Simon Lumsdon 1

Hi Jon, sorry, to be clear i am screwing idle in a bit and checking it throttles up ok as you describe. Next step is to replace o rings and manifold paper gasket to eliminate possible air leaks

Correct, That was the absolute slowest i could get it to run, screwing the low speed idle clockwise, inwards until it cut. (12x6 prop, optifuel 12% fuel) in comparison the os 91 runs at 9600 max revs and will idle slightly slower but definitely a more reliable idle that the sc. thanks to all for all the help, i find this incredibly useful, so much to learn

Sorry, tried to save it in a compatible format but failed, not easy is it …

Edit.mp4

Well ran it on the bench this morning and end float issue resolved, only normal float now spent some time dissling with the low speed idle and could just about get it down to 2800 revs, wot gives 9100. compression seems fine to answer a prev question. Will give it another chance in a model but wondering if inverted position is a factor. Loathe to use an onboard flow

Its on the test bench (upright) ready for the weekend and some more running in and testing. Compression seems fine, my moneys on the carb …

Bearings replaced and end float reduced to acceptable amount Engine still wont idle below 3500, fiddled with low speed idle but thats not the issue, got fed up, whipped it out and changed it for an os 91 fs i had, immediately did 9600 on a 14x6 and would idle 2500 nicely. Was able to go to field and practise landings with Mustang, much improved Need to pull sc 91 fs carb apart and perhaps try new o rings etc? Hmmm

Sorry 10mm

Interesting, dont think front bearing sits on a shoulder in this instance, just a plain shaft. Suspect the taper collar isnt seating back far enough and leaving a gap allowing crank to float in and out. If it does it again i am going to buy some 8mm shims of ebay and pack between from bearing and taper collar which should fix it

Thanks Engine Doc, fitted new bearings and rebuilt engine, compression seems fine. Thinking about it cannot see how end float occurs unless taper behind prop driver not properly seated? The crank is pulled against the driver so no float unless that taper wasnt seated. Dont think it can be the bearings floating etc Anyway will bench test it this week and hopefully sort out the low speed running

I had thought about thread lock but how would i get the bearing out next time? However might be forces to look at this

Thanks to all for this fantastic advice. Agreed two likely separate issues have ordered new bearings, £10 so no reason not to. Suggestion of ensuring taper is firmly against front bearing is gold advice, if not securely seating that would allow end float. low speed running, will set it up on the bench once above all sorted, agree it should easily do 2000 revs (and i now have a tacho to check)

Thanks, yes, new bearings ordered, i will then have another bash at the low speed tuning.

Thanks Jon, noted on the lean low speed needle. I bough a tacho, very useful, full throttle on a 14x6 gives 9300 but low speed difficult to get below 3000. Noticed engine would bog down in flight when idling and throttle opened, took some time to pick up think you might be right and front bearing is becoming loose in crankcase, witness marks on outside of bearing are suspicious new bearings ordered

Have a newish ASP 91 fs which i have fitted in a Mustang and have been struggling to get it to idle nicely, below 3-4000 it just cuts. Have adjusted the low speed idle to optimise things but it still wont reliably idle? Runs fine at WOT and plenty of power, just wont idle slowly which makes landing the Stang a bit trixxy. More worringly i notice that once its hot then it develops a noticeably amount of end float on the crank which doesnt feel good. I think whats happening is the crank is slipping on the bearings and moving in and out! Just stripped the engine and there are witness marks on the inside of the backplate and the conrod. I also notice that there isnt a shim behind the tapered prop driver, it just faces up to the front bearing. This isnt the same design as the os 91 which uses a woodruff key and does i think have a shim. Have stripped the engine and it has minor rust on the crank and bearing but all still seems smooth, ( I might replace the bearings but not sure they need it) Quite tempted just to fit an OS 91fs which i have but its frustrating to have problems with something that could/should be a good engine.

Im on my third artf wot4 and this one has a os fs 52 which suits it beautifully, not over powered and lovely throttle. These are a good quality artf and fly really well. One thing i do is glass the fuel bay and undercarriage bay to strengthen things up and fuel proof them. Lovely planes

Well repaired the undercarriage today and went to the field and things were much better, bit more wind helped but landings much improved by slowing things down with a bit of elevator. Flies really well. had some trouble with asp 91 fs and realised idle speed is too high (cuts out if throttle reduced past a point) and i need to fiddle with low speed needle. Also difficult to prime the engine once hot so need to get to the bottom of that have also taken some lead out of nose that i dont think it needs, very relieved after a few good landings, just need to fettle the engine now and get the idle speed down

Thanks Jon, really useful advice here, i really like idea of setting up ele trim into flap control (need to do this on extra which does have mixed flap/ailerons also) to slow things down. think i now have a plan, fly some slow passes and feed in elevator to understand stall speed and then start to slow things down. I can do this on my fun fly’s so no reason why cant do it with mustang its great to be able to get all this helpful advice, thanks to all

Thanks all and thanks Martin, some great points here. I can certainly fly my Panics nose into the sky along the field and get the point being made. One observation is our field orientation means the plan is usually point towards the pilot on landing so dont get that side perspective, maybe i should bring the model closer in and practise a more nose up approach. I think i generally let models sink/glide in which means a fast landing and running out of room. Starting to realise i need to fly them in, will try some nose up slow passes perhaps

Thanks Brian, i know how to use throttle for height but think i am too scared of stalling to use the elevator for speed, need to practise this

Just maidened an old Mustang ARTF (jamara spirt of America) with a 90 asp fs which flew beautifully, not overpowered but really steady and enjoyable. BUT my landings were dreadful, i tried to wheel it in but it ended up pitching down and breaking the ridiculously weak undercarriage. I can do a nice slow approach over the field boundary but dont seem to be able to judge the elevator control to land her horizontal, seems to touch down slightly nose down at which point it digs in? CG and wheel position is fine, its pilot error. Most of my landings take half the strip to get the height/position right, then a good landing but run the danger of running out of room. What am i doing wrong? Need some advice on landings pls many thanks simon

Thanks JD, yes that all makes sense, i always reinforce firewalls and glass the fuel tank area. Am planning an os fs 26 which should be plenty power wise. havent tried rhino tape, is that like duct tape?

Have just picked one of these off ebay and want to convert to IC power, thinking os 26 fs. Q. Does anyone have any experience of this model and any advice on switching to ic power. Will the airframe be strong enough i also notice cowl is plastic and might melt from heat from an fs engine? many thanks simon

I will go for OS 52 FS and OS 40 F boring but bulletproof

Agree with above comments, i use silencer extension pipes and they do work well, modern synthetic fuels are less messy and a quick spray from a bottle of water ans washing up liquid and a quick wipe down is all you need