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Old Oct 22, 2012, 06:27 AM
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Gary Cee's Avatar
United States, MI, Marysville
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Yes , 1 1/2 times the diameter is the rule of thumb . The thread pitch and material hardness are other factors . Fine threads in soft materials do not hold as well as coarse threads . If the thread pitch is 0.5 MM , 6 threads would be 3 mm . Rules of thumb , like thumbs are often broken. There is little need for a lot of tension on the backplate cover so this is not a maximum clamping force application .
Studs rather than screws at any rate are a safer bet as they square up better and allow full thread purchase. . If you are using a bushing , by the time you allow for an inside and an outside thread it would seem that just using a larger screw could be a better option . If the screw in use is a 3 MM , the 3.5 mm screw or even a 6-32 could be an option as they are smaller than 4 MM .
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Old Oct 22, 2012, 10:07 AM
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As long as the clearance hole for a 4mm screw leaves enough material on the lug of the backplate, that's the easiest way to go.

Greg
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Old Oct 22, 2012, 10:21 AM
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Quote:
Originally Posted by gkamysz View Post
As long as the clearance hole for a 4mm screw leaves enough material on the lug of the backplate, that's the easiest way to go.

Greg
Of course,
The 3.5 MM and 6-32 were given as options in the event the 4 MM (preferred) was too large . However , a 4 MM threaded bushing would not have sufficient meat to adequately accept a 3 MM internal thread .
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Old Oct 22, 2012, 10:24 AM
The Prez....... again
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United States, IA, Rockwell
Joined Jul 2011
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Quote:
Originally Posted by gkamysz View Post
As long as the clearance hole for a 4mm screw leaves enough material on the lug of the backplate, that's the easiest way to go.

Greg
I'll look at that tonight when I get home. In my mind right now it seems that lug on the back plate is not very big. If I do go the bushing route I would be able to keep all the screws the same size. I hate it when I need a different tool for one out of four bolts. I would like the repair to look "professional" instead of a cobbled up repair. Not that a larger screw would looked cobbled, it just doesn't match.

Ken
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Old Oct 22, 2012, 12:52 PM
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Quote:
Originally Posted by gkamysz View Post
I would use a helical thread insert.

Greg
That's what I suggested, safest way. Or send the casting to Clarence Lee if you do'nt want to risk your engine.
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Old Oct 22, 2012, 09:28 PM
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Old Oct 22, 2012, 09:42 PM
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Canada, ON, Caledonia
Joined Aug 2007
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I just bought this model, video is from John the previous owner.

Saito 300 on C&H
Saito 300 on CH Ignition and 1/3rd Sopwith Pup Assembly (12 min 7 sec)


Bill
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Old Oct 23, 2012, 07:23 AM
I HATE GLOW PLUGS!
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United States, NY, St Lawrence
Joined Feb 2012
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Originally Posted by williame3590 View Post
I just bought this model, video is from John the previous owner.

Saito 300 on C&H
http://www.youtube.com/watch?v=I9_saL9qVTo

Bill
A 300T on C&H CDI is a dream to operate.

Stay W/a full synthetic oil for best results.
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Old Oct 23, 2012, 10:08 PM
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United States, LA, Shreveport
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OK I am glad I found this site dedicated to Saito's. I have a Saito 82 mounted on a tiger 60 upright. I broke it in per the manual and have gotten numerous good flights out of it (a couple of gallons if that much). Then it started back firing and at the time I didn't relize that a rich high end would cause this. I adjusted the valves with the supplied guage and the back firing stopped (best of my memory). Now I cant get it to run up to full RPM by needle adjustment to save my life. Its extremely sloppy on the top end and I cant get it out with the needles. Could it be the Valves I adjusted? So anyway I could use some help getting everything set back to a good starting point. I can't find the valve guage so I geuss I need to know what this should be set at and second a good starting point on the needle settings. And anything else I might be missing or need to consider.
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Old Oct 23, 2012, 10:09 PM
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United States, LA, Shreveport
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Quote:
Originally Posted by williame3590 View Post
I just bought this model, video is from John the previous owner.

Saito 300 on C&H
http://www.youtube.com/watch?v=I9_saL9qVTo

Bill
Awesome model!
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Old Oct 24, 2012, 09:35 PM
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Quote:
Originally Posted by Reginald View Post
That's what I suggested, safest way. Or send the casting to Clarence Lee if you do'nt want to risk your engine.
Yes,understood. A Helicoil will still be a 4 mm OD,depending on pitchh. A bushing much larger than 4mm. The options are limited by space at times.
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Old Oct 24, 2012, 09:45 PM
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Hmmmm thought this forum would be a little more helpfull!
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Old Oct 24, 2012, 10:03 PM
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Sometimes people are busy. Idle needle is flush with the throttle arm and the main 2.5turns out for basic setting. If you can't turn in the main needle enough to lean the engine it's possible the needle seat or needle are damaged. Valve clearance is .0015-.004". The manual is on the Horizon site for the product if you've lost yours.

Greg
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Old Oct 24, 2012, 10:03 PM
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Old Oct 24, 2012, 10:10 PM
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United States, LA, Shreveport
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Quote:
Originally Posted by gkamysz View Post
Sometimes people are busy. Idle needle is flush with the throttle arm and the main 2.5turns out for basic setting. If you can't turn in the main needle enough to lean the engine it's possible the needle seat or needle are damaged. Valve clearance is .0015-.004". The manual is on the Horizon site for the product if you've lost yours.

Greg
Sorry! Didn't mean to sound pushy or rude. How can you tell if the needle or seat are bad?
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