karolh

The new RCGF Stinger 20cc engines depending on which exhaust location you want uses a different size spark plug. The rear exhaust version uses the common and pretty much standard among most brands a CM-6 or equivalent (10mm) plug, while the side exhaust version uses a not too common 1/4"- 32 (6mm) plug. Seems to me that using a plug size that is most common to the industry would be the way to go or is there some technical reason behind this that I am not aware of. Would appreciate hearing your thoughts on this.

RCPILOT99

I just got a Stinger 20cc side exhaust with the small spark plug I managed to break the plug before I i got in . Had to order two new ones but had trouble finding them and they are pricey . So the engine started easily and ran good so i mounted it in my Sea Gull Ultimate bipe. On the fourth flight the engine quit . The plug came out. How this could happened is beyond me. I torqued it in good and tight with a new ring. On the next Fourth flight the engine quit same thing This is really crazy that was yesterday today I am trying to make a locking washer or think of a way to prevent the plug from unscrewing itself. I will come back soon with an update on my troubles.

karolh

I have a friend who bought a Stinger 40cc twin and is quite impressed with the quality of the Stinger engines but mentioned that the threads in the plug hole never matched the overall quality of the engine and that the plugs were quite loose while being screwed into the cylinder head. Sure hope that you find a way in solving your plug problem.

I was very interested in getting one of the Stinger 20cc SE exhaust engines but have been turned of by the use of the very fragile 1/4-32 plug. Hopefully sometime soon RCGF will see to making a change to using the pretty common and very sturdy CM-6 plug.

RCPILOT99

I drilled out a star lock washer and installed with the plug will go flying today fri may 7 to see what happens

Truckracer

My Feedback: (19)

How are you making the seal between the head and the plug with the star washer?

RCPILOT99

Star on first then brass ring compression was fine but after 3 mins the engine quit the plug came out both washers lost i did not just want to go home so i put the plug in bare compression was good started good ran strong so i flew two flights and all was well but near the end of the second flight the engine got noisy when i landed i found the muffler loose my friend suggested liquid gasket fill on the screws and muffler he is going to email me the kind he uses the saga continues .

RCPILOT99

JUST GOT EMAIL FOR THE MUFFLER Permatex Ultra Copper. NOW THINKING SAME THING FOR PLUG

karolh

Hopefully the Permatex Ultra Copper will solve you problem as that's what I use and I have no issues. What size prop are you using on the engine and what rpm are you getting ?

RCPILOT99

16x6 do not know rpm but i will have one of the guys check next trip out

karolh

It would be interesting to know if this particular spark plug issue with the RCGF Stinger 20cc SE engine is something that others are experiencing.

RCPILOT99

Just a warning to anyone thinking about this engine you can not safely replace the plug with the muffler installed the plug is very fragile and will break with the slightest side load . I believe the engine expanse faster than the plug material and that causes the looseness they should also do something about the muffler attachment same thing hard steel screws into aluminum. Hopefully i can resolve these problems before disaster had three dead sticks already with only 10 flights. My friend has the same plane but with the rear exhaust version and he had a two dead sticks but lost the plane on the second one. He was also having trouble with the muffler coming loose and had to pull the engine out to tighten he told me about the perm gold his engine had a larger plug his flame outs were due to running to lean trying to get max rpm on the ground. Another friend of mine has the same engine as me and swapped it out with a dle after having constant run problems headed to field today just got the prematex last night so not used it yet

RCPILOT99

Stinger 20 se performance 16x6 fiberglass prop idle 3500 peak 9400 pulls my seagull models ultimate bipe from 50 feet to 400 feet in 7 seconds two flights today came home and cleaned muffler and plug and added permatex will fly again wed hopefully things will stay together for a while so i can finally put the cowl on.

Truckracer

My Feedback: (19)

I think you are a bit under propped on that engine. You might notice a performance increase at lower RPM going to something like a 17-6 which is pretty much a "go to" prop for modern 20 sized engines. A 16-8 might be an alternative if ground clearance is an issue. You don't need to be turning up in that 9000+ range. These high revs might account for some of the problems you are having.

RCPILOT99

Just ordered a prop to give it a try thanks

RCPILOT99

Well the permatex did not work plug came out before i left the bench. Just ordered a $40 recoil kit wish me luck going to take 10 days to get here did not run long enough to see if the permatex helped with the muffler coming loose i guess we will see in a few weeks. This engine is under warranty but i would rather try to fix it than send it in. But if this does not work i will request a new head if they will not send me one then i will send in the engine unhappy with the engine and the company who sold it.

karolh

Sorry to hear you are having such an unfortunate time with your engine. From your previous post it seems to be a very strong performer but if it won't stay together then that's a major problem. Sure hope
it has a happy ending for you.

RCPILOT99

Got the recoil kit removed head drilled and tapped then inserted coil with lock-tight per instruction installed plug tightened up next day I took off and engine ran great and plug stayed in could only do one flight and that was a fright because the wind was from the west which created strong turbulence on our runway from the hill will fly again Friday probably three or four if it makes it past two that will be a record. i did find that the metal in this engine is very soft . if this does not work i will see if i can tap for a larger spark plug if that does not work i will order a different engine for my ultimate

karolh

I really hope that the coil insert solves your plug coming loose problem. The Stinger engines seem to perform quite well but based on the issues you and others are experiencing with them I will hold off purchasing one until hopefully RCGF can resolve the seemingly teething problems they are having, as I still have a bad taste in my mouth from my Mintor 22 experience.

RCPILOT99

OK now have 10 flights on the stinger 20 with the recoil kit for the spark plug in the engine no problems and the engine is running smoothly and strong. have not tried the 17x6 prop yet but will this Friday mainly because the guys think i am a little noisey.
the muffler did not stay on with the permatex so i used locktight on the screws now is is staying on. all happy for now. June 2 2021

RCPILOT99

changed the prop to 17x6 will see how that goes monday june 7.

max1998

My Feedback: (23)

I have been running a VVRC RCGF 40 twin with the 1/4 plugs for a few years now, put about 7 gallons through it and had zero plug issues. I have changed the plugs once and no issues removing or installing. They make the motor much narrower,

it will fit inside cowls that the same motor with CM6 plugs would not. I really like them.

tdenbrock

The easiest fix to your plug and muffler coming loose is to safety wire them. I had the same problem with another engine so I safety wired them and not another issue

karolh

RCPilot 99 used a suitably sized recoil kit which solved his plug coming loose during flight problem.

Truckracer

My Feedback: (19)

Karolh, I’ve been flying my Stinger 40 twin all season (it uses the same cylinders as the 20 side exhaust) with zero issues. Its a real sweetheart of an engine. I was worried about the slightly loose plug threads put it has proven to be a complete non-issue, at least so far. If it ever becomes an issue, I will certainly use one of the available thread inserts. I don’t care for the small plugs but so far I think I can live with them. I would much prefer they were CM-6 plugs.

karolh

How did the 17x6 prop perform ?