Hyjinx, the carbs on these engines cannot move the fuel through them. The os FF240/320 carb (ft160) will solve all problems. Also make sure 20% of the oil is castor to protect the cam ring and followers.

Thanks Maxam
I am not sure I have a problem with the carb yet. Too new to me to modify without a little more time ( and or performance problems). I was just considering the pump cause I have one.lol
The castor is interesting, I have a desire to run synthetic red line in this engine without any castor for a less corrosive and non gumming film after clean out from run to storage. The redline boasts excellent corrosion resistance.
Am I off track here, I have followed the threads concerning corrosion in these motors. Seems to be a real concern.
In short , what is the benefit of the castor?

The castor coats the metal surfaces more tenaciously than the synthetics. The followers drag directly on the cam ring and the ring wears quickly without castor oil.

Hyjinx also suggested using a Perry pump. I'm wondering: given the way the two variants of Perry pumps work, is there really any reason to expect that they'd work for radial engines?

-tih

Thinking the vibratory pulse type may work. The radials run smoothly but the pump should still pulse I am thinking.
Still of the mindset that with proper tuning and fuel mixes it shouldn't really be a necessity anyway.
Sounds like castor will be an additive Maxam. Percentage as mentioned earlier in the thread.
Thanks for the thoughts folks, enjoying the 7-77 ums.
Almost makes me want to fire up it's first off version. I have the original Seidel made by Wolfgang on a shelf.
Haven't run it. Bought the UMS Horizon Hobby knock off for an everyday 1/4 scale airframe.
Like to come up with a 1/4 scale Steglitz for that one and keep it all German!

I have the original ST540 and the supplied carb for an OS 10 was terrible. The Saito 90r3 carb is much better!

Fuel
 

I bought ums pre-mixed fuel from Ritches Brew at Perry last year. It has 9% synthetic. I have some blendzall racing Castor. How much would I add to my gallon of Ritches brew to bring it up to the 20% as last recommended?

Do you run that 540, or display it with your collection.
My 770 was a running motor when I aquired it, but I have shelved it with my other radials.
Parts availability may be a problem.
That 540 is rare!
I haven't been able to find any original manuals posted anywhere.
I will mount it if a come across the right airframe.
Or sell off a few and get another Moki. Lol

Oops, getting on a rabbit trail, sorry to be off topic.

Add 2.5 oz of castor. -Tom

I fly the 540 in a 1/4 scale Pietenpol Sky Scout. -Tom
Post 1749 for pictures.

Thanks thanks Tom I'll do that.

Hey Maxam, Thinking about ordering a UMS 7-90. Have you had any exposure to one yet or anyone else?

Do you mean a 9-99 9 cylinder?

Tom, I am building a Robin Hood 99 and I plan on putting the 7-77 in it.
how much did you shorten nose for balance?

Cannonfodder. ...how did you mod the landing gear. Picture looks like standard gear. Really nice plane

Badangle, I think one inch. I have the batteries in the tail to balance the 9-90. The 7-77 is a more appropriate engine for the RobinHood. A great airplane!!!!

Tom, did you beef up wing ?
I'm not sure adding struts is enough...
Any changes to firewall ?
the 7-77 is heavy and i worry about strength of design of Robin Hood 99.

Hey all
Just maidened a 1/4 scale Stearman weighing in around thirty pounds auw.
Was running a 22/12 for the first flight, was tacking just under 6000 rpm.
The plane failed on climbout (can't tell exactly in video, seemed to just lose power on the way up and stalled into the wind at about 100 feet. The test pilot was able to drop the nose and right it before it went it. Miimal damage to my self constructed landing gear. Pilot is the best!
Broke the 22/12 on impact
Beefed up the gear, installed a 24/10 (max by manual), and all I had.
it flew scale but was scary in turns. Need greater air speed to fly it safelyi feel.
i am tempted to tether it attached to a pound scale and make comparisons based on a 22/12, 23/12 and 24/12s
Any initial thoughts?
I have scanned the threads on prop data, there is help there but I am really hinky on this thing.
The prop calculators are helpful. But hands on data means more to me.

Don't want to stuff this thing into the ground with this engine on the front of it.😲
​​​​​​

Please excuse grammar and punctuation, didn't see the boo boos before hitting send.

Yes adding struts is plenty, remember I have the 9-90 on my RobinHood. I had to install the batteries in the tail. The firewall is fine but I did install a sub floor so the tank would be raised. Also the front windshield frames were strengthened by adding 1/32 ply to the front and side surfaces overlapping the fuselage and frame glue seams.

Hyjinx, too small of a prop and RPM too high. Use a 24x12 on your Stearman.

Thank you
I weighed it today at 34 lbs. It has no ballast aft 30% with the 7-70.
Sounds like I am under powered.
Hmm
Maybe the Tech No Power 9/90 down off the shelf..😁

Hey Tom
thanks again for your interest put. I have read the threads over and gained a lot. More than once. Greet reference material. Appreciate all the contributors have posted from experience.
Aaron

Oh shoot.

Thanks again
In put..
Great reference..
Lol