new to gas engines , US 41cc - RC Groups
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Dec 31, 2007, 02:28 AM
pro R/C crash-test pilot

new to gas engines , US 41cc

well i got a jumpstart to gas engines , was at my hobby shop today and originally went to go get some CA and ended up with alot more than that , got a 90% finished Robinhood 99 , with a US 41cc , ive never run gas motors before and need input on how to tune/etc. as far as i can tell it has never run , been sitting for a few years so ill give gas a try , been running nitro forever but i couldnt pass up this plane for $100! thank all , Gary.
Last edited by Rcgary20; Jan 01, 2008 at 12:04 AM.
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Jan 01, 2008, 05:50 PM
pro R/C crash-test pilot
nobody?????? dont know the essentials for running gas engines , recommendations on oil , or anything about tuning , any help would be appreciated.
Jan 02, 2008, 11:32 AM
Registered User

I'm new to gas too but I can tell you my little experience.

I used 20:1 mix during brak-in. Hi octane unleaded gasoline and 2T semi-synthetic oil for brak-in. After a galon or two, you can go to 40:1 with synthetic oil.

I have a 45cc engine with a 20x8 prop. I think that for a 41cc a 18x8 should be ok.

I found that these engines are very similar to nitro ones. You have 2 needles (Hi and low) but they run at lower RPM (7.000 or so).

Somebody also told me that gas engines need to warm up a little to be ready to fly.

Well, it's no much but surelly somebody will help you more.

Jan 03, 2008, 11:40 AM
Registered User
flypaper 2's Avatar
Run 40 to 1 mix. of regular chainsaw oil. Give her an extra dab for the first gallon. Regular gas is fine. It's a tough little engine that will give you years of good service. 18-8 is the standard prop for it as said. To prime it, stick your finger in the carb and pump the prop up and down like a pump handle. no need to turn it right over. When your finger gets wet with gas, give it a about 4 more pumps, they like to start wet. Wind the spring backwards for half a turn, just enough so it flips over compression when you let it go. If you wind it up any more, you'll ruin, buckle up the spring. Make sure it's well tied down. Give it 1/4 throttle and it should kick off on the second flip. Be carefull.

Jan 03, 2008, 07:11 PM
pro R/C crash-test pilot
thanks for the info , im not sure about those spring starts , not sure if i like it , but ill use it for now untill i can afford a starter for big motors , my brother told me for gas engines he used lawn boy oil for the first gallon and redline for the rest , he is running a DA 85 on an edge 540 and a Fuji 64 on his christen eagle , but ill use what i can for the time being , thanks for the help!
Jan 03, 2008, 07:23 PM
Registered User
flypaper 2's Avatar
When you get your finger rapped with that 18 in. prop, you'll apreciate it Gary. Just like getting hit with a hammer. Been there many times.These mag. ign. engines have to be swung over the top fairly quickly to get a spark. That's where it pays off. Lawn Boy oil will work fine.

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