Convert GMS 120 glow to Gas
 

Hello all,
I'm planning to convert my GMS 120 glow ignition to gas ignition. This is what I'm planning to do.
1. Change the stock carburetor to Walbro Wt-644. This carburetor is a replacement for Zenoah 23 - 26 CC engine. So I'm assuming it should be good for my GMS 120 which is same as 20CC. Do you guys recommand this carb?

2. I'm planning to use 40:1 gas/oil for fuel, therefore I'm planning to harden the crank pine and replace the bronze bushing with needle bearing.
Question on this part. Is it possible to heat the pin area on the crankshaft to cherry red and dip it into kasenite which is a case hardening? I want to avoid cutting the pine and press fit a harden pine.
Also where can I get needle bearing that small for the connecting rod? Does the needle bearing have to be pressed fit into the connecting rod hole?

Also for ignition I'm planning to use a ignition module from C.H.

Please provide from help if you know anything about conversion of Glow to gas.

Thanks
Borna

RE: Convert GMS 120 glow to Gas
 

GAS-GLOW.........

RE: Convert GMS 120 glow to Gas
 

Gas-Glow??

RE: Convert GMS 120 glow to Gas
 

http://www.rcuniverse.com/forum/m_12...tm.htm#6166729

Browse through this thread.
The last 10 pages should cover most of what you'll need.

RE: Convert GMS 120 glow to Gas
 

Hello all,
The conversion completed. You can look at the engine at this site.

http://www.floridaame.org/discus/mes...tml?1189378581

RE: Convert GMS 120 glow to Gas
 

what did you do with the crank pin

RE: Convert GMS 120 glow to Gas
 

I heated the pine to bright red, dipped into to Kasenit. Repeat the process 3 times. and then reheat it again and quench it into water.
Test the pin and made sure is harden.

Borna

RE: Convert GMS 120 glow to Gas
 

borna: This is some of the best photos posted on here! That is some very good work you did. I want to thank you for sharing your ideas with all of us engine people. Where did you get the needle bearing to fit crankpin? Did you need to polish the crank after hardening? Best Regards Capt,n;)

RE: Convert GMS 120 glow to Gas
 

Thanks Capt,n.
I got the needle bearing from http://www.mcmaster.com.
For crank I just used the scotch pad to polish it a little. Since I used Kasenit for hardening the pin, I didn't have to heat it above the color you see in the picture, therefore didn't distord the metal.

RE: Convert GMS 120 glow to Gas
 

how hard is the pin doing it that way? I have been boring the crank pin and replacing it with a hard ground one, rc 65

RE: Convert GMS 120 glow to Gas
 

I also just get the high speed needle baerings from a local suplier. Lots cheaper than paying shipping and handling cost, and on some engines you need to replace the front crank bearing, I run 50:1 gas in mine . I have several gallons run thru

RE: Convert GMS 120 glow to Gas
 

Did you have to drill out the rod to put in the new berring? If you did how did you do it and is it somthing that can be done with any old drill press?

It is nice that you gave us your ideas. some peaple do not like telling us how they do the grate things they do.

Paul

RE: Convert GMS 120 glow to Gas
 

I had posted pics and descriptions in another thread some where about how I do the super tiger .90's and 2300's plus pics and some videos on my website, some of my threads get deleted by moderaters , they think I'm trying to sell something. I get emails all the time people wanting one and to this day I haven't sold any because I am not selling them . but you can look for the thread

RE: Convert GMS 120 glow to Gas
 

Yes I had to. The key is to find the exact center of the connecting rod. There are many methods out there for finding the center of the hole. I tested my procedure 2 or 3 times on piece of scrap aluminum to make sure each time I can enlarge the hole correctly.

Can you do it with a drill press? That I’m not sure but you must get the hole within .0001-.00005 under size to press fit the bearing in.

I started with finding the center of the hole. Then I used very sharp and short drill bit to make the hole a little larger in order for the boring bar to fit in. Then I started to bore out the hole using a very short boring bar in a boring head on the milling machine. The boring process will give you a very accurate result. When you are about .0001 -.00005 under, you can press fit the bearing in the connecting rod. So the problem with the drilling is that you may not be able get the hole under size to press fit the bearing. I think you should also check Ken Lambert web site. He has some nice pictures there for reference.

Once I test my engine and make sure everything is running ok, I will post more pictures and more of what or how I did it.

Borna

RE: Convert GMS 120 glow to Gas
 

I did a test on a piece of mild steel using Kasenit and it got hard enough that I could not use a file on it anymore and I broke the tip of center punch on it.
So I think is hard enough to handle the bearing. But for sure the better method is what you suggested to replace it with the harden pin.
What you think about machining the pin and press fit a harden cap into it?

Borna

RE: Convert GMS 120 glow to Gas
 

I tried that method with the 2300and the cap would come lose every time so I bored the pin out and presed in a hard one and works great and not really any more work just cost more the 8mm pins are high.have to buy 50 at a time and are about 4 times higher than the 6mm

RE: Convert GMS 120 glow to Gas
 

also on the pickup sensor ring I found a way to make five or six at one time instead of one at a time and they look nice.

RE: Convert GMS 120 glow to Gas
 

I see you put a pump fitting right on the carb. how did you do that. I like that idea.

RE: Convert GMS 120 glow to Gas
 

Easy, look at this picture. Remove the cover on the carb. Drill a hole in there with #16 drill and tap with tap it for 6-32 thread. Also make a hole of the same size in the back cover of the engine (See the picture above) and use a fule nipple.

If you decided to drill a new hole in the top cover, make sure the other hole on the side is covered. Or if you don't want to drill a hole there, just use the small hole on the side.

Borna

RE: Convert GMS 120 glow to Gas
 

I haven't had a chance to run the engine yet, but talking to a guy at the field, he mentioned in the gas engine, both end of connecting rod should be equiped with the needle bearing if you want to run the engine with a low gas/oil ratio. Those of you that have converted the glow to gas are using needle bearng on both end of connecting rod?

Thanks
Borna

RE: Convert GMS 120 glow to Gas
 

no I use a bushing on top with extra holes for oil , the top just moves a little back and fourth so the bushing will work fine.

RE: Convert GMS 120 glow to Gas
 

Even though is not necessary, but I was told if I want to run the engine with a lower oil 70:1 gas/oil ratio is better to equipped both bronze bearing with needle bearing. So it did it anyway for fun of it.

Also I was told the surface hardening of the crank pin may not be good enough to tolerate the needle bearing after maybe 100 runs, therefore I grind the pin to remove the surface hardening and then machine it to a smaller diameter and hard press a harden pin made of tool steel.

I have been so busy, therefore still haven’t had a change to run the engine. I maybe get a chance to run it this weekend, if not it will be 2 weeks from and provide more pictures.

Borna

RE: Convert GMS 120 glow to Gas
 

Very nice gas conversions. This was educational, I wasn't aware of the crankpin issues and solutions. I'm curious to know what rpm difference you see with gas, and then could you try E85?. Also what ignition timing did you settle on after tuning it? I set my Saito 120 to 35BTC with the E85 fuel and CH-Ignition. I've heard there's less power than with glow, but I wonder about E85 since it's 85% alcohol.

RE: Convert GMS 120 glow to Gas
 

Correction on the crankpin. I mentioned that I pressed fit a crankpin. I meant to say I pressed fit a sleeve over the crankpin after I machined it to a smaller diameter.

I'm not sure how E85 works with the Walbro Carb? I live in Florida and never seen it in any gas station. But would be an interesting experiment.

Borna

RE: Convert GMS 120 glow to Gas
 

I have been running two weedie type motors on E85 with the stock Zama carbs they came with. One is on a bicycle, the other is my leaf blower. Since E85 uses a 10.6:1 air/fuel ratio its close enough to gasoline that opening the main needle valve one turn is all that's required, and a minor adjustment on the low end needle valve. In fact, E85 is close enough to methanol's 6:1 air/fuel ratio that it runs ok in stock glow engine carbs with some exceptions, like my Satio 120 which was a little rich on the midrange. I closed up the midrange slot in the carb with some solder and reprofiled it, and that runs good now with CH-Ignition on E85. I have been able to make a GP .42 engine run real nice on a mix of E85/glow fuel at 2:1 ratio, using a hot glow plug. Check out that thread for more details.
There's an E85 pump in Miami at the U-Gas. That seems to be the only one in southern Florida right now that is open to the public. Here's the address if you or someone you know gets down that way:
210 NW 79th Ave
Miami, FL 33126
305-269-7006