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Saito 91 on Gasoline

Old 03-25-2008, 08:07 PM
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Jezmo
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Default Saito 91 on Gasoline

I just finished my GP Big Stick 60 and put a Saito 91 on it that has been converted to run on gasoline/oil mix. I flew it for the first time this weekend and I was impressed with how strong the engine is on gas. I kinda expected to lose a little more power than it did but who's complaining. It went down from 9800 running on 15% glow fuel to 9400 on 16:1 mix gas/oil. The engine has about 10 hrs. on it as a glow from it's previous life and now has about an hour and a half as a gasser. About an hour of that is on the test bench figuring out what it likes for timing and such. I did not use a pumper type carb instead using the stock glow carb. It runs surprisingly well and the needle is less sensitive than my SuperTigre 51 on gas. It's still a little sensitive just not as much so as the ST. I intend to start cutting back on the oil to numbers more inline with what Saito is recommending for the G36. The 16:1 brew was already available from my SuperTigre 51 project so I have been using it. It starts super easy and idles reliably down to 1400 with the 14X6 prop I have on it.

Here are a couple of pics of it. [8D][8D]
Edited to add: The ignition is CH and is one of his top of the line with synchro spark.
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Old 03-25-2008, 08:52 PM
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buck1856
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Default RE: Saito 91 on Gasoline

Nice job!It looks like your using muffler pressure to presurize the tank,is that correct.Ive heard thats not to wise.But who knows,why couldnt you use the crankcase pressure fitting.
Old 03-26-2008, 08:03 AM
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pe reivers
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Default RE: Saito 91 on Gasoline

Nice job Jezmo. If plugs stay clean, I would not reduce oil content. 1:16 is not bad for small engines.

@ Buck
Jezmo did not use a pumper carb, so he needs tank pressure.
The crankcase vent is just that, and should serve no other purpose.

Old 03-26-2008, 10:52 AM
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Default RE: Saito 91 on Gasoline

I was always concerned about hooking a gas tank up to a hot exhaust.

For some reason it just doesn't seem like the proper thing to do.
Old 03-26-2008, 03:30 PM
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Default RE: Saito 91 on Gasoline

Been running this thing for a couple of hours now with no ill effects. Also using muffler pressure on the ST 51 and it has about 30 hours on it now. Each has to do what his (or her) conscience dictates but I don't personally see a problem.

You've kinda got me wondering what you think might happen with the muffler pressurizing the tank.



Pe, the only reason I was thinking about reducing the oil was Saito recommends 20-30:1 on the Saito G36 Gasser. 20:1 to break it in and later, if desired, you can drop to 30:1. If I do that, then I can run the same fuel in both the Saito and my Zenoah G26. I may continue using the same mix I use in the ST 51 however because it's not really that much more oil. The Saito spits almost no oil out of the exhaust. There were maybe 10 specks on the wing after about 30 minutes of flying and you almost had to have a magnifier to see them they were so tiny. The case vent is another story as it puts out almost as much as it did when running on glow. I have it running down the gear to keep it off the plane so it's not really a problem either. I guess the old saying "Better too much than too little" applies here. Have a good one my friend.
Old 03-26-2008, 04:32 PM
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Default RE: Saito 91 on Gasoline


ORIGINAL: Jezmo

I just finished my GP Big Stick 60 and put a Saito 91 on it that has been converted to run on gasoline/oil mix. I flew it for the first time this weekend and I was impressed with how strong the engine is on gas. I kinda expected to lose a little more power than it did but who's complaining. It went down from 9800 running on 15% glow fuel to 9400 on 16:1 mix gas/oil. The engine has about 10 hrs. on it as a glow from it's previous life and now has about an hour and a half as a gasser. About an hour of that is on the test bench figuring out what it likes for timing and such. I did not use a pumper type carb instead using the stock glow carb. It runs surprisingly well and the needle is less sensitive than my SuperTigre 51 on gas. It's still a little sensitive just not as much so as the ST. I intend to start cutting back on the oil to numbers more inline with what Saito is recommending for the G36. The 16:1 brew was already available from my SuperTigre 51 project so I have been using it. It starts super easy and idles reliably down to 1400 with the 14X6 prop I have on it.

Here are a couple of pics of it. [8D][8D]
Edited to add: The ignition is CH and is one of his top of the line with synchro spark.

Hello jezmo
I also converted my 90 st, but I used a carburetor walbro, because with his original was unusable for intermediate regimes.
In your 51 st carburettor which uses?
Old 03-26-2008, 06:19 PM
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Default RE: Saito 91 on Gasoline

Yes, the SuperTigre G51 uses the standard glow carburetor but I have now modified it just slightly. I ran it unmodified for about 10 hrs before deciding to make changes to lean the area just slightly off idle. I changed the angle of the slot that is milled into the throttle barrel at the end where low end mixture is controlled. For about the first quarter of throttle movement it doesn't move out as much as it used to leaving the idle needle in the cats eye (fuel discharge) just a little longer to make it leaner just off idle. The mid range and high end are unaffected by doing this. The engine throttles as good, after the mod, as any glow engine I have ever owned.

I also have a SuperTigre 90 that I am converting and have made an adapter to mount a Walbro carb. I have also converted the rod to needle bearings so I can run it at lower oil ratios. I ordered the ignition for it last night and hope to start running it on the test bench soon. (As soon as CH can make and ship the ignition and about 1 week for shipping)
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Old 03-26-2008, 08:27 PM
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Default RE: Saito 91 on Gasoline

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
Old 03-27-2008, 06:50 AM
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Default RE: Saito 91 on Gasoline


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
Keith is the inspiration for my ST 90 project. Ken Lambert has also contributed and the little ST 51 was just an experiment to see if I even wanted to proceed with the 90 project. The hardest part of that has easily been the hardened pin on the crankshaft. I've had so much fun with the little 51 that I'm getting anxious to get the 90 going. The Saito on gasoline is cool but I just love that two stroke howl.

Hope all is well out in Arizona and Happy Flying.
Old 03-27-2008, 05:34 PM
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Default RE: Saito 91 on Gasoline

I have not modified the slot, but I built a series of needle idle with various taper and I removed the cat eye.
I have not used the discharge pressure for fear of fire as the adjustment is not constant.
I have ardened original pin, mix 25:1, propeller 15x4w,10500 running
sorry my english (maccaroni english)
Old 03-27-2008, 09:06 PM
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Default RE: Saito 91 on Gasoline

Sounds like you are getting it figured out. I am looking forward to more stick time on the gassers this weekend, can't wait.
Old 03-28-2008, 05:51 PM
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Default RE: Saito 91 on Gasoline

Very interesting Jezmo; congratulations!!
I'd like to know how you feel the engine transition from idle to WOT.

Alfredo
Old 03-28-2008, 08:37 PM
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Default RE: Saito 91 on Gasoline

Alfredo, I wish I could post some video. I think you would be impressed with the throttle response and transition. It transitions very much like it did on glow and if anything accelerates just a little quicker. As I mentioned in post 1, the only real drawbacks are just slightly less top rpm's and the needles are more sensitive. It runs hotter too but that hasn't proved to be a problem at this point. If it becomes a problem I will post back with information about it.
Old 03-29-2008, 12:55 AM
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Default RE: Saito 91 on Gasoline

Here ya go.

Try http://www.rcuniverse.com/

The on the left side on the bar you will see Buy & Sell
2nd bar is RCU Videos, click there.

The rest is even easier.
Old 03-29-2008, 06:22 AM
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Default RE: Saito 91 on Gasoline

Yep, that's the easy part. Now if I can just get some video and edit it down we'll get 'er up there.
Old 03-29-2008, 03:39 PM
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Default RE: Saito 91 on Gasoline

Jezmo: Thanks for your info.
Would you care to explain me how to find the proper point of the magneto reading?
I am new into convertions and I have several engines that would be fine to convert into gas. Are the installation of the magneto and new threads for a gas plug all what you have to do?
Old 03-29-2008, 09:52 PM
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Default RE: Saito 91 on Gasoline

Window Movie Maker

It's a free download from MicroSoft.

It's a pretty easy program to use, after all I figured it out.

Here is a video I did using it.

http://www.rcuvideos.com/item/80HMB3SYWNYB42GR
Old 03-31-2008, 10:21 AM
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Default RE: Saito 91 on Gasoline

I flew the Saito for almost 2 hours this Saturday and found one minor problem with it. The big stick has a 12oz tank which for gasoline is a bunch on an engine this size. After about 20 minutes the engine starts getting too lean and I would have to land and either fill up or richen up the needles just a tad. 20 minutes isn't bad for a run but that's only about 1/2 to 2/3 of a tank so I may look into putting a regulator on it. (or maybe a pumper carb, Zama or Walbro) I just filled it up each time instead of playing with the needles because 20 mins of looking up is enough for my old neck.

Alfred, I am probably not the right person to try to explain setting up the ignition timing. It's not hard and if you buy one of the CH ignitions (others may include them as well) they come with a paper explaining how to set the timing as well as a paper degree wheel. I am not changing the threads and instead I am using a 1/4X32 sparkplug that screws right in place of the glow plug. It's made by Rimfire although NGK makes them as well.

Ralph, it's all the work that troubles me on the video. I don't have a lot of time to spare for that type of thing but I will try and get some video up. (To try and put it into perspective, I work 40 hrs a week for a major airline, run a small business of my own, volunteer all day Friday at my church, and somewhere in there do all of this converting and flying.)
Old 03-31-2008, 11:27 AM
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Default RE: Saito 91 on Gasoline

Have you though about taking up another new hobby?
.... Maybe juggling.
Old 03-31-2008, 12:21 PM
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Default RE: Saito 91 on Gasoline


[quote]ORIGINAL: Jezmo



Alfred, I am probably not the right person to try to explain setting up the ignition timing. It's not hard and if you buy one of the CH ignitions (others may include them as well) they come with a paper explaining how to set the timing as well as a paper degree wheel. I am not changing the threads and instead I am using a 1/4X32 sparkplug that screws right in place of the glow plug. It's made by Rimfire although NGK makes them as well.

Jezmo, thanks for the info.
I understand that in your convertion you did not change the carburetor, I bet that you have your leaning (and maybe the heating) problem right there. Please keep on posting.


Old 04-01-2008, 06:32 PM
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Default RE: Saito 91 on Gasoline


ORIGINAL: Ralphbf

Have you though about taking up another new hobby?
.... Maybe juggling.
The wife would shoot me sure as I sit here if I did. (I didn't name all the hobbies earlier - Boat, parasail, water skiis, Nascar, etc. Yep, she'd shoot over another)

Alfred, I didn't use a special carb to keep the cost down. I do have a WT173 Walbro that I may try to adapt onto it later but that's another project for another time. It's actually flying good enough for my liking and I just wanted to give others a heads-up on the shorter runs with the stock carb. Again, this type of thing isn't for everyone, but I just love to tinker and 20 mins on a tank is fine for me.
Old 04-05-2008, 08:04 PM
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Default RE: Saito 91 on Gasoline

My new ignitions arrived from CH Friday and i put the one Bill and Terry built up for the four stoker in it today. It looks real nice in the Big Stick. Bill put me a 45deg McDaniel connector on this unit and it works better on the 4 strokes because of the odd angle the plug sits at. As always the ignition equipment I get from Bill and Terry at CH is absolutely top quality and this round is certainly great stuff. Everything is ready for another big weekend on the Big Stick Saito gasser.
Old 05-19-2008, 08:42 PM
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Default RE: Saito 91 on Gasoline

I checked the plug today after flying. It's the same plug that spent 30 hrs in the SuperTigre 51 and it was only changed because I had a Hall effect sensor going bad and I thought it was the plug. When I discovered the sensor I had already changed plugs and realizing there was nothing wrong with the old plug I put it back in service in the Saito. It now has just shy of 7 hrs in the Saito for a total of 37 hrs and it's still running good as new.

The Saito is running superbly and I am having a blast flying the Gasser Big Stick. Pic to follow.
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Old 05-19-2008, 10:13 PM
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Default RE: Saito 91 on Gasoline

Those little baby plugs sure are cute. Looks like your mixture is about perfect.

Pics! We like pics!

AV8TOR
Old 05-20-2008, 03:53 PM
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Default RE: Saito 91 on Gasoline

If I cut the ign. right after I land it looks even better. In this pic the plug is a little darker than normal because no one was at the field but me and I had taxied all the way back in to the spectator area which kept it at idle for a considerable time. Of course you already knew the plug darkens when idled for a time. Have a fine one av8tor.

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