Macs any good?

[Alan Coats]

I have heard some say that Mac engines are just fine, and others say that they are very unreliable. What do you think?

If Macs do tend to quit in the air, what is the usual mode of failure, and what can be done to avoid it?

Does the carb quit carbing?
Does the crank quit cranking?
Do the pistons quit.....going up and down?

Actually, the question is serious.

Thanks in advance for you constructive replies.
Alan

[MMorgan]

Alan,

A couple of guys locally have Mac's......Mike Gaspard and Rod Reed....maybe Mike will post but I will tell you what I've heard them say.

The mag is one of the problems and since Mike G. put a CDI on his it has been trouble-free.

Temps are a problem also as you are sitting directly in front of the cylinders that need the airflow. The timing can be retarded a few degrees to allow the engine to run a bit cooler.

Again, perhaps Mike Gaspard can jump in and give you a few more details.

[Alan Coats]

Thanks, Mike.

I am planning on being at Bastrop in September and have been told that there will be some Mac users there, including Mike G.. I certainly plan on getting all the information I can from them while there.

Alan

[gyromike]

Alan,

I have had one engine out on my Mac so far, sue to a piece of trash in the carb. I was close to the airport so it was a non-event. I had a few on another gyro, but there was a hairline crack in the case that would open up when it warmed up, leaning out a cylinder and siezing. The case was replaced, and it is still flying today.

I did have magneto troubles, but I've been running Rick Whittridges CDI for about 15-20 hours now, and have had absolutely no trouble (unless I flood it).

I run my timing at approx. 21-22º BTDC which keeps my CHT's around 325º during cruise. They'll creep up above 400º when I keep the power in, but cool off rapidly when I pull the power back. I don't have EGT gauges, but I jet the carb for a dark tan/light brown color on the spark plugs.

I did break a ring once. It kept running, but I noticed a lack of compression when I pulled the prop through to fly later. I probably didn't gap it correctly. Pulled the jug, changed the ring, and went flying the next day.

The carb, a Holley 1940, is pretty straight-forward, and you can still get rebuld kits for them. Run a good filter, and you shouldn't have any trouble.

The engines are dirt simple, ruggedly built, and easy to work on.

That said, if you run it too lean it'll sieze. But so will a Rotax.
Overheat it, and it'll sieze. But so will a Rotax.
They shake a lot at idle, but smooth out above 2000 RPM or so.
You gotta hand start prop them, so there's a chance of getting your hand in the prop.
They tend to be noisy, but mufflers help (maybe :rolleyes: ).

But when you drop the hammer, you're goin' somewhere! :D
I like mine now with the CDI.

[Chuck Irby]

Thanks for the good report, Mike. Are any special tools requirred for the Mac, and if so where can they be purchased?

Is there any way you can take off from work and be at the Bastrop fly-in, Mike? It would be a better fly-in with you there.

[joeheli]

I agree with Mike. I also have a Mac 90. They are verry powerfull! :D . I remember I use to have trouble staring the engine. Until I got Ricks CDI system,Now I just start it on the second prop pull, and do something that on a mac is rare to do " Idle like a motorcycle". I remember that if you start the engine and live the engine idle, it will quit. Now I don't have that problem no more. About what to buy, you shud try to get the same Holley carb. that Mike has (1940). Spark plug I use to use (with out the CDI) the NGK A-6 spark plugs. Now with the CDI I use the one Ricks reccomend me (Champion 506). And the most important thing get a good oil. They tend to overheat with out a good oil. Rick recommend me for the Mac the Blue marble oil 2 Cycle. Is expencive but belive me, is impressive what that oil does to the Mac :eek: .
More power, More rev.,alote less temp, and a long lasting engine :D .
I will place a link of the oil Blue Marble Oil (http://www.off-road.com/snowmobile/reviews/nulubes/nulubes.html). I hope this coud help.

[Rick Whittridge]

You bet i like the MAC! The Mac is the best weight to HP ratio you can get for the GYRO.Yes they can give you fitttsss sometime but the simplicty of these engines & the weight savings are the real PLUS! As most people have heard of the infamous MAC ATTACK is usually caused by the ignition. Timing is critical on any two cycle, It has to be right. When i got into gyro`s & saw that the igniton was one of the problems with the Mac i set out to cure that with the C.D.I. that I offer.No ignition will do you anygood if you have a engine that is not in top shape. Fuel is your best FRIEND & lots of it! With the C.D.I. you can jet the Mac richer to keep the engine COOL.The fuel & the correct timing + Blue Marbel oil is the right combo to making the Mac live. I have spent countless hr`s in my engine shop trying to make the Mac better with great results.


I Can say I`m dedicated to keeping the Mac ALIVE!

[Caribean_gyro]

Lets talked dtata since I am also bias withg the mc. What we want is power to weight ration. We want 1 HP for every pound.
MAC weight 100 pounds and ca give you around 62 to 72 HP so you get .72 HP to 1 pound.
rotax wieight 110 pounds with out water at 65 HP , so you get .59 hp to 1 pound

Now the advantage of the MC with CDI/ dual Carb is that is a simple instalation.

The 1840 carb is less effective than the 1920 due to CFM flow. But has dual floats that this is a plus. 1920 sigle flotas breaks. Minly due to gyro traveling in trailer with no fuel on Bowl.

Rotax advantages , recoil starter or electric. Due to the reduction gear you can swing a 3 blade bigger prop. Bottom line we want trust (Ron didi I spell it correct) . If your gyro weight 600 pounds and you can get 300 pound of trust with a MC or a rotax then you are ok. Also R&D in plano texas has all necessary parts for your MC.

ChuckP.

[Caribean_gyro]

I for got, just changing from mineral to synthetic your CHT will drop. What can be done is
1: CAm grind the piston to allow expansion growth.
2: ceramic coated to allow more heat on the head.
3: Change to Para-synthetic oil. I dont like synthetic due to rust inability protection. Blue marble, spectro oil. Make sure it has the lates TCW111 rating.
4: Ionize fuel.

This engine above fly at 3,400 CHT 350 fuel consumption 3 gal per hour. In a hot day temp will go up to 400 max

ChuckP

[Chuck Irby]

ChuckP, Ron can't spell it either. :D

It's properly spelled: "thrust"

[stuart]

How is Amsoil compared to Blue Marble in the Mac? I already have a gallon of Amsoil (I'm mixing it at 8 ozs/5 gals), so I'd like to use it up, but I'm willing to trash it if the Blue Marble is better. thanks, stuart

[darrellwittke]

Use at least 100 low lead Aviation gasoline in the Mac's to keep it cool and control detonation. I think this is the most important thing, haven't seen this obviously stated yet.

[joeheli]

Stuart you can use Amsoil for now. It is a very good oil!. When you finish the gallon, try Blue marble oil. And then you will see the difference.You will take your conclution of which is better :D .

[Rick Whittridge]

Darrell, We have talked about fuel here before on another topic & you are right that 100 LL is required for the Mac to make the engine live.I have found that with R&D work on this engine that Blue Marble oil is the best oil you can use period! Don`t leave the airport without it!

[Rick Whittridge]

I have recieved some requests for info on my C.D.I. so for those that havn`t seen one here it is. Heres a picture of my engine with the ignition installed.

[Caribean_gyro]

I use to use amsoil , we have rotax engine with twice the engine life still flying with no major overhaule. Now I dont recomend synthetic due to like I said they dont protect to rust as a mineral or synthetic blend does. So if you are not going to loose too much money I would suggest switch to a better oil. If not consumed the amsoil and switch.

Rick. did you ever use the golden spectro 2 cycle oil.

ChuckP

[joeheli]

I agree with Rick, The best thing you can do for your Mac is:

*Gets Rick's CDI system.

*Get a Holley 1940 carburator.

*Use 100LL Aviation gasoline "ALWAYS" with the correct oil mixing.

*And Use Blue marble oil PERIOD!!

with all this thing you will have a good, powerfull, reliable,and long lasting Mac. :D

Like Rick use to say to me " Gasoline is your friend" don't lean the engine get the correct jetting.

[joeheli]

I have spent countless hr`s in my engine shop trying to make the Mac better with great results.


I Can say I`m dedicated to keeping the Mac ALIVE!

Just with this words you can see that you can trust him. :D

[Alan Coats]

Guys,

Thanks for all the good info. I look forward to getting my hands on the Mac and implimenting all your suggestions.

Alan

[scottessex]

Doggone Rick that is pretty, Stop it! :D

Stuart has one of your CDI's on his, and it seems to run very well when I heard it in Macon.

[joeheli]

I you don't have the Mac yet...I think that Ricks can make you a "Super Mac" for you. The Super Mac is more powerfull and more reliable that the single carburator Mac. It has 2 Holley Carbs.

[Caribean_gyro]

Rick it seems you have a beleiver with you.

Perhpas my 19 years dealing with my Mc dont count. Just remember guys when you do an overhaule new rings and cylinder do a breaking with sinthetic. But what the heck I am not the one flying the gyro.

Opinions with out data is just that opinions. I think we are all saying the same. Oils(blend type ) ignition CDI , carb is ok to use 1940.

ChuckP

[Chuck Irby]

ChuckP,

In the post above, it sounds like you are saying to break in a newly rebuilt engine with a synthetic oil.

If that is, in fact, what you are saying, I strongly disagree!

[Paul Golphy]

Instead of going CDI. Has anyone tried just getting the magnets in the magneto recharged to get that hotter spark?
Paul

[joeheli]

Yes! I am a beliver of some one that is really dedicated all his time on a MAC.
That everytime that I have a problem, no mather what it is, anything that he says to me has work on my engine....not good!.... impresivelly!!. A person that because of his time dedicade to extended reserch has made posible what no one has done before on a MAC a good CDI system . Maybe he sells CDI. But he "dosen't sell" his good willing, good friendship to help me and others, no mather what!..I can see that he enjoys to help people. And that is what it counts!. You were also beliver becouse you to "Belive" on his CDI system when you use to have a Mac. The point is he cod be a buisness man, but he is not winnig money helping me or others with other things that is not from his system. This is the mening of this sport, Helping, and enjoing. That way you built a good friendship. That's exacly what happend not only with Rick, but with other guys on the forum expecially Chuck Irby, Ron, scott, and you too! (sorry guys they are to many names of good guys! :D ) and I thank you and everyone that has help me.

[joeheli]

Paul, you can charge the magnet if you want to. But the Mac Magnet is not natural magnet you have to charge it every time and the spark is not consistant. :o , I forgot how long it last :rolleyes: . I use to have a 12volt battery system on my magnets but this is not goin to work forever. So if you are willing to :

*Take out the difficult magnet out :mad: ,

*charge it :) ,

*put it back :mad: ,

*time the engine ignition back :mad: ,

*and willing to deal with the "MAC ATTACK" :mad: :mad: sometimes. you can just charge it every time.

But with the CDI, you will have a mantenience free system :D , with a constant spark :D

[GyroRon]

Just waited and waited for someone else to jump in here and be the party pooper, but since no one else has beat me to it....

Just remember that Mac engines were designed for a very short life, low hours of use. They were designed to power remote control Drone airplanes to be used for target practice by the military.

They DO have a great power to weight ratio and are quite simple. I would love to have a gyro with a Mac engine, something like Dave Praters or Gary G's, or especially the GoGo Gadget machine of Ricks. But after hearing all the horror tales, and knowing the engine wasn't designed for long term use, I would not stray too far from home with it.

Also they are very loud, even with a good muffler.

[joeheli]

Ron, Whe have people here that has Mac engine for about 15 year or more :eek: . This engine was desing by the airforce and belive me anything that the airforce make is good. For know I have heard that are made to last 1000 hrs then you have to rebuid it. The only bad thing is that this engine was not made for gyrocopters. So you have to make some modification to use it on a gyro. The secret is to use the correct oil to make it last for that long.


PS: I still on vacation, when I come back I will send you the video. :D

[Paul Golphy]

I agree with you Jose that CDI is the way to go but I was just wondering if guys like Chuck P., that have flown Macs for years, have had any luck recharging their mags and if they felt the procedure was worth the effort.

Some of us may only fly our Benson 1/2 hour a week in the summer and the expenditure of the CDI may not be worth it. I think I read somewhere that recharging the Mag. every 25hrs of flight time was advised.

Paul

[Ron Black]

My first post !!!!!!!!!
I sold a Benson with a Mac on it some 10 years ago.
I forgot the guys name. It may have been Mike. From around the Jennings area.
I have owned two Bensons, one with a VW and the Mac.
I am enjoying this forum very much.

[StanFoster]

Aw ...the ol Mac engine. Brings back memories of my ol Bensen. My record consecutive hours without a forced landing was 11 hours. It was so bad and also I was having a career change...so...I mothballed it for a few years. Tom Milton ended up with it...

I would like to have it back in the hanger and take that ol beast up once in awhile. It flew very nice.....just those darn mac attacks. :mad:

Stan

[gyromike]

Stan,

I went up to Tom's and bought a load of Mac parts.
Your old engine might be the one on the back of my gyro.
Or some of the parts anyway. ;)

[gyromike]

My first post !!!!!!!!!
I sold a Benson with a Mac on it some 10 years ago.
I forgot the guys name. It may have been Mike. From around the Jennings area.
I have owned two Bensons, one with a VW and the Mac.
I am enjoying this forum very much.

Da Cajun Man!

Black,

I'm the guy who bought your old machine.

Welcome aboard!

[Friendly]

Rick,
If the magnets in the mac must be recharged , then you must use your own stator assmy. What about replacement parts on the CDI if it does go bad. Like the pick up coils or the stator. We we be able to get those locally. By the way that is nice machine work from the picture. As you know I am intrested in a CDI for my Mac, maybe more than one now.

[rgraffeo]

Gaspard,
Now how could that man forget you!

[Caribean_gyro]

Let me see if I can answerd all questions. ChuckI I am been sarcastic.
Since I am getting that synthetic is so great! then try to breakdown a new engine. You are going to blow it. What I am saying is that each oil has its purpose and there is no magic combinations .

MC designed for low time? Where is this written. They were designed to work at full power cut off in the air burried in the ocean, clean them and up they go. Now what is the factory recomendation mineral oil and charge magneto every 25 hour. Since almost every 25 to 50 hours you have to take carbon out of the pistons then you recharge the magneto.

Now what is the problem with the magneto beside the charging. That in order to get a high out put in the secondary"Plugs" you need to rev the engine. SO this is why in the pass you could see 3 guys dealing with a gyro. 2 cycle dont idele for long.

Now Bill parson designed a reed valve system. This solve the power reduction MC encountered when the octane came down from 145 to 110ll and we were force to retard the Spark.

Then R&D came with a CDI that increase the primary voltage to the actual coils , this was ok since you can use magneto and CDI. But the unit burn off with time. I almost landed over 50K power lines due to powwer loss, you need a battery but MC dont charge battery . God save me that time. The CDI was ok but using magneto coils were no good.

Then came Rick I was the first in PR to have his cdi . The after perhaps 2 years later others follow me. SO we had take a 1939 engine and brought it to the modern era. So now that we have the electric and fuel problem taken away then we can experiment with oil.

SOme one ask what is the problem with recharging , It dont last too long and as I said MC dont idle so you need to start it and step on it. Now make sure you dont flood the cylinder becasue it will not start.

Now Jose let me give you some information. First your battery is 7v. The primary side of the coil will be burn if you use 12v. Where was that invention made. Here in PR. You have a 50-30 prop . Where that combination was found here in PR. In the state they use a lower pitch to get more RPM and a faster TO. We want lower RPM in crusing ,less fuel consumpt. and lower temp.

There are many other things we have done here that no one out of the small island haven't seen. Can day eventually come to the same conclusion yes.

What it bothers me that been new to this comunity you have neglected the experience of pioneers of local comunity. ( and I should'nt be since every body is entitled to do what ever is please) .

Perhaps I am wrong or felt neglected but I see you looking for advice up state and then locally. The guys in the mainland will give you what have work for them. But not every thing works her as equal.

Even knowing this we are willing to help (kind of diferent of you above statement). DO you know how many hours Marcelino has. (marcelino is like Craig wall, shouts a lot) But has more than 50 years building gyros and fixing MC.

Sorry guys o make this long but I have to take it of my heart .

Charles Peterson
n114cp/n34cp

[Chuck Irby]

ChuckP, Thanks for the explanation on the break-in oil. I thought you knew better than that.

[Caribean_gyro]

fRIENDLY
the CDI I had never failed. I had 2 guys come back to me with theire CDI disasemble and telling me to fix it. I send it To rick and he check them out OK. I put them baCK and show the guy is theire priming sequence. SO to my account I have had never seen it failed.

But if happen please send it to Rick is cheaper and more effective that way.

ChuckP.

Yeah Now I am a beliver

[joeheli]

Mr Charles Perterson:
I forgot that it was 7volts. and not 12 volt ( I think that is becouse I never use it, I change it to CDI quickly). Charles, I will be a new person on this sport but I am not "Stupid". I love to read "Alote" and I love to heard opinion from everyone that is what this forum is about,helping,and learning. Other thing is that I follow what really WORKS on my engine what Rick has tell me has work like he told me. What I do? I tell Marcelino heard his opinion and if I see aht he tells me. then I take a conclution together and we pass it around here so every one can benefid from it. Every day technology change. Thing get better, and better, every day. On the state there are new good things on , that we don't know. And there some things here that on the state don't know. The thing is" I LIKE TO KNOW" does new thing that, here in PR, don't know. And like helping others on the States to know what
we know.This is a community to help and learn! That is why we have this forum (thank you Todd :D ). You know every one here is on his way. Is not like on the States that every one seat together and talk about the new things and stuff better for there engine. Every one is apart... I will like to brake that chain between
each other and between the states. Like I say before we suppost to be a community that help each other . Not always habbing the $$$ on are heads just for doing a small favor .

[joeheli]

Look we are so apart. That only you and I from PR are the only one register on this forum.

[Rick Whittridge]

Mark,The magnet recharge MYTH is something i have heard for years.This was set into the minds of Mac owners as the cause for all there mag problems.Infact the magnets will last for years without recharging.This was a real Money maker for the Few that provided this service.When fixed winger`s do there annual every year do they pull there mags & recharge there magnets every 25 hr`s? The mag that was built for the Mac was a Bendix mag that is standard aircraft Technology of the time.It is the points,cond,internal coils,cap,rotor,that cause the problems with the Mag not the magnets. All of my C.D.I. MAGS are hand made in the USA with the same componets that have been tested on every racetrack,dragstrip,bonneville salt flats,& aircraft around the world. I have hundreds of hours on my OWN C.D.I. #1 prototype that has never let me down.

[Paul Golphy]

Thanks guys, this is all very good information and a very interesting thread.
Paul