by ffkiwi » Sat Jun 11, 2011 5:41 pm
As with other replies to similar questions ('engine won't start')you need to check a few things-especially as on your own admission the engine had been in a crash previously. I hope it is clean and has no dirt in it-being a rear intake, you shouldn't have got any dirt into it via the intake-however if it was being flown in open exhaust condition it is possible dirt may have entered through the exhaust (if it had a silencer attached you can ignore this concern.
If it has sat for a long time there is a good chance the engine will be gummed up with congealed castor-the cylinder-the ring (this engine uses a Dykes ring)-and the plug. The carb jets may also be blocked. The engine may be stiff to turn over, and/or the crankshaft bearings feel rough or 'lumpy' as the engine is turned over.IF you suspect dirt has got into the engine, DO NOT ATTEMPT to TURN it OVER! I would advise putting it in a domestic oven for about 20 minutes-and on removal, take the head off (the heating will soften any residual castor and make the screws easier to remove) and check the cylinder for dirt once the head is off-if all is OK then a quick wipe of any castor residue with a soft rag and a bit of oil in the bore before you replace the head again. Check the needle jet-making sure you establish the needle setting by screwing it all the way home and counting the turns before removing it to clear any sludge or congealed castor from the jet. When you removed the head, you should also have checked the condition of the glowplug-and seen whether it still works.
These engines had fairly rudimentally throttles-essentially 'full bore' and 'stop'-the pylon rules of the time did not require anything else! They have a fairly large carb bore-so suction is minimal. On the bench you should be able to get the engine to run on suction-but you may well have to play around withe the tank height to help this-but overdoing it will result in gravity feed and easy flooding.
These engines were also designed for high nitro fuels-so use at least 10-15% nitro-and I don't mean the rubbish they sell for model car use-the oil content is far too low! A decent aero fuel with at least 20% lube-your call whether it is castor or synthetic-most commercial fuels are synthetic lube these days. A 10x6 prop (this is not a pylon prop-but is a common size for 'cooking' 40s) but will give you a decent load and a bit of flywheel effect-which is more than the pylon 8 and a bit- inch diameter ones will. And splash out on a new plug if the existing one looks in anyway suspect.
Ensure the engine is solidly mounted, and you have some provision to adjust the tank height, fit the prop (you'll need to ream the centre hole to fit the stepped driver), set up the glowplug for a decent orange glow and try an exhaust prime, and a good solid flick-if it runs on the prime OK you should be in business-try for 3 turns open on the needle to start with-but watch out for flooding. JKeep an eye out for any bubbling around the head or crankcase joints, which would indicate a compression leak-these engines did not use any gaskets, relying on good machining for a metal to metal seal. Be prepared for a racket! It'll be noisy!
These are good honest vice free engines-but totally outclassed for pylon these days. I have 3 of them-I use them in .40 FF Open Power models-but on pressure feed. On a 10x4 or 9.5x4.5 APC they really pull
'ffkiwi'
PS. My reply presumes that you have suitable starting equipment-fuel squeezy bottle, tank, glowplug driver or power panel, glowplug clip etc. Electric starters are optional.
PPS One of the characteristics of Dykes ringed engines is they have very little compression when turned over slowly by hand. The setup of the L-shaped Dykes ring is that it is designed to seal under combustion pressure from above, so turning over 'cold' gives no real indication of the engine's condition