OS FS70 Surpass problems

[Peter Roberts]

Can anyone help please. I have an OS 70 FS Surpass which has been a delightful and reliable engine over the last few years. (Engine is 12 yrs old but sat in my garage for 9 and started first time).

Recently after a period of in activity it would start run on idle for a while then cut. This happens irrespective of idle speed. I have changed pipework and tank filter, and plug. I don't know what to try now other than send it off top Just Engines for a de gunk and service. Any suggestions will be gratefully read.

Cheers Peter

[Aslan]

Peter,try a small piece of tubing on the high end needle valve.If it still cuts,try opening the low end 1/4 turn,it might be idleing a little lean,which will cause it to overheat.Great engines.Have four and needed to put tubing on one of them,so try that fix first.

[Peter Roberts]

Hi Aslan - many thanks for the advice - sorry to be thick but how / where exactly does the tubing fit?

Many thanks

Peter

[Aslan]

It fits on just above the existing o ring which is just above the threads.It is there to stop the engine drawing air through the needle valve
holder.Good luck Peter.

[Bladerunner]

You should also give it a good clean if it's been standing for a while - check carb and tappet clearence. This is especially true if you are using castor in your fuel and the engine stands for a long time. Good luck.

[Colin Hostler]

Have a look into the exhaust port
(with the complete exhaust removed) if the valve stem is carboned up that could be your problem)use a good quality synthetic fuel.

[Allan Jordan]

Hi. Peter, The advice given by the other forumites is sound. But just a word of caution, I suspect that you have only a limited knowledge of i/c engines. If this be the case I would suggest that your idea of sending your engine to a reliable company
for servicing would be the best bet, maybe
the engine has been run using castor as a lubricant.this is death to a four-stroke!
Make sure you only use a synthetic oil in future. Best of luck, Allan J..TTFN

[Peter Roberts]

Thanks guys for your posts. I'm certainly no engineer.

However I have been using Prosynth 2000 with all my engines for the last couple of years which seems less messy than previous fuels. Before that I used Duraglo on 2 and 4 strokes but I prefer 4 strokes. They start easily, sound great and tick over beautifully. We it did do until it stopped doing so!

Cheers TTFN

[Engine Doctor]

Hi Peter you say you motor was laid up for a few years. Is it still in the original air craft ? or are you using your old fuel tank? The nitro methane used in model fuel attacks copper. The brass fuel pipes contain copper and the fuel eats this away leaving a very brittle and perforated pipes. This Could be the cause of your problem with eratic running .If you use fuel with any Nitro content ,change the tubing inthe tank to aluminium. A club mate had similar problems and when I checked the tank all the pipes were totally roten.
Regards
Phil

[Peter Roberts]

Hi Phil,
Many thanks for the suggestion - I'll take the engine and tank out and check all the metal pipework over. Certainly never thought about the metal pipes. I have already changed the ordinary fuel pipes. The engine is about 12 years old and laid up for the first 9-10 of its life - but hadn't been run. It started first time and has given nearly a couple of years good service. About 9 months ago I stopped flying it and came to use it after another 6 months with the result that it would run and cut for no apparent reason.

I'll try your suggestion thanks and post my experiences back here.

[Dave Caldecourt]

One of my tanks had a problem with the silicone clunk tubing going soft and closing up in use.This has only happened to me once - the tank had been in use for a long time.
Dave C

[Peter Roberts]

Thanks Dave - I'll try the engine with a different tank.

[Tim Mackey]

Castor is NOT death to a four stroke !
It still has certain properties which make it an ideal model engine lubricant, and before all these fancy synthetics came along, it was pretty much the only fuel lubricant available ready mixed as a commercial fuel to us 20 years + ago.
I ran many engines, both 2 and 4T, including Lasers, and never experienced death of any of them, other than when I once converted a nice OS Surpass 48 to a ard earth tent peg:(
Synthetics are certainly cleaner, and an engine lubricated by castor oil will almost certainly show signs of brown staining. I do actually use the synthetic based fuels myself these days, but only because they are cleaner. Indeed, I would even dare suggest that for a novice, castor based fuels are better, as they are more tolerant of an overlean setting than most synthetics. It is actually the methanol that causes intenal corrosion, due to its hydroscopic properties, not the oil, or indeed the nitromethane which is also often blamed ! Incidentally, I always use a drop or two of "after run oil" down the carb, and the engine turned over, choked, to spread it around. This gives some protection against internals corrroding, and burns off almost immediately the next time the engine is started. I just use commercially available 2 stroke oil ( the red stuff ) and also please remember to drain off as much fuel as possible after the last flight. Best practice here is to actually pinch off or disconnect the fuel supply tubing to the carb, whilst the engine is running, being ever vigilant for running props !!
Just my 0.02P worth.

[Peter Roberts]

Hi Timbo,
Your two penneth sounds sensible advice and worth being noted by all. Many thanks.

I must admit that I do sometimes forget the after run oil. I have some red in my flight box and some Model Technics in the garage.

I do remember when I first bought my OS 70 Surpass (1995)that they sold castor based 4 stroke fuel as a distinctly separate one from 2 stroke fuel. But it is helpful to have one fuel which will suit both types of engines isn't it.

At least thats what the Pro Synth claims its capable of and I have generally found it to work in all my ic engines.

Thanks for your advice. I was hoping to get out this beautiful afternoon to tinker with the engine but sadly work got in the way.

PS has anyone any experience with an OS 120 mk III? I just bought one. Maybe I should start a new thread but I was wondering about mounting issues because some people have said to me that mounts in engines of that power have to be very particular beasts.

Cheers all

Peter

[Tim Mackey]

I think the difference would have been about the amount of oil as a percentage of the fuel, rather than the type of oil. Fourstrokes are ususally ok with a lower oil percentage than 2T. I curently use just the one fuel ( coolpower 5% synth )for all my IC stuff, including 2T and 4T
I think on the engine mounting front, metal is probably the safer way to go than the nylon jobbies for anything bigger than a 90. having said that, I use 2 x seperate nylon /glass filled bearers in my 90 4T Spit, with no problems so far...also remember something other than the engine itself breaking in a bad landing /crash is no bad thing :)

[Phil Baker]

I reckon the guru who suggested the o ring in the needle valve is nearest the mark. I recently fired up a Blue Bird 0.46 (identical to the ASP, dist. by MFA in the 80s) started beautifully first turn of the starter. Only problem? On high revs you could see the fuel spraying out of the needle valve, round the threads, due to venturi effect. Conclusion ? O-ring deteriorated over time! At low revs? Idling nicely then CUT! Time and time again. Conclusion? Air getting in past the o-ring on the needle. If only I'd known about the bit of tube trick!! Will try that soon and see if it fixes things. If so I've got a 21 year old engine, twin bearings, loads of power, runs like an OS 46FX and is worth about a quid! Who cares if it does the job?
Seriously, I used to work as an ind. chemist for Dunlop and one of the BIG bugbears for the "boffins" (Sun talk, sorry) was the effect that oil has in the long term on natural rubber products. It makes them "dry" and brittle and they lose their bounce! With an o-ring, no seal today. So the oil residues in your carb over the years have zonked your o ring. With great respect to the experts at Just Engines, I think there's no harm in trying a 10p new o-ring (try a decent car parts firm, or plumbers merchant, even our local DIY does a mixed bag of little o-rings) and see if its "Eureka" time. And if not, where's J.E.'s phone number??
PS I just invested in an OS FS70 Ultimate 'cos I's fed up of engine unreliability probs! Haven't run it in yet, but if it don't idle nicely then, I shall commit harikiri!