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Saito 91 on Gasoline

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Old 05-20-2008, 11:13 PM
  #26
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Default RE: Saito 91 on Gasoline

Jesmo: You got some intereting gas conversions there! I have a .90 Tiger. Could I remove the standard crank pin and press in a hardened pin to fit a needle bearing? Can you elaborate a little more on how the rod was done to take a needle bearing? Thanks Capt,n
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Old 05-21-2008, 09:37 AM
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Default RE: Saito 91 on Gasoline

Hi captin,

Yes you can drill out the crank and press in a hardened pin. That's the only way I know of to get the correct surface hardness for the bearing to ride on which is around 62 rockwell. Some have talked of Case Hardening the existing pin with Kasenite but the bearing I am using would be too small to fit over the original pin. If one were to use a larger needle bearing that would fit over the original crankpin the OD would be so big there isn't enough material in the rod to drill it to size. The way I am doing it, the rod is drilled and then finished with a reamer to get the correct size for the bearing to press into. NTN has a good web site that lists all of the dimensions for their needle bearings and information is available on that site to guide you on the correct amount of interference when pressed into the rod.

The ST 51 and one of my ST 90's are running at 16:1 fuel to oil ratio with the standard bushing in the rod and doing very well at that ratio so I'm not too inclined to do the bearing mod on my future engines. It's a lot of work to put the bearing in and I don't really mind the extra oil in the mix. 16:1 is only 8% oil, way less than glow fuel.
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Old 05-22-2008, 08:55 AM
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Default RE: Saito 91 on Gasoline

Jesmo: Very good reply. I will take your advice and try the 16-1 when I go for it. Next is what to do for a carb. I culd make a adapter and use a walbro....but I do wonder if a lot of air flow to engine? Best Regards Capt,n
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Old 05-22-2008, 09:03 AM
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Default RE: Saito 91 on Gasoline


Quote:
ORIGINAL: av8tor1977

I have a Super Tiger .90 that Keith at BME modified for me to run on gas. I'm running it on Gas/Glow, and am very happy with it. It handles very nicely.

AV8TOR
Hellow AV8TOR: When runing your gas/glow Supertiger .90 do you notice if the engine runs hotter with that mix. Is cooling more of a concern. Best Regards Capt,n
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Old 05-22-2008, 10:05 AM
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Default RE: Saito 91 on Gasoline

Thanks for sharing Jezmo. I did a similar conversion on a Saito 120 with the CH Ignitions and the Rimfire plugs. My plug kept fouling up, now I know why, I was idling a lot. I was also running 10% castor in E85. I'm going to try some Klotz synthetic oil next time at the 16:1 ratio, which is about 6% oil? -Tom
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Old 05-22-2008, 11:17 AM
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Default RE: Saito 91 on Gasoline

Hi Captain John,

I imagine my Super Tiger .90 runs a little hotter than it would on pure glow fuel, but it hasn't been a problem at all.

AV8TOR
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Old 05-22-2008, 02:28 PM
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Default RE: Saito 91 on Gasoline


Quote:
ORIGINAL: wingspan99

Thanks for sharing Jezmo. I did a similar conversion on a Saito 120 with the CH Ignitions and the Rimfire plugs. My plug kept fouling up, now I know why, I was idling a lot. I was also running 10% castor in E85. I'm going to try some Klotz synthetic oil next time at the 16:1 ratio, which is about 6% oil? -Tom
My Saito is still spitting a significant amount of oil from the vent tube indicating ample amounts of lube are getting to the bottom end. Good luck and let us know if the Klotz stops the plug issue. I have guys at my field talking about using ignition with glow on their Saito's and they might be able to use the Klotz to keep the fouling down.
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Old 05-22-2008, 02:41 PM
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Default RE: Saito 91 on Gasoline


Quote:
ORIGINAL: captinjohn


Quote:
ORIGINAL: av8tor1977

I have a Super Tiger .90 that Keith at BME modified for me to run on gas. I'm running it on Gas/Glow, and am very happy with it. It handles very nicely.

AV8TOR
Hellow AV8TOR: When runing your gas/glow Supertiger .90 do you notice if the engine runs hotter with that mix. Is cooling more of a concern. Best Regards Capt,n
captin,
On the ground my ST90 running on gasoline runs just over 300 degs full throttle. In the air it is running between 255 and 270 as measured with my Eagle Tree FDR. According to the experts (Dave Gierke being one) 330 or so is fine. (I have read that anything over 400 is BAD but I have one piece of lawn equipment with a two stroke and it runs 365 and another that runs 385 to 390.) The one that runs 385 is over 20 yrs. old and the engine runs like new. I do now and have always run them on the highest octane fuel available at the pump and the way I understand it, when they get over 400 degs detonation becomes difficult to control potentially damaging the engine. Maybe the high test has helped me keep that old thing going and I didn't even know it. (Didn't check the temp until last year.)
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Old 05-22-2008, 02:47 PM
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Default RE: Saito 91 on Gasoline

Jezmo

I assume you are the dude that was flying the Stick, with the convered Saito and an LA Racer Monday morning. We were the only two out there at the time. After talking with you about the conversion, I decided to check RC Universe and there you are. I am not as knowledgeable about engine details as you, but enjoy the info you provide. Keep it up!

May you have as many landings as takeoffs.

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Old 05-22-2008, 02:51 PM
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Default RE: Saito 91 on Gasoline

Yeah, the ultralight airplane two stroke engines are redlined at around 420 degrees. However, when I am flying one, I get really nervous if the CHT gets up near 400, and/or the EGT over 1200, and I throttle back, increase speed, etc.; whatever it takes to bring the temp down. They are really much happier in the 300 to 350 range...

One ultralight aircraft engine maker using a special cylinder/piston combo brags that their engines are good to 600 degrees! I would have to see one run at 600 without seizing to believe it, and as a matter of fact there have been a lot of seizure problems with their engines.

AV8TOR
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Old 05-22-2008, 07:45 PM
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Default RE: Saito 91 on Gasoline

Silverfox,

Yes, that was me. Happy to see you here on RCU.

av8tor,

I agree, no way I want to be in an ultralight with the CHT at any 600 deg. I need to put the Eagle Tree on the Saito and see what she runs in the air but just guessing it's less than 320 because it only runs 330 to 340 on the ground as measured with my Fluke. Anyway, have a fine one.
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Old 08-16-2009, 05:22 AM
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Default RE: Saito 91 on Gasoline

I found this thread after I became interested in modifying some of my old engines to gas. The "spark" that ignited my interest came from this ad: http://www.justengines.unseen.org/ac...s.html#aJW2014
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Old 08-16-2009, 11:24 AM
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Default RE: Saito 91 on Gasoline


captin,
.... I have one piece of lawn equipment with a two stroke and it runs 365 and another that runs 385 to 390.) The one that runs 385 is over 20 yrs. old and the engine runs like new. I do now and have always run them on the highest octane fuel available at the pump and the way I understand it, when they get over 400 degs detonation becomes difficult to control potentially damaging the engine. Maybe the high test has helped me keep that old thing going and I didn't even know it. (Didn't check the temp until last year.)
[/quote]

The reason they run so hot is because of air pollution.
Just like our cars, they make them run hotter to burn cleaner.

I hold my glow engines until they reach 190 degrees, then I put them in the air.
Colder than that they do not run reliably.

So would 190 be the proper minimum that engines should be ran?
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Old 08-30-2009, 10:15 AM
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Default RE: Saito 91 on Gasoline

Jezmo Is your ign on your 4 stroke different than whats on a 2 stroke ? as the 4 stroke fires every other time the piston comes up. Thanks Rich
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Old 08-30-2009, 06:57 PM
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Default RE: Saito 91 on Gasoline

The ignition on our model four strokes fires every time the piston comes up

But . . . . Nothing happens on the overlap stroke because there is no compression and the fuel mixture is not correct for combustion.
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Old 08-30-2009, 09:58 PM
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Default RE: Saito 91 on Gasoline

It's the same ignition as w8ye said. Most lawnmowers are doing the same thing, just firing every stroke. Nothing is lost firing on the end of the exhaust stroke as there is nothing in the cyl except spent gases as w8ye noted.
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Old 09-10-2010, 01:25 AM
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Default RE: Saito 91 on Gasoline


Quote:
ORIGINAL: wingspan99

Thanks for sharing Jezmo. I did a similar conversion on a Saito 120 with the CH Ignitions and the Rimfire plugs. My plug kept fouling up, now I know why, I was idling a lot. I was also running 10% castor in E85. I'm going to try some Klotz synthetic oil next time at the 16:1 ratio, which is about 6% oil? -Tom
Oh do you have any pics from your converted Saito 120 ?
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Old 09-10-2010, 09:47 AM
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Default RE: Saito 91 on Gasoline

Lots of good data about temps...thanks Guys. That Saito 1.20 photo would be nice too. Keep the photos & videos comming....it adds very much to the forum! Best Regards Capt,n
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Old 09-11-2010, 06:06 PM
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Default RE: Saito 91 on Gasoline

Here is a link to my Saito 91 on the test bench. Sorry about the chatter from the videographer (read wife).

http://www.youtube.com/watch?v=CQ_ph1qqcPc
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Old 09-11-2010, 11:23 PM
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Default RE: Saito 91 on Gasoline

Thinks for posting the video.

I noticed your were using the stock carb

Saw the carb was a little sensitive but appeared to be manageable
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Old 09-14-2010, 05:52 PM
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Default RE: Saito 91 on Gasoline

Yes Jim, it is a little sensitive and I would not recommend it to someone that not good at tuning. Sometimes I miss and have to land and tweak it just a bit but it does run very good though and everyone here in the Houston, TX area that's seen it run are quite impressed by it. I may put a small WT Walbro on it someday but that's fodder for another thread.
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Old 03-16-2011, 02:06 PM
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Default RE: Saito 91 on Gasoline

*
Hi Jezmo

I just got this link from a Friend. Very interesting discussion over a few years! I am Very Seriously considering converting a Saito 200R3 to ign gas.

I was worried about all the usual stuff. Master and link rod bearings, crank pin, enough lube getting to the gear case for the cams , burnt valves etc etc.

I was originally trying to find Charlie Steven of Houston. I believe he used to sell Saito Gas Conversions. I needed to find out about gas oil mix ratios, but you seem to have answered that question. 16 or 20:1 is no problem, it seems.

Are you using Hi-Octane Unleaded (Premium 98 here in Ozzie Land) and what type of oil do you mix?

Regards RossG
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Quote:
ORIGINAL: Jezmo

Yes Jim, it is a little sensitive and I would not recommend it to someone that not good at tuning. Sometimes I miss and have to land and tweak it just a bit but it does run very good though and everyone here in the Houston, TX area that's seen it run are quite impressed by it. I may put a small WT Walbro on it someday but that's fodder for another thread.
-

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Old 03-16-2011, 03:46 PM
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Default RE: Saito 91 on Gasoline

Hi Jezmo, Sounds like you have a winner there. I have a Saito .91 that I run on a Tequila 40, it's about 6lbs and even at this altitude of 6100' MSL it will do a vertical eight from the bottom. The best prop I have found is an APC 12.5 x 10. I get about 2x the vertical performance of the MA 14x6 I had on there. I want to try some E85 and a little nitro on glow. Have you tried adding nitro to your fuel mix? -Tom in CO
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Old 03-16-2011, 05:05 PM
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Default RE: Saito 91 on Gasoline

I just run regular pump gas at 20:1 with Pennzoil aircooled two stroke oil in my Saito 150. It has a CH type conversion using RCEXL ignition and the Saito carb
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Old 03-16-2011, 05:14 PM
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Default RE: Saito 91 on Gasoline

*
Hi Tom

I know it was almost 3 years ago (!!), but I was wondering how you went with the synthetic oil in the Saito 120. Has the engine actually survived long term on gas? Would ordinary "2 stroke oil" for garden tools be suitable? Was there a special reason for running E85 fuel (85% Ethanol)? TIA.

Regards RossG
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Quote:
ORIGINAL: wingspan99

Thanks for sharing Jezmo. I did a similar conversion on a Saito 120 with the CH Ignitions and the Rimfire plugs. My plug kept fouling up, now I know why, I was idling a lot. I was also running 10% castor in E85. I'm going to try some Klotz synthetic oil next time at the 16:1 ratio, which is about 6% oil? -Tom
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