Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
I googled the MZ202 engine
**NOTE: This is a C&P from another source and one persons experience and observations. Some of the info may have changed since this article was written. Please don't shoot the messenger.

The MZ201 engine has a long history. It is an Italian design dating back ~ 12 years. The really big difference between the Hirth and the MZ is how they are made. The Hirth is a cast molding process that uses vibration to remove any air trapped in the pouring process. This type of casting leaves the aluminum more brittle and less dense than other methods. Case in point, it is very common to strip the spark plug threads in the Hirth heads. Talk to owners and you will find many have had to put some form of thread reconstruction to fix the problem.

The MZ201, MZ202, MZ301 are manufactured using a high pressure injection molding process. This makes the crankcase, cylinders and heads more like billet aluminum. Injection molding assures no air introduced during the molding process because only liquefied aluminum is passed into the mold, no vibration is needed. The result is a stronger engine able to transfer heat more efficiently to the cooling fins.

The MZ201 was designed as a free-air engine and worked fine in a tractor configuration, however, cooling proved to be a problem in a pusher setup. (No, this is incorrect. The 201 only has one carb,it runs at less rpm and produces less hp than the 202,therefore it produces less heat as it is not working as hard, max power is achieved at 4700-5000 rpm.It can be used in tractor or pusher config) Thus the introduction of the MZ202. I am unclear who introduced the MZ202 fan cooled engine. However, Leon Massa purchased the manufacturing rights for the engines. His company, Compact Radial Engines, Inc. is located in Surrey, BC Canada. Leon still has the engine's major components molded in Italy. When he receives the components they are then CNC machined to within 2 mil (0.0005" depending on the part and the fit needed) tolerances for final fit. I know of no other company that uses this good of a specification.

The MZ cylinders are Nikasil, which is a ceramic coating (and nickle) on the cylinder bore. This type of cylinder is much stronger and heat resistant than pressed in steel cylinders. The Nikasil bonded to the aluminum allows the more efficient transfer of heat from the cylinder wall to the cooling fins. Should you have the misfortune of a piston seizure a Nikasil cylinder can better stand up to the overheated piston. With a steel cylinder a piston seizure will, more often than not, require it to be bored to clean up the melted aluminum that fills in the voids in the steel.

When Leon first started marketing the MZ202 in the USA there were some problems. Some were created by Leon (not likely) (OK Leon, your pride is showing) and some (all) ( ) were caused by the end user.

Leon's biggest problem was the final assembly setup that left the factory. That problem caused most engines to run rough and often times "4 stroking" which is a term used to described a condition similar to running with the choke in the full on setting. It was not an easy problem to overcome for most owners.

The problem itself was simple to correct after discovering that Leon was shipping the MZ202 with the carburetors jetted two full steps below sea level. (This carb setup was done on purpose and was "setup" by a "Bing" rep right from the Bing factory.The setup was that the carbs were set rich at sea level so that customers could run the engine right out of the box without worrying about "running it to lean", all customers need to "tune" the engine for their own conditions so the factory carb settings were in most cases too rich.We could not possibly setup every engine to suit everybody) A fact that Leon forgot to tell his customers about. (No, It should be obvious that you would have to "tune" the engine to your own conditions and enviorment) (if that is the case, the customer still needs to know the engine is tuned way rich!) His reasoning for the very rich carburetor setting was to assure a problem free engine break in procedure and he never knew at what altitude the engine would be put into service. (more on the break in procedure later)

Several owners and dealers ended up sending their engines back to Compact Radial Engines because the engines would not run good. I was one of those owners. However, rather than sending my engine to him, I loaded it in my car and drove to the factory.

Leon was very accommodating and spent his entire day disassembling, inspecting with a micrometer and caliper and then reassembling the engine. I spent the full day at his side and learned a great deal about the full manufacturing process. I was very impressed indeed.

Each cylinder after final CNC machining and Nikasil coated is inspected for tolerance and is given one of three classifications (A, B, C). The pistons are also made to match each of these A, B, C, classifications. The result is a cylinder and a piston that match the MZ clearance specification. I will tell you these variances from cylinder to cylinder are very small but one that Leon was concerned about. After all this was to be an engine for aircraft, not land locked vehicles. He knows first hand that a pilot can't just pull over to the side, get out and fix a problem (yes, I'm a pilot too (GA and PPG)

My problem was nothing more that an engine with way to rich jet settings throughout the rpm range. Once that was corrected by jetting, re jetting and re jetting again, I got it right. My MZ202 in a pusher configuration does not vary more than 30 degrees F from idle to full power or anything in between. The transfer from each jet's range to the next jet's range is near perfect. And, the MZ202 runs great!

The other problem Leon has seen is poor lubrication. There are a great deal of different 2-cycle oils on the market. According to Leon most are marginal at best. Therefore, Leon has elected to use oversize ball bearings on the crankshaft. These large roller bearings on both ends of the connecting rods help protect the engine from poor performing 2-cycle oils.

During my visit Leon addressed the oil issue in great detail. He showed me two MZ202 engines that experienced engine failure due to lack of lubrication.

The first engine was disassembled with the crankcase halves exposed. I could easily see that the connecting rod bearing had been overheated to the point the rod itself turned blue from heat. Interesting thing is the air and oil/fuel mixture enter the engine at the position of the connecting rod bearing on the crankshaft. At this juncture the rod bearing would be the first thing the air oil/fuel mixture would come into contact with. It looked to me as though the owner forgot to mix oil with his fuel. Don't take bets that the customer ever admitted to doing that, because you would lose.

The second engine failure I saw was due to a rod bearing failure on the piston. This is a crucial area where good lubrication is a must. Leon let me feel the underside of the piston and it felt like it was rubber coated. He then showed me the wrist pin. It was blue from high heat. Leon stated this area of any 2-cycle engine gets the least amount of lubrication, therefore the oil used must be of the highest quality or failures will occur. Leon then went on to teach me about 2-cycle oils.

I have been a believer of high quality synthetic 2-cycle oils for years. I used them in my racing snowmobiles. Anyhow, Leon told me about an environmental requirement in the USA for new oil sold in the USA. All new oil must contain 10% recycled product Thank you Ralph Nadir. Leon said he highly recommends Castrol TTS synthetic oil because it is made in Italy from 100% virgin stock. He then went on to state lubrication is never an issue with the TTS oil. He has not had an engine failure to date with owners using this oil. That doesn't mean that other high quality oils won't work, he just has a lot of faith in TTS oil.

Leon used my engine to show me another advantage of TTS oil. I had been using Red Line Racing Synthetic 2-cycle oil. Leon took a scraper from his pocket and pushed it across the top of one of my pistons. The crud just pealed off in a soft gob of black. Leon said this was unburned oil and would be the reason de-coking would be needed often. He then showed me a piston and head using TTS oil. There was a complete absence of carbon build up and you could see the jetting of this piston and head had been right on. Would you care to guess what brand of oil I use now? Problem is Castrol TTS oil is hard to find. For more information where to get TTS oil, send me a private email. I am not telling you this just to sell oil.

Final thing - the engine break in procedure is well detailed in the owners manual and full break in takes less than 10 minutes. With this step completed, re-jet the engine using Bing carburetor's jetting charts and go fly.

As far as being a test pilot for the MZ202, that phase has been done. In fact a single place light weight helicopter called the Mosquito uses the MZ202 as it's only engine option. In this setup the engine is running at full sustained power all of the time it is in flight. Now that is reliability! (yes, and I think I have shipped about 60 MZ202's so far to the Mosquito guys, maybe more I lost count)
(one last comment..... you must run premium or high octane gas to prevent pre-ignition)

My current engine settings are as follows:

Here is my present setup:

Spark Plug CR8HS
Main jet 185
Jet Needle is the stock needle and the clip is set in the center notch.
Needle Jet 2.74
Idle Jet 45
Air Screw 1/3 turn out (turn in air screw to seat then 1/3 turn out). With this setting I have no burp when the throttle is thumped. This is important when you have to make a quick application of rpm increase like in a go-around because of a bad final approach.

I am at 910 elv. and use the same setup when at Idaho's 3,550 elv.
At the elevation of 910 and temps over 90 f. the engine does get a little rich. To compensate I raised the clip on the Jet Needle to the top position which in turn lowers the needle in the Needle Jet. This leans out the engine through out the rpm range until you get to wide open throttle.

My temps indicated on my EIS system run from 1130 F. at high rpm to 1190 near 3,300 rpm range. I cruise at about 4800~5000 rpm with temps about 1160 F. The fan end cylinder runs about 15 F cooler than the prop end cylinder. I was able to improve the overall cooling by placing black gorilla tape on the seam from the fan shroud to the cylinder shroud.

I use only Castrol TTS 2 cycle oil at 13 ozs per 5 gallons of gas. That is a 50:1 ratio.

The spark plugs are one step from the stock plugs the engine ships with. I was told the CR8HS is leaner running than the stock CR7HS. It is about equivalent to a 1/2 step change in main jet size.

Nice read mate.
Good info there.

If you look around the Mosquito forum you will see some other issues that have come up as well.
I'm not the expert, Eddy Thompson and others put a lot of time into this.

Just to summarize, as I understand it....

- When using A, B and C cylinders, the rings were the same, this means that the ring gap is slightly greater for B and C cylinders. This extra play allows the rings to bump and stress the anti rotation pin and it can work loose.
Mosquito helicopters only use the A cylinders now, though there are B and C out there already.

- The original rings were cast iron which is too soft for the Nikasil cylinders, so they would wear prematurely.
Mosquito helicopters use chrome moly rings now.

Others with more experience can pipe in here, I thought it might be nice to summarize it here.

Lorne is correct - with the continued use of the MZ202 by Mosquito family it has over time evolved - different rings, going to the A size only cylinder and an upgrade from the original Meteor pistons to the Wiseco
After reading original post I disagree with what he said about the spark plugs.

"The spark plugs are one step from the stock plugs the engine ships with. I was told the CR8HS is leaner running than the stock CR7HS. It is about equivalent to a 1/2 step change in main jet size."

CR8HS IS A COLDER PLUG THAN THE CR7HS and therefore it should run richer. Here is a NGK chart that explains what each number/letter represents:

Attached Files Thumbnail(s)
Spark plugs are not leaner or richer. They're hotter or colder, which refers to the operating temperature the plug is made to run at in a particular motor. They don't affect the mixture, or have an equivalent effect on the mixture.

With a hotter spark plug, the spark area of the plug has less metal mass connecting it to the outer threaded part, so therefore the spark area of the plug runs hotter in temperature than a colder rated plug, which has more metal mass connecting it to threaded part of the plug.

The more metal mass connecting the two areas of the plug, the better the spark area part of the plug can transfer heat to the threaded part, which transfers heat to the head, thus cooling the spark plug.

If a plug regularly carbon fouls, using a hotter plug will help keep it clean because the carbon doesn't form as easily because the spark area of the spark plug is hotter in temperature due to the design of the plug.

If a plug is too hot, it erodes (self destructs) due to excess heat. If it's too cold, it carbon fouls. The gas to air ratio of the carburetor has nothing to do with it, other than the plug will burn cleaner (not carbon foul as much) if the mixture is too rich. Everything else would still carbon up, just not the spark plug tip. It would not make any difference if the mixture is too lean.

My dad drove his pickup truck 3 miles back and forth to work. Plugs were always fouling because by the time the motor came up to operating temp, he shut it off. I put in hotter plugs and cured the problem of plugs fouling in 5,000 miles. After he died and I got the truck, I had to go back to the original heat range plugs because I drove it to work 22 miles. Plugs were severely eroding because they were too hot. Going back to the colder plugs kept them cooler and they didn't self destruct due to excess heat.
Thanks JBaum for the correction on spark plugs, also I know that running too hot of a spark plug can burn a hole in the top of a two stroke engine piston or jettting your engine too lean may cause the same effect on a two stroke engine piston. Its important that before you change anything on your engine, such as changing the heat range of spark plugs or rejetting the engine, check with someone who knows how to read plugs or the manufacturer.

If you have anything to add , please feel free to do so. Corrections are always appreciated. Joe
There used to be a chart on the counter of the local car parts store showing plugs in various conditions, with a caption explaining the problem and correction. I had a moment of lucidity and looked at it one day. It was very helpful information. The spark plug can really be an indicator of what's going on inside the cylinder in relation to timing and mixture when the heat range is correct for the driving being done.

In my above message I said metal mass connecting the inner and outer parts of the plug... that's incorrect. It's the ceramic insulator mass that makes the difference.

The reason incorrect heat range (too hot) plugs can melt pistons is because the tip of the plug gets so hot, it ignites the gas mixture by itself without a spark, causing pre-ignition (too early, the same as ignition timing being too early) and extreme temperatures and stress on the pistons.

Here's a good guide to spark plugs and how to read them:

and for the YouTube lovers, an even better explanation of how to read the plug:

Hmm, would it be a bad thing to request that this thread become a sticky? There's some very good information here, and I'm sure there is even more that can and likely will be added in the future.
Good stuff JB, Thanks

Forum Jump:

Users browsing this thread: 1 Guest(s)