jackalope54

My Feedback: (2)

I purchased a used YS 63 (not the "S") that has me stumped. The regulator seems to be over pressurizing. Right after purchasing, I went through the engine and replaced all the o-rings and gaskets, replaced the front and rear bearings, replaced the diaphragm (eventually replaced the plunger and spring also - found it had the wrong plunger installed - the old plunger was approximately twice the diameter of the new plunger), verified the cam timing and adjusted the valves, replaced the piston and ring (the surface of the ring was very shiny), cleaned everything and put it together. I set the regulator to flush, the low speed needle to one turn open and the high speed needle to 2.5 turns open per the manual. It started easily but was putting raw fuel out of the exhaust - it was running too rich to set either needle. I closed the regulator in small increments til it is about 1.75 turns in from flush - can finally set the needles but it is still running VERY rich and is now pushing fuel out of the intake tube where it enters the head (this when the engine is NOT running). I suspect I've bottomed out the regulator - I just got home from the field and removed the diaphragm, spring and plunger and found the regulator screw only goes in a little more than 1.75 turns from flush before it bottoms out.

Fuel is Cool Power 30%
12x6 APC prop
Low speed needle 2.75 turns open - 1980 to 2010rpm idle but it loads up after 20-30 seconds
High speed needle 1.5 turns open
Transition is very slow - if it cleans out it turns about 10,700 rpm WOT - I backed it off to about 9800 rpm.
It bogs badly in transition and has a very heavy smoke trail (looks like it has a smoke pump).

Any ideas out there in YS land?

Thanks,
Jack

jackalope54

My Feedback: (2)

If the intake valve is not seating properly, could the result be the described symptoms? If so, can anyone recommend a suitable compound for lapping the valves? Toothpaste, perhaps? Maybe I'm grasping at straws...

jjoos99

My Feedback: (12)

FWIW On my 120 I have the regulator screw set at only 1/2 turn out from being bottomed out. Runs great with good transition.
Jeff

ThumbSkull

My Feedback: (57)

Sounds like you need a new diaphragm and/or plunger. They are regular maintenance item.
Any time you get more than a turn from flush, it's time to replace.

petec

My Feedback: (58)

First issue is the raw fuel, if it is so rich that is it pushing raw fuel out the regulator is not closing. That issue needs resolved first. Since your initial post states you replaced the diaphragm and plunger I am wondering if you replaced the spring as well.

As for lapping the valves I know guys who have used toothe paste or baking soda to do that job.

jackalope54

My Feedback: (2)

Hi Petec,

I've replaced all the parts in the regulator, ie. the diaphragm, plunger, nipple and spring. I've come to believe it's not over-pressurizing but is an intake valve problem. When I disassembled the engine, I found carbon on the intake valve stem and on the backside of the valve - more carbon on the intake valve than on the exhaust valve possibly indicating the intake valve is not seating. I have access to a set of virtually brand new YS 70S valves and springs - they share the same part numbers as the 63 per Central Hobbies. I'm going to install them and see what happens. I guess I'm looking for confirmation that this makes sense. And I'm also looking for any other ideas for the cause of the symptoms my engine exhibits.

As for the fuel forcing its way past the intake manifold o-ring at the head when the engine is NOT running, my guess is that is what happens when the regulator screw is bottomed out.

Thanks

jackalope54

My Feedback: (2)

Success! I replaced both valves and lapped them in using toothpaste. Engine is responding well - now just need to fine tune it. I'm running a 13x6 APC - max RPM about 10,800 - richened to about 9800 until piston and ring are seated.

Huge thanks to my brother-in-law, Ben Galloway (pylon racer and all-around great guy), for suggesting the possible intake valve leakage.

Four Stroker

The intake transfer tube O-rings should never leak. I use the 1.9 x 9.8 mm McMaster 9263K644 Viton O-rings for the 53/63/70. Oddly enough, I have YS official O-rings that will not go in the head. 2 x 10 mm is too damn big.

jackalope54

My Feedback: (2)

Well...not so successful after all.

I got 3 good runs out of it then it started pouring fuel again. It's actually coming out of the carburetor and running along the intake tube. Has to be a sticking regulator as Pete suggested. This engine was purchased used and I'm not sure it has the correct regulator assembly or there is wear around the plunger and/or the plastic nipple. It has a new diaphragm, plunger, nipple and spring and I've verified several times there is no debris in the system. When I replaced the plunger, I noticed the new plunger has a much smaller diameter as compared to the old one and the regulator body was machined for the larger plunger.

I've ordered a new regulator body and screw from Central Hobbies - I'll take some measurements from the new parts and compare.

I hope the new parts solve the problem - this one has me stumped.

Thanks Petec and Four Stroker.

Jack

jackalope54

My Feedback: (2)

Hi Pete,

I got the new regulator body, screw, plunger, spring, nipple, diaphragm and o-ring for the screw. And I finally have an engine that runs like a REAL YS.

I compared the new regulator body with the old but could find no measurable differences with a caliper. I did notice less play around the plunger stem where it passes through the bore in the new regulator body. Perhaps that was allowing the nipple to hang open intermittently.

I'm still using Cool Power 30% Heli fuel and now have a 13x6 APC prop - 1980-2040 rpm idle - 10800 rpm peak richened to 10200 rpm.

Current settings:
Regulator about 1 turn in from flush
Low speed needle is a bit more than 3 turns open
High speed needle is about 1 1/3 turns open

Engine still smokes heavily with lots of oil in the exhaust - I'm wondering if the Cool Power 30% Low Smoke would be a good idea?

Anyway, HUGE thanks for the advice on the regulator.

Jack

petec

My Feedback: (58)

As long as you do not go under 20% oil content you should be OK. I like a nice smoke trial personally. If it is smoking a lot at idle you could back the idle needle out a taste to lean it. Do not let the idle go over 2300-2400 RPM as at that point you are on the regulator and not the idle circuit.

TCBLightning

My Feedback: (5)

I have the 63FZ S and am having the same fuel issues as Jack. I have replaced all the O-Rings, bearings, diaphram and adjusted the valves. Still blowing raw fuel out the exhaust and the carb fills up when the engine stops. I'm going to run the engine again tomorrow and adjust the regulator some more to see if I can slow down the fuel push.

Not sure what the difference is between the regulators but interesting that the S is having the same problem. I have two of the Ss and both are doing the same thing and both started having problems at the same time.

Tim

Joebinderjr

I'm looking for the book or VHS tape for the combat model F-16. I was told that you might have one or point me in the right direction. Any thing at all will be more than I have now

Hardy

I have been having the same problem with a Ys 63 fz . It would dump raw fuel from the carb at about 4000 rpm, but hold the fuel under full tank pressure when the engine was stopped. So I phoned Ys service, They said the idle air screw is not very sensitive and can be opened as much as FIVE turns. At four and half turns open it started to work. The idle screw on this engine is just a screw that blocks or opens an air hole in the carb inlet butterfly. Now I'm just down to fine tuning. My 63 fz has been a wonderful little engine. I replace the diaphragm, spring and reg valve, adjusted the tappets it did not help. The manual did not say open idle to five turns. Good thing the service department is on line.