OPS Maxi "conversion"
 

I picked up an OPS Maxi 30. This is a discontinued Italian glow engine. It is really well made and has bearings on the crank pin. It runs 7000 rpm with an APC 20x8 as pictured. It does slightly better with no muffler at all and a larger carb. The larger car does not tune right though. The pitts muffler is actually for a CRRC 40. I made an adapter plate. It is a bit heavy by modern standards but it does run really smooth and start easy. It idles down really low.

RE: OPS Maxi
 

You might do better with your carb tuning if you turn that velocity stack around. Ram air pressure confuses these carbs...

AV8TOR

RE: OPS Maxi
 

These are very well made engines. I have seen a few run on glow quite a few years back, they have a relatively long stroke and handle large props well. The instructions called for 95% methanol with 5% Castor. The original D'ellorto pumper carb reacts fairly slowly to needle changes. I still have one NIB and plan an ignition conversion. Evidently methanol / spark makes them quite powerful. I believe they are still available, along with a few other models, directly from OPS.

RE: OPS Maxi
 

I recently converted a Maxi 30 to gas ignition. I machined a new head button for a CM-6 plug and used one of the cheap Hobby King ignition sets. I couldn't get the Dellorto carb to tune properly but found a Walbro that works great. It was turning an 18x6 prop at over 8000.

RE: OPS Maxi
 

That is how I did It. I removed the two studs from the prop hub and checkered in the pattern where they were. I removed some material from the head disk yesterday. The squish band is really minimal now 0.005" that bought another 100 RPM. The bearings are a bit rough so I have some new ones coming. I'll check the ring when I have it apart. If needed a Bowman ring might be in the future. The carb I have have on there is OK but not optimal. I it an 11mm. 13 mm is too big. I am thinking something with a choke and about 10mm might be a good fit. For refrence, what size is used on the DLE30 or other 30cc engines?

RE: OPS Maxi
 

An 11mm carb should not be too big for it. The DLE 30 uses an 11mm carb. The Zenoah G-26 uses a 12.7 mm carb. I use 11mm on 20 to 25cc engines, and the 12.7mm on 30cc engines. 11mm should work fine on that OPS. But as I mentioned, getting ram air into the carb like you have with your particular velocity stack arrangement can cause all kinds of weird tuning problems....

AV8TOR

RE: OPS Maxi
 

I now suspect an air leak. Fuel drips out from behind the prop hub. The bearings are not so good as I initially thought. I have a new set with seals on the way from Boca. I plan on removeing all the rubber seals except the on right behind the prop hub.

The original carb seems to work. But, only if the idle mixture screw is all the way in. The rubber bits inisde are in pretty good shape. I did clean it carefully to remove the dried castor oil and free up all the passages.

I may contact Frank Bowman and see if he has a ring on hand or, can make on without me shipping my engine. I am thinking I might be getting some blow by causing the crank case to be pressurized. This could be from an old ring and or the ring is glued in place with dried castor oil. If I am going to take it apart I might well replace the ring.

RE: OPS Maxi
 

The OPS 180 has alwas had a wet nose.

RE: OPS Maxi
 

The bearings went in without incident. The ring was indeed gunked in place with carbon. I got the ring out, without breaking it. I cleaned everything up and compression has gone to pot. A Bowman ring is on the way.

RE: OPS Maxi
 

It is running pretty good. I put Frank's ring in it. I also installed a WTA-6 carb.

http://wem.walbro.com/walbro/product...6-1&Series=WTA

It works the best so far. I am turning up 8000 with an 18x10 APC and 7000 with a 20x8 APC. I am pretty pleased. The WTA-6 is acting funny. I did intall all new rubber guts. The metering needle is the kind with the soft tip. I eyeballed the pop off lever to be alittle above level to the casting. So, what it is doing is that the mixture screw settings are weird. The idle screw is at about 1/2 turn out and the high speed screw is about 3/4 turn out for proper running. Other carbs have also acted strange, as far as mixture screw settings also.

Is this because this engine has the inlet throught the crank? Should I not expect to have it tune like piston port engine?

I have no way to test pop off pressure. Should I lower the pop off lever a little?

RE: OPS Maxi
 

NM

RE: OPS Maxi
 

I would tweak the lever a little down, give you more resolution on needle settings

RE: OPS Maxi
 

Good call! It is working very well now. Thanks.

RE: OPS Maxi
 

I have one converted to gas. I used this link as a guide and it's awesome! Thinking about putting it on my Mud Duck and make it a "Super Duck" :D

http://tech.flygsw.org/OPS.htm