TomTreese

My Feedback: (1)

I have a Great Planes Venus 40 and have used an OS 40 FXI for 110 flights ( the engine has 320+ flights) Recently I have had problems keeping this INVERTED engine tuned and running consistantly. I have taken it appart and changed almost everything. I think it is just worn out. ( I use idle-bar plugs) I plan to replace it with a OS 46AX. Has anyone had a problem with a 46 AX mounted upside down??? I want to stay with a 46 2 stroke that will fit my mount and cowling. Thanks.

sigrun

320 flights x.2 = approx. 64hrs running. Surely your P&L can't be worn out after just that? Even for an O.S. FXi, I shouldn't think so...but then I suppose it does bear the FX suffix?

If it is, I sure wouldn't be replacing it with another O.S.[:@]

da Rock

If the engine has decent compression it's probably not worn out, at least the piston/sleeve isn't.

Is it black inside the cylinder? And have you been running a fuel with a lot of castor oil? If yes to both, then maybe you've built up varnish inside the sucker. It's fairly simple to clean varnish out. A search should turn up that process.

Also, a lot of times a well used engine is ok, but it's carb has lost some of it's integrity. It might have lost it's seal to the crankcase. Check out how tightly it's still attached. Also look to see if the drum still has it's seal. Is there any play as it rotates?

If the engine has that much time, then has the tank and it's tubing been run that long too? I've had tank fittings fatigue over time on a well used airplane. The engine started running badly and trying to figure out what was wrong with the engine turned up what was wrong with the tank and fuel lines.

When you've pulled an engine to work on it, it's very often eyeopening to slap it on the bench and run it once or twice. It ought to run good there. If not, then you don't have to pull it back out of the plane to sort it out. If it does and then doesn't run in the plane, then there is something in the plane that needs fixing. Simple and easy.........

I've found bad running engines that had..........
loose engine mounting bolts (and missing bolts)
loose motor mounts
bad throttle servo
broken throttle connectors/clevis
clogged fuel filter (they open easily for a reason)
fuel line holes
clunk line disconnected in tank
new tank was upside down in airplane
tank leaking (worn out at corner that rubbed)
tank stopper leaking (hardened and lost sealing)
bad panel in guy's field box gave intermittent gloplug heating
weak glo igniter
and a number of other "engine" problems

da Rock

BTW, I had a buddy who often would rebuild his worn out engines. He even swapped piston/sleeves at the field a couple of times.

When his piston/sleeve swaps didn't seem to work a couple of times, he "gave" me the two engines that hadn't responded. When I opened them up I found that the connecting rods were worn/beaten loose. There is often a tiny bit of play where the conrod connects with the crank pin and with the wrist pin, but the holes in the conrod should still be round. When he saw how good one ran with the new rod, he handed me the money for the rods and took his engines back...... chuckle..... I didn't want them anyway.

When they ran after his swap of the piston/sleeves, they were the devil to crank and wouldn't hold a setting worth spit. With all the slop removed, they ran better than new.

BTW, if an engine with decent compression has trouble drawing fuel, check out the carb thoroughly.

TomTreese

My Feedback: (1)

darock< The engine has great compression and runs great right side up with the cowl off. Inverted it is hard to start after the first two flights and I have to turn the plane over to start it. Starts right up. When I tune it for good performance at the high end it goes deadstick when I idle back for landing. I have adjusted both ways on the low end. It seems to fly well the first flight or two then after a 30 minute rest it's hard to start and the problems start. It's the uncertanity that bothers me. I use a Fox Long idlebar plug and 12.5 nitro. This engine has 120 flights in this aircraft but the problems have occurred over the last two months.
Thanks for your comments thus far.

TomTreese

My Feedback: (1)

darock, I have not changed all the fuel lines. I will do that and try it again this week. Thanks, Tom

da Rock

From the sounds of it, the engine is fine right side up. That would suggest that if the problem is in the engine it's caused by being upside down. Hey, don't laugh.

So what about the engine would or could react to being upsided down? I'd check the carb and see if it's loose. If it's O-ring has worn and allows the carb to slip but only when upside down....... etc etc......

An airplane that's been that good for you deserves an "annual". Give the tank a leak test. Plug all but one line and blow into the free one. Pinch it off with pressure in it and then plug it. See if the pressure is still in it after 5 minutes. If not, then there's a leak. Pull the tank and check to see if the inside pipes are still where they are supposed to be. Look at how all the fuel lines run now. I've had some lines wear through from vibrating against a corner of the engine. They'd actually not leak unless the airplane was pulling g's in one direction. I guess their elasticity was holding them against the corner until overcome by the g's. Stuff like that is what you look for.

Good luck.

TomTreese

My Feedback: (1)

I did blow in to the various fuel system lines and saw no leaks. The problem seems to me to be the carb. I have had it off a couple of times and it seems o.k. but the low speed needle seems to turn too easy and may be vibrating during flight.

TomTreese

My Feedback: (1)

Rather than spend $60.00 for a new carb I think I'll go with the 46AX. After a while it just isn't worth the uncertainty of the engine cutting out every flight for $100.00. This is my Pattern plane and I'm afraid of it cutting out on stall turns etc. It's not worth loosing the plane on a touchy engine. I'll save it for a backup in another plane.

I also don't want to put a 4 stroke in the 40 size A/C. If I'm going to 4 stroke I'll go to the 60 size venus.

Thanks for all your advice and help.

Tom

TomTreese

My Feedback: (1)

darock: Today I changed all the fuel lines even though they tested ok. I have a fellow pilot who has parts for an OS 46 FX and he gave me a carbeurator which I installed. The Venus started right up and after a few adjustments ran fine. I will try it on Wednesday. If I have more problems, I'll have learned from the experience and buy the AX 46. If not I saved $100.00. Thanks again. I don't want to ignore my Quote.
Tom

da Rock

Kewl.... [sm=thumbup.gif]

When the carb or something in it is loose, all manner of strange things happen. A lot of them have an O-ring to seal their base to the crankcase. Those will harden or wear (if the locking screws work loose) and the blasted thing will drive us nuts. Lots of things like that won't look obviously bad when we tear the engine down, so will go uncorrected. A lot of times, just taking everything apart and putting it back together will fix problems because we've moved the gaskets or O-rings or simply tightened screws tighter.

You know..... If I'd known that you WOULDN'T buy a new 46AX if you fixed your old engine, I'd not have been so eager to help. I think the best solution to any problem is getting a new engine. It not only fixes the problem but it's like Christmas to boot. I always figure the best solution to any problem is a solution that requires buying a new tool or engine. Oh well.... sorry it worked out for you otherwise.

TomTreese

My Feedback: (1)

darock, I've had the carb. off recently and when I removed it today all the screws were very tight and the "O" ring was in good condition. I want to try this latest change tomorrow just to satisfy my curiosity???

I will, probably, still get the OS 46AX. You can always use a great 46 engine.

Thanks again for your comments.[sm=thumbup.gif]

Tom

danny31292

Is it possible that the fuel clunk is flipped around.

TomTreese

My Feedback: (1)

No. The enging stopping is a carb problem. It's funny that we got into all this fixing the old engine discussion since the Original Question Was: Has anyone had a problem with a 46 AX mounted upside down???

Most of my fellow pilots insist that's the cause of the current problem??? The 46 FXI is inverted. However, that's why I use the Idle-bar plug. With a regular plug you have to turn the plane over to start it.

Thanks, Tom

GutZee

Tom,

I'm running an OS 46AX in my Venus 40, no problems starting or running, but I do get some fuel dripping out of the carb some times prior to starting. I think this is due to the location of the fuel tank in the Venus. It sets pretty high in relation to the carb.

BTW.. this is my 1st glow plane (been flying e-planes 2 yrs) and I just love the Venus! Really makes me want to learn more aerobatic maneuvers.

Jeff

TomTreese

My Feedback: (1)

Thanks for the response. Today after all the changes and a replaced carbeurator the Venus with the FXI 46 performed great. Plenty of power and no dead-stick landings. We will see how this goes. I think an AX 46 is still in the plan. THanks again to all who responded.

GutZee, YOUR CORRECT THE VENUS IS A GREAT AIRCRAFT. I have over 120 flights on mine and every flight is a learning experience. It will even hover on the prop. Enjoy.


Tom

TomTreese

My Feedback: (1)

I tried to fly the Venus with the inverted OS 46 FXI today in a Pattern Event. DISASTER!!! The first flight it stalled on the runway. Second flight I got airborne and received the third highest score of the day even with my first flights off of a macadam runway. Third flight stalled on runway. Out of the event.

I have decided to give up on inverted 2-stroke mounting. The Venus allows for a side mount with a Pitts Muffler. I have this arrangement in My Ultimate and it runs perfectly. It will require a new cowl and remount the throttle servo and linkage but that will be easy.At least it is worth a try????

Tom

TomTreese

My Feedback: (1)

SUCCESS!!!!! THe horizontally mounted OS 46 FXI works perfectly. Twelve flight all without a hint of engine trouble. After mounting I hade to richen the high end by 2+ turns and lean the lowend by 1/8th turn. With the Pitts Muffler it seems to have 20% more power and runs like a charm. I recut the cowl and re-fiberglassed the old holes and it looks as good as it runs.

Lesson Learned!!! DON'T MOUNT 2-STROKE ENGINES UPSIDE DOWN!!!!!!!!!