91 C spec ps with header tank

[Helodad]

Oh Fury gods help me. I have found a problem if I use my header tank and place the over flow line in a nipple of the tanks runs lean. If I se it up like the book pg15 works great butt no header tank. All who are using headers with pump sys are you all buying the additional nipple and running overflow to your main tank pg14? I think this caused my over lean problem in my X-spec. I might be getting to much pressure in the header tank. (I know fuel magnet I to lazy to change foam every 2 months and how know how much they will be) Be sides I like my header tank

[DavidH]

When I was using the PS motor. I t'ed the line from the check valve into the fuel line where it just exited the tank. I never really had any problem. I also used a header tank. When using a header tank, an ELD fuel magnet is not going to help.
The header tank does not have too much pressure, it has the same pressure as the main tank.

Putting the line from the check valve into the third nipple on the header tank really should not be a problem. I have seen many OS 91 PS motors connected that way and they ran fine.

David

[Helodad]

could it be that the chunk line in the header is to thin and contracting? I can not explane why it runs better with out header its night and day dif with the smoke.

[DavidH]

Maybe you don't have the plumbing hooked up correctly for the header tank.
The supply line from the main tank, should run to the top nipple on the header tank( Hayes 2 oz). Then the supply line from the header tank should run to the intake side of the pump. Then the supply line from the pump should run directly to the carb fitting.
I te'ed the return line from the check valve, right into the supply line from the main tank where the fitting is located that is in the tank.

David

[Helodad]

Yup just the way I have it. I'm going to ck the tank to see if any air leaks.
:dontknow

[Helodad]

ok I dont what this means but my idle mix screw was only set 1 turn from close and factorty settings should be 2 turns. (i never tuched it) the header tanks is ok no leaks. :dontknow

[EricLarson]

Watch the fuel lines in the tank very carefully. They should be replaced every 2 months or so anyway. Also my overflow line runs into my main tank. That is the only way that I was able to get my motor to run right in the mid range. If I overflow into the main fuel line, the mid would not act right.

Others may have different experiences. I just use the magnet, replace fuel lines, rear bearing, and clunk every month or two. Cheap motor insurance for me. I got over 100 gallons on my main motor last year before it finally gave up this last week due to my own fault. I would definately not go over 3 months without replacing fuel line and rear bearing.

[Helodad]

Thank Guys I think that what I am going to do. DavidH Are you the same on the MA site? Thanks Eric if it works for you I will do it. On your site I see that idel mix screw is at 90% how many turns out is that. Mine was out only about 1 turn I fixed it its out 2 now.

[Gary O]

The idle screw on a C-spec only goes 90* from the center position right and left. I'm not sure what you mean by 2 turns on the idle screw. I have had numerous C-Specs and none of them come out of the box set at any particular setting. You have to set them with your own settings before flying them. I wouldn't trust OS to set the needles anyway. I don't run the return line since I use the needle jet conversion on that carb. Once you get out of a hover the return doesn't put anything back in the tank much anyway since it's using it all on the high end.

[Helodad]

:dontknow Idle screw should be turned out 2 turns from closed per book. Once it’s out I locked brass plate then you can only turn it 90* by needle jet do you mean 3rd needle? If so I had one on. I took it off. It brand new engine I want to break in first then put the 3rd needle back on. But I still want the engine to run good with my header tank.

[DavidH]

Helodad,
The OS 91 Cspec PS or the OS 91 Cspec carb do not have an idle screw that screws in or out. The idle adjustment on both carbs is a cam type barrel. You can only turn the idle adjustment screw nearly 90 degs each direction from center position. The carbs come with the idle adjustment centered and will usually allow the motors to idle nicely and transistion with it centered.

Also the third needle for the PS motor that goes on the mid range does not work like a normal needle. The third needle you screw the needle clockwise to richen the mid range. The needle screws counter clockwise to lean the mid range on the PS. This is opposite of how a normal needle setup works.

Look on page 20,21 of the instructions for the Os 91 Cspec PS.

Idle screw should be turned out 2 turns from closed per book.

I must have missed it but never saw the above statement anywhere in the instructions.
http://www.os-engines.co.jp/english/line_up/engine/heri/herindex.htm

If you have turned the idle adjustment two full turns, it is time to send the motor in for repair.

David

[Helodad]

Page 29 top where it says Adjusting chart. I just got the engine back from OS it had a bad pump.

Or page 16 in the link you list.

[Helodad]

OK got my answer. The idle mix screw we all know is a cam screw in out 1-2 turns does nothing you just want it out where the cam (high end) is facing away from the center. Then you adjust it 90* Rich or lean.

[DavidH]

Idle Mixture Control Screw:
at basic position when the engine leaves the
factory.


The above is what the instructions state for the idle control adjustment. On both of my Cspecs and PS motors I have found that the idle worked best just like it came from the factory with the slot centered.

David