RE: Convert GMS 120 glow to Gas
 

capt you haven't converted those yet? I am working on a kit that will be a bolt together , no machining for the end user, for the .90 and 2300. Mine all use 50:1 gas no extra oily mess.

RE: Convert GMS 120 glow to Gas
 

Hello Capt,n
I am running the 51 at 16:1. I ran the ST 40 for about 2 hrs at 20:1 and upon thorough inspection found no discernable stress nor unusual wear. That one is almost 20 yrs old though so I don't know for sure what the newer 51 will tolerate. 20:1 is as low as I think I will try and only after some hours of breakin. It has maybe 1 1/2 hrs now so I am thinking maybe when it's 5 or 6 hrs old I will start taking some oil out. It doesn't leave as big a mess on the plane as glow but it does still put some residue out. (Kind of a honey golden brown stuff) I don't have an explaination as to why but I am blending 50/50 Pennzoil with Zenoah synthetic. Some of my untralight buddies have shown me tests with the pennzoil being superior to the synthetics in every respect including deposits. I have seen the pics of the engines after torn down and the pennz had less wear and less deposits. Flyboy Dave has some very interesting points about synthetics from his many many years of motorcycle technician experience. My experience pretty much mirrors his. Ken Lambert and Keith at BME put needle bearings in the 90's so you can get the oil ratio even lower for less mess and put walbros on them for better fuel control. Since borna did both I am quite certain he is going to be real happy with his conversion. My power did not suffer as much as I thought it would. The 51 pulls my Super Sportster around on gasoline better than the 40 did on 15% glow and burns about 5 oz in 30 mins of general sport type flying. In another thread I mention it turns an 11X6 prop 13,400 on gasoline and was turning that same prop 14,100 on 15% glow. If you decide to convert I think you will be happy. I have a 90 as well and it is on a 60 size Super Sportster. I am thinking of put bearings in it with a walbro and running it on gas. Good luck with yours.

RE: Convert GMS 120 glow to Gas
 

Jezmo: I think I am going to try the .90 Tiger with a 20-1 mix using the Pennziol. I have read that more oil = more power to a extent. I am not worried about the small mess on aircraft. It is a good Idea to clean them off anyway and check fittings. I Have read about the needle bearings Ken has installed. That was very nice of him to share data and photos of the process. Not many people would take the time & effort he did. I got to get a little more handy with my Lathe and Mill to try the needle bearings right now. Also I am working on a Holt 4 cylinder stationery engine. Best regards, Capt,n;)

RE: Convert GMS 120 glow to Gas
 

Pictures worth a thousand words.
I’m sure there are a few slow learners like me that could have been confused by finding the TDC. So here is the explanation with some pictures

Based on what I learned form the previous postings.
Pic1, Secured the engine with the vise
Pic2, Take the plug out. Turn the crankshaft until the piston is almost at the top. I used 1/8” rod as a piston stopper in the drill chuck.
Pic3: Attached a protractor to the crankshaft. Hand tight the prop nut. Used Dial indicator pointer to track the reading on protractor. ( The actual dial indicator is not used)
Pic4: Turn the crankshaft counterclockwise slowly until the piston hits the piston stopper. In my case, the piston hits the stopper at 82 degree.
Pic5: Now turn the crankshaft clockwise until the piston hit the piston stopper again. In my case, the piston hits the stopper at 154 degree.
Pic6: Now the TDC is 154+82 / 2 = 118 degree on the protractor is the TDC
For my initial test I set the ignition at about 27 degree before TDC. Therefore turned the crankshaft counterclockwise until the reading was at 91 degree. Hold the crankshaft, loosen the prop nut, turned the drive washer until it sparked. That setting is 27 BTDC.

Borna

RE: Convert GMS 120 glow to Gas
 

This afternoon I took the engine to the nearby flying field for another test run. Last week I had no luck, the engine didn’t start at all. It looks like the timing was setup wrong at 39 before TDC and I was thinking that I had it set at 27. After I corrected the timing, I was ready for the second test run. Prime the engine and it start it up with a touch of starter.

Now I think I got some tuning to do. The idle was about 3000, which I think it was too high and max RPM was 7740 which I think is kind of slow. Since it was getting dark, did have much time to deal with any adjustment. I ran the engine for about 15 mins.

Now what are some of the steps need to do to improve the max RPM and lower the idle?
Does that have to do with the ignition timing?
Any help appreciated.

Borna

RE: Convert GMS 120 glow to Gas
 

looks realy nice , I hope to get back to my machineing in the near future.

RE: Convert GMS 120 glow to Gas
 

Tuning hintsset timing to 30 Degrees BTDC, adjust carb way rich THEN lean for max power using a Tach.
Is your ignition a syncro spark?? Or are you using fixed timing?.
What sized prop? Did you ever get a base line using glow fuel?

RE: Convert GMS 120 glow to Gas
 

The protractor you are using is a little awkward. However, what you want to do is this:

Eyeball the piston at TDC. You can use a rod or something and feel for it, or use a dial indicator. Then set your degree wheel so that the pointer is pointing at Top Dead Center.

Then install your piston stop. Rotate the crankshaft so the piston touches the stop and note the degree reading.

Rotate the crank in the other direction until it touches the stop and note the reading.

If the readings are exactly the same, you lucked out and set the degree wheel properly by chance.

More likely, the readings will be different by a few degrees. Let's say one reading was 44 degrees before top dead center, and the other was 50 degrees after top dead center. Move your pointer or degree wheel to half that distance. (In other words split the difference and move the wheel or pointer 3 degrees.)

Now rotate the crank in both directions and note the readings again. They should be equal, or very close. If they are off a bit, adjust the wheel or pointer again. You want the reading to be the same each time the piston touches the stop.

When you have achieved this, you can remove your piston stop, and now when the pointer/degree wheel indicates zero, or TDC, the engine will be at it's true Top Dead Center.

You can then set your ignition timing, check your port timing, etc.

The site www.ch-ignitions.com has a printable degree wheel you might find helpful.

To prove to yourself that a dial indicator doesn't show true top dead center, try this. With your degree wheel and pointer in place, install the dial indicator to indicate off the top of the piston. Now very slowly turn the engine over until the dial indicator stops rising. Find the exact point where the indicator stops rising, and then stop turning the engine over and note the degree wheel reading. Now once again, slowly turn the engine over in the same direction until the dial indicator starts back down. You will notice that you can turn the crank several degrees before the dial indicator starts back down. This is called piston dwell, or the time the piston spends literally stopped at TDC while the crank "flops over" and starts pulling the piston back down. This amount varies from engine to engine, and is related to the rod/stroke ratio and other factors, but it is why a dial indicator can't ever show you true TDC unless it is used to measure a certain distance down on either side of TDC, just like the simple and preferred "Positive Stop" method.

AV8TOR

RE: Convert GMS 120 glow to Gas
 

I like this degree wheel a lot.

http://www.tavia.com/free_degree_wheel.html

Print it out, put packing tape on both sides and then cut it out.

I used a length of clothes hanger for the pointer. Bolted it to the engine
while the other end I bent a for the pointer.

When you find true top dead center, mark the case and shaft so you can easily find it again.

It will make this whole thing simpler.

RE: Convert GMS 120 glow to Gas
 

Now if your Glow to Gas conversion is about ready, a simple way to set timing is to just guess where timing ring with magnet is about in the place you want it. Get engine running and warmed up. Set throttle to full RPM. Adjust HI needle valve to fairy smooth 2 cycle-ing. Check RPM with tachometer. Now if you do not think Rpm is at it best....reset timing ring ...advacing it only a tiny bit at a time. When you get full RPM, leave it there if you do not hear detonation. Of coarse you may have to fine tune carb too. Capt,n

RE: Convert GMS 120 glow to Gas
 

Tee hee.... You just never give up do ya Captain? ;)

The tricks we old time engine lovers can get away with often times don't work for the newcomers; they just haven't developed that natural "feel" yet. Nothing wrong with being precise either....

We still luv ya!

AV8TOR

RE: Convert GMS 120 glow to Gas
 

The best thing about this way Capt,n is every engine is different and you get the best out of each engine.

If you have a car with a distributor try this method to get that hidden extra power and gas milage.

RE: Convert GMS 120 glow to Gas
 

Wow, I think Borna covered every little detail on the conversion. IT seems a little complicated to convert from glow to gas and need to have some machining shop experience.
Very nice and thanks for sharing this

Jim

RE: Convert GMS 120 glow to Gas
 

Hey Borna,
Where did you buy your customized connecting rod?
Also where can I get the adapter you have for the carburator?

Jim

RE: Convert GMS 120 glow to Gas
 

Those "newcomers" will never learn what may be the easy way do do something...unless they read how. For my engines no matter how I timed the engine to the most accurate way...I am still going to adjust for to RPM the way I described. How else you going to know for sure if its set right. Yes it may be set right...but now you know for sure. Capt,n;)

RE: Convert GMS 120 glow to Gas
 

How's the 120 working out? Did you get a better idle? Let us know how it's going.

RE: Convert GMS 120 glow to Gas
 

Hi Jim.
The connecting rod is the one that came with the engine. Basically I replaced the bronze bushing with needle bearing. For doing that you need to have some tools and some machining skills.

As far as the carburetor adaptor, I made that myself, so I’m not sure if you can buy them or not.

RE: Convert GMS 120 glow to Gas
 

Hi Jezmo,
I'm planning to do another test this week. Will let you all know soon if I get any improvement.

Borna

RE: Convert GMS 120 glow to Gas
 

KenLambert --- Please keep me updated on that conversion kit. I would probably be interested. I'm very happy with my converted Super Tiger .91, and would like to have a 2300 if I can somehow afford it.

I was just perusing your website. Nice shop, nice planes, and nice work!! But I am way jealous of that great looking grass flying field. I haven't seen grass like that since my parents "uprooted" us from the Ohio/Pennsylvania area 40 years ago and moved us to "Arid Zona". ;) (Of course now I'm having a great time flying off of beaches in Mexico, so there's some justification... ) :D

Anyway, nice website.
Happy Holidays,
AV8TOR

RE: Convert GMS 120 glow to Gas
 

KenLambert: Sorry I did not catch your post sooner. I am really thinking about a SuperTiger 2300 on gas. Do you think the gas version would come close in power as the glow version? It seems like Dick Hansen had a 2300 set up on spark and liked it real well. not sure if was spark ignition for sure. I have been busy with too many house projects and what time I do have left...I am working on a model 4 cylinder Holt 75 Catapilliar engine. Best Regards Capt,n

RE: Convert GMS 120 glow to Gas
 

Hey yall, a guy in our club was breaking in an Evloution 26cc the other day at the field. It was a fairly impressive runner. Anyway I got the manual and was looking at the parts break down and the carb adpter is available. I figured it can be machined to work some how. I was thinking of a conversion on an OS 160 I have laying around as it is basically similar in size. I ordered a Melody ignition for it. Where can I get a spark plug that fits the glow plug threads? What do you all thing of this conversion?

RE: Convert GMS 120 glow to Gas
 

Spark pulgs...and any engine imfo try http://www.rcignitions.com/forum/index.php Best Regards, Capt,n

RE: Convert GMS 120 glow to Gas
 

Today I readjust the timing to 30 BTDC from 27 BTDC that I had on my previous run. The RPM improved about 1800. The prop I'm runing is 14 X 8.
The idle still too high at around 3000 PRM, any idea what should be the next adjustment?

Thanks
Borna

RE: Convert GMS 120 glow to Gas
 

If you are sure the throttle is closing all the way, then it's another problem. Does the butterfly in the carb have a little hole in it?? Not the choke, the throttle butterfly... If so, you will have to solder it shut.

If that's not it, then look very carefully at the carb butterfly, and see if it has a "v" shaped groove, or a small, half moon shaped cutout at the edge of the throttle butterfly. If so, you may have to find another carb that doesn't have that little cutout. It makes an engine idle a little smoother and transition better, but on small engines it can let too much air pass and cause a high idle.

If it's none of these things, it has to be an air leak. Your manifold adapter, gasket, or something is allowing air to get in and causing the high idle.

AV8TOR

RE: Convert GMS 120 glow to Gas
 

For the plug try CH-Ignitions.

C.H. Ignitions, Inc., PO Box 1732, Riverton, Wyoming 82501
PH - 307 857 6897
24-HOUR FAX: 307 857 6900
http://www.ch-ignitions.com/