Diamond Geezer Posted October 18, 2021 Share Posted October 18, 2021 Hi guys my Irvine 61 been playing up it’s ok on the ground but starts to play up when it’s in the air seems like it’s hunting a poppin n fartin any stripped it down the carb that is is found nothing untoward reset the.bottom end using the pin and tube technique same with the top end still the same but I have noticed when I hold the nose up everything seems ok but when I hold the nose down I have bubbles in my fuel line the engine starts to play up and cuts out any ideas why I might have bubbles in the line when I hold the nose down at a 45 angle. Quote Link to comment Share on other sites More sharing options...
Don Fry Posted October 18, 2021 Share Posted October 18, 2021 Fuel pickup, at the back of the tank, sucking air? Quote Link to comment Share on other sites More sharing options...
Diamond Geezer Posted October 18, 2021 Author Share Posted October 18, 2021 Hi Don yeah I suppose I’ll have to the bullet and dig the tank out the guy I bought the plane off has used spray foam to hold it in Quote Link to comment Share on other sites More sharing options...
Don Fry Posted October 18, 2021 Share Posted October 18, 2021 No, why would you try to run a motor nose down, full throttle, the clunk is likely to be sucking air. Is meant to be at the back of the tank. In flight, how often do you hold full throttle, in a 45 ° dive. Enough to empty the fuel line? Why is holding a plane 45 ° down a diagnostic test for anything. Bubbles should be expected. Hunting and poppin and fartin are not great descriptions, but as it’s not stopped, it’s more likely rich than lean. Lean= Stopped. If it picks up nicely from tickover, bottom end is thereabouts. Suggest, then a bit leaner top end. Quote Link to comment Share on other sites More sharing options...
Diamond Geezer Posted October 19, 2021 Author Share Posted October 19, 2021 Thanks for the reply Don I think it is rich but whe I lean it out and the engine starts 2 stroking as it should it’s worse Quote Link to comment Share on other sites More sharing options...
Nigel R Posted October 19, 2021 Share Posted October 19, 2021 plug still ok? dirt in tank? carb o rings leaking? gunk in carb near needle? remove motor, check for gunk, refresh o rings, refresh the plug, bench run it, tune the needles, prove the motor is ok by itself, on to tank install, fresh fuel tubes, fresh clunk tube, check no pinholes in the brass tubes divide and conquer Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted October 19, 2021 Share Posted October 19, 2021 If you have brass tubes in tank change them for aluminium. Nitromethane in fuel will dissolve the copper content in the brass and cause minor air leaks due to perforation of tube walls. Obviously check silicone tubes for leaks as well. Quote Link to comment Share on other sites More sharing options...
Andy Stephenson Posted October 19, 2021 Share Posted October 19, 2021 DG, One other thing to look out for is the carb barrel free to move axially against the spring that pushes against it in all throttle positions. There will only be a small amount of movement but this is critical because you will get the wrong mixture if it sticks at any point. Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted October 20, 2021 Share Posted October 20, 2021 On 18/10/2021 at 19:59, Don Fry said: No, why would you try to run a motor nose down, full throttle, the clunk is likely to be sucking air. Is meant to be at the back of the tank. In flight, how often do you hold full throttle, in a 45 ° dive. Enough to empty the fuel line? Why is holding a plane 45 ° down a diagnostic test for anything. Bubbles should be expected. Plus if the model is in a full power dive it's unlikely the fuel will fall to the front of the tank ? Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted October 20, 2021 Share Posted October 20, 2021 Also check the front bearing, I had an Irvine 53 start to run erratically and a new front bearing cured it, it could be that the bearing seal has worn and allowing air in. 1 Quote Link to comment Share on other sites More sharing options...
Diamond Geezer Posted October 20, 2021 Author Share Posted October 20, 2021 Thanks Frank how would you check that Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted October 20, 2021 Share Posted October 20, 2021 Feel the bearing and move it side for side, up and down, for any movement. Too much oil coming from there is a sign too. Replacing the front bearing rules out any chance of a pressure or oil leak Then plumbing check, inside and out, to find the pressure leak preventing tuning and reliable running. Quote Link to comment Share on other sites More sharing options...
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