I just installed a G51(RC version) in my Tutuor II.  It came out of a RC plane that I'm donating to a club as a club trainer.  I replace the carb with a ST venturi and NV.  Can I expect much of a CL run from this engine "as is", or do I need to replace the cylinder liner with the CL sleeve?  My intention is to run it like it is and see how it does, first.  Advice?              Glen

Thanks, Peabody.  That engine was a real powerhouse in RC mode.  I had it in a "60" size, very heavy trainer, and it yanked her around the sky with authority.  I found that with a tongue muffler (without all that stupid exhaust plumbing), it weighs about the same as the LA46 with stock muffler.  Thought I'd try launching at about 10-10.5K, and use the 11/4 ProZinger.  We'll see.............Glen

Dont Quoate me on this, but I have heard some say that the Timing on the RC  version is better suited for stunt than the control line version FWIW

The R/C version is happy running high RPM and low pitch.  The C/L version will give you a traditional stunt run using higher pitched props.  Mine is happy with a ProZinger 12X5 launching at 8500 RPM.  Growls in 4 and kicks into 2 just when you need it.

Well, I did it!  Broke the ring!   Guess it's Frank Bowman time.  A man's gotta know his limitations.  Glen

Steve, Frank is working on the engine right now; may be finished by now.  I really did it up good; he said the ring was broken in three places, and that the con-rod bushing at the crankshaft was loose, so he's rebushing that.  Lesson learned: If, after reassembling, it doesn't feel right, don't mess with it; send it directly to Frank!      Glen

Got the engine back from Frank, today.  He did the ring, end gap, new bushing for con-rod, and replaced the front bearing, which he said was rough.  I was pleased at how reasonable he was.  Louis, I think you mentioned that you run Prozinger 12/5.  Would that be a good prop to run with the engine on a TutorII?  Thanks...........Glen

Hi Glen,

Louis will correct me if I'm wrong, but I believe that is exactly the set up he is running on his Tutor II (which doesn't LOOK like a Tutor II!)

Hi guys, I have a ST G51 and wouldn't recommend this engine for nothing but a boat anchor. It doesn't like to 4-2-4, had Frank put a new ring in her. With Frank's work, engine runs great, I don't believe they are made for stunt. I have Merco's, Fox's, K&B 61's, Enya's and older ST engines. These engines are the only stunt engines I have had that are any good. The G-51 likes to run at a hundred million RPM's sound like S&&h to me. I guess each to their own, I still love the old sound of the 4-2-4 runs. Gary

Yep, to each his own.

But it is odd that yours doesn't like to 4-2.  I have had three, and they have given the best 4-2 runs I could ask for.  Every bit as good as my ST 46s, ST 60s, and even my Foxes!  IN fact, two of the very best planes I have ever had used the ST G51: a 64 oz SV-11 and a 54 oz. USA-1 which Derek Barry said was one of the best set ups he had ever flown.........

Hi Bill, is your G51's Italian or the Chinese type? I bought mine about a year ago from Tower, so did my brother, they both run the same. They start to run a hard four them seem to load up (acts like a bad glow plug), pinch fuel line for a few seconds, finally go into two cycle. Maybe to much fuel, reset needle valve, quarter turn, goes into two cycle.  Acts like venturi to large, its the same as my OS max 46 SF ABC piece of junk and the ST 46 Bullring piece of junk. Good looking motors just don't seem to run like my ST 46 G21 or my ST 60 V. The K&B 61 has a great 4-2-4 run, so does all my Merco's (35, 40, 49, 61 all of these Merco's run great!). If you heard a Enya 60 7032 or the Enya 46 model's 6001 and 6002, what great sounding engines. I just haven't had any luck with the other types, just me, had to gripe. I have a old Sig chipmonk that is set up for the OS 46 SF or the ST 46 Bullring and the ST G51, they fit and isn't it strange they all seem to run the same way, Ha Ha. Thought maybe tank, so I bench run each one of them, that wasn't the problem. Maybe fuel, I use GMA 10/22, add castor oil to 25%. I tried just the 10/22, didn't seem to make a different. All three of the engines run great, just won't 4-2-4 for me. Installed hotter glow plug, same problem. Missing something, take to R/C field, Ha Ha.  Appreciate your input, Gary

I bought one of the Chinese G51's as a throw away to use on a Tutor II arf.  I didn't want to put an Italian G51 on an untested plane.  Aside from minor cosmetic differences I can't tell any differences between it and the Italian 51's.  I run it in a fast 4 cycle, turning a 12-5 Rev Up prop, and it has more then enough power.  I've had a few issues with the engine running funny and they always trace back to a problem somewhere else in the system, a leaking overflow cap, bad fuel, bad plug, etc.  After correcting the problem the engine always comes back to running like a clock.  It's the polar opposite of the OS 46SF-S.  The OS has never run right, always inconsistent, running away, and generally disappointing.  Even after having it reworked it's still not in the same ballpark as the bargain basement Tigre 51. 

The R/C version is happy running high RPM and low pitch.  The C/L version will give you a traditional stunt run using higher pitched props.  Mine is happy with a ProZinger 12X5 launching at 8500 RPM.  Growls in 4 and kicks into 2 just when you need it.

Louis,
I used an RC ST51 with an APC12.4 X 3.4 prop. This precludes any reference to high RPM. The motor is not going to do a 4/2/4 but is very consistant in it's running characteristics. Oh and to clarify further it was used in a funfly type R/C model with a reasonable amount of verticle maneuvering and throttle management to do the maneuvers. Very dependable smooth running motor. I'm going to use it on my next C/L project. I do have 2 C/L versions to fall back on but I'm not in the mood to run in another motor.
dennis

The improved starting is probably due to better ring fit. It's my belief that insufficient ring gap is likely a huge problem with these engines, causing runaway, overheating, and no 4-2-4 break. A Bowman ring, gapped exactly, and installed properly, should make a huge difference in satisfaction. Inadequate ring gap may also explain why some recommend zero nitro and 25% castor oil. Too much ring gap might explain why others use 15% nitro and 20% synthetic/castor blend with success. Something to consider, anyway.

The only G.51 I've run was retimed in the manner of George Aldrich, has stock compression, and a fairly small venturi. It likes 5" to 6" pitch, 11 to 11.5" diameter.  I like an 11 x 6 Graupner, or 11.5 x 5 APC on it. The 12-5 Revup was not good, nor was a 12-5 Bull Y&O, a 12-4 APC, a 12.25 x 3.75 APC, etc. I'll soon have two T&L G.51's to try in the same plane, and expect a full 12 x 5 APC, Graupner, or Pro Zinger should be good starting points. Maybe even the Thunder Tiger Cyclone 12.5 x 5.5?  Steve