Just double-checking that this is the design being discussed:
http://www.modelenginenews.org/etw/roller/page52.html
To correct my spring numbers above – It's 1/4" OD, so the relevant stiffness figures are 0.07 – 0.12 lb/in
(If the scale factor is 1.4, I think the spring wire should be about 0.015" dia ).
Posted by John Rutzen on 01/03/2021 14:46:23:
I've found that the engine will only run very rich. To get it to start I have to inject a small amount of neat petrol into the intake and the exhaust is visible. If I try to lean it out it stops. The air slide is pretty much shut, if I open it the engine stops. I've tried messing about with the ignition timing and find it runs best if the spark is at about TDC or just after. It will run continually but only with the air slide shut. This is the first IC engine I've made, I've been a steam loco man up to now.
Have you run it long enough for it to warm up? (Not unusual to have to lean out the mixture considerably over the first minute, or so.)
What happens if you open the throttle? (I presume you mean the spring loaded sleeve when you say 'air slide ' ) – Apologies if I have got the wrong end of the stick.
Edit to remove random smiley – have just seen latest info.
What size of primary choke are you using? (The hole in the side of the carb)
If the primary choke is too big, or there isn't a good seal between the air sleeve and its cylinder, the carb won't develop enough vacuum to draw the fuel through. Might be worth trying with a bit less than 2" height difference.
Edited By Andy_G on 01/03/2021 18:17:54