Brent Brown or anyone else; Help, Please!

[Chuck Irby]

The link below is to a "Ski Doo MXZ 670 ROTAX Snowmoble Engine"

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=2484968923&category=42608

Question: What would it take to get it ready to fly on a gyro, complete with gearbox?

[nsheryka]

:confused:

first you will need to make a down payment on a coffin..

:eek:

[Chuck Irby]

Nick,

Is that all you have to say? You don't care to elaborate just a little? I didn't start this thread as a joke. If you know something, I would appreciate hearing about it, and perhaps others would also.

[ToddP]

Chuck,

I would recommend talking with Steve Beatty at Airscrew Performance. He has done several of these conversions and is very knowledgable. Alot of people have had run ins with him, but my experience has been positive, he was very helpful and informative.

I recently bought a polaris 700 twin snowmobile engine that I'm working on for a conversion.

Nick, c'mon offer up something constructive. If you've done much reading and research you'll hear stories from guys that had engine outs numbering in the teens flying their Mac Powered Bensens. I'm not advocating putting a less reliable engine on any machine however if its in pursuit of building something better, there isn't a better platform than a gyrocopter for testing.

In my opinion, there isn't anything very impressive or amazing about these Rotax Engines. The engines are prone to cold seizures, the parts are incredibly expensive, the ignitions while electronic are nothing special and I'm told a fairly archaic design for electronic ignitions.

On the other hand the Polaris Engine I'm working on has the following things going for it:

1. Makes incredible power with a very smooth power band. 115 HP @ 8100 RPM. So fly it at a derated 7000 RPM and still get close to 100 HP.
2. Electronic Ignition that automatically advances and retards based upon RPM, making the engine both easier to start and smoother running. This opposed to finding a "middle" ground for the Rotax.
3. Parts are 1/2 to 1/3 the price. Set of Pistons for a Rotax, over $400, for the polaris pistons are about $110 for a set.
4. These engines are thoroughly abused by the snowmobile guys and nearly bulletproof I'm told. When I mentioned cold seizure they said "cold what"?
5. Case Reed Valves as opposed to Rotary Valve. I've been told this is a much better setup, but I don't know much about it.

Cheaper is one reason to look at these engines but I'm more impressed by the fact that these engines have been engineered in the last 10 years and offer some improvements as a result.

[Chuck Irby]

Todd,

Great post. Very informative. I wasn't interested in that particular engine, but the conversion of that type of engine for AC use, and I figured that Brent would know, thus the title. However, you seem to be very knowledgeable on the topic and make a good case for the use of the Polaris engine in lieu of the Rotax. I had Scott and his need for an engine in mind, and still do.

When I was racing outboards, I did major engine mods on Mercury, OMC and Yamaha. All three utilize the reed valves. They all worked very well, and we turned those engines up close to 10,000 rpm.

Thank you for the information, and please keep us posted on your Polaris conversion. Incidentally, I have a Polaris 4 wheeler that I have really abused for six years now. I used it today and it performed perfectly.

[ToddP]

Chuck, Did you use your 4-wheeler to pull your tractor out of the pond? :)

[Chuck Irby]

Todd,

No, I did move the tractor with the four wheeler though once I got it out of the pond.

Would you believe that I had two buddys come over with their 40 hp tractors and they, together, wouldn't pull it out. I finally got it out with a 5 ton chain hoist. It took 1 1/2 hours of pulling on the chain to get it out. Each pull of the chain moved the tractor 3/8 of an inch. I just got it running yesterday and mowed with it today. I'll bet I won't do that again.

[ToddP]

Chuck, I just did a search at Barnstormers.com, If you search for Rotax 670, it turns up one engine that has been converted with a "C" box.

I'm sure that Steve Beatty has done conversion with the 670. Here is his information:
Contact Steve Beatty - AIRSCREW PERFORMANCE located Glendale, AZ USA • Telephone: 623-842-3902

RD Aerosport also does 670 conversions: http://www.rdaerosports.com/

[Chuck Irby]

Todd, thanks again.

[MikeBoyette]

Hey Chuck,
Dad built a two place with a 670 on it about four years ago. It had gobs of power,but only lasted about 38 hrs as I recall. The engine conversion was done by the same guy who builds custom tuned exhaust. I can not think of the name of the business. The Gyro was owned by Russ King. The engine puked at Bensen Days and he later sold it to Doug Riley. Doug put a 618 on it and flew it like that until he recently put a 912 on it. When asked about the 670 my dad and russ both said they would not mess with it again.

[nsheryka]

Nick,

Is that all you have to say? You don't care to elaborate just a little? I didn't start this thread as a joke. If you know something, I would appreciate hearing about it, and perhaps others would also.

just a joke, i am sorry if you took it the wrong way.

i was merely pointing out the unflattering appearance in the picture, however i do not claim to be an expert i engine overhauling.. so i wish you the best of luck.



:)

[Chuck Irby]

Mike, thanx a lot for that info. I'm convinced that one should not attempt to use the 670 for AC. I really like the sound of the Polaris 700 that Todd is working on though.

Nick, not a problem. I knew you were joking, and I was too, in part. The written word can be taken the wrong way far too easily, huh? Good luck with the Bee. Keep us informed with your progress.

[Brent_Brown]

A cold seizure in water-cooled motors should not happen if you run it with the right thermostat. Air-cooled motors get shock cooling and cold seizure not water-cooled. Put a 135 degree stat in it.

As for the 670 don’t use a 3 to 1 gearbox and use a NEW crank not a used one.
The motor I had ran great it was the gearbox that didn’t hold up so I traded it in for a MZ 202P

I still think it can be made to work just use it as if it was a 618. I would not go over 7000 rpm. If you get 90 HP at 6800 that is great with a 130 pound flying motor. R&D made both Russ King and my 670. Russ had a Rotax 3 to 1 gearbox on his; I was there when it broke. My motor had the MZ 3.11 to 1 box on it. This is why I think they died. The 3 to 1 put a bad vibe on the his crank and my gears. I would put any other ratio on it next time.

I don’t see why he doesn’t just use that Suzuki he has. It is just as good as a rotax 532 good for 65 hp and you can still get parts for it. I can use it on a tractor gyro I have in mind if he will let me.

What more do you need to know about the motor?

As for the motor in the link above I was told only to use 1992-94 670s don't see why they look the same to me but that is what R&d said.

Brent

[Chuck Irby]

Brent, I knew you would have some good info. Thanks a lot for sharing it with us. I'll make sure Scott sees what you have said about his Suzuki.

[gyrodude]

I have had both a 500 Suzuki and a 530 Suzuki out of an Artic Cat on an Air Command single seater. Both ran with never a problem once the jetting was worked out. Parts were half of what Rotax parts cost. There are some nice engines in snowmobiles these days.

[Chuck Irby]

Gary, thanks for that info. What gear boxes did you have on them and how difficult were the conversions?

[gyrodude]

A simple adaptor plate was used to mate a Rotax A or B gearbox with a 2.58 ratio. The 500 Suzuki was redlined at 10,000 rpm but pitching the prop for a max of around 6500 gave a max of around 8000 on the engine. The 530 was redlined at 8750 but set up for 6500 on the prop also. Both engines ran great.
The 530 Suzuki I bought from Steve Beatty at Air Screw. The engine was supposed to be complete but was missing the carbs and the CDi ignition looked like something out of his scrap pile. The engine appeared to have been in a crash and had some external damage of the block. It ran great but Airscrew was less than honest with me. I do not recommend Airscrew or Mr Beatty to anyone. He has been in business a long time but there are many people not happy with him in the ultralight crowd.

[Chuck Irby]

Thanks a lot for the good info, Gary.