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-   -   UMS Gas Radial Engine Enthusiasts Rabbit Hole (https://www.rcuniverse.com/forum/gas-engines-142/11698637-ums-gas-radial-engine-enthusiasts-rabbit-hole.html)

okcrcpilot 04-20-2022 12:04 PM


Originally Posted by marksp (Post 12724669)
Thanks Gary, and yes still have the big Stearman w/Moki S215. Still have yours? Have you picked up a UMS radial???

Cheers

Yes, still have the PT-17 (see post #11 above) and sold the Moki to Tom, picking up a UMS 260 in it's place. Definitely NOTHING wrong with the Moki; it just didn't look scale to me and I am way anal in that respect. Good to see you on this threat and letting us know what you are up to. Happy flying season ahead!!!

Maxam 04-20-2022 01:16 PM

Hey OK! I am sure you put 2 and 2 together. That is your 257 on my new Fly Baby! -Tom

Maxam 04-20-2022 01:30 PM

A review of the 5-55
 
So I got the 5-55 from Adrian 'cause it is cute and a nice small size. Got it mounted up and used a 22x10 prop. The engine can turn it to 4500rpm. True hp at this rpm is 1.5. Sure it can develop more hp at a higher rpm but then much smaller prop. The UMS glow style carb has the classic way over rich condition at mid throttle. The trick of adjusting the throttle mixture at half opening still was unsatisfactory. I made an adapter on the lath for the Saito 90r3 carb and that was the ticket! Beautiful ideal mixture at all throttle settings with immediate response. All cylinders at same temp. A 4oz tank runs the engine for 15 minutes with some part throttle settings. The question now is will the seals in the Saito carb hold up on gas? Reliable idle at 1000rpm

-Tom

okcrcpilot 04-20-2022 02:52 PM


Originally Posted by Maxam (Post 12724697)
Hey OK! I am sure you put 2 and 2 together. That is your 257 on my new Fly Baby! -Tom

For sure, Tom, I thought that engine looked familiar!! Would really like to see a picture of your Fly Baby at the field, fully dressed and ready to go!!

Linkan2 04-21-2022 12:26 PM

engines with cdi systems and which are difficult to run well in all situations.
There you can advantageously drive with iridium spark plugs.
stronger spark and better combustion.
goes well with a slightly richer setting.
I have it on some methanol engines.
Lars

Maxam 04-21-2022 01:28 PM

Better pictures!
 
https://cimg2.ibsrv.net/gimg/www.rcu...dd24ae2cd0.jpg
https://cimg4.ibsrv.net/gimg/www.rcu...58d9ad2bb9.jpg
https://cimg3.ibsrv.net/gimg/www.rcu...234c8b8be2.jpg

okcrcpilot 04-21-2022 01:53 PM

Very, Very nice Tom and thanks for posting the pictures. I would really like to see this plane in the air sometime. I'll let you know the next time we head your way.

Gary

Maxam 04-29-2022 05:02 PM

Alert! Loose bolts...
 
I was running my 5-100 and it was developing more vibration. I shut it down and spotted a hex bolt on the floor. It was from the front timing chest. The other bolts were quite loose! I cleaned everything off and reinstalled the fallen bolt and tightened all of them up. Vibration gone. I checked my new 7-35 and the front bolts were loose there too! Check your bolts folks!!! -Tom

Maxam 05-08-2022 03:55 AM

It is a shame that this thread has faded. The most important information will be how well these UMS engines last after several flights. I hope information will begin to trickle in. -Tom

GIJon 05-08-2022 04:06 AM

UMS 55cc
 
Thanks for the info Tom on the carb. Since you're concerned about the seals on the Saito carb, I wonder if it would be better to adapt the UMS 75cc carb instead.

Maxam 05-08-2022 04:51 AM

GI, the one UMS engine I had problems with was the 75. I bought one and Adrian sent me two Walbro carbs with it. One was overly rich at idle and full throttle because you had to with an ultra lean midrange throttle position. The other carb was the opposite with an overly rich mid throttle position. The engine also built up massive carbon on the heads preventing valve closure. The 55 with the Saito carb and the stock 5-100 are basically perfect runners. Adrian took care of me with the 75. He believes in customer satisfaction. -Tom

okcrcpilot 05-08-2022 06:06 AM

Well, maybe there just aren't that many guys putting radials on to their planes and that's why things have quieted down here. I flew my "17" four time this past week which brings the total flight count up to 30 with the UMS260cc up front. I cannot say enough good things about this engine. Needless to say it is nothing remotely similar to it's predecessor.

Maxam 05-08-2022 07:48 AM

I was at the AMA headquarters last year for the warbird meet. 20 radials I counted! Probably a lot more in Florida and out west. Very glad to hear your 260 is serving you well. Adds confidence. I do have a Moki 215 on a Super Flyin' King with 300 flights over 7 years. Shows no wear.......I do add gear oil to the timing chest. -Tom

GIJon 05-09-2022 06:33 AM


Originally Posted by Maxam (Post 12726995)
GI, the one UMS engine I had problems with was the 75. I bought one and Adrian sent me two Walbro carbs with it. One was overly rich at idle and full throttle because you had to with an ultra lean midrange throttle position. The other carb was the opposite with an overly rich mid throttle position. The engine also built up massive carbon on the heads preventing valve closure. The 55 with the Saito carb and the stock 5-100 are basically perfect runners. Adrian took care of me with the 75. He believes in customer satisfaction. -Tom

Tom,
Would you consider machining another adapter for my 55cc and I will buy the Saito carburetor?
I will be working on my Gilmore Red Lion this year to put the UMS 55cc in.

okcrcpilot 05-09-2022 07:02 AM

Tom,
What brand/weight of oil/grease do you use in the gear case?

EDIT: I should have said "Cam Gear Case".

Gary

Maxam 05-09-2022 10:45 AM

GI, I have an extra Saito Carb WITH an adapter. You can buy it from me at cost. PM me later.

Maxam 05-09-2022 05:15 PM

OK, the oil is Red Line GL4 gear oil. Grease is molybdenum high temp grease.

okcrcpilot 05-11-2022 04:26 AM

Tom,

Thank you for providing info on what lubrications you use. It might benefit some of the new guys (me included) if you spelled out how you go about lubing your radials. I assume you use the Redline for the day's "first flight" and the moly in the cam gear case but exactly how does the process play out?

Gary

Maxam 05-11-2022 02:10 PM

Gary, both lubricants go in the cam case. Tragic day. The wings failed on my new Fly Baby. The Moki 257 shaft is bent as well as ten push rods. One of the finest engines I have owned. A year and a half work gone as well as a lot of money.

okcrcpilot 05-11-2022 03:07 PM

Tom,

I am SO sorry to hear of the demise of the Fly Baby, as well as the damage to your 257. I can only imagine what you are feeling today.

Gary

GIJon 05-11-2022 04:06 PM

Tom,
So sorry to hear about your fly baby. I can't imagine after all that work. There is another Schlunt fly baby here at Joe Nall with a Volach twin cylinder.
Is it rebuildable or is it too far gone?
Jon

Maxam 05-11-2022 04:37 PM

Thank you OK and GI. Oh yes, totally gone. I am just sick about it. Part of the hobby though. The 257 was running PERFECTLY of course. I can only imagine what a new crank shaft will cost. Out of round about 20 thousands. The prop tip would be around a half inch or more. An expert could straighten it I am sure. The engine still turns freely. -Tom


partshunt 05-14-2022 12:37 AM

This UMS forum is what I have been looking for. I just bought a 50cc, 7cylinder ums on gasoline. Does anyone have experience with the 50cc? It is not supplied with the Walbro carb, it has the UMS carb. Cant wait to fire it up.I have two Mortons but they are apart, wont star, too low compression. This UMS 50cc -7cylinder good for what wingspan.?

Maxam 05-14-2022 01:08 PM

Ums-7-50
 
I have the UMS 5-55 and the Glow 7-35. I have seen the 7-50 run and it is a good engine. Some of the UMS's carb have too large of a choke area and when tuned for max power at full throttle run too rich in the mid throttle positions. Experiment with tuning the engine at lets say 3/4 open and tune for max performance (after break in). This can help make mid throttle with a better fuel mixture. Often at the lesser carb opening and retune there will be little to no loss of power due to as previously said the choke areas tend to be too big. I suggest a 22x10 prop. -Tom

partshunt 05-14-2022 07:41 PM

thank you for that information. Mine will come with the UMS carb, not the Walbro but it is an option The 50cc 7 cyl the UMS carb is standard , optional is the Walbro as you probably know. . ... thanks... Joe


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