Edgar Westbury Wallaby ignition

[Andy CameronParticipant @andycameron27025]

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.

[Roger BParticipant @rogerb61624]

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.

[JasonBModerator @jasonb]

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

[Andy CameronParticipant @andycameron27025]

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.

[Andy CameronParticipant @andycameron27025]

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.

[Roger BParticipant @rogerb61624]

Excellent

[Andy CameronParticipant @andycameron27025]

In summary, the issue was the ignition timing which was set bang on TDC strange how it didnt even try at that setting but advancing simply by eye approx 10-15deg got her running. The carb isnt the best marriage for this engine so if anyone has any ideas on a better alternative that would be great. I now need to change the cooling to add in a water pump to move water around the engine instead of just relying on the heat syphon method i will still use the old water tank with sprey bar (or maybe get a radiator). Thanks everyone for your help on this.

[Roger BParticipant @rogerb61624]

Carburettors for small four strokes are a problem. Most commercial ones are designed for high revving two stoke engines. I built a small constant depression (SU type) carb for my twin which worked well. It is now running with mechanical fuel injection.

Computer CPU cooling radiators are cheap and work well along with their electric fans. In this case there is a gear type water pump for circulation.

[Andy CameronParticipant @andycameron27025]

Where did you get the water pump from ? i can find one with ideal inlet/outlet sizes to avoid pipe size increase i.e. pipe in pipe but it is 12V and 5ltr a min, even say at 6V that pump might be a bit aggressive. do you have a water header tank or is a reserve built into the cooling radiator ?

[Roger BParticipant @rogerb61624]

I made the water pump for this engine, it is built into the distributor drive. I have used a pump like this with a 5V supply as a fuel feed for another of my engines. At 12V it should supply more than enough.

bedienungsanleitung-207894-modelcraft-modelcraft-kraftstoff-getriebepumpe-benzinfest-foerdermenge-06-lmin.pdf (conrad.com)

I fixed a small filler/breather to the top of the radiator but otherwise I just use the reserve that is there.

[Andy CameronParticipant @andycameron27025]

In addition is the radiator/fan unit from china ? the only integrated units i can find are from china.

[Andy CameronParticipant @andycameron27025]

Thanks i found that pump, the water tank i have is quite large holds about 1ltr and has a sprey bar at the top water input from the engine. So for now the pump circulating coolant around that tank might be ok.

[Roger BParticipant @rogerb61624]

I think that the radiator, fan and finger guard were bought separately. The fan and guard probably came from Conrad and the radiator from Amazon Germany (I live in Switzerland). This allowed me to choose the size and voltage. I am using an 80mm radiator which is borderline. You should probably think about a 120mm one.

[duncan webster 1Participant @duncanwebster1]

Heater matrix from a scrap car?

[Howard LewisParticipant @howardlewis46836]

The radiator from a car would be an overkill, since it is designed to deal with the heat rejected from 50 or more bhp.

This engine is small and of low power, so the matrix from a car heater, or an old under seat box heater from a bus should provide more than enough cooling.

I would not bother with a spray bar, to minimise restriction to coolant flow.

I am not even sure that a circulating pump is necessary.

The old Fords and Austins used thermo syphon to cool their engines which produced no more than about 40 bhp.

So their cooling systems only needed to dissipate the same amount of heat (If you do a heat balance, the heat to coolant , and heat to exhaust, each roughly match the power at the flywheel ).

The Ford export coolant pump was only used by the special builders, and 750 Club racers where the engine had been tuned to deliver more power. And being a side valve, an 1172 cc engine is unlikely to be capable of delivering much more than 50 bhp per litre.

So an engine of 29 cc is unlikely to be rejecting more than 2 bhp to coolant. Calculating the B Th U or Calorie equivalent of 2 bhp should give a good idea of how much cooling is required.

Howard

 

 

 

Edited By Howard Lewis on 08/10/2022 12:30:54

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