hsukaria

You must be using a unique spinner, cuz I have my stock setup with an aluminum spinner and an Master Airscrew 11x6 with no problems.

BTW, I flew the GX-40 6 flights today at approx.10 minutes each. It was quite rough at first, but got better each flight. It would not idle in flight, but on the bench at first. But each subsequent flight it would idle longer during landing. I leaned the LSN a bit before the last flight to help the idle, but during the flight, the back piece of the muffler fell of and the engine quit. I was not able to find the piece out in the field. I will steal the piece out of the AX-40 and put a mousse can on the AX-40 muffler instead.

I consider this engine fully operational and as powerful as my Super Tigre G51 that I had on the Escapade before installing the GX-40.

edit: I was using about 3-4 ounces for each 10 minute flight. Not bad!!! I will now wait for the next bigger NV engines gasser

Charley

My Feedback: (2)

Obviously, you aren't using the spinner that came with the Escapade. I'm not happy with a stud that isn't fully bottomed in the crank nor am I happy if the the stud doesn't protrude through the prop nut at least two threads after the nut is tightened. I know that many GX-40 users are running it with the stud just partially screwed into the crank but I don't like that idea. I want the load distributed over all the provided threads.

I had a ST 51 & a .56, both powerful and fuel hogs. I still have a .60 & a .40 ABC, all Saturno engines.

How many RPM is your GX-40 turning the APC 11x6?

CR

hsukaria

I did not check the rpm's unfortunately, it was changing every flight as the engine was breaking in. I will do a more thorough check by next week when I have a new mix done with more tuning and break-in time.

By the way, the reason the back piece of the muffler fell out during flight wasn't because it came loose. It was because the rod that attaches both muffler pieces broke. I don't know why it broke, maybe gas vibration is more than glow? My glow AX-40 muffler lasted me 8 years with no issues ever.

Charley

My Feedback: (2)

I imagine the nut at the back of the muffler loosened up in flight & let the rod vibrate itself to destruction. Mine is quite tight; have to ck it now and then.
My GX-40 is turning the APC 11x6 right at 10K on the test stand. I'm at 1750' MSL. Using 92 octane gas that's up to 20% ethanol, mixed with Beanol.

CR

hsukaria

I shoulda checked the muffler nut, but since I never had to deal with it on the AX-40, I didn't think about it. Lesson learned, I guess.

aspeed

As the muffler warms up, it expands more than the steel bolt. If it is too tight, it can stretch the bolt, which could maybe break it. I think the gas muffler may get a bit hotter than glow. Just a thought. Maybe not quite as tight, with a locknut is the trick?

hsukaria

Maybe the heat is a bigger factor than vibes. I can't tell if the GX produces more vibes from the construction than the AX, but you are getting more output for the same displacement. So, to me that means a higher pressure pulse from ignition than the glow at a lower rpms.

But the muffler does feel hotter on the gas.

I have always been a fan of one-piece mufflers, like the MACs. No fussing required and is lightweight. If this problem persists, I know how to solve it long-term.

Charley

My Feedback: (2)

Yep, that's the other side of the coin. It looks like a long stud that threads into the front tip of the muffler, has a nut on the other end. If the stud is stretched to its max eIasticity it could break if stretched much beyond that point by the expansion of the muffler. I considered that but didn't want to belabor the point.

CR

Charley

My Feedback: (2)

No doubt that the gasser runs hotter than the glow version. I ran a Saito 1.50 on gas with ignition all one summer. It definitely ran hotter on gas than glow. Does the stud (bolt) look like it "necked down" at the break point? That's tip-off to stretch breakage.

CR

Billsky

My Feedback: (37)

I have three GX-40's for sale at the below link. I have given up trying to get them to run reliable. Selling for $85.00 each.

http://www.rcgroups.com/forums/showthread.php?t=2482705

hsukaria

Sorry to hear that.

Charley

My Feedback: (2)

I've concluded that there's nothing basically wrong with my engine. I's air leaks in the fuel system that are the enemy.

CR

hsukaria

Yep, I've had plenty of those issues, including regular glow engines. I did have a problem with my fuel tank last week flying the GX-40 because the fuel tube inside the tank was not flexible enough to keep up with the planes roll rate and consequently, it would cause the engine to lean out in a turn. I have since switched the tube from Tygon (yellow) to Viton (black). Does anybody know if there is a problem with using Viton inside the fuel tank?

Charley

My Feedback: (2)

I've been looking for Viton tubing in small quantities. It's used in automotive fuel tanks. Also the needles in needle-&-seat valves in carburetors have Viton tips. Where did you get it? I can't find it locally.

CR

erieqc

McMaster Carr

the pope

I have got my tank line from the lawnmower shop . Its a lot more flexible for use in small tanks than the viton and tygon tubing . Cost me about $3 per 4'' , very expensive here in aus but if u use it just inside the tank than thats ok . Cheers the pope

hsukaria

I got it a long time ago from the local hobby store. But I don't remember the brand though. I think they still stock it.

Charley

My Feedback: (2)

My GX-40 stops after running for a couple of minutes. The throttle setting doesn't seem to matter. It acts like it has gone lean and stops for lack of fuel. It has to be primed and the HS needle richened in order to restart it. It will do this even if the battery is connected to the glow plug. After it cools off it will restart and run normally for a minute or so, then it stops. I can't find evidence of any air leaks or oil oozing from any mating surfaces. Sometimes, after the engine stops, air bubbles appear in the fuel hose; coming out of the fuel fitting. The O-rings on the high speed needle and the carb base are new. I have tried a new glow plug with the same results.


The fuel tank has been re-plumbed and all hose connections internally and externally have been clamped. The fuel is new 92 octane gasoline mixed with Benol. The gas contains an unknown percentage of ethanol. I don't know how many head shims are installed. I'm at 1700 feet altitude, humidity usually over 50%.


I'm at my wit's end. Any hints?


CR

DaOldGuy

Charley... you are describing what I have seen since I got this thing. I yanked the NV off my Plank and I am looking at the OS GGT 10 as a next purchase. This silly motor is as moody as both of my ex wife's combined with a few shots of whiskey.

I know Bill has sorta given up his quest on the 2 that he has as well.

Charley

My Feedback: (2)

Dmitri, from NV, says he thinks my engine is overheating. He suggests adding a head shim. I have some head shims & a new gasket so I'll do it this morning & see what happens.

CR

aspeed

Sounds like overheating to me as well. I had a couple of motors that did that, and solved it by polishing the crank in front of the rear bearing. The bottom of the case was getting too hot to touch. It was an older Taiwan Magnum Pro .28 that was the worst offender. Could not do nothing after even a short run, no compression, fuel boiling.... Cooled of, and compression came back and life was good again. Don't remove too much material, or oil will spit out the front of course.

DaOldGuy

I got a slightly different response.
"Hi Ron,

Sorry to hear about the problem. Is is impossible to give you advice as
there are so many variables. You can always replace a head adaptor and
use the engine with nitro - it should work fine with nitro.

Regards,

Dmitry

We have been watching the temps on this one, no real issue and it seems the head turns a off color if they get hot, I have no signs of that.

aspeed

Is the bottom of the case hot? Good to know nitro will work. Maybe everyone can ship their junk ones to me. :-)

DaOldGuy

Shipping to Canada is a bit too pricey.

aspeed

I can pay, and even afford the USPS, I just have to weasel someone out of their Norvels!!!!!