jjoos99

My Feedback: (12)

I got my ultimate out this year with a 120sf motor. It is idling good and wide open it good. While taxing around when I started to throttle up in the mid range it will stumble, spit and sputter and then die. I have played around with the regulator screw alittle bit but it doesnt help. If I run it in alittle it will die as soon as I remove the glow starter. Any suggestions?
thanks
Jeff

petec

My Feedback: (58)

Jeff,

Sorry I was out of touch for a while, my work had me buried but I am hopefully seeing light at the end of the tunnel. In regards to your issue, I need a little more info for troubleshooting purposes.
1) Fuel used
2) Glow Plug used
3) Prop
4) HS Needle setting
5) Regulator setting (turns in or out from flush with housing)
6) Does it seem to be lean or rich when it dies
7) When you say you played with the regulator what exactly did you do and how did the engine react to each change.

Pete

jjoos99

My Feedback: (12)

I have a regulator problem. I was running it last night and the problem occurred after a period of idle and when it died it would drip fuel from the carb throat. I took it apart before running it last night and it was clean of all debris. It appears to be about flush with the housing. I replaced the regulator parts maybe 3-4 years ago. Should I replace them again or maybe adjust the regulator screw some more. I am sure that it is flooding, it will stay running with the glow plug igniter still hooked up so I believe the glow plug is getting hit with fuel.
thanks
Jeff

petec

My Feedback: (58)

If you are dripping fuel the regulator is not shutting all the way. When you cleaned it did you flush everything out really well with raw fuel? It doesn't take much to keep the silicone plunger from staying open a bit. Also if you closed the regulator screw all the way it will take a set and not function properly.

jjoos99

My Feedback: (12)

I flushed it out real good today and leaned it out some on the regulator screw. It helped with the dripping issue but it is still loading up while in a prolonged idle. Not as bad as before and if I go to wide open it will clear itself out and throttle up good. I went close to being too lean as the idle wouldnt settle down for about 20-30 seconds after cutting full throttle. I will probably change out the regulator parts. I have seen posts of people changing the whole regulator housing. Is that necessary to do?
thanks
Jeff

petec

My Feedback: (58)

No need to change the housing, they don't wear out. If you flushed it out and it got better I am wondering if you don't have some old gelled fuel in there. Did you pull the brass screw and spring out and then pull the plunger apart and clean it all out and blow out the passages? I use pipe cleaners, q-tips and an old soft toothbrush to clean my stuff in a bowl of raw fuel. If there is ANY fuel dripping it isn't closing. When it's all clean and back together set the regulator screw at flush and then take it from there an 1/8th of a turn at a time. 3-4 years on regulator parts should not wear them out unless you fly a LOT and then you would be due for ring and bearings too.

Pete

jjoos99

My Feedback: (12)

I took apart the entire regulator system tonight. Everything looked good. I got it running and set high end. when coming to a idle, it would slowly continue to drop rpm. I started to lean it out some and then it wouldnt throttle up. righen the regulator and it loads up after 30 seconds of idle or so and will stumble and die as I slowly throttle up. I will look up the regulator parts and probably order new parts. Not sure where else to go with this.
thanks
Jeff

apereira

Besides the regulator, have you checked the internal passages on the engine are not clogged? Did you change all the gaskets specially the rock cover? The internal pressures on this engine have to be correct, this is if the regulator is working properly

jjoos99

My Feedback: (12)

I havent changed any of the gaskets. I flushed out the fuel passages leading into and out of the regulator. I have another question. When at an idle I can hear the air being drawn into the engine and it has a wet sound to it. I am thinking that is what is flooding the motor.
Jeff

apereira

It is obviously like previously mentioned a fuel pressure regulator problem, but not due to a bad regulator, if the regulator does not have the correct reference from the internal engine pressure it may not regulate the fuel pressure but keeping constant pressure, it obviously works because it is changing the fuel setting, That is why I can only recomend to check/replace gaskets and O rings.

Dave Harmon

Jeff....what Al has mentioned so far has been good advice but I thought I whould chime in here with some of my experience.

You never mentioned what plug your are using....it must be an OS-F.
If you don't have one I would get one before you go any further.

So far....it sounds to me like the idle and transition mixture is too rich.....this also can be caused by a too cold/wrong/bad plug.
You can verify this by leaving the glow driver connected while attempting to adjust the low speed mixture.
It can be easier to adjust the mixture by observing how it operates during the transition and temporarily ignoring the idle mixture....ie...adjust the transition for best response without getting too lean.

I had trouble with the regulator housing.....I had a drip that would occasionally happen and the idle would change occasionally.
The fix was.....I removed the housing and took it apart and looked closely in the passage that the plunger goes through.
That passage had some machineing debris trapped in the passage causing the plunger to drag and make the mixture weird.
These chips were 'glued' in there by some process YS uses. I poked them out and ran a right sized drill bit through there carefully by hand...then flushed and blown.

The throttle barrel has a similar problem.
Remove the barrel from the carb housing and look very carefully at the fine slot in the center of the length of the barrel.
That slot has been known to have metal chips 'glued' in there and also is a crap trap. You can make sure it is absolutely clean by dragging a razor blade through it and closely inspecting the slot with a jewelers loupe.

Closely inspect the carb gasket....the engine is old enough to still have the brown paper gaskets that get mushy around the passages.
Replace all gaskets with the newer, better quality black gaskets available from YS PartsandService.

The regulator plunger (Central Hobby part 48 YSE0176) has been a particular problem for me on several engines.
You can inspect this part with the loupe.....what happens is this part is cut off a mold tree by a worker with sharp cutters.
Sometimes they get sloppy and nick the plunger in the area where it seats....this causes the drip from the intake and also can mess up the idle and transition idle.
This leak almost never affects full throttle because the leak is not enough to affect the large amount of fuel going through at full throttle.....but a small fuel leak here at idle may put the mixture out of range of the adjustments.
Also....there is usually a 'bead' of left over mold flash around the circumference of the plunger that is not trimmed off. This might also cause the plunger to not seat properly or hang up so it will not open and close rapidly according to the crank case pressure pulses.

Also....you have not mentioned what fuel you are using.....it must be at least 20% nitro and no less than 18% oil.....no castor in 4 strokes.

That wet sound at idle is pretty normal.....these engines have a slight slurping sound at idle.

Try to use a test stand when trouble shooting the engine....it is a lot easier than in an airplane.
Make sure the engine runs dry. Clean the engine with alcohol or lacquor thinner/acetone and then run the engine looking for fuel leaks.
Gaskets and O-rings leak in both directions....they leak fuel or oil and can suck air as well.
Both will mess up the mixture.....especially on the carb casket and backplate casket.

Remove the needle socket (part 55) and inspect for trash in the carb housing....remove needle valve and inspect in there too.
I have had problems caused by small chips of fuel line that got in there and caused huge problems....the fuel line chips are almost invisible....they are almost transparent.
Flush and blow in both directions.Flush all new fuel tubing before use to get rid of the silicone chips.

This is getting too long so try all this and let us know how you are doing.

jjoos99

My Feedback: (12)

Thanks for all the help. I installed new gaskets into the engine yesterday and installed a set of used plunger, spring, and diaphragm yesterday to no avail. It will run fantastic full throttle but If I hold it at about 4k rpm it will start running rough and die. Stills drips fuel out carb after it dies. I guess i need to quit fooling around and order new regulator parts. I turned in the regulator screw and it didnt seem to make a difference.
Jeff

apereira

Jeff,

Did you blow compressed air through the regulator passages?

Dave Harmon

Jeff.....Likely what you have is some restriction in a passage cause by trash. Look for those very small pieces of fuel line chips that can get gouged out of the side of the fuel line when you push them on a nipple.
I have had a lot of trouble with this over the years. Those chips are almost invisible.

I'll bet your main needle valve is open too far to compensate for some restriction.....if so....this will put the midrange and idle mixtures outside of the adjustable range of the regulator.....

How many turns open is the needle valve when adjusted for full power?

Remove the throttle barrel and check the very fine slot for trash.

jjoos99

My Feedback: (12)

I believe I finally got it worked out. I did all the suggestions today in the way of blowing out all the regulator holes and took apart the carburetor and cleaned it all. I installed another new f plug and ran it again. It was better but it did still die and drip some fuel. I ended up running the regulator screw in a 1/4 turn twice and it wouldnt die after that. Still had a slight stumble while throttling up after a 30 second run at idle but didnt die. I would like to try to turn in the screw another 1/4 and see how well that works. Thanks for all the support. Everybody's advise keeps you going on these stubborn problems. I love the way this motor runs when it is right but sure is frustrating when it isnt.
Jeff

Dave Harmon

That's great Jeff!

The midrange 'test' is a good way to get the regulator adjusted but you should keep it slightly rich in the midrange.
Then the idle mixture should be within range....if I remember correctly that engine has an airbleed for the low speed idle. If so...remember that out is lean (more air bleed and in is rich...less air)

You might mention how far in the regulator brass screw is from flush with the housing.
You can unscrew it while counting turns until it is flush...hold a tool across it so you can easily see when it goes flush.
Each engine is a bit different so the turns wil differ.

One thing....the spring under the brass screw is shaped like a funnel....the small end fits over the bump on the regulator plunger, the large end goes toward the brass screw...BUT....it is possible for the large end to get jammed sideways to one side of the brass screw. The spring must be flat against the inside of the brass screw. If in doubt....remove the regulator and take a look...but be careful when reassembling....get the spring flat against the screw.
If the spring is slightly sideways the plunger won't seal....causing a leak and other weird mixture funnies.

If you turn the regulator screw in any more....at this point I would change to 1/8 turn cause you are close now....don't want to get too lean in the midrange.