Andy Blackburn Posted June 5, 2008 Share Posted June 5, 2008 I have a second-hand OS 46 LA bought from a fellow club member, mounted inverted in a Great Planes Venus 40; starting is OK although it occasionally starts backwards when starting by hand. In its previous incarnation, it ran fine when mounted upright. Full power looks OK (about 11,000 rpm on an 11 x 7) but the problem is that it just won't idle for any length of time, even when set quite fast (3-4,000 rpm). The idle is a bit erratic anyway and gradually gets slower over the course of about 20-30 seconds and then it stops. If the throttle is opened before it stops it hesitates and there's a lot of white smoke from the exhaust so it's clearly running far too rich, but no amount of fiddling with the carb air-bleed adjustment makes any difference at all. The fuel system is as per the kit (3 line set-up), and the tank won't fit any lower. Something is clearly Not Quite Right, but I have no idea what it might be. Anyone got any ideas? Andy Blackburn Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted June 5, 2008 Share Posted June 5, 2008 poor o ring seal around the main needle / loose carby / duff plug ?? Quote Link to comment Share on other sites More sharing options...
winchweight Posted June 6, 2008 Share Posted June 6, 2008 Two things to check on the LA series, is the backplate sealed up tightly (I run silicon around it), and are the two small black philips screws present and tight under the carb (one each side). Quote Link to comment Share on other sites More sharing options...
Andy Blackburn Posted June 6, 2008 Author Share Posted June 6, 2008 Thanks for the suggestions, I'll fettle it over the weekend and probably try another run next week. BTW, tried 3 separate plugs without success.It did subsequently occur to me that the carb air bleed hole might be blocked. Or maybe the needle is bent? Quote Link to comment Share on other sites More sharing options...
richard cohen Posted June 7, 2008 Share Posted June 7, 2008 Andy, certainly worth checking the air bleed as i had an inverted 40LA in my T180 trainer and i could land deadstick before i learnt how to land under power as it always cut at idle. The solution for mine was to reset the slow speed air bleed as per the OS instructions book. I know a lot of club hacks say they are factory set but if the weren't to be touched they wouldn't be adjustable !. It can be downloaded from OS website and page 25 has detailed set up info. The main needle needs to be set at max revs first and then patience is needed to slowly make the adjustments to the slow speed mixture but when mine was finished it never cut out again. Got to be worth a looksie....rich Quote Link to comment Share on other sites More sharing options...
Alex(biggles) Wilkins Posted June 11, 2008 Share Posted June 11, 2008 hi, im having the same problem with my 46la, ran fine the right way up, but cuts even on fast idle while inverted, very annoying, last weekend i had it running fine for around 30 seconds by the time ide carried the plane from the pits to the strip the engine died. ive also tried a load of different plugs, screwed the airbleed screw in and out, god knows how many times, and tried two different fuel tanks no luck. I read somewhere using an OS type F plug can solve the problem, anyone else tried this? Quote Link to comment Share on other sites More sharing options...
Andy Blackburn Posted June 11, 2008 Author Share Posted June 11, 2008 I've taken the engine out and checked the backplate (which was OK) and the carb (which was secure, with both screws present). It's not the plug (tried several). I'll look at the air bleed hole and the main needle over the next few days, if that doesn't work I'll try an OS type F. I have to say, though, that it looked more like a fuel issue than a plug problem...Andy Quote Link to comment Share on other sites More sharing options...
Captain Slow Posted June 18, 2008 Share Posted June 18, 2008 I had probs running both the 46LA and 55 AX inverted. They jsut took a while to setup and needed an OS #8.Both run sweet as a nut now. Don't be afraid of trying the low end screw as a last resort. Do it a little at a time and be patient. Quote Link to comment Share on other sites More sharing options...
Andy Blackburn Posted June 18, 2008 Author Share Posted June 18, 2008 I believe the OS 46 LA manual reccommends that you turn the air bleed screw "...half a turn at a time...". Does that sound about right, or not? Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted June 18, 2008 Share Posted June 18, 2008 Yes. Quote Link to comment Share on other sites More sharing options...
Stuart Tanner Posted July 12, 2008 Share Posted July 12, 2008 well my LA46 was fine in the Piper Cub but I have put it in a Seagull Decathlon sideways and it will not start. Full tank and needle valve open 2 turns. I notice htat it took ages for the fuel to come up the pipe and airbubbles did appear in the pipe near the carb and yest it is new pipe. A rather depressing day as to be honest I expected a straight-forward setup and a taxi around and possible a little flight but no.What is it that I am missing as to it not working.It seems like a fuel problem. I must admit in the Decathlon the fuel tank is in at a steep angle and possibly a little low as a consequence but as this is ARF and is not a new l designed model I was not expecting there to be errors, although the manual is full of them.HELP so that I may get a happy flight tomorrowSTuart Quote Link to comment Share on other sites More sharing options...
cymaz Posted July 17, 2008 Share Posted July 17, 2008 I have a Venus .40 with an inverted J'en .57. I had a problem of rough idling and poor acceleration. I installed an OS four stroke plug which helped until I blew it---duh. Then I put in a Model Technics plug especially designed for inverted 2 strokes and changed to a uniflow tank set up.MUCH BETTER NOW Quote Link to comment Share on other sites More sharing options...
Mike Hawkins Posted July 18, 2008 Share Posted July 18, 2008 With the inverted engines have you tried a plug with an idle bar. I have an OS 40 LA which is inverted and usually would cut out if run at idle for too long, a fellow club member suggested this type of plug and explained to me why it worked. A piece of metal runs down the center and the fuel is sprayed to the side rather than landing on the plug and putting it out. Engine runs perfectly now. Quote Link to comment Share on other sites More sharing options...
Andy Blackburn Posted February 24, 2009 Author Share Posted February 24, 2009 After much faffing around, it looks very much to me as though the issue is with the fuel tank height - on close inspection , fuel is dripping from the spray bar and I think the tank is just just too high for an inverted set-up with an engine that has a cheap carb, it might or might not be any better with a more sophisticated engine. I've got it to the point where the top end is fine and the idle has been adjusted to be as good as it's going to get, using the procedure described in the O.S. manual. However, it still stops in flight after about 10-15 seconds of idle, or when spinning (this after testing with a variety of plugs, including an O.S. A3 and 8, and a Taylor plug with an idle bar). I must admit, if I'd had a box of matches at the field today I'd have rescued the 2.4 GHz Rx(es) and set fire to what was left . Quote Link to comment Share on other sites More sharing options...
Doug Ireland Posted February 24, 2009 Share Posted February 24, 2009 The "Idle Bar" plug type is a good idea, I use them in all my engines. Sounds to me like the engine is flooding at low RPM? Quote Link to comment Share on other sites More sharing options...
Dave S. Posted February 24, 2009 Share Posted February 24, 2009 Andy, I had a Venus with an ASP 52 for about half a dozen flights, also trouble with starting due to fuel tank height. I got fed up with it and sold it, same fate as all of the ARFs I've tried. Better off with a decent Rossi DF and an F-4, ring any bells? Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted February 26, 2009 Share Posted February 26, 2009 A thing to try is to start & run the model upside down so that the motor is now the right way up.....how does it idle now??? Air bleed carbs are pretty unsophisticated so if as you say the tank is a bit on the high side gravity can tend to push too much fuel through the main needle. A twin needle carb would allow you to restrict this flow & might work better.....it means spending money but might a replacement carb (with twin needles!!) be the answer??? Just Engines could help here Cheaper options....can you lower the tank? Can you tilt the engine slightly so its about 15 degrees off inverted.....this can help as it stops the glowplug becoming a "sump". An engine that won't idle is a nightmare & will almost certainly result in the death of your model when the engine cuts out whilst you're low 'n' slow Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted February 26, 2009 Share Posted February 26, 2009 hello andy-shot in the dark if the tank is to high and the carb can't cope with the fuel at tickover-try running the engine with out the pressure from the exhaust-may/not help-worth a try..............good luck........ ken anderson............... Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.