Ernie Misner

I am getting ready to rebuild my Saito 82 carb. The kit is mainly different size o-rings I think. Anything I need to know? One is a really tiny and delicate looking o-ring. Did someone say that goes on the spray bar and he ruined a few trying to install it? Does the slit in the spray bar go straight down like usual? My 82 has been getting a little hard to tune and I'm hoping the new carb kit might improve that. I can tune the low and high end great like always but it kind of wants to go lean at about 1/3 throttle or so and I'm wondering if there is an air leak somewhere with the old o-rings in the carb (about 10 years old) ..... and getting a few dead sticks occasionally with that. The intake manifold o-rings are new along with the new aluminum backplate so that is not a problem. Thanks for any carb rebuild tips.

Rudolph Hart

The tiny o ring i referred to is inside the main needle tube.They tend to weld themselves in place for want of a better way to say it.I used a short length of piano wire with a jag on the tip,the opposite end of the wire has a bit of heat shrink on it to roll the new o ring in.If you loosen the hex screw and slide the throttle barrel out be careful not to lose the spring which sits behind it.

SrTelemaster150

The slit in the spray bar (catseye) goes toward the manifold.

Ernie Misner

Thanks you guys. Were your engines giving you any problems before rebuilding the carbs?

blw

My Feedback: (3)

Ernie, if you're taking the engine out of the model you may be interested in what you find by running it on a test stand with different fuel/vent lines and tank.

I used to wonder why W8YE always recommended changing tank, brass tubing, fuel lines, the works, every year. He's right, imo. There's so many places to get leaks and cause lean runs on a good engine.

w8ye

My Feedback: (16)

7. Is the one that goes in the end of the high speed needle valve body.

Ernie Misner

Jim, this is awesome. Where did you get this diagram? This is for the 82, or generic Saito info? I would like to see if there's more info there. Thanks so much!

Ernie Misner

No one has had a particular tuning problem that rebuilding the carb cured? And which o-ring is usually the culprit or weakest link? Thanks again.

Rudolph Hart

I was going to say the o ring that failed Well..yes,otherwise you would'nt bother re-building the carby.From my experience the intake tube o ring that sits against the head gets hottest and flattist.If you run long high speed needle extensions the vibration from the needle will hammer the o ring inside the tube.Your problem might just be in the rest of your set up re fuel lines and tank etc as mentioned above.I've had holes in silicone fuel tubing that were very difficult to find.Some don't even leak fuel but are quite happy to suck a bit of air for you.

Rudolph Hart

I've been thinking how convenient hsn extensions are if the engine is cowled and you cannot easily get to it for an adjustment,particularly if you have to fly it with the cowl on in the test flight stage.When we bench run engines for break in and tuning it's just the short factory needle which is fine.I've got needle extensions on a couple of aircraft cut as short as possible and still be able to tune while the engine is running.My question is,has anybody bench run a saito single and cut the wire to length from really long to quite short..in effect to try and tune the extension (piano wire in my case) so that you can observe a sweet spot where it may hardly vibrate??

w8ye

My Feedback: (16)

This was part of an old post 3 or 4 years ago. I just saved the picture.

Ernie Misner

Well by golly upon further review, the carb might not be the problem. Thanks for repeatedly reminding me to double check other things.... The center line of the tank is well below the spraybar location in the carb. It's such a simple setup on a little 3D profile plane - engine on one side of the profile fuse, and tank on the other. It looks like the tank is lined up well but the Saito 82 carb sits up higher when the engine is mounted horizontally like that. So the tanks is actually a good inch or so too low. Won't ever get a real dependable tune that way, right? I do have room to move the tank up and relocate it easily. So what's the rule of thumb for a "perfect" setup? The tank center line should be 1/4" higher than the spraybar? Thanks for the carb advise anyway. I did rebuild the carb and learned some things.

Rudolph Hart

Hey right on there brother!...when's the test run due and will you give us some fuel and prop figures?

ps don't forget to hammer the brass bits back into the carby real hard will ya?..now don't forget or we'll have to keep reminding you won't we?

SrTelemaster150

When the tank is a bit low the tune will usually be OK when the tank is full, but go lean as the tank empties. Having the tank centered on the spraybar helps even out this phenomina. It's the fuel level that is critical, not where the clunk is in relation to the spraybar.