Starting a G-Mark .03

Below are my last notes on the engine in the other G-mark thread, I have not touched it since then...

Surfer_kris wrote:It is an odd engine, don't know what to make of it.

Mine runs strong now, without the muffler I'm seeing around 21700rpm on the cox 4.5x2 prop and 10% nitro, but the throttle is pretty useless...

Perhaps it is all the SPI and the fact that the carb has no low end correction. It also runs hot to the touch but doesn't sag and the needle is not very sencitive (at a constant throttle setting). I tried shiming both the head and below the cylinder (head shims for the cox .049 are a nice fit) but it doesn't seem to help with the temperature or the throttling.

thanks friend!

How far exactly could the pressurizer be placed?
what internal diameter should the pressurizer have?
From already thank you very much!

Thanks Surfer_kris!
What proportions of fuel would be ideal for the engine?
I am using in the soften R20 / N8 / rest Metanol

1/2A Nut wrote:
The engine runs hot and needs 22% all castor and high nitro.
This is a good engine for winter time.

Brad, I'm using 20% castor, you indicate 22%, I'm in trouble?
I can adjust to 22%, but the manual does not indicate percentage of oil

Happy to help you my friend!
How much rpm are you getting right now????

Drill and tap where I indicated you want 1/2A size pressure nipple so around 1mm diameter 2.5mm threaded tap.
Not in trouble with 20% castor you have already noted by now just how hot this engine gets;
18 to 24% castor is the range. Higher % castor would be helpful so you don't have to run it so rich in
order to hold a good top end NV setting. More castor in this case will allow more rpm - that is the trick!

work to work Brad!
Here there are no pressurizers, so I have to manufacture it ... then step by step ...

Ready!
I have started, but I find that I should study the carburation, since the engine stops not wanting to regulate ... anyway, it is 1:18 am and my neighbors are sleeping ... time not to disturb .... tomorrow I will continue with the tests!

Surfer_kris wrote:Below are my last notes on the engine in the other G-mark thread, I have not touched it since then...

Surfer_kris wrote:It is an odd engine, don't know what to make of it.

Mine runs strong now, without the muffler I'm seeing around 21700rpm on the cox 4.5x2 prop and 10% nitro, but the throttle is pretty useless...

Perhaps it is all the SPI and the fact that the carb has no low end correction. It also runs hot to the touch but doesn't sag and the needle is not very sencitive (at a constant throttle setting). I tried shiming both the head and below the cylinder (head shims for the cox .049 are a nice fit) but it doesn't seem to help with the temperature or the throttling.

This comment is very interesting, I can interpret that you do not find a reliable gear in the engine, that is to say a couple ... I hope to discover that my engine is working well, I will be sharing my driving experiences with you.

They do not exist or at least I have not found good videos of this engine, showing its progress in high, medium and low ... I will make my experience ...

Good work Mauricio!  

First test vid it idles just fine ....



Published on Feb 6, 2016
G-Mark  .030 /Cox 4.5x2 /17.72k / 34mph / 5.64oz Thrust

Second test vid open exhaust:



Published on Jan 20, 2018
G-Mark .030 stock prop 115Mx50M 17,280rpm
Engine has  SPI  removed muffler / rare stock prop: 115M x 50M  / 4.53x1.97
Static 17,280 Best Peak / 5.7oz thrust / .062hp / 46.3W / 32mph

3rd test did not record per the pressure tap the rpm came up more as previously stated.
The engine does take some time to break in which will help it run cooler to compensate.
All we can do is use a good fuel mix with high nitro to help the idle and keep good pressure
so fuel starvation never occurs if it does the engine sags fast. Kris made a good backplate
which should help it cool better it really needs a aluminum carb body too will have a better
seal to the carb as the stock setup is not so great. RC carb gets loose over time as I have
experienced. Air bleed hole may help it some too. The turbo plug adaptation is nice, 2 extra
fins would help it cool better.

Friends, I was experimenting with the engine and I checked that it did not work perfectly, so I started thinking about making some modifications and also sealing the engine to avoid leaks!
Here are the photos and details:

Engine part:



checking that the plastic part is seamless:

I have placed glue to prevent leakage in the crankcase:


The motor brings a hole in the exhaust chamber, therefore to avoid pressure leakage, insert a tin plug:

A: paper joints, to avoid leaks.
B: piece of neoprene to prevent leakage.
C: place steel thrust washer.
There you can also see the tin plug.


again the engine ready to restart the tests:

Here are the first results!
It seems that it has all intentions to work well!
The reliable minimum gear range exceeds 6000 rpm.

Mauricio!

I am glad you are happy with it so far, just needs some break in time and it won't
over heat and sag down as much when you gun the throttle wide open. With good
oil flow to the engine it should last many years. You can take the head clearance
down a bit after you break it in for a bit more rpm.

Interesting info shared by all, thanks. I didn't know the G-Mark .03 had SPI. It now is a special and rarer engine because you don't see many these days. I heard that when they were being imported by I think Bill Cannon of Cannon who manufactured small RC systems, there was a large shipment of engines that somehow became waterlogged with salt water at sea, something happened to its container. Almost all the engines were heavily rusted and non-usable. Thus ended the G-Mark importation. Now they are a part of history.

I found more of my data:
Tested with the Carbon HQ 4x4.5 prop
Static 16,957 / 3.4oz thrust / .040hp / 30w / 72 mph

Stock prop increased rpm as expected with the pressure tap:
Static 17,764 rpm / Idle was excellent at 4,530.7 best read with the new tacho
6oz thrust / 67 mph / per calc: .067hp / 50w



Best idle with stock prop:

Thank you very much for the information Brad! ... 4600 rpm !!! is something great !! ... I can not get to it for the moment .... below 6000, my engine is planted, maybe it's talk time ....

Well ... I was thinking about giving the G-Mark a chance, so here is the Pocket Rocket brother ... let's see what goes on !!!

Nice project Mauricio,

Yes just fly the engine it will get up to par over time and the idle will get better.
My engine has had more run time is why it hit 4,530.7rpm the laser tach is very accurate.
I only break it out when I need a good solid number.

Look at this power output!  

wow that's explosive friend !!!