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Engine basics => Engine set up tips => Topic started by: Steven Kientz on June 01, 2011, 12:09:59 PM
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I have a Twister with a GMS .32. Last year the engine had the rc carb on it, couldn't keep it running for more than a minute. Over the winter I decided to put a venturi on it to see if that solved the problem. I found out today it didn't. Here is the setup Gms .32, evo venturi(smallest) Gms remote nva, os spraybar. I'm running a Brodak tank centered on the engine case. It doesn't seem to matter whether its on muffler pressure or not. I'm going to replace the GMS with an Os 40fp, because its my only plane set up for a stooge, but I'd like to get this setup to work. I have considered replacing the Gms rnva with a Brodak nva. It will run in a hard 2 cycle, then I back the needle off, to about 75%(rpm), by the time you get to the handle the RPMs are down, half way back to the plane it's stopped.
Does this sound like an air leak? Thought I ask for advice before I tear into this.
Thanks
Steve
Ps I'm running Byron 10% (20% oil i think)
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how much run time do you have on the motor? it could also be something goofy in the tank plumbing, a crack in the pickup tube, or some such, try a different tank perhaps
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Are there any bubbles at all in the fuel line? If so, there is a problem there. It could be a fuel quality problem, too.
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I have seen this happen also, turned out to be a bad glow plug, might try changing it.. n~
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My GMS 76 would stop randomly when I put a small muffler on it. Went back to the big muffler and everything has been fine since.
Also consider air leaks at the remove NVA and the front bearing.... GMS favourites.
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Try a different fuel with at least 20%-23% synthetic/castor oil. Byron fuel with an unknown oil quantity is asking for trouble. Sounds like you're over heating from low oil content.
Bob
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Try a different fuel with at least 20%-23% synthetic/castor oil. Byron fuel with an unknown oil quantity is asking for trouble. Sounds like you're over heating from low oil content.
I think trying a different fuel is a good idea, but I ran Byron fuel for quite a while, and tested the content, and the 20% oil fuel was about 20%, and the 16% oil fuel was 16%, at least to the accuracy of my test. It also ran *much* smoother than any other fuel, and also was about the only fuel that wouldn't give me the occasional flame-out on several types of engines. It was weak for its stated nitro content and it was rather expensive, but otherwise, it worked very well for me.
Brett
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I have some Brodak "all" castor. I could " bum " some fuel at the field. My mentor adds castor to his Rc fuel.
I think I'll ditch the Rnva, replace with the Brodak and change the glowplug and change tanks. This engine has very little time on it.
I have a GMS .25 that was on my Skyray(RIP), but my Twister is "heavy" thats why I'm going with the OS40 fp.
Thanks
Steve
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May have found the issue. The fuel line from the tank to the rnva had a hole in it. Still swapped the rnva for a brodak nva. Hope to at least run the engine at the field today, if the weather cooperates.
Steve
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Ran the engine in the driveway, ran fine with one exception. What is the trick to keeping a needle setting when using the Brodak nva? It wanted to wander, even after tightening. Would a small piece of fuel tubing between the jam nuts keep it from moving?
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If this is like a ST needle, with the jamb nut on the end then carefully snugging the jamb down some more shoul provide enough friction ti keep it in place. If everything elae is ok you should'nt need anything to keep it in place.
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On this last point steve, I had a similar problem with my nva nuts working loose. I solved the issue by wrapping thin copper wire (the type used for making Salmon flies) between the nut and the venturi. The advantage of using this instead of a small copper washer is that you can add as much as you need to get the right thickness, and it squashes down easier too. Worked for me..
Phil
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An FYI: I have gone to using the PA NVAs because they have the nylon (or something! LOL!!) insert in the "locking nut". This eliminates any air leaks and eliminates the needle working loose. Finger tight, or a touch more, is all that is needed to keep the needle in place. They really ARE the best NVAs for our use.
Big Bear
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I agree with Big Bear, the better quality NVA REALLY makes a difference! Just re-fitted two troublesome engines with Randy's NVA...problem solved! Yeah, a little more $$, but lots less hassle and frustration.