Jon H Posted August 27, 2018 Share Posted August 27, 2018 Posted by Ronos on 27/08/2018 09:11:15: Setting the high needle yesterday, was a little frustrated, while leaning it out, screwing in the needle about 1/8 at a time, at full throttle, the engine was very slow to respond to the change, became very erratic going to about 9300 revs from about 8400 revs, then back again. sort of got the high end set but not happy with it because of the inconsistent revs. Tried a new plug (F type,OS) still the same, and new fuel. I have ordered some Laser 5% to see if they run better, they recommend to 5% I am using optifuel 12% because been using it on my Escale Seafire SC120FS and that's fine. Any idea? new engines or am I being impatient. ASP needles are not known for their accuracy and can leak air slightly when you twiddle them as they move in their housing. Try sliding some fuel tube over the joint between the needle and the carb, this might help. Remember too that rpm will drop as the engine heats up so if you are spending a long time at full power trying to tune it then you will start chasing your tail. Don't tune with a tacho either as this will also lead to rpm chasing. I have seen rpm chasing many times with customers as they tach the engine on its first run up to full power and see, for example, 8500rpm. They then tweak the needles, check revs again and find 8300-8400. This is normal and due to the engine heating up. They then spend the next few minutes at full power screwing the life out of the needles trying to get their 200rpm back. All the while the engine gets hotter and hotter, and slower and slower. Tune them by ear, it should take no more than 10 seconds to find the optimum position. Then hold full power for 15-20 seconds and if there is no noticeable sag in the revs during that time then its ready to go. Listen too for a sharp cracking noise. Its subtle, but if you hear it then you are knocking slightly and might need to go 1 or 2 clicks rich. Quote Link to comment Share on other sites More sharing options...
Paul C. Posted August 27, 2018 Share Posted August 27, 2018 Jon, Good tip to use fuel tube over the needle I have some spare o rings but the fuel tube sounds much better. Learn something new every day Paul. Quote Link to comment Share on other sites More sharing options...
Ronos Posted August 27, 2018 Share Posted August 27, 2018 Hi Jon, been using the ear on the high needle, then dropping a could of clicks as it loses revs, then doing a pinch test but using the tacho setting the idle and doing a pinch test at that. the idle is nice at a steady 2300. Quote Link to comment Share on other sites More sharing options...
Ronos Posted August 27, 2018 Share Posted August 27, 2018 Never to old to learn Paul. Posted by Paul C. on 27/08/2018 11:18:20: Jon, Good tip to use fuel tube over the needle I have some spare o rings but the fuel tube sounds much better. Learn something new every day Paul. Quote Link to comment Share on other sites More sharing options...
Paul C. Posted August 27, 2018 Share Posted August 27, 2018 That's for sure Quote Link to comment Share on other sites More sharing options...
Jon H Posted August 27, 2018 Share Posted August 27, 2018 Posted by Ronos on 27/08/2018 11:24:27: Hi Jon, been using the ear on the high needle, then dropping a could of clicks as it loses revs, then doing a pinch test but using the tacho setting the idle and doing a pinch test at that. the idle is nice at a steady 2300. ok that's good. Personally I have never used the pinch test and instead slam the throttle open from idle to check the pickup is strong. That said, 2300 is a good idle rpm for an ASP 70 so its not really important how you got there. What props are you running on them? Quote Link to comment Share on other sites More sharing options...
Ronos Posted August 27, 2018 Share Posted August 27, 2018 13x6 Jon. Quote Link to comment Share on other sites More sharing options...
Jon H Posted August 27, 2018 Share Posted August 27, 2018 Posted by Ronos on 27/08/2018 13:35:57: 13x6 Jon. they should be revving like crazy if they are APC. I expect 10000 out of that prop on a laser 70 and a friends OS70 was slightly up on that if I recall. Another friend has an SC70 and he used 13x7 JXF props but I cant recall the rpm. I think it was mid 9000's Quote Link to comment Share on other sites More sharing options...
Ronos Posted August 27, 2018 Share Posted August 27, 2018 Here's a little update. Got home from work, straight into garage, rocker cover off, checked the valve setting one was very slightly out. Reset both valves to 0.1 and fired it up, slight better at the high end, then I noticed that the pipe from the vent on the tank to the exhaust was smaller then the carb one. I don't know if it was this but after firing it up again got to a steady 9400 revs full throttle and 2400 idle, happy days. Quote Link to comment Share on other sites More sharing options...
Ronos Posted August 27, 2018 Share Posted August 27, 2018 Hi Jon ,it's Masters Airscrew K . Quote Link to comment Share on other sites More sharing options...
Paul C. Posted August 27, 2018 Share Posted August 27, 2018 I found that my hobbyking tachometer only works with the black master airscrew props the grey coloured apc do not appear to register correctly. Was thinking of getting a better tachometer but I don't think that I would get that much use out of it. Paul. Quote Link to comment Share on other sites More sharing options...
Paul C. Posted August 27, 2018 Share Posted August 27, 2018 Hi Ronos, might be worth running the engine for a few more times to be sure you get consistent running. Just to be sure to be sure Paul. Quote Link to comment Share on other sites More sharing options...
Ronos Posted August 27, 2018 Share Posted August 27, 2018 Your right Paul, just incase it's fluke. I'll fire it up tomorrow, see how it runs. Quote Link to comment Share on other sites More sharing options...
Jon H Posted August 27, 2018 Share Posted August 27, 2018 Posted by Ronos on 27/08/2018 16:19:19: Hi Jon ,it's Masters Airscrew K . Those will be a bit slower so mid 9's is probably fine Quote Link to comment Share on other sites More sharing options...
Ronos Posted August 27, 2018 Share Posted August 27, 2018 Thanks all for your advise and knowledge, a great help. Quote Link to comment Share on other sites More sharing options...
Ronos Posted August 27, 2018 Share Posted August 27, 2018 DavyP, mines a Turnigy, its OK but you have to tilt it to see what's on the screen. Quote Link to comment Share on other sites More sharing options...
DaveyP Posted August 27, 2018 Share Posted August 27, 2018 Ok thanks, I'll have a look online. I thought a tacho might be useful to get the idle speed right. Quote Link to comment Share on other sites More sharing options...
ASH. Posted August 27, 2018 Share Posted August 27, 2018 "Remember too that rpm will drop as the engine heats up..." Why is that Jon ? I would like to know the technical reason for that? Is it because the chrome plated cylinder expands? Quote Link to comment Share on other sites More sharing options...
Ronos Posted August 27, 2018 Share Posted August 27, 2018 Posted by DaveyP on 27/08/2018 19:42:37: Ok thanks, I'll have a look online. I thought a tacho might be useful to get the idle speed right. They are handy, because I've got a mossie, it will come in handy to compare how far or close they are running together. Quote Link to comment Share on other sites More sharing options...
Jon H Posted August 27, 2018 Share Posted August 27, 2018 Posted by ASH. on 27/08/2018 20:00:58: "Remember too that rpm will drop as the engine heats up..." Why is that Jon ? I would like to know the technical reason for that? Is it because the chrome plated cylinder expands? yea the whole thing expands, valve clearances go larger, the fuel charge entering the cylinder is warmer/less dense. There are many reasons Quote Link to comment Share on other sites More sharing options...
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