Kev Bamber Posted June 18, 2009 Share Posted June 18, 2009 I'm running an SC52 4-stroke, upright installation, & having idling problems. The engine is set-up so it runs and transitions well, but when left idling for more then 20 seconds, it then starts to hesitate and miss before stopping. I can blip the throttle to keep running, but would like to get to the root cause. I've tried different plugs and the slow running needle settings, but cannot cure. Any ideas please? Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted June 18, 2009 Share Posted June 18, 2009 hello kev-it could be that a hotter plug might help-as it sound's as though the fire is getting put out at the low/20 sec tick over-leave the glow attatched see what happen's-if it keep's going that is the prob-then it might be to slow a tickover-or try different fuel-and finally when you do alter the slow running screw-take it gently-not massive alteration's....and make a mental note where you started from....... ken anderson......... Quote Link to comment Share on other sites More sharing options...
andrew wise 2 Posted June 18, 2009 Share Posted June 18, 2009 Hi Kev. How old is the engine? Had the same problem with my SC 52 when it was new. Now it has run an hour or two it is fine. I didn't make any adjustments to the slow running and used a normal plug. If it is newish just give it chance to settle down I am sure then you will find it a very reliable little engine. Good luck with it. Quote Link to comment Share on other sites More sharing options...
Kev Bamber Posted June 18, 2009 Author Share Posted June 18, 2009 Thanks for the replies; it's not a new engine, certainly well run, but still feels fine compression wise. Ken - yes I'll try with the glow lead attached. Andrew - what fuel are you using? Quote Link to comment Share on other sites More sharing options...
andrew wise 2 Posted June 19, 2009 Share Posted June 19, 2009 Kev I'm using Model Technics Contest 10. Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted June 19, 2009 Share Posted June 19, 2009 kev-one more thing-i lost the carb on a OS264st--i had an extension on the needle-and what happen's ove time is the needle due to vibration-work's like a tuning fork and elongates the hole that meter's the fuel(make's it egg shaped instead of round)...then it is impossible to tune the engine ....i don't think this is your prob--but worth checking to save you some grief............. £30.00 for a carb ken anderson.......... Quote Link to comment Share on other sites More sharing options...
Phil Claridge Posted June 20, 2009 Share Posted June 20, 2009 try an OS F plug they cost a fiver but work well, never had to change one yet Quote Link to comment Share on other sites More sharing options...
Bruce Richards Posted June 20, 2009 Share Posted June 20, 2009 OS F plugs are now £7.50. I have stopped buying them they are just too expensive. Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted June 20, 2009 Share Posted June 20, 2009 here here bruce-i use the technic's plug's a bit cheaper-taylor are good one's as well....£7.50 for an os plug is ridiculous......................no wonder electric model's are making the inroad's as they are..................... ken anderson........ Edited By ken anderson. on 20/06/2009 08:47:22 Quote Link to comment Share on other sites More sharing options...
Kev Bamber Posted June 20, 2009 Author Share Posted June 20, 2009 I think I've solved it The throttle barrel is sprung outwards to keep it in a constant axial position against the side of the scew that holds it in. My throttle linkage was pushing axially inwards, so the barrel vibrated/moved axially at idle, cos the linkage overcame the throttle barrel spring. By ensuring there is no pre-load axially on the throttle linkage, all is now fine. I wonder if this is generic to the SC carbs. Quote Link to comment Share on other sites More sharing options...
the unmagnificent man Posted September 18, 2009 Share Posted September 18, 2009 Hi Kev, if thats not it then check your valve clearance, it could have moved a little. I have just written a full explanation how to do it on another thread called "SC52" but seeing as this was originally posted back in June I expect you have sorted it now! Al Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted September 21, 2009 Share Posted September 21, 2009 Kev, I'm sure thats your problem.....the angle at which the slot in the throttle barrel is cut has a huge effect on transition....there is obviously a small amount of clearance between the slot & the screw that guides it so if its is moving in or out this will definitely affect the mixture. Might be worth just s-t-r-e-t-c-h-i-n-g the spring slightly to get a good positive force pushing the throttle barrel out......don't overdo it though......... Pretty much all modern carbs are like this so I'm sure its a potential problem on all engines.... Certainly one to remember for the future Quote Link to comment Share on other sites More sharing options...
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