Bark-RCU

I bought an OS 70 fs online a while back it ran fine when i got it.I put it on my airplane inverted and stored it nose down with fuel in the tank for a couple of months.That probably was'nt a good idea.I was waiting for tower to get an exhaust manifold to route the exhaust under the plane.(they still don't have it got one from performance specialties).Anyway i got the part a couple of days ago and installed it on the plane.When i tried to start the plane it was very hard to get it going.I did get it to run a few times but there is fuel leaking from the front of the engine where the spinner backplate goes,and there is no puff of air pressure when i disconnect the pressure line.The fuel tank pressure comes off the crankcase.I suspect that the front bearing has gone bad acct. i left fuel on it for so long.I'm not sure though,as i have never replaced one.I appreciate any input.THANKS.

bob_nj

My Feedback: (62)

I'm not real familiar with that particular engine. Does OS make a .70 with a pressurized fuel system? I'm confused as to what you are expecting when you disconnect the fuel line. Do not connect the overflow fitting on the back of the engine to the tank!! As far as storing the plane with fuel in the tank and nose down, my first reaction is that it will not cause any problems as long as the tank doesn't leak on the floor. Do you use any after run oil at the end of your flying sessions? I use it religiously. Although changing bearings is sort of second nature now, it's still a project, especially in a four stroke. Not sure about the running sound of a four stroke that needs bearings, but a two stroke has an unmistakable "whine" or "whurr" while running. I never ceased to be amazed at how many flyers are tweaking engines that desperately need bearings. Eventually they come un-glued and it's messy. Let me know how you make out_Bob

Bark-RCU

Hi bob,thanks for the input.There is a pressure tap on the bottom of the crankcase that i use to pressurize the fuel tank.Normally after running the engine when this line is disconnected there is a "puff" of air that was pressurizing the tank and forcing fuel to the carb.Now it appears that the crankcase itself is losing press. because of the absence of the "puff" and when the engine is running fuel is leaking from where i assume the front bearing is.I don't normally use after run oil,though i may begin to.I'm a bit intimidated about changing bearings.I hear you have to warm the engine in the oven to get them in and out.I may be calling on your experience for this project later Thanks.

bob_nj

My Feedback: (62)

Try running the engine with muffler pressure only. Do not use the fitting on the bottom of the crankcase. It's just a vent for the engine and not designed to pressurize anything. Let me know_Bob

kadamstex

My Feedback: (2)

Bark,

I think you have your engine hooked up wrong. How much experience do you have with four-stroke engines? Four stroke engines have to have the crankcase vented to the atmosphere or they will not lubricate properly. Where exactly is this fitting on the engine that you are connecting to the tank? I do not have a FS-70, but have had several OS 4-strokes, and I've never seen one that has a line on the actual engine that you connect to the tank. Do not run the engine with the crankcase vent fitting connected to anything. This will prevent the bottom end of the engine from lubricating properly and will ruin the engine very quickly.

Scorpionjack

Ditto Guys;
I had 4 OS 70 4 Strokes on my B-17. Bark you have it setup wrong! That is a vent fitting on the bottom of the OS 70FS not a pressure fitting, Use the muffler pressure just as you would on a normal 2 Stroke. Never store your engines Nose down If they are going to be in that position for a long time with no after-run oil in them. Plus it will make a mess in your shop dripping every so often. Fuel will separate and the Castor will just gum up the bearings and in time without a good cleaning can virtually sieze your bearings with Gunk.
Pull the plug and use some Marvel Mystery Air Tool oil or even ATF for your car and put a few drops in and spin it through lubing everything.
Then when your ready to fly, Fill the Tank and with the Plug removed Open the throttle and spin it through to get fuel through the system/engine. Now your ready to put the plug back in and your engine is clean.

Hope this helps.

Bark-RCU

Oops! I guess you live and learn.It did'nt come with the manual i assumed that the nipple was to press. the tank.My experience with four strokes is lacking.I will reconnect the plumbing and hope that the engine is'nt ruined. I'll post the results.Thank you all for your help.

Scorpionjack

Your Welcome Bark;
Anytime, It's a common mistake i've seen it many times.

Bark-RCU

Well i redid the plumbing and engine is running fine.Thanks to everyone!My next question is how do i set the needle valves? I've got it pretty rich now on both needles,i think. It starts OK,and when i go to full throttle there is a nice smoke trail but when i go back to idle it will drop to a high idle for about four seconds and then drop all the way down to idle.Is that normal with four stokes or do i need to do some tweeking?

Scorpionjack

Okee Dokee Bark!
Now take the High speed needle and adjust it till you just hear the Engine Lag a bit, right at being to lean. Now back it off about 300-500 Rpm for the first few tanks. Leave the low idle alone for a few tanks. Then you can adjust it to give yourself a nice idle. Let the Engine run at the recommended manufacturer's setting which is approx where I told you thus far.

When it's ran those tanks you can go to the Low Idle adjustment (by the sound of it you may be a little lean) so adjusting the the low idle in is richer out is leaner(I know this sounds strange but the low idle needle on engines is opposite from the high end needle. Now just adjust about 1/16" in at a time, let it sit and idle then ease the throttle forward listening for any hesitation. continue doing this until you have no hesitation. You may have to lean the low end vs riching it so only make very small increment adjustments.

Let me know how you do and have fun always.

Bark-RCU

Well i've been learning a lot about this engine the last few days.I was adjusting the throttle travel screw instead of the idle needle. The hi speed needle became harder to turn so i took it out and cleaned it along with the idle, and fuel intake ports.this cured the problem perhaps it was gummy from fuel deposits.Once all back together the engine would not start.After about an hour of spinning and flipping the prop i found that the glow plug was registering but not heating.I changed it.The engine would now start but not until i put fuel in the carb.and even then it would only run backwards.I know that this is an indication of a rich mixture on a two stroke i suppose that this is also the case for four strokes.I began adjusting the "right "idle needle valve but the same thing happens.It won't start until i prime it and then it will only run backwards.I've been to both extremes with the idle setting and encountered the same symptoms.What am i missing?

wbrian

Not to be a wise guy but try changing the order you’re approaching this hobby from. Trying, asking, and then reading – to: reading, asking, and then trying.
I only say this to avoid any further damage to your defenseless engine.

You can get most manuals online and yours can be found at: http://www.osengines.com/manuals/index.html

good luck!!

Bark-RCU

I've been in this hobby four over ten years.I've never had a four stroke engine before,hence the purchase of a used on online to see how they work.Would read manual if it were so equipped.Thanks for your input.

Scorpionjack

Bark;
Not sure what you mean that your high speed Needle became harder to turn?

So lets start here! Just a little Trick, take and screw in the low speed needle all the way till it stops.(The little screw that is inside a round ring). Now take a piece of fuel tubing and attach it to the fuel nipple on the carb and while blowing in the tube start backing the low speed needle out (Just until you hear a slight hiss of air coming out of the Carb). Now leave it there this is your low speed starting point for idle. Now remove that fuel tubing and hook up your tank to the engine (main line from the clunk to the carb and the vent line to the muffler) adjust the High speed needle all the way in clockwise and back it out approx 2 turns or a little more(This is a real rich setting). Now start your engine with the throttle about 1/4 open it should start. Once you have it running advance the trottle to full which will be slobbery rich and start easing the high speed needle in until it peaks and you hear the engine Sag/Lag on the high end back the needle off about a half a turn. Engine should now be running at peak. Now lower the throttle to the idle position it should idle now. If not you may have to adjust the low speed needle 1/16th to 1/8" in either direction to get the idle set just right.

Hope this helps you understand a little more.

Bark-RCU

I had forgotten about that method.I'll try it and post the results.I've begun racing the cars again(1/10 gas truck)and am juggling the two.I'm spreading myself kind of thin,but it sure is fun.Thanks for your help Scorpionjack.

Bark-RCU

HI Scorpionjack,just tried your suggestion on my engine.YOU DA MAN!!Running fine again.The idle setting was too tight.Have new problem now though.RACE OR FLY.But that's the kind of problem I like!!Thanks a million,and thanks to RCU for such a helpful website!!

Mighty Mouse-RCU

My Feedback: (145)

Scorpionjack,

QUOTE:"the low idle in is richer out is leaner(I know this sounds strange but the low idle needle on engines is opposite from the high end needle."

Not sure about this one Jack. Were the old OS 70's a airbleed?

Scorpionjack

Your Welcome Bark;
Glad to help. MM from time to time it doesn't really matter. The low end needle on and engine acts opposite to the high end.

MM

As with my prior post I had (4) 70's on a B-17 and tuned another not more than 1 1/2 years ago in Japan for a guy. The OS 70's are really sweet engines not as powerful as a YS 63 but atleast equal to a YS 53.(I've turned into a YS Zealot) : ). But anyhow the OS 70 adjusted just as easy and in the same way as your two strokes and mine.
The 70 was a Surpass it had a carb OSMG2526 44081000 Carburetor FS70SUR . There hasn't been any changes to that engine that I know about since it's cames out. As for your question reference airbleed. ( I'll get flamed for this but anyhow) I've never had a problem with a 4 stroke carb treating it opposite as a high end needle. In! is a richer setting out is a leaner setting. airbleed or not.