Help required OS 70 - 4 Stoke (Acro WOT)

righty , spent most of the afternoon, One glow plug battery and one spinner battery later (after full charged last night) still not having it started !! Yes glow plug is fine, I've had it off and checked it, still Grr

I did have a sputter then it cut out, more luck than chance i think on that one, but at least it proved its wants to start. Tried the usual things on turning screw slowly and Im pretty sure the fuel tank lines are set corretly after looking it over.

Seeing as this my first for stroke id like a hand maybe in a workshop environment to look at it properly, happy to travel to where ever on get one of you experts to get there hands on it who knows what they are doing, phil had a quick look on the patch Saturday just gone, and he seems to think the engine is in wrong ?!

The guy assures me who i bought it from had it running a couple weeks ago, but hey ho thats just word of mouth.

Any of you fine fellow thats up for the challenge for a cold winters little project to help a newbie out ? id be more than happy to donate a bottle of what ever u drink to help me out.

PM if you don't wish to as well.

Sounds frustrating Lee. Have you checked that the clunk is in the right place?. If you don't have the handbook for the engine, you can download it from the OS website, then you can re-set the slow running and main needles. Did you have the throttle cracked open about 1/16"? Might seem a stupid question but, how is your failsafe set? Its easy to leave the transmitter in a state that turns the engine off , that would leave the throttle completely closed, and not responding to throttle stick movements. Apart from that, if the engine has been stripped for some reason, the timing just may be out by one tooth, easy done, I speak from experience, my OSFS .70 had the power of a wet paper bag until I re-set the timing properly. Another thing springs to mind, are there any pinholes in the fuel lines, inside the tank as well as the external lines., and Is the crankcase breather free and clear?

Lee, after yesterday's look over the Arcrowot, I did say you needed to sort that throttle linkage out. If it was to start you may find it is going flat out or at least half chat and not an ideal surprise. That prop is also a scythe and not forgiving.

The carb barrel is not getting full travel and by the look of it, it isn't closing down to an idle position either. The throttle control rod link is hitting the engine mount bolt. This is because the carb has been turned round. You will be flicking and flicking till kingdom come and you are not giving yourself a good chance of getting it going of any fashion.

Remove spinner, prop (this will have two locknuts - 14mm and 12mm. Then the cowl off, disconnect the throttle linkage, unbolt engine from mounting. Undo the two carb screws and carefully pull off carb. The manifold will follow. Watch out for the gasket! Check "o" ring for perishing. Refit carb with mixture screw upwards. Temporarily place engine on mounting and eye up the throttle arm with the firewall. Mark it because this is where you need to have your linkage.snake to appear. If I remember rightly there was already an alternative throttle linkage guide in place.

Get that done, then you have removed most of the issues.

I will be up the field probably on Tuesday if you want to bring it up and I'll sort it in between my own projects.

If it turns over too easily it is probably a stuck valve (very common with castor oil based fuel).
Just squirt loads of fuel directly into the carb venturi (model inverted), turn it over by hand without glow to lubricate the valves and piston. Clear out the excess fuel by forward/backward movement of prop with the model not inverted.
Probably will start next flick but watch out for backfire! Otherwise see you next week at field where there will be a least 10 experts with different solutions :oops:

John, it's got compression. Also primes when finger over carb/exhaust. Throttle linkage is totally wrong. Judging by the cut outs in the cowl the carb was round the other way once. Why someone fiddled with it I don't know. It probably was running till the carb was turned round but probably not since.

Brian wrote: Sounds frustrating Lee. Have you checked that the clunk is in the right place?. If you don't have the handbook for the engine, you can download it from the OS website, then you can re-set the slow running and main needles. Did you have the throttle cracked open about 1/16"? Might seem a stupid question but, how is your failsafe set? Its easy to leave the transmitter in a state that turns the engine off , that would leave the throttle completely closed, and not responding to throttle stick movements. Apart from that, if the engine has been stripped for some reason, the timing just may be out by one tooth, easy done, I speak from experience, my OSFS .70 had the power of a wet paper bag until I re-set the timing properly. Another thing springs to mind, are there any pinholes in the fuel lines, inside the tank as well as the external lines., and Is the crankcase breather free and clear?

Brian u lost me at "sounds frustrating Lee"......lol :dry: like I said very new to this engine thing, need someone that generally knows what they doing, and Im far from it.

Sorry Lee, I didn't mean to sound too technical. One thing that came to mind is............Can you see the throttle barrel through the carburettor intake? Does it rotate OK when you operate the throttle stick? More important, can you see a hole the same size as the intake when you open the throttle? If not, go to the menu on your transmitter and reverse the throttle servo. I mentioned the "clunk" this is the weighted end of the fuel line inside the tank. Sometimes in a vigorous "arrival" the clunk gets pitched towards the front of the tank. This means that fuel can't get through because the clunk isn't down in the rear of the tank. Check with an empty tank, hold the model nose up and give it a good shake from side to side, you should be able to hear the clunk rattling. If it doesn't, a couple of sharp taps with your hand on the fuselage side close to the engine should dislodge it. One more thing might help. Perhaps there's some dirt around, either in the clunk inlet or, more likely in the carburettor. Take off the fuel line, remove the main needle, attach a clean piece of fuel tube to the nipple on the carb, and blow. Just one more thing, OS four strokes seem to like OS F plugs best, expensive but reliable.

Brian, I will refer back to my earlier post,

Quote" I did say you needed to sort that throttle linkage out. If it was to start you may find it is going flat out or at least half chat and not an ideal surprise. That prop is also a scythe and not forgiving. The carb barrel is not getting full travel and by the look of it, it isn't closing down to an idle position either. The throttle control rod link is hitting the engine mount bolt. This is because the carb has been turned round"

Carb and throttle need sorting first. Then whilst the engine is off, check fuel lines. Without having full control of throttle he will be going round and round in circles. That's my 5 penny's worth.

Should have read the whole thread, sorry Phil.

ok update:

Me and john been playing for couple hours, cowl off etc etc, stripped right back now.

Found out the throttle servo needed reversing as open was closed closed was open, so at least now its going the right way,
still not starting though !!!! doesn't seem to draw fuel in?? and now it seems to be almost locking up, I remember phil mentioning something like hydrostatic locking!

So back to the drawing board and more scratching of heads !