My guess would be a prototype (test set-up) solenoid driver, but I am sure Xanaphyst can tell you exactly.

Its nothing more than a copy of the hard work already put in by other people. The only difference in my setup is I had to change out some of the programming
code because I used a different environmental sensor for pressure and temperature. I am however working on a small PCB design that will very compactly put
all the parts together neatly and offer a very simple building and wiring solution. That PCB will still use the already proven design from Mr. "raleighcopter"

https://github.com/raleighcopter/my-mixture-controller



I'm planning for the future to develop my own version using a different controller that has all the components integrated into a single board. The board for this purpose is
a:

Adafruit ESP32-S3 TFT Feather - 4MB Flash, 2MB PSRAM, STEMMA QT

Adafruit Feather board with initial programming for the BME280 sensor on the I2C interface. The wired sensor board at the bottom will not exist in the final version as the sensor will be embedded.

This project while ongoing is not priority at this moment though.

Priority 1. Obtain or build solinoid housing to complete my injection solinoid system for my Saito 72

Priority 2. Build the newly developed air bleed design and try it on my Super Tigre 2300. However this MIGHT be just an experiment as Brutus says the 2300 can be tuned for gas just fine with the stock carb. My talent for that is much lower than Brutus so in the end maybe I’ll use my rough tuning combined with a small adjustment of an air bleed curve

https://cimg4.ibsrv.net/gimg/www.rcu...60f379592.jpeg

Thanks for all your responses and explanations. I know that asking questions without reading the previous material is annoying and rude. I read most of this post a while back and just recently saw the air bleed suggestion. I don't plan on using a fuel solenoid to control the fuel supply. That's why the air bleed solution peeked my interest again. It may not be as good as having a fuel solenoid but it seems like a workable solution. I'm going to ask a question that probably has been answered previously in this thread or other threads. I hope you don't mind. I think that if you add a CDI system and spark plug to a nitro engine and then run gasoline through it with the proper oil ratio that your engine should run OK at idle and at full throttle but the mid range is not good and if you don't slowly open the throttle you risk having the engine stop running because of an overly rich fuel mixture. Is that correct? Does that apply to most nitro engines even the smaller ones?

My other question is can the BME280 sensor be incorporated into an air bleed system to correct for atmospheric conditions? I think I need to go back and read the posts regarding the BME280 sensor and how to program/incorporate it into the process. Do you know what post numbers I should begin to look at? If not, I will spend the time to look for it. Are there any other threads I should be reading to help me convert nitro engines to gas? I appreciate your patience with me. I seem to be suggesting things that have already been thought of and discussed.

Don't worry about asking questions again. As you can see this thread has grown to almost "unreadable" proportions. So at least me, I'll give quite a bit leeway for "repeat questions"...

To answer them:
1: Yes, ALL engines do that, on account of a number of factors, mainly the widely differing fuel/air ratio (glow fuel is approx 1:6, gasoline is 1:14) leading to the fuel metering of a carb designed for Methanol to open too rapidly when throttle is opened.
Even if you set proper idle mixture and proper full speed mixture, the carb will, coming off idle, admit too much fuel and the engine becomes extremely rich extremely quick.
Another major factor is that with glow ignition, the ignition timing is depending on fuel/air ratio, meaning that a rapid opening of the throttle, the relatively rich mixture (to retard ignition) rapidly leans out, advancing the ignition which greatly assists in accelerating the engine. Spark ignition lacks this correlation between fuel/air ratio and ignition timing. Although they are both reciprocating piston engines, the entire principle of ignition and mixture is vastly different.

2 Short answer; nope, for reason that the airbleed principle is NOT linear

Let me try and explain, and sorry, a bit of theoretical background is needed: the BMP280 returns 2 separate values, (pressure and temperature) that can be applied to the common gas law of (p x V)/T=constant.
By simply assuming a baseline value, and applying the values to that formula, the formula returns a relative value for ^V (delta V, the change of volume relative to the baseline).
The exact values of the baseline are academic and irrelevant (this is one of those things where math and physics CAN be a bit hard to grasp) because the correction is applied from the get go, before you even tried to run the engine. It reversely "forces" the user to set a fuel curve value that, without the correction factor following from the gaslaw formula WOULD be valid for the baseline value of pressure and temperature.
In order for that to work, it is absolutely necessary, that the controlling element in this system responds linear to the correction factor.
The solenoid, in combination with a needle valve, does that. The solenoid alone does not because of inertia in the liquid, the needle valve alone ALSO does not because viscosity is not "ideal", but a needle valve setting a maximum flowrate, and the solenoid "chopping up" this flowrate, suddenly becomes a very linear responding system, because inertia is greatly reduced and can be considered not a factor of relevance, and due to the needle valve opening being constant,
Proportional Air throttle valves never are very linear due to viscosity and varying pressure differences and such. They simply aren't... To give an example of this: Start any random engine, set idle, measure RPM, take a pic of the throttle position. Set full throttle, and measure RPM. Now reduce throttle until you reach exactly 50% of max RPM and take a pic of the throttle opening. Check if the throttle lever is in the mid position. It won't be, it probably will be at best about 25% open, IF that...

3 There IS this old thread on RCGroups that still contains quite a bit of valuable info, and it dealt with the times when Raleighcopter, others, and I were still in the developmental phase, bouncing ideas back and fort.
It has been polluted by what I would call "the anti-vaxxers of model engineering", and therefore a bit mutilated, but if you take the time, at least the basics of why things are, and how we figured out what was needed, can be found there.
The "anti-vaxers" went crazy on us, things got a bit heated, moderation on RCGroups turns out to be the lamest of any forum I have ever been at, and the result was that we now find ourselves here, where moderation is as moderation should be.

That thread: Start saving big on fuel costs. Build our controller and convert to gas. - RC Groups

I really appreciate the time you took to explain that. I started to read this thread and am up to page 20. I have a lot to go. The members contributing on this thread have a greater technical knowledge than I do so at times I have difficulty following the discussions. My goal is to find a way to convert some, mainly 4 stroke nitro engines to gas. Ideally using the existing carb makes sense for simplicity. I saw in the earlier discussion some success with reducing the venturi of the carb. My main experience is converting commercial 2 stroke engines to plane engines. I have learned a lot and found that the new rotary Walbro style carbs work pretty well. some of them have limited tuning capabilities while aftermarket ones have a specific high speed needle. Some have hidden needles. Some have no needles. The Walbro rotary carbs used on the 4 stroke gas engines typically have smaller venturi. Some of them less than 10mm. I am thinking about setting up a system to be able to try different Walbo type carbs on different engines. I still like the idea of using the existing carbs with some mods like the slot alterations or using the air bleed system. I'm not looking for the highest performance from the mod. More like an engine that will not dead stick but also doesn't have the greatest performance. As stated earlier in this post, use the American way by increasing the engine size to get more thrust. Our RC club was donated a bunch of nitro engines. Only one member in our club flies nitro and it isn't me. I have volunteered to go through each of the engines to assess their present condition prior to selling them. It's time consuming and I have concluded that I will need to try and bench run the ones that look like they will actually run prior to selling them. I have about 40 4 stroke nitro engines. 20 of them being YS engines. Those engines have silicon parts that can't handle gasoline. Their design intrigues me and makes me want to try to convert one of them to gas. I will use a Magnum 91 as my first attempt to convert to gas.
I picked up that you guys had moved this thread. I'm sorry that you had to do that. I will go back to read the thread you suggested. Any suggestions to help me have success in a conversion is appreciated. I don't think I am going to go the fuel solenoid route.

I'm retired but it is amazing how little time I seem to have when it comes to hobbies. I still want to fly, I have 50 engines to go through for the club, I am married and want to stay married. My point is that it may take me a while to actually try a conversion.

On another note regarding CDI systems. I converted a green machine chainsaw engine which just happened to be a Zenoah 62cc engine to electronic ignition using the Chinese scooter CDI systems. I hand started that engine but kept running into back fires which were painful and dangerous. I was looking for a way to adjust the timing and came up with the idea of using two hall sensors. One set at TDC and the other at 28 degrees BTDC with a toggle switch in the hall sensor circuit. It works great. I start the engine on the TDC hall sensor and when it's running throw the switch and it runs on the 28 degree BTDC hall sensor. Just incase others were having similar issues. I attached a photo of my set up on the Zenoah and other test engine.
https://cimg7.ibsrv.net/gimg/www.rcu...e549edc53.jpeg
https://cimg0.ibsrv.net/gimg/www.rcu...0d1d13780.jpeg

Back in the day they made a device called Jump Start for Zenoah engines, worked very similar to your setup. Does your engine ever start and run backwards? I'm think the old style mechanical advance engines were set 5 BTDC at idle and 28 BTDC at full throttle. I still own a few D&B engines that use the REICHMUTH design ignitions that employ two hall sensors with auto advance.

The Jumpstart was something entirely different than what Paul is talking about.
In short, the Jumpstart was intended for engines with a Magneto-ignition, not an electronic one, and what it did was temporarily power the ignition from a battery instead of the Magneto,
That way the engine had an equally strong spark even when turned over.
The big issue with those magnetos was that if the flip-over was not vigourous enough, the magneto would generate insufficient power to trigger a spark, and the engine would only start if swung over really rapidly (hence many people using springstarters). The jumpstart did nothing to spark timing.

I am however not knowledgable enough about the Zenoahs to confirm whether the Magneto engines had auto-advance or not.

@ Paul: RcExl ignitions as used to convert glow engines, DO have auto-advance, as well as a separate ignition delay to facilitate starting, and should not need a dual-Hall sensor set-up.
Although theoretically possible, I still have to experience my first kickback, and I usually start by hand. The RcExl ignitions very much assist in an easy starting engine, although the general engine condition (compression etc) and fuel/air ratio (priming, preparation for start) are the two major contributing factors here.

I overlooked this part of your post, apologies.
I would stay away from converting YS engines to gasoline, for reason that they are supercharged, and depending on fuel quality, I have no idea how that would work out with knocking/detonation. And that is aside from them having silicone parts.

If you are interested in non-solenoid based modification, you might find this thread helpful (the first few pages are less interesting as that were really my very first steps in converting, and those pages dealt with the less interesting subject of selecting a plane and engine), because fhat thread describes the entire process of discovery of what works and what doesn't.

It is in Dutch, but Google Translate or other automatic translation options should help with that.
The first 25 pages approx handle the conversion of both a 2-stroke and a 4-stroke, and are giving a lot of "general information" valid for basically every engine.

Test: Methanolmotor op benzine | ModelbouwForum.nl

I appreciate all the replies. I spent most of yesterday reading the threads trying to catch up on things so I don't ask too many questions that have been already answered. Tony, To answer your question regarding if my engines sometime start backwards, the answer is yes. The Zenoah hasn't done that but I have a Stihl conversion that sometimes during idle it backfires and then starts running the other direction. I'm pretty sure that is timed near 28 degrees BTDC so I don't understand why it does that. I actually set up a 25cc Craftsman weedwacker engine to run backwards because I have in in a twin engine plane. I have another 25cc poulan engine running normally. I did that for counter rotating props. The engine running backward runs as well if not better that the other engine.

Bert, I'm aware of the rcExl ignition systems and their timeing curves. I like to try different approaches to things and finding less expensive ways to do things is a bonus to me. I have used the Chinese scooter CDI's and they supposedly have timing curves build in. I have never tried to confirm that. You can get those systems for about $15. You need to reverse the hall sensor signal to get them to work. My brother made a simple circuit to do that. They actually make reverse hall sensors but they are more difficult to mount. I recently have been using the Stirlingkit 6-16v CDI High Voltage Pulse Ignition system. That cost $20 and is really small and light. It doesn't have a timing curve but with an electric starter or hand pull start they have worked great for me. Neither the Chinese or Stirlingkit systems have a shielded ignition cable. I have never had radio interference using them as long as I have resister plugs or use the resister in the Stirlingkit system. I can attest that not having any resister in the circuit will result in lots of radio interference. I just ground the engine directly to the CDI. I converted an Echo 21cc engine and a Stihl 27 cc engine and left the pull start on the set up. I did it at first more as a novelty but now I really like the convenience of the pull start. I also use steel threaded couplers for prop hubs. They work really well and solve the problem of having to machine your own prop hub. I also make my own mufflers by hand using a small aluminum box I get from amazon. I like to increase the size of the wheel that hold that magnet for the hall sensor trigger because it makes it easier to time the engines. You will see a use a 3" cutting disc and glue a magnet to the edge of the disc. It works well. I also make my own hall sensors as you can see. It's just soldering them to old servo lead.

In regards to the YS engines I was thinking of disabling the supercharger and going the Walbro carb route and using the pressurized system to feed the Walbro. I have read they can get 6 - 9 psi in the tank from the YS engine pressure system. That should be more than enough for the Walbro. That or use the pulse from the intake tube to drive the Walbro. I will go to your suggested post to learn more about conversions without the fuel solenoid. After reading so much I realize that the contributors on this thread and others have a much greater knowledge of engines and systems than I do. I will do my best to learn more.

I'm aware that my recent posts may be high jacking the thread and I don't want to do that so please let me know if others are thinking my posts are off topic to a degree.

I have added some photos of the Echo and Stihl conversions in case others are interested in some of my methods. Both have pull starts on them.
https://cimg7.ibsrv.net/gimg/www.rcu...5bb54b5a9.jpeg
https://cimg9.ibsrv.net/gimg/www.rcu...1408aa405.jpeg
https://cimg0.ibsrv.net/gimg/www.rcu...62c1b7521.jpeg
https://cimg1.ibsrv.net/gimg/www.rcu...4804b6545.jpeg

Almost there……

https://cimg9.ibsrv.net/gimg/www.rcu...566fa13891.jpg

Layout

https://cimg8.ibsrv.net/gimg/www.rcu...81841676de.jpg
BME280 J5 will be on same side as Seeeduino with OLED J2 mounted on opposite side. Diode of original design replaced with SMD voltage regulator so you can use any voltage supply from your reciever up to 18 volts. 6 pin header J3 used for clean wiring. J4 is the jumper to GND and VIN pads on the underside of the Seeeduino.

If you read the top paragraph on the right hand column of the attachment you will find that the spark occurs just after passing TDC, it did change the the timing.
Zenoahs used a three magnet hub, in order to get the engine to start, one had to start the flip before the compression began to rise, you needed to flip the engine thru just about 150 degrees, if you flipped it with the prop on compression the the engine would just pop. Almost everyone used a spring starter and they worked great because the strater turned the prop thru 270 degrees.

I cannot comment on the timing of Zenoah, I never studied the way it works. but... No.. the spring starter worked because of the rotational speed it generated.
The magneto simply did not generate enough power to deliver a sufficiently spark by handflipping. Not much different than the smaller Magneto-Zenoahs being near impossible to flipstart but very easy on the recoil starter.

The common statement is that starting an engine is a matter of a good mixture, good compression and a spark at the right time, but it is not just that, the spark-part is more than "just a spark", it ALSO has to be strong enough.. I have fought with stubborn engines that had all three (mix, comp, spark) and refused to light because the spark, although there when taking the plug out of the cylinder, although timed right, did "not meet the requirements" and there are several things that can cause that. The most common issue in flipstarting a magneto, is that the compression raises arc-resistance, and the magneto not generating enough energy, the visible spark when testing the plug and timing in open air, simply does NOT jump under compression. Less common is alternative spark paths (cracks in the isolator for example, or moisture in the plugcap) or incorrect gapping.

1: The combustion process takes a minute bit of time before peak pressure is reached. 28 deg timing serves to let that peak pressure coincide with TDC so power is optimal. Without retard/advance curve, the ignition remaining at 28 deg BTDC, at low RPM the engine reverses because peak pressure is reached quite a bit before TDC, pushing the piston down again before it reaches TDC, effectively reversing the engine.
Once it does, it is entirely depending on the exact properties of the ignition system whether the engine will continue to run in reverse, because the requirement of "spark before TDC" remains so the ingintion HAS to deliver the spark at a different crankangle for the engine to keep running. Some Magnetos do that, some mechanical points-triggered ignitions also do that.
Some Hall triggered systems, if set up to trigger at approaching magnet, and depending on the size of the magnet, also can do that.

I know for a fact, that the way RcExl is set up (spark triggered by the retreating magnet), running in reverse is impossible, because the occurrance of the spark will shift the wrong way making ignition impossible.

2: I have ONE Stirlingkit (Cison) ignition, a 4 cylinder unit. I have, like you, "resistored" the sparkplugs, as well as completely galvanically separated the ignition from the RC parts. It works well for it's application (a boat) but it clearly shows signs of affecting nearby servo's (HF overspeak) and I would never EVER use one of those in a plane. That is despite using 2.4 GHz for that one.
The RcExl ignitions that I have (about 15 of them, including a twin, two 4 cylinder and one 5 Cylinder unit) basically all are fed from the receiver battery, the ignition current passing the receiver busbar. Those ignitions really are a class of their own WRT reliability and suppression of RF interference. I allready used them without issues using "MegaHertz radios", and now with 2.4 GHz it is a total non-issue.
Looking at the price of a plane, and the price difference between Stirlingkit and RcExl, I think the savings are not worth the possible damage.

3: I guess that is possible, but TBH, that would kind of defeat the point of it being an YS... Because without the supercharging (and looking at that CR of those engines is designed with supercharging in mind) I think that it would result in a rather gutless engine.
It most definitely SHOULD be possible to do that, I just don't see why...

Oh, and no, you are not hijacking anything. Sidesteps to non-glow engines can help understanding what we are facing when modding glow engines.

Well here's what the Zenoah instruction manual covering the complete line (G23 to GT80) has to say. I removed the spring starter on both my G62 and GT80 for weight purposes and using correct procedure hand started both everytime. Once you learned how to flip 180 degrees it was no problem.

Tony. I concur with your Zenoah assessments. My G62 had the larger flywheel since it came from a chainsaw. I could hand start that one. I did switch to CDI for the G62. I was given a Zenoah 45 with the smaller flywheel and magneto. I couldn't hand start that one despite reading all the posts on the technique you described. My electric stater couldn't start it either. Great compression on that engine. I later switched it to CDI. With the smaller flywheel you need to generate even more speed on your flip to get it to fire.

Bert I am reading that post you suggested for converting to gas but not using the solenoid. I think I have read that in the past. I really appreciate your efforts to make the modifications simple enough that most modelers can duplicate without metal lathes or other tools. For the 4 strokes can you get away without having the round off the exhaust valves? Cutting the slot in the carb barrel seems easy. Removing valves is something I haven't done in these engines. I have in car engines but not these small ones. I imagine I can do it with a little practice. So the practical steps seem to be isolating the carb from heat, adding the slot in the carb barrel, rounding off the exhaust valve, and adding a delay to your throttle. That seems pretty simple. Do you recommend trying the air bleed device over the slot in the carb barrel? Have you tried using smaller carbs in the engine to correct for the richness that occurs with the original carbs? I imagine you have.

I appreciate your comments regarding electrical interference from your Cison engine. My use of the Stirlingkit CDI has been on converted 2 stroke commercial engines using full size resistor spark plugs. The CDI comes with a resistor and I leave that in place. I have not tried the CDI with a non resistor plug such as a 1/4 32 plug. I will be doing my initial testing on a bench so I will pay particular attention to any servo abnormalities. I also build many of my planes from Coroplast so I don't have a lot of money invested in the plane. Not that I ever want one to crash but I would be testing the system in a plane that isn't very valuable.

I have many YS engines to work with. I like experimenting.so trying to convert one to gas and see how it does would be interesting to me. Finding substitute O rings can't be that difficult and if I'm using a Walbro I really don't need the regulator that has the silicon diaphragm. I could eliminate that part of the fuel circuit and just use the pressurizing system to the tank and a line from the tank to the Walbro. I may need to actually reduce the pressure to the Walbro if the tank pressure can get to 9psi. Only testing will figure that out.

I really appreciate the feedback and will continue read more of your previous posts.

Free fueling systems
 

OK, so far Anaphyst and JS440 would like a free fueling system for the price of shipping. What about you, Bernett?

I'll go to the shop and search around for them when I can get away. I think I have 4 or 5. I'll post pics when I find them all.

Lonnie

yes thanks!! I definitely need one for my project !!

thank you !!!

I would probably be crazy not to take you up on that offer. It doesn’t come with the solenoid correct? Thank you very much.

I have done the "rounding" of the exhaust valves on a few engines, as I saw ash (white deposits) on that edge, and I feared that the glowing ash could cause pre-ignition issues.
Although rounding the valves absolutely cured the deposition of ashes, I have only done so with my first 2 or maybe 3 engines, and never seen or noticed any negative effects from omitting that rounding. It still is something that I would do if I were to be intent on excluding all possible issues, but it is not really a big deal I guess.
I also stopped lowering Compression ratio. It noticably reduces power, on top of the 20% reduction resulting from the chemical properties of gasoline alone.
Maintaining original compression ratio, it takes a minute bit more attention to breaking in the engine (things run a bit hotter, so you need to take a bit more care), but it is no real problem, unless your engine by design has a higher CR than say 10:1 (I believe 12:1 is about where higher octane rating like "premium" or such are needed, but I like to keep some headroom).
Also, in case CR remains unchanged, keep in mind that you do NOT want your ignition timing to be earlier than 28 deg BTDC.

The grinding of the carb profile, the first times you do that, start with a tiny bit (like really tiny, 0,1~0,2 mm), and test. This can be a tedious job, because every time you make a small correction to the profile, you need to retune the idle needle.
It took me 2 or 3 engines to get a feel for it, and basically the rest (I have done close to 30 like that for customers mainly) ran acceptable at the first attempt (meaning, I think they were flyable) and more or less "as good as it gets" at the 2nd try.
In case of grinding the carb, do NOT forget to place an extra spring under the throttle barrel (there is usually a spring under the throttle barrel, pushing out the clearance of the original groove. Since you increase that clearance, a slightly higher spring force is required, or the intake vacuum can start pulloing in the throttle drum).

In case of SuperTigre carburettors: DO NOT GRIND! SuperTigre carbs have a brass insert in the carb, that comprises of the fuel barb, the spraybar with Cats Eye and it serves simultaneously as the HS needle holder. That brass insert is usually held in place with two M2 slotted cheesehead screws.
Slack those two screws a bit, and turn the brass insert, in order to tune the midrange. Turning the fuel barb down (towards pointing at the mounting lug) will lean out the midrange, turning it up (towards the head) fattens it up. Total effective movement range is maybe 45 degrees or so, so make small adjustments, and tighten the cheeseheads for testruns (be careful not to overtighten). Take note of the sideways view in the 2nd video in the last part. You can clearly see how the fuel barb is significantly turned downwards.
This adjustment changes the attitude of the spraybar relative to the airflow in the carb barrel, reducing fuel suction at midrange.

Here a few vids of SuperTigres that were simply "adjusted" instead of "modified":
G2300


I even did a then 50 year old baffle piston SuperTigre 45 that happily accepted running on gasoline, but I do not have a good video on that.

If you are NOT going with the solenoid, yes, I do recommend the airbleed method as described by Chris (Cat1), for reason that grinding is a one time affair. If you go too far, and also, you can "by and large" get the mixture "about correct" over the range, but you cannot go back in case you went too far, while the servo-operated option allows a more exact tailoring of the mixture over the entire range, and you can go back and forth. You can even decide to return to methanol if you would decide to.

I have indeed, but not very extensively, tried smaller carbs. It does not do much.

One thing you did not mention, but which I see as imperative: Muffler pressure is VERY helpful. The exhaustgas contains residue that contrary to engines running on glow fuel, is very undesirable to enter the tank, so you need a craptrap of sorts. It is very advisable to use a 1" sacrificial piece of silicone as first connection to the pressure tap on the muffler, then a short piece of brass as connector, and the rest of the pressure system as Tygon. The Tygon cannot stand the heat from the muffler, but it CAN stand liquid gasoline. The silicone can stand the heat, but not liquid gasoline. At the muffler tap, the gasses are hot enough for the vapours not to attack the silicone. That sacrificial piece will easily last a few years and is a doddle to replace.
A craptrap suitable for aerobatics is fairly easy to make, I have described that several times in the various threads that you have access to.

A precise set-up of the fuel system also is of great influence: Use a 3 line set-up, NEVER a filling valve in the fuel line to the engine.
Use a feltclunk, NO inline filters.
Use as short and straight as possible fuel lines from tank to carb.
Open the drain of the craptrap when filling the tank, so liquid fuel will not enter the muffler, but drain out of the craptrap. You need to drain that anyway between flights, so no biggie. That can cause nasty effects upon first next start. As a minimum a very dirty plane, in rare cases a nasty fireball...

Thanks for the advice and clarifications. I will look up the construction of a crap trap. I may have access to a Super Tiger 2500. It sounds like that is a good candidate for conversion to gas.

It is the complete ready to use setup.

I did some research regarding electrical noise from CDI systems. The Rcxel systems use shielded HV cable. The spark plug wire. It seems you get the greatest protection from the noise by grounding the shield closest to the spark source. Which is the spark plug. The Rcxel system does that with their spark plug cap that firmly attaches to the spark plug which is screwed into the motor. The ground wire from the CDI box should also be connected to the motor. What I don’t know is if the shield end that attaches to the CDI box is grounded inside the box. If so that could cause a grounding loop. There seems to be debate on if you should only ground the shield at one end or both ends. A copper mesh shield is the best material to use if possible. The Stirlingkit CDI that I have been using doesn’t have a shield and also has minimal insulation around the spark plug cable. Using resistor spark plugs with that system seems to eliminate enough noise as
to not cause radio interference. If I want to use that system with 1/4 32 plugs, which are not resistor plugs I should at least use the resistor supplied with the CDI at the end nearest to the spark plug and probably add a copper sheathing and ground that at the spark plug end to the same point I ground the CDI box, which is somewhere on the engine. Copper sheathing is relatively inexpensive to obtain and should be easy to install. I will experiment with this and let others know what I discover. I’m sure most people will just use a Rcxel or CH CDI, but maybe someone will pursue alternative CDI systems.

Especially the SuperTigers with the large finned "square/oval" shaped heads, I have always wondered whether these perhaps were specifically designed with gasoline in mind. Those designs, ALL sizes from .45 upwards, are thermally VERY suitable, and the carb allows for direct tuning for gas, as you can see in the vids I posted.
The only thing to consider is that you need to check whether the conrod has needle bearings (AFAIK, the larger ones have) and if that is the case, the needle bearing conrods have an oil content limit of MAX 20:1 but can handle less, like 30:1. The bushed rods need 15:1 or fatter, depending on engine size.
Mind you, for those engines, the advise WRT muffler pressure, craptrap and fuel tank arrangement remains valid unchanged, but literally the only thing you need is a suitable ignition system, of which there are several very good options.
CH ignitions, RcExl, Runtronic are the best, but there are others as well, as you know.