Chuckc21

Hello all. This is going to be long so bare with me. I have an O.S 160fx on an Aeroworks Yak 54 90-120. I have had this plane and engine for a year now. Until now the engine has been the best engine ever. I have flown it in IMAC contest placing second in the basic class with it at one contest. Only hiccup the engine has was several months ago and it wasn't a big deal, easy fix. Now....with that said here goes. I went flying the other day and the first flight was great, as usual. The second, third, and fourth was a different story. The engine died on the second third and forth flights, leaving me to dead stick it 3 times. This engine has never done anything close to that before. I took it home and I changed the tank, and the fuel lines. I cleaned the carb, and the fuel filter. I installed a new glow plug. I pulled the high speed needle out and cleaned the needle housing and flushed with fuel. I then went and got new fuel. Took it to the field yesterday thinking that surely this was a small issue and what ever happened was solved by everything I had done. I primed the engine, attached the glow igniter, and bumped it with the starter and bam!! she fired right up. As it always dose. I took to the skies. I performed several of the maneuvers in my IMAC sequence, including several stall turns with and extended down line and when I finally pulled to wings level and fire walled the engine it throttled up with no hesitation and off we went. I got to the spin maneuver which I may add I saved for last for a reason. I performed the spin, pulled to wings level and the engine died. I have taken note that all of the flights that it died on was after the spin except for one. It died after a stall turn on one flight. I land the plane and I had to prime the engine again to get it to fire. It is like the dang thing just ran out of fuel. It acts like all the fuel is being spun out of the engine during the spin maneuver. Again this engine has never had this issue in the year that I have had this engine. I am at a loss as to what is causing this. Any suggestions would be greatly appreciated. I have heard of people having to use Perry pumps with the 160fx, and I am thinking of going to that next. Thanks again.

speedracerntrixie

My Feedback: (29)

Check the pressure nipple on your muffler. Some times they can get some debris that will restrict the line. I would also try a felt clunk. That being said, it is common with the larger gasoline burners to have to bump up idle a hundred rpm or so higher for flight then taxi/land. I actually have a switch set up on my TX for this. My feeling is that by going to a felt clunk and using a slightly higher idle your issue will be gone. Welcome to IMAC, I'm 16 years into and still look forward to every contest I am able to attend.

Chuckc21

Ok lol let me elaborate on a few things because I am getting the same feed back on the idle thing. I have a switch on my radio and I have 2 idle settings one for landing and one for flying. I have a pretty high idle on the high side, and the Idle has not ever been an issue. The high idle so high in fact that if I taxi around with it and never touch the throttle stick. My low idle is only used for landing and starting the engine. I did not accidentally bump the kill switch on the transmitter and I did not accidentally hit the idle switch. The O.S 160fx is not a gas engine it is a glow engine. Speedracerntrixie I will check the pressure nipple, I think the felt clunks are for gas engine only I am not sure they would work well with glow.

jetmech05

I wonder if your just under too lean. Then you spin or hammer which reduces cooling airflow engine overheats and dies. Try richning the low end an 1/8th of a turn.
Or at idle pinch the fuel line off to the carb. The engine should run ok for a second or two before it revs up.
If it dies pretty quick you are too lean
Good luck

jester_s1

I'd suspect a tank problem or an air leak, given your description. You could have a pinhole leak in your clunk line, a bad carb o ring, a leaky gasket at the backplate, or a bad needle valve o ring. The fact that you have to reprime the engine after it deadsticks is the telling part. You're not drawing fuel properly at idle, at least not in certain attitudes. With muffler pressure, an engine that is leaking air in the lines will still draw fuel fine at higher RPM because the tank pressure goes above atmospheric, pushing the fuel though the lines. You can see a fuel leak in that scenario, but not an air leak. But at idle you have basically no muffler pressure, so that's where you'll get bubbles in the fuel line and an engine that goes lean and dies.

Chuckc21

I have tried that. I have done all the obvious things, reset the needles to factory and retuned, replaced o rings and gaskets, made sure all screws were tight. I am wondering if there is something else about a 2 stroke engine that I am unaware of? Again all the obvious things have been gone through. The engine will idle all day long and transition to full throttle great no problems both on the ground and in the air. It will fly wide open throttle until the tank is dry no problems. It dies when I drop it to idle, not when I throttle up. In other words, when I exit a spin I never get the chance to throttle up, it dies as soon as I go to wings level. This problem had baffled some of the old timers that I fly with that have been flying for 20 plus years. Nobody has heard of an engine that runs great at idle, transitions to full throttle great, and runs at full throttle great, but then dies when brought back down to idle. Before anyone else brings it up, no there is not a loss in compression or power. I mean we have gone through every obvious thing you can think of. I am looking for someone that might come up with something out of the ordinary that might be wrong with this thing. People say put a Perry Pump on it and I probably will, but....It never has needed a pump before, so why would it need one now? and would that actually fix the problem?

Chuckc21

OK guys I will go through this one more time The fuel tank has already been replaced, gaskets replaced, o rings replaced, fuel lines replaced, carb flushed out, all screws are tight, needles set to factory and engine retuned. I have done all the OBVIOUS things. I did all of that before I ever posted this thread. I posted this thread because all the obvious things have been done, and I am looking for someone that might have some suggestions on the not so obvious things. Maybe someone knows about the inner workings of the engine, maybe someone had had this problem or heard of this problem and knows how to fix it.

d_bodary

My Feedback: (85)

The only thing i can think of is during the spin the inertia from the plane is not enough to keep fuel at the back of the tank so it uncovers the pick up. Now this does assume you have not added a pump to the engine. Possibly a OS bubbleless clunk may help. Try doing the spin earlier when the tank is still full and see what happens.

speedracerntrixie

My Feedback: (29)

Chuck, I'm aware that the 160 is glow, i mentioned the higher idle because its common practice on larger engines in general. Obviously you are having a fuel draw issue during maneuvers where you are at idle and fuel is sloshing around. A felt clunk will help with this. What rpm would you say this is happening?

Chuckc21

Ok I will try a bubbless clunk or felt clunk. I cant do the spin early because I fly IMAC, so I fly a set of maneuvers that are done from 1-10, and I fly the sequence twice per round and then land. The spin is the 10th maneuver. That is another thing that is hard for me to grasp because I have flow this plane in 2 contest this year, and I have flown the sequence in practice all year and this problem just started.

speedracerntrixie

My Feedback: (29)

You may be in for a new set of bearings. When they get play the seal between the case and crank is compromised and you get an air leak. Seems its an air leak issue from somewhere you just need to locate.

Chuckc21

Thanks Speedracerntrixie now we are talking. I did not even consider the bearings because I did not know that bad bearings would cause an air leak like that. I will be getting a new set of bearings, along with the perry pump. I have not changed bearings before but have watched many youtube videos about it. It seems pretty straight forward. Any tips though?

speedracerntrixie

My Feedback: (29)

Yes, get the bearings in along with the crank and a prop. No piston and rod yet. Place this in an oven at 200 degrees for 1/2 hour, take out and firmly stike the case a couple times with large screwdriver handle. This will perfectly align the bearings. On the pump. Between the Perry unit or the Cline, I prefer the Cline. Zero adjustments and holds the needle better.

dingo9882

SPeedracer...your right. I have a 1.20 and it had the same exact problems this guy is having. It sounds like his bearings are bad. You couldn't tell though because when I would try and wiggle the prop nothing would happen. I even changed the fuel. I found out when I was running it on the ground and it stopped completely in its tracks. I looked in and the rear bearing race came apart and went into the piston!

dingo9882

I also found out the 1.20 has the same type of bearing as the 1.60

Tony Iannucelli

My Feedback: (193)

I'd suggest you write a note to Bill Baxter on the OS help forum. Bill knows his stuff. Bad bearings are a possibility I think, but it sounds like a fuel feed issue. I'm thinking it's not an air leak. A Perry would probably handle the issue, but even that's not fool proof. Hope you solve it. Don't risk that AW Yak! One incredible flying plane.

Chuckc21

Thanks guys, I think I am going to go ahead and replace the bearings, not sure I will replace the crank though, it should be fine. I am going to go ahead and replace the ring and piston sleeve as well. I am going to then place a pump on the engine. I was thinking back to the small hiccup I said I had with this engine in the past and it all makes scenes now. The hiccup in the past was that the engine was running fine one day and had been all day long. Then bam it started running lean. I noticed it on the long vertical up line at first. I landed the plane and opened up the high end a bit. All was good for a flight then it started running lean just flying wings level. I landed it again and then nothing I did with the needle would help. I richened that thing up to the point I was afraid I was going to completely unscrew the needle, and it still ran lean. That issue fixed its self though. I let the plane sit for a bit started it up and all was good for a couple of weeks then it did it again. This time I took the engine apart and cleaned every part of that engine and checked the bearings since the guts were out. The bearings at that time looked good and spun freely with minor varnish on them. I reassembled the engine and that was several months ago and it ran like it was brand new after that until now. It would seem I am having a fuel supply issue of some sort that seems to come and go for some reason. Like I said I have seen many people say that they had to run a pump with this engine. Would every body agree on the fuel issue?

dingo9882

Chuck, I wish I had video of what I was going through so that you could see for yourself. I had other people looking at it, changed fuel, changed props, changed the fuel lines, glow plugs, everything!! Then that one day it happened right before a pattern competition and the bearing race shot up through the piston. Everything you have gone through is what happened to me. I found out by others that these particular engines eat bearings. Now I replace the bearings about every 2-3 years so I never have to deal with this again. Its getting to about that time again for me to change them out as we speak. I even bought a $100 bearing press at Harbor Freight to get the job done. When you replace these bearing do both of them and the piston ring while its out. One complication I found is that sometimes after heating the engine I will pop out the crank and the Rear bearing is still on. So you might have to work the bearing off. I have it down to a science so I can replace my bearings in about an hour now. Good luck. If you need any help ask. Speedracer hit the nail on the head. Heat the baby up and those bearing and its insides will slide right OUT!!

Chuckc21

Awesome dingo, I must say that my engine is only one year old, even though I have flown the snot out of it I sure hope it dosent eat bearings every year. I can handle every 2 years or 3 years but not every year.

speedracerntrixie

My Feedback: (29)

Chuck, there are some things that will accelerate bearing wear. Leaving fuel in the engine between flying sessions is the number one. I always pump the tank dry and then run the engine dry at idle. This burns off the methanol and nitro but leaves oil behind. The second is lean runs. Going lean will cause pre detonation and will hammer the rear bearing. As noted the 160 shares the same bearing size and the 120 and IMO is a bit small for the task at hand. What you have described sounds like some debris got into the carb, caused the engine to go lean and then accelerated the bearing wear. In all my power airplanes I have a filter on the filler line of my gas can and another filter between the fuel tank and the carb. I never run fuel through the airborne filter while filling as that will deposit dirt on the wrong side of the filter.


Welcome to IMAC. My first contest was in 1997. I worked myself up to unlimited in 2007 and then took a break for a few years. I have flown one contest this year in advanced and will do one more before the season ends. If you happen to dead stick coming out of your 1 1/2 turn spin, level out as you would if you still had power. The maneuver is over after traveling 3 airplane lengths. You then should be allowed to land, restart and take off, fly your second sequence. I don't know of any CD that would not allow that especially in basic class. There are provisions in the rules for electric airplanes to land and replace batteries between sequences. As someone who has sat in the judges chair a couple hundred times I would encourage a restart if I was sitting in the chair and someone had a flame out during the spin on their first sequence. Don't give up your throw away round so easily.

jetmech43

My Feedback: (9)

The stock bearings are junk replace them

jaka

Hi!
It could be the bearings but if you haven't done all ready, change your tank to a Tettra "Bubbleless" or a ordinary Tettra tank. These tanks have a rubber plug with a neck and doesn't rely on an expanding rubber plug as most other tanks do. Being a pylonracer for 40 years I have had many troubles with Sullivan and similar tanks.
An option if an ordinary tank is used , is to go for the two clunk installation , called Uni-flow (which gives a more uniform fuel delivery).

CafeenMan

Well, you've gotten suggestions on just about everything and without having the engine in our hands; who knows, right?

You've changed the tank and lines and it's unlikely that you've got a hole in the same line causing the same problem.

I had the nipple on the carb come loose on one of my OS engines and it caused havoc until I found it. Basically it was finger-snug normally but at rough running speeds (idle and transition) the vibration would cause the nipple to back out as much as the tubing would allow (maybe 1/20th of a turn) and it would leak air.

It could be a structural problem with the plane. Maybe a joint around the firewall is cracked and causing vibration. Or maybe the tank mount is loose. If it's something like that it could cause all kinds of vibration at certain RPM which would cause the problems you're having.

It would be great if you had another plane you could fly the engine on and see if it works there.

speedracerntrixie

My Feedback: (29)

actually there is some merit with that statement. I have been ordering bearings from R/C bearings.com and have been very pleased with the quality. I beleive they are better then the stock bearings at half the cost.

Jaka, being that this is an OS 160 we are talking about installed in an IMAC airplane I am going to assume a 20 oz fuel tank. Does Tettra make one that large?

Lifer

My Feedback: (1)

Does the clunk reach the back of the tank? If so, shorten the fuel line til there is at least 1/2" clearance between the clunk and the rear of the tank.