wingspan99

My Feedback: (2)

Hi folks,
I have a used Saito 180 and an electronic ignition module lying around. I'd like to convert the Saito 180 to gas ignition so I can enjoy a very lightweight 180 four-stroke engine. The engine w/out muffler is 31oz, and I figure another 8oz for the module and battery. That's 2.5lbs for a 180 fourstroke gasser. My question is how much oil content would I have to run in gasoline? I've heard 10% 2-stroke oil for the 2-stroke conversions. Those engine's bottom ends see a lot of gasoline that would dilute the oil whereas the four-stroke seems to have a very nice bath of pure oil since the bottom end is lubed only by piston blow-by. I'm thinking 5% oil would be enough for the Saito 180's con rod. Any thoughts on 2-stroke vs 4-stroke gas/oil ratio differences?
-Tom
Dallas, TX

cu. in.

I don't have any experience with four-stroke gas conversions, but I know that some of the Saito rods are not bronze bushed. The 120 rod is not bushed for sure. I don't know about the 180, but pull the back cover and look. I would not run less than 10% initially if the rod is not bronze bushed.

Bruce

tkg

My Feedback: (1)

Raise the crankcase vent up so that more oil is in the bottom. Even inject some clean oil into the crankcase before each flight.

wingspan99

My Feedback: (2)

I was going to run the engine side mounted which would probably keep a bit more oil in the crankcase. One of the things I did with my .91 Saito glow engine is to direct the breather line directly into the carburetor inlet by making a piece of brass tubing. This put the goo into the top end where it get's blown back out the exhaust, eliminating the breather tube's mess on the bottom.
I'm going to pull the backplate tomorrow and check the rod. If it's not bronze bushed, I'm not even going to attempt the conversion.
I really want a four stroke gasser, I like the torque and sound but would like to run on gasoline if possible.
-Tom

wingspan99

My Feedback: (2)

I pulled the backplate off and sure enough, the conrod lower end is all aluminum, no bronze bushing. I guess there's two ways to look at it, the aluminum in a conrod is the structural component, and so this is probably stronger since the bronze bushing requires some aluminum to be cut out in order to place the bushing there.
If I run this puppy with too little oil, it's doubtful that an all aluminum con rod will wreck the crank pin. There's two nice holes in the con rod's crankpin end. If indeed I'm right that a fourstroke has a better oil bath there than a 2-stroke then maybe I can get away with less than 10% oil content. I guess the only way to find out is to try it. How much could a conrod be anyway?
-Tom

ZAGNUT

My Feedback: (1)

also remember that with gas the engine only uses half the fuel that it does as a glow so even less oil is passing through the engine... and since it'e a 4-stroke i doubt the rod will be seeing any of the gasolines lubricity.

how about making a needle bearing rod? if you're short on room for the bearing the rod could even be made from steel to maintain strength.


dave

4 stroken ron

My Feedback: (29)

How do you intend to keep this engine cool? Did you ever notice the large cooling fins on a gasser? Do you know that gasoline burns a LOT hotter than alcohol? No wait, that is not true, actually alcohol burns hotter, but it is not all burned in the combustion process and the excess, with the unburnt oil is carried out the exhaust with excess heat (then you wipe it off your wing). therefore your cylinder head temp is a lot higher on gasoline than with alcohol. I am sure you know that, all that alcohol and oil going through a glow engine acts as a coolant. Now your proposal is to run half as much fuel (gasoline) and half as much oil. I think things are going to get awfully hot. I think if you do this you will need TWICE as much oil content in your fuel not half (now you have messy wings again). You will also need a smaller carb. The needles on the 180 carb will not give you a fine enough adjustment, and the 180 carb has too large of venturi area for gas, the 180 carb has O rings that are made for alcohol, not good for gas. I think you will need a carb from a 91 sized motor and find rubber O rings for it. I tried this many years ago with a OS 120 and ran into all the above problems. I finally abandon the project and ran glow fuel in it with the ignition. That worked very well and there were a lot of old OSs around doing that same thing. I wish you good luck with this and I hope you can make it work. Cause if you can I want to convert my 180 as well.
Ron

cu. in.

wingspan99,

The Saito 150 conrod costs $22.46 from Horizon.

Both Ron and ZAG have made good points. The conversion could be a long process, but that is how you learn. If I were in your shoes, I would have to ask myself how much spare time and money I want to invest in this project. In my case, the money isn't a problem, but I don't have the spare time.

As I see your situation, you have five choices:
1. Do nothing
2. Enjoy your engine as is and save time and money by running it on glow fuel with glow ignition
3. Save some time and some money by running it on glow fuel with spark ignition
4. Attempt the gasoline conversion..... after all, no guts, no glory!
5. Simply sell the engine.

Best of luck whatever your decision.

Bruce

Hobbsy

My Feedback: (102)

I have a Merco .61 two stroke that was designed to run on gas, TKG replaced the stock ignition with a CH SynchroSpark which made the engine run much better, however it would get hot and quit. I solved that by adding 4 oz of castor to the LawnBoy ashless oil I was running. I also converted an OPS 30 Maxi, 1.8 cu. in. two stroke by putting a CH SynchroSpark on it, but I changed it back because it had small cooling fins spaced far apart and ran too hot. It had a needle bearing rod and ran very well but got hot.

Sky Viper

Isn't Aluminum more abrasive than bronze? I think you would need more oil on aluminum.
I'm also not convinced that cooling will be an issue. Yes, the alcohol cools a glow engine, but take a look at the RCS engines. They have realatively small cooling fins compared to Fuji, Zenoah, etc.
Also, running 4C means you won't be making as many fires per minute as a Fuji 2C Gasser.

I would venture a guess that the standard 2 cycle mixes would get you close enough to figure out an optimum setting for your engine.
40:1 - 32:1. I'd start with heavy oil and work just to be safe. You said 5% (20:1) but that may be too much, but try it and see.
Don't forget, gas lubes too.

Tom

wingspan99

My Feedback: (2)

I have to say I think the cooling fins are a bit small for a gasser, maybe some decent baffles could help the head cool down a little but that would be a battle always, especially in Texas heat. I guess no one has tried this type of 4-stroke conversion yet. I do recall that Maynard Hill ran his OS 61 four stroke on ignition for his world record 500 mile cross-country with an RC plane. I don't know for sure if he ran gasoline but I believe he did because he said that he could carry more energy aloft with gasoline. He had a lot of troubles with the timing, but then he was trying to get the consumption down to 1/3 of an ounce if I recall correctly. He didn't have the benefit of electronic computer controlled ignition back in the 80's. I think he used a needle bearing on the conrod. There used to be a company that offered titanium conrods with needle bearings for boat engines due to the high revs. I've heard the Supertigre 2500 runs good on gas, probably because of the abundance of heat fins on the head. But I'm intrigued by the possibility of using a common engine to run an inexpensive fuel. This is the case of spending $500 to save $200, but hey, this is a hobby not a business and I've gotten quite an education from the hobby.
-Tom

cu. in.

wingspan99,

Glen Dye made a TiRod when he was in Minneapolis, many years ago. I believe he is in the Salt Lake City area these days.

Bruce

Antique

My Feedback: (4)

The crankpin in a SuperTigre is too soft for the rollers, maybe the Saito is the same...

cu. in.

RCIGN1 has a good point. The Torrington needle bearing engineering literature calls for a minimum shaft (crank pin in this case) hardness of 58 Rc and a deep case of .030" minimum, if the steel is of the case hardening variety. The literature also calls for very accurate shaft surfaces that may not be present in a used engine due to wear.

Bruce

wingspan99

My Feedback: (2)

Well all this discussion does point out a void in the current offerings out there. The only 4-stroke gasser that I know of is the Ryobi 4-stroke and I understand it's very heavy for it's output. Are there any other 4-stroke gassers in this size? Perhaps the only way to get the power/weight ratio good on a gasser is in the 2-stroke size? I think there just hasn't been the R&D done for it yet.

cu. in.

RCIGN1 converted a Honda GX25 some time ago, so he is the person with first hand knowledge. I would think, however, that an in-depth analysis of available four stroke gassers vs. the Saito 180 would reveal a number of differences. To begin with, the lubrication systems are different as I recall. Perhaps Ralph can shed some light here.

Bruce

Antique

My Feedback: (4)

There at least 4 four stroke 25cc engines, Honda, Shindaiwa, Stihl, and Ryobi..The Honda and maybe the Ryobi have a crankcase that holds oil, the others mix oil in the fuel...My GX25 turned a Mejzlik 18-6 about 7500, the Shindaiwa about the same..Have not seen the Ryobi and Stihl...The Honda is on the way to New Zealand for testing by Willdo, should be there soon....None of the four strokes are what you would call a powerhouse, but sound good and burn hardly any fuel....

Honda GX25

wingspan99

My Feedback: (2)

It looks like the Shindaiwa unit uses a supercharging not unlike the YS engines. The Stilh 4-Mix engine produces 1.4hp and is 31cc, and has no reservoir full of oil.