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Convert GMS 120 glow to Gas

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Old 12-05-2007, 09:47 PM
  #51
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Default RE: Convert GMS 120 glow to Gas

I had a reply explaining how this can be done with a dial indicator (timed out)....I will post a photo later. More easy to understand for who...ever. Capt,n
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Old 12-05-2007, 09:54 PM
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Default RE: Convert GMS 120 glow to Gas


Quote:
ORIGINAL: av8tor1977

Sorry to disagree Captain, but I don't want others to be mislead. A dial indicator will not show true top dead center.

AV8TOR
HEY...I am not misleading as you suggest..... That is BS Capt,n
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Old 12-05-2007, 11:32 PM
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Default RE: Convert GMS 120 glow to Gas

I think I get where you're going, if you go say .050" down from TDC before and after and mark the angle on each, that'd give you the same thing... little more effort, but the same thing
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Old 12-06-2007, 12:02 AM
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Default RE: Convert GMS 120 glow to Gas

The only problem with a dial indicator is when the plug is slanted. Then all you can use is a piston stop.
The dial indicator works great is you use .050 or more down the bore.
But a cobbled up spark plug is pretty cheap and works in more places.
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Old 12-06-2007, 03:41 AM
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Default RE: Convert GMS 120 glow to Gas

Don't get your feathers ruffled Captain. I didn't say, or mean, that you would purposely mislead anyone.

AV8TOR
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Old 12-06-2007, 08:55 AM
  #56
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Default RE: Convert GMS 120 glow to Gas


Quote:
ORIGINAL: tkg

The only problem with a dial indicator is when the plug is slanted. Then all you can use is a piston stop.
The dial indicator works great is you use .050 or more down the bore.
But a cobbled up spark plug is pretty cheap and works in more places.
Yup that is true about the slanted plug hole. I had that all in my reply that timed out and the post never appeared. Say you have the cylinder head off engine and you wanted to make sure your degree wheel is in proper place...I would think a dial indicator would work...because your screw in plug won,t then. Capt,n
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Old 12-06-2007, 09:30 AM
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Default RE: Convert GMS 120 glow to Gas

All I can say is I’m enjoying all these conversations. Just a bout a few months ago I had no idea how to convert Glow to gas and now I’m the master of that task. Earlier this week I was trying to start my engine and nothing happened. Well I can say the reason is I way off 20-30 degrees BTDC. I though as soon as the piston stops moving I can just backup 30 degree and that would be my 30 BTDC. Well no wonder engine wasn’t starting; maybe my setting was 45 D BTDC and thinking that I got it right.

Borna
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Old 12-06-2007, 10:40 AM
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Default RE: Convert GMS 120 glow to Gas

Quote:
ORIGINAL: captinjohn


Quote:
ORIGINAL: tkg

The only problem with a dial indicator is when the plug is slanted. Then all you can use is a piston stop.
The dial indicator works great is you use .050 or more down the bore.
But a cobbled up spark plug is pretty cheap and works in more places.
Yup that is true about the slanted plug hole. I had that all in my reply that timed out and the post never appeared. Say you have the cylinder head off engine and you wanted to make sure your degree wheel is in proper place...I would think a dial indicator would work...because your screw in plug won,t then. Capt,n
So put the head on. This isn't Rocket Science.
If your building a V-8 with DOHC then a dial indicator is a must have.
If your building a full blown racing 2c than a dial indiactor is way good, if your streighten a bent crank then a dial indicator in a must.
If your building a 1 cylinder 2c with 3 moving parts a piston stop is all you need. You can set the timing, check the port timing with just an old long reach spark plug. What else is there?
As far as timing an engine with a battery powered CDI, you ALWAYS time the spark not the sensor and magnet. There are to many variables in the magnet strenght and the sensor sensitivity
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Old 12-06-2007, 11:50 AM
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Default RE: Convert GMS 120 glow to Gas

quote:
ORIGINAL: tkg
As far as timing an engine with a battery powered CDI, you ALWAYS time the spark not the sensor and magnet. There are to many variables in the magnet strenght and the sensor sensitivity

what? now this is something new how do you time the spark?

Borna
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Old 12-06-2007, 12:02 PM
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Default RE: Convert GMS 120 glow to Gas

I have four dial indicators, including one with a spark plug hole adapter. I still use the positive stop method. When I'm building a hot rod V/8, and I want to dial in the cam timing and the heads are off, I still use a positive stop, with a strap bolted across the cylinder with a bolt in the center to stop the piston. It is the same way builders of $50,000.00 race engines find TDC. Once again, it can be done with a dial indicator, but you must pick a measurment, say .050" piston down in the bore, and rotate back and forth to that while adjusting your degree wheel. That negates the effect of piston dwell on finding true TDC.

There are a few manufacturers, Rotax is one, that specify the ignition timing not in degrees, but in a certain distance of piston travel before TDC. In this case, I do use a dial indicator with a spark plug adapter to properly set the timing. One of their engines has an angled spark plug hole, and the procedure is to use a dial indicator with a roller tip, and their measurements take into account the angle of the plug hole. Their specified measurements for the timing done with a dial indicator take into account the piston dwell time at TDC, so one does not need to use a positive stop to accurately find TDC.

Anyway, I guess we beat this one to death....

AV8TOR
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Old 12-06-2007, 01:07 PM
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Default RE: Convert GMS 120 glow to Gas

Timing the Spark.

Set crankshaft to the place where ignition should occur, say 28 degrees.

Rotate magnet, in this case, in the direction of normal rotation.

When spark occurs the timing is correct.

This is also called Static Timing and was used back when cars had distributors that moved.
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Old 12-06-2007, 02:32 PM
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Default RE: Convert GMS 120 glow to Gas

Ok Ralph, I think underestand what you meant by timing the spark.
Good thing you mentioned that, because I was going to do it like this

Find the TDC, then advance the magent forward 28 degrees from where the ignition happend on TDC.

Not sure if that was going to do the same you suggested or not

Borna
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Old 12-06-2007, 09:30 PM
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Default RE: Convert GMS 120 glow to Gas

Yes, you want the actual spark to occur at about 28 degrees before top dead center. It's hard to tell exactly where that might happen just looking at the sensor and the magnet. (When the magnet is under the sensor, just approaching, just passing, when?) But if you have everything hooked up and powered up, and you see the spark happen at the correct point, you know you've got it.

AV8TOR
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Old 12-06-2007, 09:35 PM
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Default RE: Convert GMS 120 glow to Gas

Quote:
ORIGINAL: borna

Ok Ralph, I think underestand what you meant by timing the spark.
Good thing you mentioned that, because I was going to do it like this

Find the TDC, then advance the magent forward 28 degrees from where the ignition happend on TDC.

Not sure if that was going to do the same you suggested or not

Borna
Close but no cigar.
Find TDC, set pointer to 0 degrees. Hook up ignition, ground spark plug to engine, turn on ignition. THEN rotate the prop hub in the direction of normal rotation. When you hear the ignition spark, look at the pointer and degree wheel. Thats you timing. Adjust untill the correct Degrees BTDC is reached.
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Old 12-07-2007, 01:41 AM
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Default RE: Convert GMS 120 glow to Gas

Your way is a little different.

The way I explained it will give you actual timing.

The only variable would be ignitions with advance built in.
Then you would need to know at what RPM the advance started working.

Say that at 8000rpm you had 10 degrees advance built in yout EI then you would
adjust the crankshaft placement accordingly.

You would set the timing at 10 degrees less because of the built in advance.
This would also make it easier to start.
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Old 12-07-2007, 03:33 AM
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Default RE: Convert GMS 120 glow to Gas

WHOOPS...

Your turn Terry....

AV8TOR
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Old 12-07-2007, 10:33 AM
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Default RE: Convert GMS 120 glow to Gas

Don't know how all the different ignitions work for advance/retard. BUT the CH unit is a retarder. So you set the timing to the full advanced position and the ignition computer RETARDS the timing for start up and low speed operations.
The CH unit provides 26 degrees of timing movement. So seting the timing at 30 degrees BTDC gives you 4 degrees BTDC at start up. The ignition computer has an infinite number of steps between 1100 rpm and 4000 rpm where it goes to 0 retard or full advance
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Old 12-07-2007, 02:15 PM
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Default RE: Convert GMS 120 glow to Gas

I think I will go with the piston stopper method. So this is what I figured out from all the reading.
To confirm the steps, let say the piston stopper stops the piston a few degrees before TDC. So I start turning the crankshaft counterclockwise until it hits the piston stopper. Let say it hit the stopper at 95 degree on the degree wheel. So at this time I will start turning the crankshaft clockwise until the piston hits the stopper again. Let say it hit it at 105 degree on the degree wheel.

I now take the stopper out and lock the crank at 100 degree which is the mid point between 95 and 105. In theory at 100 degree should be the TDC?

So let say I want the ignition to happen at 28 degrees before TDC. I then turn the crank clockwise 28 degrees back from the 100 which was determined to be the TDC and then turn the driver washer which has the ignition magnet on it until I see the spark.

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Old 12-07-2007, 03:01 PM
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Default RE: Convert GMS 120 glow to Gas


Quote:
ORIGINAL: av8tor1977

Sorry to disagree Captain, but I don't want others to be mislead. A dial indicator will not show true top dead center.

AV8TOR
This is why this got beat to death. I was just saying it is possible with a dial indicator. With it use you can zero in the degree wheel. Capt,n
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Old 12-07-2007, 03:58 PM
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Default RE: Convert GMS 120 glow to Gas

make a fixture to mount inside the case and set the crank pin all the way up mount the degree wheel set the indicator on O then remove fixture and set timing , works every time and the fixture I have works with several different engineseliminates the guess of TDC.
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Old 12-07-2007, 04:11 PM
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Default RE: Convert GMS 120 glow to Gas

YOu do not have to be right on the money for this. Setting the timming will have to be pinpoted with a run in.

What I do it bring it up to tdc or close to it. Let it sit for some time for the competion to leak out. put the wheel on it and put it a 0 Move the crank back and forth You should get 10 to 20 de on the wheel both dirations. 1/2 of that is your tdc. then set it to were you want. 28 or so. Run the engine and tack it. Stop the engine and Move the timming no more then 2 de one way. run it to see if your rpms go up or down. if the go up more it 1 to 2 more de the same way and see if it still is going up. stop the engine to set timming every time then more it agian When you rpm stop going up and start to come down move the time back to were you had it. I drop the timming 1 to 2 de just to me on the save side. but that is just me.

For me this is the best way to get the timming right were you want it. and it will take about 15 to 20 mi to do it all.

Paul
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Old 12-07-2007, 05:53 PM
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Default RE: Convert GMS 120 glow to Gas

KI8FR: I just guess about where to set timing. Then get engine running. Advance timing to get top RPM and retard a couple of degrees. But I like to throw a timing light on to see what the timing is actually. Capt,n P.S. The photo below is engine running. You can read prop size on it...also see advance in degrees as you increase RPM.
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Old 12-07-2007, 08:51 PM
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Default RE: Convert GMS 120 glow to Gas

Borna, your getting closer. A degree wheel reads 0 degrees at TDC if you do it right. Your plan will work IF you can tighten the collet/hub with out it moving on the crank.
Often times its easier to tighten it down and lock it, then move the sensor to fine tune things.
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Old 12-07-2007, 09:19 PM
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Default RE: Convert GMS 120 glow to Gas

Borna, you are going to really like this engine if you get everything dialed in right. Even without the walbro carb my little SuperTigre 51 runs great on gasoline. It starts very easy and runs flawless. I have flown it now for about an hour and it is getting stronger with each run. It was a brand new engine that I broke in for 32 oz. on glow fuel and then ran 12 oz. of gas through it on the stand. I hope you get it going soon, you're really going to like it. I can't remember which ignition you are running but the CH uses very little battery to run it. I have a 4.8 volt 1000 mah nicad pack and it takes almost nothing to recharge after 45 mins of run time. It will far outlast my transmitter battery. Get ready man this is good stuff. Like everyone else said, work with your mixture and timing until you get it right and you'll be happy. Start with it about 20 BTDC and advance it until you get peak then back it down 1 or 2 deg. I am running mine at peak and the top of the piston looks like brand new still so I don't think I am going to even back it down at all. Good luck.

P.S. Let us know what your head temps and all are. Also what you wind up with for total timing advance.
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Old 12-08-2007, 12:17 AM
  #75
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Default RE: Convert GMS 120 glow to Gas

Jesmo: Sounds great. I got 2 SuperTiger .90 engines just setting. One is like brand new. I am thinking gas also. How much oil is in your gas mix? Thanks Capt,n
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