Daniel-EL

My Feedback: (9)

I have an original YS 120 which ran perfectly when I put it away 12 years ago to take an overseas assignment. I have now re-activated it, or at least tried to, but can get no fuel to the carb unless I choke the heck out of it. The tank has good pressure build-up, but there is no fuel coming from the diaphram housing (pump) to the carb. I replaced the diaphram, but still nothing. The ports around the diaphram look clear, they seem clear, but I have no way of verifying that they are indeed clear. When I choke the carb while spinning the engine over, it will fire, but will not sustain the run once my finger is removed from the carb air intake. This makes me think the fuel ports are clear, but heck, what do I know? I have installed a new glow plug (OS F), new fuel lines, cleaned the tank and fuel filter....everything I can think of, but still no joy. Can anybody help me with this, or maybe tell me where I can send the engine for a YS expert to look over?

dmccormick001

Don't send it off just yet.

Make sure the fuel line coming from the clunk up to the tank stopper hasn't collapsed. I've seen these small diameter lines get soft after being exposed to nitro for a few years and begin to collapse so much that you can only get a trickle of fuel through them. If that isn't the problem, then I'd suggest you go through the fuel system like this:

Take the fuel tank out of the plane (so you don't get fuel inside the fuse), and start moving through the fuel system item by item. Connect the line from the regulator to the check valve, then on to the tank vent. Make sure the check valve is pointed in the correct direction. Remove the fuel line from the tank stopper that normally goes back up to the regulator/carb, and turn the motor over with your starter. After a few revs you should see fuel squirt out of the stopper. If not, re-check the pick-up tube inside the tank. If you do see fuel, then re-connect the fuel line going to the regulator and next remove the short line going from the top of the regulator to the carb. Again turn the motor over and look for fuel. If none, then the regulator isn't opening to allow fuel to flow. Turn the regulator screw counter-clockwise 1 turn and see if it begins to flow. If so, then your plunger inside the reg may be sticking, or there may be varnish or gunk left over from fuel trapped inside it years ago that is blocking the ports. Take it apart and clean it with automotive carb cleaner and re-test. If fuel flows out of the reg to the carb, then remove your high-speed needle valve and clean with carb cleaner. Try to spray some cleaner into the nipple where the fuel line connects, and also into the hole where the needle valve screws in. Carefully clean the end of the needle, but be careful not to scratch or score the needle. No sandpaper or anything that could mar it in any way. Just use a rag or cloth with cleaner.

Hopefully, one of these will fix it. If not, we can try a couple of other things, but since you said you don't think you have fuel to the regulator, these are the ones I'd try first.

David

petec

My Feedback: (58)

It could very well be gelled fuel in the port from the regulator to the carb or in the carb or needle valve. Pull the needle valve out and open the thottle while turning the enginr over WITHOUT THE GLOW DRIVER...You should get a pretty good amount of fuel out of it.

Did you clean out the regulator? I had a 63FZ that would always need a good cleaning out in the spring. I never could get all the fuel out of it unless I took it apart.

Give that a shot and let us know what you find.

YS Parts and Service would be the place to send it if you can't get it running.

www.YSPartsandService.com

OldFart1

If you send it to YS service, they should be able to diagnose it quick - as mine is there now with the same problems

Gulliver

Would you mind telling me how you managed to get the regulator on the 63FZ dis-assembled ? (ie get the two halves separated ?)

petec

My Feedback: (58)

I had the 63 FZ not the 63 FZ-S

Daniel-EL

My Feedback: (9)

Thanks for the advice. I renewed the fuel tubing everywhere and blasted out all the ports with carb cleaner. Everything is clear. One thing I noticed on the isometric parts drawing on the YS 140 Sport (no YS 120 Sport diagram was found, but they are very similar) is that the plunger is in TWO parts (both listed as #49), one fits just below the diaphram, the other between the plunger shaft end and the plunger spring. Am I reading the correctly? If so, I am missing that "second" plunger part 49 which appears to fit between the spring and the plunger shaft.

Please advise if I am correct. I'm about to give up and send it in.[&o]

petec

My Feedback: (58)

The plunger is two pieces. If you are missing the part that interfaces with the spring then the regulator is not going to function properly.

Here is the link for your engine if it the original 1.20 SF

http://www.centralhobbies.com/Engine...YS120SFEX.html

The part number is the same between the SF and the 1.40 sport so you might want to order one if you are missing the plastic part of it.

Daniel-EL

My Feedback: (9)

Thanks for the help. I am indeed missing the spring interface portion of the plunger and have ordered one from Central. Why this peice is missing is beyond me! Maybe somebody was messing with it while it was in storage, don't know.[]

petec

My Feedback: (58)

If Central ever can't help you, Aerotech in Akron stocks a lot of YS parts (or at least they did).

OldFart1

Petec, if the spring were missing entirely - might that be my "no fuel pressure" issue?

petec

My Feedback: (58)

That would most certainly be a possibility, but If parts are missing or incorrect then troubleshooting issues becomes that much more complex. Until all parts are the correct YS parts it would be hard to diagnose. Are you missing the spring? If you are then certainly get one.

OldFart1

IIRC, there wasn't a spring in it. Motor is in Minden now - I decided I'd let YS give me a good baseline.

Daniel-EL

My Feedback: (9)

Roger that, and thanks.

One final dumb question: The part labelled "regulator body" which contains the plunger can be installed two ways. One way has the "slanted" port tunnel towards the aft end of the engine and the "right-angled" port tunnel toward the front. The other way is the exact opposite, 180 degrees turned around. I can't tell for sure which way is correct. Can you please advise? I should have looked at the proper orientation before I disassembled it.

dmccormick001

Not a dumb question at all-I ran into the same thing with my YS140 Sport. You'd think they would either make the part so it can't be installed wrong, like locating the mounting screws in different places, or at least put some sort of indexing mark on the two halves. I'm not sure if it makes any difference, but I think the correct way is with "slanted" port tunnel towards the aft end of the engine and the "right-angled" port tunnel toward the front.

David

petec

My Feedback: (58)

I had to go pull one out of the cabinet but it has the slant forward and the right angle bump towards the rear.

Daniel-EL

My Feedback: (9)

Sounds like it can be installed either way. I'll try it Petec's way first and if that doesn't work, I'll switch it around as per David's recommendation. Much obliged, guys.

petec

My Feedback: (58)

A picture is worth a thousand words. I took this picture of one of my never run YS engines.

Daniel-EL

My Feedback: (9)

Can't argue with that! Thanks, petec, you've been a great help.[sm=thumbup.gif]

mjfrederick

It CAN be installed either way, but the engine will never run right with it installed incorrectly from what I've seen.

OldFart1

Mine is winging it's way back from Minden - I'll post what all got "fixed" (could barely hear him yesterday as I was on the airfield - pesky 747's)

petec

My Feedback: (58)

Yes it can be installed either way, but if the one in the picture is backwards it was put on backwards by Yamada. The engine I photographed is a spare NIB engine...never seen a drop of fuel.

42etus

My Feedback: (2)

Actually there is an indexing mark. There is a little tab on the base of the regulator body. The regulator should be installed so that this tab is forward or toward the prop. If you look real close on the exploded diagram on the instructions, you'll see this. Better yet, download the instructions and open them as a pdf and then you can zoom in close and see it.
Paul

dmccormick001

Yeah, I see the tab on the front of the reg body, but unless you have instructions or a picture you wouldn't know which way was correct. The best kind of indexing marks are those that have a mark on both surfaces, like a tab that lines up on both pieces, or just a mark or indention that continues from one part onto the second part. That kind of mark is easy to figure out and doesn't require instructions. It would be nice on any part that's made in such a way that it can be installed more than one way to have a little better indicator of the correct way. Of course, the ideal thing would be to make it so it won't go together wrong, if it does in fact make a difference. Especially on a part so prone to needing cleaning or service to the parts inside it.

I'm curious now which way mine finally wound up being installed. I had big problems with my 140 Sport at first, (hole in the carb barrel needed drilling out) but once I finally got all the demons excorcised out it's been running like a top! Good smoke at full power, good mid-range, idles at ~2000RPMs forever, and then transitions back up with no hesitation or sputter at all. Runs as good as anything I have.

David

Daniel-EL

My Feedback: (9)

Well, I got my plunger part(s) from Central Hobbies, installed the regulator as per Petec's photo above and am happy to report my YS 120 is just as savagely beating the air now as it did in '95 when I put it away. This contraption is a beast! Thanks for everyone's help.

In retrospect, here's what I think happened: one or more ports on the regulator housing got plugged with jelled fuel over the years. I took it all apart, blew out the ports, replaced the diaphram, put the regulator back on only backwards, and couldn't, of course get it started. Then I took the regulator all apart again, lost the plastic spring-plunger interface on the floor somewhere without noticing, then got word through this thread that the little plastic part was necessary. The rest is history. Thanks again, guys!