Edgar Westbury Wallaby ignition

ok i had a better look at the timing, it would appear that the plug sparks when the piston is at a slight dwell at TDC i.e. not before TDC, its hard to tell for sure. I cant find where i last saw the timing references but 10deg BTDC seems familiar ? i have a timing disc for it, only way i think i can try changing is by sight of the piston to set TDC on the timing disc then adjust the points to open earlier.

10-15° before TDC is fairly typical.

I am surprised you are not getting any signs of firing. Normally something should be happening even if it won't make a sustained run. It has run so the basic mechanics should be ok unless significant leakage has developed past the valves or pistons.

One suggestion from another forum was to hold a flame by the exhaust whilst cranking to see if any burnable mixture was getting through. I haven't tried it myself but generally turning the engine over with a drill and gradually opening the needle valve has resulted in a start.

i will try that, it did fire briefly for about 2 secs very early on but since that absolutely nothing. I will try the above before messing with the timing, even if a valve was leaking its a twin cylinder so unless very unlucky one cyclinder should show some form of life.

The candle method works quite well but be careful with liquid fuel, not such a problem with gas (propane)

Don't have the ignition hooked up, just turn the engine over by hand and look at the flame as the exhausted fuel/air mix is exhausted and ignigted by the candle or lighter. If it's a big soft orange flame you are too rich, aim for a bluer smaller flame.

well i gave that a go and with the needle 1.1/4 turns open i got a small blue flame from both cylinders. So i backed the needle to only 1 turn out now so will give it a go soon. I guess at least having unspent fuel being kicked out on the exhaust stroke is a good sign.

I have now had the engine run for about 10secs, i advanced the timing. To get to run for around 5-10secs i prime the carb then disconnect the fuel from the carb. Start it and she runs for a short duration of time. tried a few needle settings without any luck, it does fire with the fuel line connected i.e. brief fire then smoke from exhaust or sometimes blowback out carb. So closer but not quite there yet.

How high is the fuel level in the tank compared to the carb? It sounds like there is too much fuel being delivered.

Can you post some pictures of the set up?

certainly will when i can figure out how too (my next challenge) the tank is actually about level with the carb. I did notice when i filled the tank that the fuel shot up the fuel line towards the carb no i guess it could be high. I can try it lower. I was also wondering about the idle mixture setting as well which does look to be well wound out which i beleive would make idle leaner so would seem correct.

Hello Andy

If you have no fuel pump the carb must always be below the fuel level in the tank. Fuel will not run uphill - and you can waste hours trying to get the mixture right if the fuel is too low.

With a fuel pump (and something to power it) things are different but more complicated.

Cheers, Tim

yeah i was wondering what could match the symptom. Prime the carb by throttle wide open finger over ventura, watch fuel come into carb along the fuel line. Disconnect the fuel line and start....engine runs well for 5-10secs. With fuel line connected it will start very briefly then die. I guess the prime got fuel in manually whereby with the line connected only its not getting enough flow. I will try raising the fuel tank as thats quite easy to try.

Thinking about it Tim it might lend well to the testing i did, because i was testing i only put a small amount of fuel in the tank which is small and approx 2/3 way up the tank is the level with the carb input, so its possible the fuel level was below or very minimally above the carb input meaning not a great flow if any. I will test this tomorrow by raising the or filing the tank fully.

Can't agree with that Tim, I've several models with the fuel tank below the carb that run fine. Just need a N/R valve to stop the fuel draining back when the engine is in "Miss" mode. Intake stroke simply creates a vacuum in the fuel line that will lift the fuel.

A picture of the carb would help as some of Westbury's designs had a float chamber which will shut off the fuel when the float is high so it doe snot flood from a high tank position. If it does have a float chamber then worth checking the float actually floats and the needle is opening & closing the fuel flow correctly.

How to post photos

The attached photo shows the bottom of the tank is just below the carb intake.

That looks to be a reasonable set up as long as the tank is less than half full.

The system will prime if you choke the air inlet but does not seem to get enough fuel to run. Could there be an air leak between the carb and the cylinder head? Have you checked that the needle moves in and out of the jet and that there are no obstructions.

Yes if i open the throttle fully and block the ventura it primes well, so i assumed no leak. I did notice when i tried with the tank connected and very small amount of fuel i.e. the tank level will have been below the carb inlet. That when it fired i watched an air bubble in the fuel line which didnt move i.e. no fuel flow to carb. I do remember on RC aircraft glow engine setups that the fuel tank was pressurised off the exhaust. Is it possible that under running there just isnt enough vacuum to syphon fuel up from the tank.

There should be sufficient vacuum unless the throttle is open too far. This is a similar carb and tank set up on my 12cc twin. It needed an initial prime with the air intake blocked. After that the fuel pipe would stay full for a couple of days.

Is the breather hole in the tank clear?

Looks like it has just been fitted with a model RC engine carb that may be better suited to higher volume of air through it rather than what a slow reving 4-stroke will pull.

Also be wary of running what looks like silicon fuel line with petrol a sit will swell the tube and also soften it. Over time a sticky sludge can build up as the silicon is dissolved. Change to the yellow "Tygon" fuel line

Edited By JasonB on 06/10/2022 13:01:26

Tank breather is clear, you could be onto something with the carb as i know from some notes that came with it that starting is best at needle at 1.5 turns out and throttle at half then once running set needle to 1.25. I was thinking of filling the tank to just above the carb inlet, prime the carb. Then pinch off the fuel line, get it running then un-pinch the fuel line to see what happens.

Ok ureka she runs and even throttles up. All i did was fill tank and start after priming and away she went, the throttle setting is critical to start, very smoky but it was probably running very rich as needle was 1.5 out.

Excellent