I've noticed the rocker arm snap rings are very ductile (bend easy). Has anyone replaced them with hardened ones?

I don't see why you couldn't replace them with harder ones. If you can find them it sounds like a good thing to do.

Why have harder springs. There is no real inertia to speak of . And you would put extra stress on push rods, cams etc.
i have discussed this with an engineering pal of mine, ( ex- ships chief engineer) and he was of the same opinion.
You only want the lightest spring you can get away with. The four stroke cycle will take care of the rest.

I believe he is talking about the cir-clips and not the valve springs.

Hi everybody,
Very interesting discussion. A lot of very nice info for me.
I own an old ST7-70 since approx 10 years now and after a (too) long inactive period, I would like to fit it on a LA-7 2,45m (CY Model).
That plane all equipped should be around 30 lb.
Do you think it will fit ?

Oli

Website shows cowl dia. To be 12.56 inches. Inside

Oh yes, there is space enough. I am just wondering if it will have power enough ?

It would be under powered. I have the older Seidels and that engine would be much better with a 20 pound model.

20 years ago, I saw a yak 11 fiber classic equipped with that engine. It ran so great !
I absolutely cannot remember technical details, I was still a young modeler...
10 years later, I bought same engine on eBay. Finally I recently decided to go with LA-7.
I will make some test run and share the results before to decide for another power unit.

Hello again gentlemen. ....I am finally done building my ziroli 77" stearman with 77cc evolution radial. Last summer. I had run engine on test stand and it ran strong. After months of oiling up engine as recommended. And turning prop to keep lubed,I tried to start engine today. It started but would die when glow power is removed...also would not get above 3000 rpm????any thought sk?

Also, please guide me to post on new carbon....and thanks for help

nOT ALL CYLINDERS FIRING DUE TO OILED UP GLOW PLUGS. (sorry hit caps lock) Remove lower glow plugs and burn them out. I hope this is your issue!

Thanks Maxim...I will do that. ..can you refer me to post regarding. Changing carburetors?

Is it really required on all 77cc radials?

Post 1610 for the carb discussion. I am very pleased with the OS conversion.

I want to ask...when I apply afterrun oil I attach a length of fuel tubing about 3" long and squirt the oil into it about 1.5"...then apply electric starter and turn engine allowing oil to be sucked into engine...is this how u do it?

No refer to earlier posts where I use oil into crankcase and NOT use the electric starter!

i also remove pushrod and apply air tool oil into engine...but is afterrun oil supplied thru carb or just squirted into carb?

i use fuel supply line to apply afterrun oil...so it goes same way fuel goes to engine

hope it wont gum up carb....speaking of carb...is CH IGNITIONS still making carb adapter for 7-77

Second this Mod !

I inject directly into the crankcase through an upper follower hole and allow draining right away through a bottom follower hole.

Well. I removed needle valve....it was dirty also checked glow plugs....some burnt bright....some not so bright...so I put the. Ones that glow bright in the bottom cylinders will start it up again tomorrow....thanks for the help

I guess confusion. Is i use air tool oil and after run oil and apply each in a different way

After run through. Carburetor. And air tool into crankcase