2 Stroke deadstick issues

[Russ P]

I have been running an OS 55AX for 2 years without it missing a beat. But just recently it has deadsticked on take off.

On the bench it runs smoothly from tick over to full throttle, but as soon as the model leaves the ground the engine dies. It doesn't cough and splutter or rev as if it had fuel starvation, it just dies.

An idea I had was that it maybe a range issue, as mine is set to fully close the throttle, but it isn't this.

I have changed the plug, enya no3, the fuel tank (SLEC) and all the tubing but it still deadsticks on take off.

Any advice would be appreciated.

[Nigel R]

Time to clean the carb, I would say, if you haven't already.

Engine has run perfectly before, so, it must be something that has degraded, or blocked. New fuel system, so on to the engine itself.

[Jon H]

Yup. Take the head off and have a look inside as well just to check the internal condition

[The Wright Stuff]

What about the fuel itself? Is it old? Have you tried a new batch?

[extra slim]

weird, I had something similar years back, and eventually traced it to a transparent piece of flashing inside the fuel tank, which sucked onto the pickup... but you say you have changed the tank.. so perhaps carb O rings, overheating??.. very strange..

If everything else has been systematically changed, then as Jon says, you need to look at internals!. A fella's engine behaved similar this weekend, and bearing wear has made it run very hot and die... new bearings on their way.

[Wilco Wingco]

Is the only thing that seems to change is the model leaving the ground, so the attitude of the tank changes?. Stupid question I know but have you tried the old "trick" of holding the model upright while getting a helper to open the throttle as on take off??. Maybe there isn't enough "suck" to draw the fuel up to the carb when the plane is at an angle??. Remove the needle and flush it out with fuel direct from your pump, wipe the needle, replace and try again. Make sure that the nipple on the exhaust id clear. A mate of mine had a dead stick problem and he found that the nipple was partially blocked.

[Russ P]

Thanks for all the replies. Will work my way throughout them.

[Robert Welford]

If it's a carburettor issue removing the needle and flushing out with fuel won't solve the problem.

The construction of the carb is more complex than most. I had intermittent problems with an OS 55 AX until I stripped the carb completely and discovered fluff that was restricting the fuel flow.

The fluff collected between the 2 'O' rings on the fuel inlet and won't be removed by flushing out with fuel. BTW the "fluff" comes from the fuel not from external contamination!

Edited By Robert Welford on 21/05/2018 17:53:49

[cymaz]

Look at the lining of the cylinder. I had/have an OS 55. After about 6 years it’s playing up. The chrome lining had worn right away. It’s about £90 for a new liner and ring. So I’ve scrapped it and swapped it out for a SC 52....great motor.

[Russ P]

I'll strip the carb first.

[Alan Hilton]

Hi Russ

Not read the whole thread so please excuse repeats .Check out all carb O rings especially the one between the carb body and the crank case

Alan

[onetenor]

The fluff in the fuel is I believe waxing as it's called. In later stages it actually forms lumps of wax in the fuel. I found that storing fuel in polythene bottles seemed to be the culprit. Wether it is actually the polythene being dissolved into the fuel or not I never found out but it seems possible. Diesel seems to be worse than glow for this.If you have an inline filter replace it or at least reverse flush it as this could well be blocked.If anyone has further info regarding this fuel chemistry I would love to hear it. I always filter my fuel every time I transfer it from one container to another. Including the tank and I have an inline filter too. Good luck.

John

P.S.Leaving fuel dregs in the tank could be a contributory factor in this

John.

[alex nicol]

Hi, one of our club members had a very similar thing with an Irvine 46. it ran ok on the ground at various speeds, then on take off about 20 feet up it just died. Tried everything, carb and needle o rings, flushed and cleaned carb out, replaced tank and glow plug, enya no3, changed fuel etc. Turned out it was the idle needle was turning, a little loctite on the idle threads and problem solved

[Tim Flyer]

One problem we used to see on high rpm engines was carb barrel wear . Engine vibration can cause wearing of the barrel and poor seal on some old engines. I doubt it is that on this engine though. O rings more likely to wear first or it’s some sort of blockage issue.

[Engine Doctor]

Hello Russ . Does your engine sound rattly or feel rough ? Bearing wear or corrosion can cause all sorts of problems and if bearings are worn then crankcase compression can suffer causing unreliable running. Check that bearings are smooth and quiet . If they are then problem lies elsewhere.

Can you tune the engine rich easily with main needle ? if you can then that will probably rule out blockage in the carb. One place to loo if engine cant be tuned rich with a turn or two of the needle is the chamber behind the fuel nipple on the carb . Unscrew nipple and check for debris . I have had this once or twice on problem engines

The chrome plating shedding from the liner as Cymaz mentioned can cause cutting out like you mention . Easily spotted by removing the cyl head. The engine also gets a bit rattly when the happens .

Hope you get it sorted as these type problems can be very frustrating.

[will -0]

Didya gettit fixed?

[ASH.]

So many different things for you to try out Russ, gosh.

The first thing that came to my mind was engine load which is at it's max at rotation until the wings get the lift proper and start flying. So my guess is it's leaning out or it's too rich. Also, the correct prop makes a big difference. If it's too light (wooden) it's not going to give the flywheel effect. If you have the engine inverted try an OS F type plug, worked brilliantly with my Irvine 53. Keeps the fire alive. Also, I've read.. white bits in fuel is castor separation especially in cold weather.

Edited By ASH. on 31/05/2018 00:24:12

[Tom Thomas]

Posted by Alan Hilton on 21/05/2018 19:04:23:

Hi Russ

Not read the whole thread so please excuse repeats .Check out all carb O rings especially the one between the carb body and the crank case

Alan

Lazy!

[Tim Cheal]

Hi Guys

I wonder if I can get get involved as I have a similar problem. I have a 2 year old OS 55AX that has been trouble free for the whole time, and flown over 200 flights in that time in a Pulse XT40. Last flight but one I dead-sticked, unusual but nothing serious I thought. But again, on the last flight it dead-sticked again. This time I noticed the engine was very hot and it also "smelled" hot. So, I ground ran it and it ran fine, but when I held it vertical at full throttle it started to hunt up and down. I suspected fuel flow and so changed out the fuel line, no change but I thought the tank might have a leak, so I put in a new tank and more fuel lines, but still no improvement. Having read this thread I decided to change the carburettor O ring, and for good measure the needle itself, but while waiting for delivery of the O ring I ran it again. It got very hot again, and I decided to have a go at changing the bearings. So, ordered those, and they arrived very quickly so changed those out. After the bearing change it seemed to have solved the problem, and I was dead chuffed, but I took it to the field and it played up again, hunting at high revs and eventually stopping. It was very hot again! The O ring and needle arrived and were changed, but no improvement (although in every case if I run it from cold it runs for about 5 minutes trouble free, then gets hot again and stops).

I have now changed the bearings, the O ring, the needle, flushed through the carb fuel inlet with fuel (numerous times) and forced air with a bicycle pump through the fuel in;et to the carb. I can't think what else I can do (although I have not stripped the carb as I am not sure what to do here, but I have removed the needle and its 'nipple' but it revealed nothing).

Although I replaced the gasket on the rear cover is it possible air is getting in here? Would this cause the overheating? Would some silicone gasket sealer be a good idea on the rear cover?

I have a photo of the engine taken with the rear cover off (on next post). What surprised me when I took the bearing out initially is that the conrod runs in a groove in the crankcase - is this correct or has the groove been worn while running? (although the conrod looks ok and not damaged or worn).

Any advice grateful received as I am now at a complete loss - and I fear the engine may be too!

Tim

 

 

 

 

Edited By Tim Cheal on 06/06/2018 21:33:52

[Tim Cheal]

Here is the corned/crankcase I described above:

[Chris Walby]

As long as the con rod is a good fit in the crank pin I am sure it has not worn a grove, that will be the manufacturer squeezing as big a con rod and stroke as possible without making new crankcases

IMO the getting hot sounds like its running lean possibly due to an air leak somewhere.

Experts please chip in..

[Russ P]

First I went the carb route, as it is the simplest, dismantled and gave it a through clean, checked the O rings which seemed ok. Put it back together, reset the needle valve and hey presto running great again.

I did find a very small piece of debris in the needle/spray bar even though I had previously cleaned it without dismantling.

Thanks again for all your ideas/suggestions.

[cymaz]

I had an OS55 ax and have described the problem I had with it a few pages back. I have a SC 52 2t. I put the OS carb and power box exhaust onto the SC body with the minimum of modification ....so far so good

[Martin Harris - Moderator]

I don't claim to be an expert but I would refer you back to Cymaz's suggestion of checking the cylinder plating - there have been many cases of it wearing and causing unexplained engine cuts. Perhaps it's due to loss of compression at full running temperature or flaking affecting the glow plug? Look for small pits or signs of the brass liner showing through...

[Jon H]

Posted by Martin Harris on 06/06/2018 22:20:22:

I don't claim to be an expert but I would refer you back to Cymaz's suggestion of checking the cylinder plating - there have been many cases of it wearing and causing unexplained engine cuts. Perhaps it's due to loss of compression at full running temperature or flaking affecting the glow plug? Look for small pits or signs of the brass liner showing through...

This would have been my first port of call, even before glow plugs and carb cleaning