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Engine basics => Four strokes only => Topic started by: Martin Quartim on April 30, 2013, 04:40:55 PM
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If any one have a Saito 40 with Bobīs modified carb, new or with little use please let me know.
Martin
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Thanks Bob, sorry folks I am not set up to do Pay Pal. Got my personal account hacked through this before and don't trust it any more. Gerald Schamp
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Gerald and Bob,
thank you!
I just got the Saito 40BR today #^ #^ #^ #^ #^ #^
Will see how it handles my Pathfinder. I will try the 12x6 JXF electric prop which has been working quite well with an old Enya 45 6001 cross flow.
Hope it is not too much load for it.
What other props should I try to get the most power?
Martin
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I've pretty well settled on the Thunder Tiger 11.3 X 6.5 for my 40's. Thunder Tiger no longer sells direct but Tower carries this prop. If you don't like the grey color they are easy to die black with RIT dye. Find a container long enough to cover the whole prop in, mix the dye with warm water and let it sit overnight. If you can't find a container go to your local Lowe's or Home Depot and pick up a short piece of 3 or 4 inch PVC pipe and an end cap. Glue the end cap on one end and you are set.
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Grey props are cool!
http://hartzellprop.com/wp-content/uploads/Hartzell-Propeller-Kit-Builders.jpg
I have a Rev Up 11x7 so I will use this one to get started.
What is a good starting point in needle turns and choke screw position?
Martin
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With the Rev-Up start at about 81 = 8200 RPM on the ground then adjust as needed for the lap times you and the airplane are happy with.
Adjust the RPM by turning the choke screw, you will have to readjust the needle with each change of the choke screw.
Always set the needle just to the rich side of full boat. I have discovered I can set the needle by ear better than trying to use a tac. I crank it lean till I just detect a sag, then crank it rich till I detect a sag. Note the position then come back to the center of the two extreme positions. This sets the needle at the max full boat position. Now just turn it to the rich side a click or two and you should be good.
If it sags overhead it's too lean, if your lap times speed up from take off to shut down more than about .2 seconds it's too rich.
By alternating between the choke screw and needle you should be able to get to the desired RPM and lap times. Most of the time I get it set for the airplane while flying and checking lap times, then after I'm happy I check and note the RPM just so I have a ground reference.
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Hi Bob,
Do you know how many turns I should open the needle to get stared?
The choke screw half close is a good starting point or should I start with it all open and go from there?
I saw the picture you posted showing how much you close the choke screw, amazing!
Thank you,
Martin
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With the Rev-Up start at about 81 = 8200 RPM on the ground then adjust as needed for the lap times you and the airplane are happy with.
Adjust the RPM by turning the choke screw, you will have to readjust the needle with each change of the choke screw.
Always set the needle just to the rich side of full boat. I have discovered I can set the needle by ear better than trying to use a tac. I crank it lean till I just detect a sag, then crank it rich till I detect a sag. Note the position then come back to the center of the two extreme positions. This sets the needle at the max full boat position. Now just turn it to the rich side a click or two and you should be good.
If it sags overhead it's too lean, if your lap times speed up from take off to shut down more than about .2 seconds it's too rich.
By alternating between the choke screw and needle you should be able to get to the desired RPM and lap times. Most of the time I get it set for the airplane while flying and checking lap times, then after I'm happy I check and note the RPM just so I have a ground reference.
will follow by the letter!
thank you,
Martin
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Hi Bob,
Do you know how many turns I should open the needle to get stared?
The choke screw half close is a good starting point or should I start with it all open and go from there?
I saw the picture you posted showing how much you close the choke screw, amazing!
Thank you,
Martin
It is really amazing just how small an air inlet a 4 stroke needs but believe this is part of the equation to getting the speed regulation we are seeing.
I would start with the choke screw about 1/2 way as you mentioned and not sure what to tell you about the needle, I usually back it off about 4 turns and go from there.
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One more question. I am setting up the Saito 40 with a Pathfinder. Where do you suggest to start with the tank height?
Martin
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Would these setting be close for a .62? I purchased a used Strega arf and have fitted it with one of my 62's to use as a test bed. Hope to fly it within the next week or so.
Brian
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Sorry guys for the delay, have had my head other places.
Martin
I usualy start with the tank centered more or less on the intake, doesn't seem to be as critical as it is with a hard tank on a two stroke.
Brian
Yes the same procedure works on all Saitos with the screw choke carb mod.
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thank you Bob, I thought so but want to make sure. I am restoring my Pathinfer and did not finish in time for flying this weekend. But I test the engine on the bench yesterday just to have a better feel how to adjust needle and the intake restrictor. Unfortunately the RPM was changing from 7800rpm to 8300rpms once all was adjusted. If I just touch the needle it would pick up RPMS indicating the NVA is leaking. I will see if I can find a bit thicker O'Ring for the Needle.
I tested with the JXF electric 12x6. After 8 min running straight on the bench from 7800 to 8600rpm it did not get hot, I was really surprised of how cool the engine was at the end. Brave little engine! Seems it could handle even bigger props! The chocking screw end up closing almost as much as you have shown your in the pictures,,,,unbelivable!
Martin
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Hi Martin,
You must have ended up with one that was converted from the CL carb, with those I have to use an OS needle which isn't near as good as the Saito. They do work but as you have discovered sometimes they are a bit loose. I have the same setup on one of my engines, it will change just by touching the needle but it seems to hold once it's adjusted. Sounds like the one you have may have a little looser tolerance than what I have normally seen. That whole assembly is used on most OS RC carbs, if you have converted an FP and still have the carb you might get lucky and find a tight one.
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To Brian:
I just got myself a Brodak Strega ARF as a testbed for a Saito 72. The .62 might not be sufficient; you may have to reduce the line length to 65 ft or so.
The best props for the .62 are: APC 13x6 or a heavily tweaked Master Airscrew 12x6 3-blade.
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To Brian:
I just got myself a Brodak Strega ARF as a testbed for a Saito 72. The .62 might not be sufficient; you may have to reduce the line length to 65 ft or so.
The best props for the .62 are: APC 13x6 or a heavily tweaked Master Airscrew 12x6 3-blade.
I made new lines for the plane, and picked 65 feet eye to eye as a start point. The prop I installed is an APC 13/6. Just guesses, but looks like that might be close.
The plane had a Saito 62 installed by it's previous owner, and he was happy with its performance. But he did wind up pulling the Saito and replacing it with a K&B 61 because he said the Saito pulled to hard.
I went to our flying field today to make the maiden flight, but their was a funeral just starting (we fly on Church grounds). By the time the service was over the winds were clocking 8-10 with frequent gusts to 14-15. I just didn't want to fly an unknown in those conditions. Oh well, maybe next Sunday.
Brian
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Here is the video of my Pathfinder with the Saito 40. I thought it would not have the guts for the job but this little thing can swing a 12x6 prop.
http://youtu.be/Wiyo8TrI6Nc
Martin
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Here is the video of my Pathfinder with the Saito 40. I thought it would not have the guts for the job but this little thing can swing a 12x6 prop.
http://youtu.be/Wiyo8TrI6Nc
Martin
What 12-6 are you using on it ?
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What can I say, great video, sounds like it's doing everything it's suppose to. From the video looks like you are running right at a 5 second lap. What ground RPM are you launching at? You said earlier you were going to try an APC 12-6, is that the prop we were running?
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Hi Bob,
The ground RPM is around 8400. The prop is a hand picked wood TF Power Point 12x6 that I thin out the blades and has true 6 pitch, one of those rare props you check and both blades match with the nominal pitch :)
I am waiting for TT 11.3x6.5 to arrive down here, it will probably work even better.
Martin