Just a note here on the head gaskets. I have not blown one yet, even after changing it out 3 times over the last 1 1/2 years and running 4 different types of gas and too many prop sizes to count. That being said, it is IMPORTANT to tighten the head correctly. For those who do not have expereince with the regular 25 and 40 motors, you need to FIRST tighten the head down with the head tool. Then tighten down the 3 allen srews to clamp it in place and keep it from loosening. If you try to clamp it down with just the allen screws without first getting the head down tight with the tool you will simply warp the head and blow gaskets every time.

Somebody should tell the factory that and tell them to wash the engines out properly while there at it . Maybe they should supply the head removal tool with the engine if there not going to do it properly at the factory !!! To expect the end user to do it without a heads up is B.S. Cheers the pope

The heads have been tight on all of my many NV engines and I just pull the back plate to check for debris. If you plan on pulling the head you should order the tool as many people have done. I bought the tool back when I got my first 25.

I did order the tool with my engine . I just didn't think I would need it so soon . I cant understand why they couldn't have machined the head a little more and used a more substantial gasket . Mine is now running ok and luckily I checked mine for debris before the 1st start up as the amount of shavings was quite substantial , even bronze conrod bushing slivers were in there .I truly don't understand that as the assembler MUST know there there and just not give a crap . Hopefully things have changed at the factory as I have every intension of getting another . I'm not just having a whinge for the sake of it , I want a good product even better which they could do with a little more effort . I'm glad you haven't had any issues with any of yours and as this is my only norvel I must be just unlucky !!! Cheers the pope

I have an AX40, which apparently is near identical to the GX40, and did some careful measuring of various parameters which I'll list here in case anyone wants to compare them to the GX40.
Exhaust opens 77 BBDC
Transfers open 60 BBDC
Boost ports (2 of) open 53 BBDC
Inlet port opens 40ABDC
Inlet port closes 44ATDC

Squish clearance (with .2mm shim) .45mm (.018")
Combustion chamber volume (including plug cavity) .49cc
Compression ratio 11.1:1

The photo shows the tool I use on the head button using three 4mm bolts although a piece of wood would work just as well. Strangely, the manual for the AX says that short 4mm screws can be used if desired to more securely hold the head button but I've never found them to be necessary.

Downunder,
The GX needs the screws as it has higher combustion pressures and temps. Personally I like the head setup on their motors and wish more manufacturers did the same as it is easy to adjust compression as well as cleaning off the carbon when necessary.

I was wondering if the threaded head part used a standard thread size or not. I was thinking if there was a die one could buy to thread a aluminum bar, one could make a more tall and deep head for a RC helicoper or something maybe.

You could make a deep-finned head and anodize it purple, the "baddest" color possible.:cool:

Not true. Methanol releases far more heat energy than petrol which is why methanol fueled engines are more powerful. Cylinder head temps may be a little higher on the GX because they don't have the advantage of the internal cooling that methanol gives.

As for the head setup, I agree it's much neater/better than the usual one piece head but a very similar arrangement is used by the Cox engines from 1950 onwards. I have a couple of engines (Rossi 45 and Enya 61) that also use a head button but their clamp ring is held by the normal screws like a one piece head.

I would guess that the thread is a standard metric extra fine thread. It may be hard to find at many places, but may be available. www.victornet.com/tools/Special-Thread-Taps/199.html was recommended on one of these forums and seems to have a lot of sizes. I don't have a motor to check, yet. As downunder was saying, you could eliminate the thread and just make a button type head and clamp ring with screws. It would be easier and have one less place to leak. There is the thread to leak, the taper on the plug (not likely) and the 4 screws with washer that could cause problems.

I have one of these and I'm selling it for $100+ whatever it cost for me to ship it to you,.. including a spare plug, half a quart of Benol, a head tool, a DUBRO spinner nut and a longer prop thread shaft. I have mine running OK, but it requires a bit more fiddling that I care to partake in plus I have it in a high-wing plane and the exhaust (which is a bit messy) points right at the wing (Mine is the tilt-down muffler.) If anyone's interested I can be reached at: psgugrad @ yahoo . com

email sent...

Bill S.

Remember that the muffler exhaust tip can be rotated.

I simply stuck one of those silicon exhaust extensions on my muffler to help keep the oil off the plane. No big deal. Since the gasoline burns in the engine the silcon tubes stay on quite well. A short length of small heater hose might work too, but I haven't tried it, I wasn't sure if the heat would affect the heater hose or not.

Hey guys,
Found another trick on these. I swapped out the stock high speed needle with the extended one they make for the glow 40. It's a little longer, thinner, and has a more gradual taper. Works great! Much smoother adjustment on the high speed and for some reason I picked up about 800rpm on the idle. Just had to adjust it down on the radio, no low speed needle adjustment needed. Not sure why, maybe it atomizes better running along the long needle. Mid range and transitions were fine as well.

I replaced the standard HSN with the extended version on my AX-40 few months ago because of cowling constraints. I thought it would simply be an added wire to the existing HSN, but as you said, it is a whole new design with improved, more gradual mixture control.

This may have been mentioned before in this or another thread.
When I did a Google search for NVENGINES , there is a message saying"This site may be hacked".
I am thinking of ordering a GX40 but I am worried about the security of the site.
Anyone have any comments about this, or good/bad experience?

Howdy , I got my engine some time back and all was OK . Cant speak for now though ! Cheers the pope

Well that is possible. But what I did was use Paypal to buy what I needed, so that my credit card information was protected via Paypal.
I took a look at the web site but my anti-virus software didn't trigger anything. But that might not mean anything though.
I sent a email to the owner to see if they know anything about it.

Thanks-I will wait till you get their reply.
Has anyone been using Castrol M for these engines?
I have 5 litres that I use for diesels so hope I can use it for the gx40 as well.

Hi there burfman here is the reply from castrol when i asked that very same question .
Hi Michael,

Thank you for the follow-up and the background information provided below.

Unfortunately, the ‘Castrol M’ is not compatible and won’t mix properly with petrol (including premium unleaded petrols).


Regards,

Product Applications & Projects
Castrol Australia
Straight from the horses mouth , I use Klotz which we can get here in Aus. Cheers the pope

NV Engines came back and responded to my Email I sent just a little while ago too.
It is nice to get such a fast response from a vendor.

It seems that the site is OK then, thanks.

Pope
Could you please tell me your source for the Klotz oil here in Oz?
I have a Castrol data sheet which seems to say that Castrol M can be used in 2stroke petroil fuels-a bit confusing!
Castrol M
Castrol M is a castor-based oil which has been developed specifically
for use when methanol-based fuel is used.
These two materials are soluble and, as such, will not separate in use.
However, for other fuels refer to the Oil/Fuel Selection Chart.
Castrol M may be used successfully as the lubricant for methanolfuelled
2-strokes, including miniature engines used for model vehicles,
aircraft and boats.
NOTE: Castrol M is not recommended or suitable for 4-stroke
engines. Companion products, Castrol Racing Oil 60, R 30, R 40 and
GP50 are our recommendations for use with methanol.
Two-Stroke Applications
All three of these products can be used as 2-stroke petrol/oil mixtures,
but it is imperative that the user check the compatibility and stability of
the lubricant and the fuel.
Note: Due to the non-detergent nature of Castrol M and R’s, engine
internals will not be as clean as they would be if Castrol A747,
TTS or Super TT were used.

hey there burf, I think hobby headquaters are the importer so any hobby shop that deals with them can help u out . I live here in gods own country S.A. and just happen to walk into a L.H.S. and there was a 1. L bottle on the shelf . I also ordered a 2.5L. bottle and had it in about a week so while it took me awhile to source it once i new who supplied it it was easy . Klotz is what everyone seems to be using and is whats recomended so its a no brainer even if its a bit dearer as u dont use much and u can save the castrol M for your other stuff . cheers the pope