..WT662-1..It has a 2 step choke, costs $38.80 retail...Only problem is the needles, they're both made with no slot for adjustment...A small cutting wheel on a Dremel fixes that...I tested one on a G26 with good results, same rpm as the larger stock carb....[8D]

av8tor1977

My Feedback: (6)

Hi,

The actual size of the carb, and what you measure, is the smallest diameter that you see inside the carb throat. If you look inside the carb, you will see that it necks down at one point. That is where you measure it to get the size.

Also, start with the needles both at about 1 1/2 turns open. Then adjust the "L" needle for a good idle and transition to 1/3 throttle. Keep adjusting it slowly inward until the engine hesitates when you jazz the throttle to 1/3 open. Then open it back up just until the hesitation goes away. Then adjust the high speed needle for max rpms, and then open it back up about 1/8 of a turn. Finally, check your idle and transition again. If it's good, go flying! If not, touch it up, then check the high speed once more. It is important to do it in this order, as the low speed needle affects the high speed setting.

Good luck,
AV8TOR

SNIGGEMANN

My Feedback: (10)

I see the venturi size is actually the smallest diameter looking through the opening in the carb. I think the needle settings on mine are what my problem has been along with a restricted muffler and bad prop choice. I am going to try and make all the needed changes and adjustments this evening and give it a whirl, I'll let you know how it goes.

Thanks

SNIGGEMANN

My Feedback: (10)

Well I made some changes and it really made a huge difference. I had been having lots of trouble trying to get the WT-324 wide bore carb to work without having hold a finger in the velocity stack to get it to keep running. So I switched carbs a couple of times first was a Zama carb which gave me about 6500 rpm. I then switched to a WT-312 (9.53 mm venturi/bore) and that one really worked well. I was now getting 7500-7700 rpm's. Then I switched from a 16X8 Master Screw to the same size APC and the RPM's went up to 7900-8100 RPM's and the transition was very nice but it was idling to high. I really wanted to see if the WT-324 would work as it is the largest bore I have. So with a dremil tool and sandpaper I messaged the carb addapter opening to match the carb exit then I cut the gasket hole to the same size opening. Installed it and it ran very nicely with open choke and no fingers in the stack. I couldn"t get a tach on it as it is dark outside but judging by the way it was 2-cycling it really sounded good. I don't think I've got the needles set right but I'll keep dinking with those till I get the right idle, transition and max RPM's.

av8tor1977

My Feedback: (6)

Hi,

Congratulations! Those numbers are more like it. Should fly really well. It does pay to tinker and get them all dialed in correctly. The neat thing is that once it's done, you will get a lot of pleasure out of it, and they are very reliable.

I'm not sure if you are using the magneto, or electronic ignition. The old RS engines site had some tests where they advanced the magneto and gained power with the Homelites. I had the timing slip from 28 degrees to about 22 on mine once, (electronic ignition), and lost about 400 rpms.

Take care and good luck,
AV8TOR

glowplugboy

My Feedback: (17)

GCBM R/C Inc. 25cc Gas Engine [link=http://www.gcbmrc.com]www.gcbmrc.com [/link]

SNIGGEMANN

My Feedback: (10)

av8tor1977,

Mine is using a CH Ignition and I set the timing at 30 deg BTDC as a starting point. I had planned on trying to advance it between 30-35 deg as the engine was well used in it's previous life. I would like to thank you for all the help you have given me as it really helped. I have been doing alot of my testing of the engine at the race shop owned by the company I work for. One of the crew members was interested in helping me and he also was having fun seeing the results. He used to work on general aviation planes like the Sea Furry and he told me he was very close to purchasing an AT-6 at one time. Some of the other crew members seem to think I should be able to get more out of the engine by making some modifications to the piston and the cylinder as well as trying to make a "tuned" muffler. I have the time and the engines to tinker with so maybe those guys can help me with making a super weedie conversion....LOL. As I stated earlier I have a 30cc Homie and today I just received a 32cc Mac from co-worker who closed his garage door on the shaft of his fairly new weed wacker which he was going to throw away. I'll probably work with those two engine on magnito but I could also use the ignition from the 25 Homie on the 30 Homie if I wanted. The problem with having all these engines is finding suitable planes to put them in. I've done some research that indicates a 1/4 Cub is probably as good a choice as any for weedie conversions. Something that I would like to investigate and I'm sure you could give me a good opinion would be to find a smaller engine 16-18cc, trim it really good, add a CH Ignition and hang it on the Space Walker ARF from Great Planes. What do you think about that combo? (I know you have a 16cc engine that you had success with at lower elevations.)

Thanks

av8tor1977

My Feedback: (6)

Hi,

I don't think you will see much benefit from using timing over about 28 degrees. These small bore engines just don't need that much timing, though a little more than stock does seem to help. Porting can help, but be careful. If you do a search there is a lot of info about hopping up the Homelites available from the boat guys that race them. Tuned pipes will work as well, but they are quite long when tuned properly. Something over 25". Pipes are available from Mac's products, as well as from the boating guys. Try www.shark-racing.com for some more info. (It takes a while to load.)

I'm flying my Homelite 25cc on a Hangar 9 Ultra Lite Stick 120, and it does great. No need to stick to only the Cubs unless you want to because there are other choices. Anything with over 1000 square inches of wing area usually works pretty good, as long as the front end is stout enough to handle the engine. There are a number of planes in that category if you look around. Even the Great Planes Big Stick will work. Just mount the servos in the rear, and go for it.

There are some Weedeater and Poulan engines in the smaller 18cc category, and one of the magazines just did an article on converting them. I really don't personally recommend them, as a Kioritz 21 to 25cc engine for example, will weigh about the same but have a lot more power. One of these Kioritz engines, (supplied on Echo equipment), would be sweet on that Spacewalker, and fly a lot better than an 18cc engine. The ports on those cheap, smaller engines are really small, and I don't think they are worth converting, but that is just my opinion.

Good luck and have fun,
AV8TOR

Chilipecker

My Feedback: (37)

Anyone flown a with a Torro?

AutoMike

LOL@Glowplugboy! $232.50[X(]