the pope

Funny about that , the same thing happened to mine . I was having trouble trying to start mine with a chicken stick and it gave one pop and then bubbles were coming from the head button area . Luckily I bought the head removal tool with the engine and there it was with a 1/4 of the gasket gone . This must be a common problem or is going to be as the gasket is pretty flimsy . Surely could have machined the sealing area a bit more and used a thicker gasket .Anyway I bought some more and norvel sent me some as well and with their prop nut so hopefully with a starter things might be on the up and up . Cheers

the pope

Funny about that , the same thing happened to mine . I was having trouble trying to start mine with a chicken stick and it gave one pop and then bubbles were coming from the head button area . Luckily I bought the head removal tool with the engine and there it was with a 1/4 of the gasket gone . This must be a common problem or is going to be as the gasket is pretty flimsy . Surely could have machined the sealing area a bit more and used a thicker gasket .Anyway I bought some more and norvel sent me some as well and with their prop nut so hopefully with a starter things might be on the up and up . Cheers

hsukaria

The head gasket issue must be a GX thing, I never had that happen on my AX. Must be the higher compression?

hllywdb

It is due to higher compression. That being said, as long as I tighten the head down good, then tighten the three allen screws, I have yet to have a gasket fail on a GX. You do have to be careful not to flood it. But if I did flood it an hydro lock, I would rather blow a gasket than bend a rod

earlwb

Aww heck, now you guys tell me. I was happily doing my thing in ignorant bliss with my NV Engines GX40 and it hasn't blown a head gasket yet.  So knock on wood, I suppose it is going to blow the gasket now.
darn.

the pope

Fired my baby up for the 1st time today . Did nothing different than the 1st time so who knows wats up wit dat !!!!!! Anyway used the starter and fired up no worries , a few fuel leaks around the needle valve but all up more than happy so far . Ran 1x6oz tank which lasted ages and got 11800 at the end but wasn't pushing it too hard just trying to go by the instructions . Its more than ready to be mounted in a plane fore the rest of a breakin if its even needed . All I can say is bring on some different size gassers as Im ready , just don't tell the misses. Cheers the pope

Ernie Misner

Are you guys checkin' the head for tightness after initial break in?

schulze rocks

Hi Ernie,
My gasket did not blow, it was torn from the factory. This will happen if the combustion chamber button turns with the locking collar whilst tensioning. The stock gasket is quite delicate and easily damaged. I did not have this trouble with the aluminium gasket that I made and yes when the initial break in was finished I checked the tension of all the screws.

Cheers BJ

the pope

yeh I agree with the rock . Way too flimsy , probably fine if you get pass the breakin period . If theres not much care taken in the assembly process you could be otta luck , I strongly suggest removing the backplate and rinsing out the engine of debris as well . Mine had quite a bit of stuff including slivers of bronze bushing materials . Having said that after actually running mine for the 1st time today Im impressed . Cheers the pope

Ernie Misner

Ahhh, so sounds like the head screws on huh? Kinda wipes out the gasket in the process sometimes. Maybe put a little oil on the top side before tightening?

davidhand

A long time ago when I was fooling with diesel engines when I mixed castor oil with kerosine it didn't blend at all. Then when ether was added it all went into solution nicely. Also could synthetic oil be used as the lubricant?

earlwb

The engine runs quite hot at higher temperatures than other engines do, so synthetic oils cannot be used as the oils break down at higher temperatrues where castor oil still works. NV-Engines says to use Klotz Benol oil with the engine. You could use other castor oil if you cannot get Klotz, but it takes longer to get it to mix with the gasoline.

Edwin

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sledge_78

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Earlwb, I have been running my .40GX for several weeks and one characteristic I see is that after about 4 minutes of flight it begins to run erratic. It will eventually quit resulting in the usual dead stick. Since I am in Arizona with temps around 100 degrees at flight time perhaps is it running too hot. I will try and richen the mixture a bit to see if it helps. It also seems that the needle settings (High speed) is very sensitive, one click makes a difference. Any thoughts? Engine has over 2 hours on it. Sledge_78

hllywdb

Hi Sledge,
A couple of questions....
Are you running the inline filter in the fuel line?
What size/make prop are you using?
Is it in a cowl?
What size fuel tank are you using?

Bill

earlwb

sledge_78, yeah you will need to run it a little more on the rich side. I am using a 12x4 propeller on mine as it is a 3D stunt fun fly type of plane. Thus I don't fly full throttle much.
The engine tends to lean out in the air as the fuel gets lower in the fuel tank. I have to run mine a little more rich too. But on mine I run it more rich so that the mid range throttle where I fly most of the time is not too lean.

You can try filling the fuel tank about 1/4 to 1/3 full and run and adjust the engine like that with the nose pointing up. That should do it. Then stop the engine and full up the fuel tank and you'll have a good idea as to how rich it needs to be. But if the mid range is too lean, you may have to go a little more rich on the needle valve too.

When it is really hot, the engines loose a lot of power and tend to overheat, so you may be forced to run the engines more rich to compensate. I remember having a lot of heat sag in Arizona in the summer too. We get it here on those extra hot calm days in August out here too.

hllywdb

Just flew mine today, August in Florida, in a cowl. Full flight with no problems. again, some more info would help. Even with a large 9oz tank mine doesn't change mixture throughout the flight. I use a heavy clunk to keep the line moving free.

sledge_78

My Feedback: (24)

earlwb, I have a 10 ounce tank, 11/6 APC prop, dubro fuel filter, engine upright no cowl. Today, I richened up the needle about 2-3 clicks. I fly at 1/2 throttle but still had erratic behavior after 3 minutes. I landed, waited about 1/2 hour and added another two clicks to richen the mixture. I started the engine and while running on the starting table it quit abruptly. I now have no compression and a 'clicking sound when I rotate the crankshaft. My guess is broken connecting rod. I have been so careful following the directions with this engine that I find it hard to believe this could happen. Gerry

hllywdb

Hi Gerry,
A bent connecting rod would explain some of this. I was going to suggest NOT filling the tank after it quit, just letting it cool down some, then restart and see if it was a tank/line issue. Usually a bent conrod comes from starting when flooded.

sledge_78

My Feedback: (24)

Well, I finally disassembled the GX .40 to view the cause of my loss of compression. My thinking the Conn rod was broken was wrong. Everything inside looks good. It appears the head gasket has blown. I am a little confused about the replacement of the head gasket. Are there twp(2) gaskets , a copper one and another one made from gasket material? Also, any hints on replacing the gaskets and tightening the head. I have just ordered the head removal tool. Gerry

hllywdb

Hi Gerry,
Make sure that both surfaces are clean. I put the copper gasket in first (it is not a gasket but a shim) followed by the sealing gasket. Then, make sure the 3 set screws are loosened up or removed, lubricate the threads of the head cover and a few drops on the surface (so it doesn't bind on the gasket). Tighten the head down using the head tool (not too tight), then tighten the 3 set screws, which lock the head down in place.

By the way, once the engine is broken in, you can remove the copper shim, especially if you are using 93 octane fuel. With over 2 hours running on yours, I would leave the shim out. Then you can sort out the fuel issue.

sledge_78

My Feedback: (24)

Hllywdb, Thanks for the info. Actually, I'm using 91 octane fuel, that's what is available here. So, you are saying to place the copper shim in first, then the gasket on top of it, and tighten down the head. Btw, NV has said the piston and cylinder assembly which includes the conn rod is NOT covered in their warranty. Fortunately I don't need them but I thought it was strange they are not covered. Gerry

hllywdb

Hi Gerry,
Unless it is a maunfacturing issue, I don't think they cover them on the gas motors as almost all bent rods are from flooding and premature wear on the cylinder/piston is only from lean runs. Same reason most chain saws won't cover a lean run. That being said, as long as you take care of them they wear like iron and will give years of great service as many have commented.

I would still lose the shim on your motor, it it's a problem, you can always add it back in. But yes, you need to seal the area closest to the head. If you put the gasket down first, then it would most likely leak a bit between the shim and the head due to the high compression on these motors.

While this is not quoting the factory here, I made sure my head was spotlessly clean (I polished it with 1500 grit on a plate of glass) and ran with no gasket for almost a year and it ran fantastic. So disgarding the shim is most likely not going to give you any issues with over compressing. Getting the head to seal without a gasket kind of comes down to how the threads line up as you tighten it down. I have been running a gasket lately, just because it's easier.

By the way, the gas engines are much easier to hydrolock, so if you do have an "oops", it's much nicer to blow a gasket than replace a rod

sledge_78

My Feedback: (24)

Hllwdb, The good folks at NV (Dmitry) has indicated my head tool has been shipped, so I should receive it in a few days. The interesting factor when my head gasket blew, the engine had been running for about 40 seconds. Just as I revved it up the failure occurred. I will follow your suggestion and leave out the shim and see how things go. Thanks for the help. Gerry

geeter

My Feedback: (110)

i can't believe the engine uses so much oil. the same as glo. by the time you buy benol and gas you have spent as much as glo fuel, even though it lasts longer. there would have to be alot more testing done before i bought one. but thats just me. thanks for all the info your putting out on this new type gas engine............RON