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Older G-38

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Old 12-17-2001, 06:05 PM
  #1  
KevinSheen
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Default Older G-38

Hi all,

I bought my first gasoline model engine recently.

It is an older model Zenoah G-38. It looks like it is fine condition, the guy even included the instructions for the motor (they are a bit brief), and it has a few options without instructions.

First, the prop hub is an older model. It has a center bolt but the hub is also tapped for 6 smaller screws and the prop washer is similarly drilled. IN ADDITION to all of that, there are 2 smooth studs that are in the hub. I'm assuming that the 6 bolt hub is optional and if I want to use the single center bolt and drill 2 additional holes in the prop, that I can mount the prop in that fashion. Do you agree? One last item, it didn't come with the 6 bolts for the prop hub/washer, just the single main one.

It came with a spring starter. It is loaded with grease and looks to be in good condition. Does anyone know what a sensible periodic maintenance schedule for this item would be?

I took off the cup mount and muffler. It looks like they were put together with lock-tite of some sort. Do you have a suggestion as to what color or type of lock-tite I should use before I run it?

If anyone has the flat mounting plate for a G-38 that they don't plan to use, contact me and lets make a deal. I don't know if I'll be using the cup mount with the plane I plan to build.

What 2-cycle oil would you suggest during the break-in. In the past, I've heard to stay away from synth's and stick with a petroleom based ashless oil (for the break-in). Is that still suggested?


Thanks a bunch,

Kevin
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Old 12-18-2001, 02:46 PM
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Jim D
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Default G38

I also have one of the older style G38's on my Stinger 120. I can address two of your questions:

I took the prop hub and had the face of it knurled on a lathe (benifits to having machinist friends;-) ) I just use the center bolt, no pins, ground them off. Without a good knurling pattern on the face of the hub where the prop seats, you will have to drill your props for the two pins, but you can still use the single bolt. Just make sure it is a good quality grade 8 bolt.

I use Honda Synthetic 2-stroke racing oil at 32-1 in mine. I get no residue on the plane and It is super quality oil Honda developed for the dirt racing program. You can get a quart bottle at any motorcycle shop for about $6. Comes in a blue bottle. Very clean burning oil and at 32-1 I know the engine is getting plenty of lube.

Also, I run a Pro-Zinger 18x8 prop and tach 8000 peak on the ground. A lot of people don't prop their G38's this high, but it really seems to like winding up.
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Old 12-18-2001, 04:56 PM
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Default Older G-38

Hi Kevin,
You should not have to regrease your spring starter sooner than every 20 flights. I used to use a spring starter on a G-38 but found that it is totally unnecessary. The technique that I use is to set the prop coming up on compression at 11:00/5:00 position. I then slap the prop in a downward motion. This generates enough speed to get a good spark.

Locktite #242 (blue) is a good choice.

The original flat mounting plate that comes with the G-38 is a stamped steel type with stamped in stiffeners. After a period of time, this mount will start cracking. The best thing to do is to get a piece of 1/8" aluminum and use the mounting pattern of your cup mount to drill holes.

I would not use a synthetic oil for breakin because it will take way too long for the rings to seat. I would use a good quality petroleum based chainsaw oil at 32:1. Run about 3 gallons through it before switching to a synthetic.

Happy Holiday
Ken
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Old 12-19-2001, 04:56 PM
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Thank you, gents. I appreciate the replies.

Kevin
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Old 12-29-2001, 02:44 AM
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Default Spring starter maintenance

I've seen spring starters that were well greased bind up after only 7 to 10 flights. The results of a spring starter binding up your engine can be catastophic to your aircraft if you go dead stick in the wrong place at the wrong time. I have removed all of my spring starters because I don't want to have to pull my engine off of the airplane after a few flights in order to maintain it, and it is just something else that can go wrong, and you know Murphy's law about if something can go wrong, it will. So, save yourself some headaches and remove that spring starter before it causes you a problem. I use a combination Sulivan Hi Tork electric starter coupled with a Miller Precision belt reduction unit to start all of my engines up to 5.8 cu. in. with no problem. I'd be very careful trying to hand start any engine on magneto in that the timing is not retarded on a mag engine and it could backfire on you, catching your hand in the prop. It's a cheap enough investment, so go get that electric starter.
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Old 09-02-2011, 01:31 PM
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Default RE: Older G-38

what kind of grease should be used for the spring starter?
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Old 09-02-2011, 02:39 PM
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Default RE: Older G-38

This is a pretty old post. Almost 10 yrs old.

Mostly I've seen Black Moly chassis type grease in them.

Some have had the white Lubriplate grease.
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Old 09-02-2011, 03:20 PM
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Default RE: Older G-38

ok i probably should have asked further. what do you grease , just the bearing ? is there any other maintenance to check on the spring starter? thanks
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Old 09-02-2011, 03:26 PM
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Default RE: Older G-38

Inside the bearing there are little bearing rollers that rest on ramps. It is actually a one way bearing. In one direction it grabs and the other it doesn't.

The problem I've seen with these bearings is the spring. Someone has wound the prop backwards several turns until they cannot turn it any more before they let the prop go to start the engine. This distorts the spring and pulls the coil closest to the engine block down against the crankshaft and pushing the "one way" bearing to the rear. This distortion sometimes generates heat in this area and ruins the bearing and rear seal on the crankshaft. Then the engine will never start.
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