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ZDZ40 tough to start

Old 07-06-2002, 09:53 PM
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Default ZDZ40 tough to start

I have a ZDZ40 mounted inverted with a JA Pitts muffler. About 5 gallons through, 96 Octane with lawnboy 32:1 so far, will switch to synthetic later after break-in, 22x8 Bolly prop on a Diablotin XL, original Brisk plug, the carb is clean like new inside, filter in the fuel line and new fresh fuel. I've got a ***tough*** time to get it to start. Once it's going, it's a marvel though.

First, what is the correct spacing on the plug? My engine came with the Vlach instructions which specify a 0.7mm (28 Mills) spacing but the Falkon instructions posted on the website indicates a .35 (14 Mills) spacing. The two are so similar in construction that I don't think there's much difference inside (the voltages are roughly the same).
What's the answer? Mine is currently at 25 Mills.

Second, the choke came originally with a 2.5mm hole in it and it took forever to get the fuel to the carb. Someone (Dick Hanson) recommended to close the hole (which I did) but it seems like it flood the engine too quickly, without even a burp when you flip with ignition on. I read on the discussion board that the latest carb from Bing come without a hole. Seems like a hole is required to avoid flooding and I just re-opened mine to 1.5mm, will see if it improves.
Any comments?

Old 07-25-2002, 09:11 PM
Thomas Williams
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Default hard to start zdz 40

The easiest way to start a zdz is to leave the throttle at idle with ignition turned on,flip engine over until it tries to start,turn off choke and continue to start engine but now raise the trottle 2 to 4 clicks.If you still have problems trying to start your engine keep riching the low end until it starts easily and you still have good throttle response I know this works because I have a zdz 60 and a zdz 120.Good luck and l hope you enjoy your zdz as much as I have enjoyed mine.If you have not tried a 20- 10 on your 40, try it, I think you will like it much better.
Old 07-26-2002, 01:32 PM
Mike Dooley/RCS
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Default ZDZ40 tough to start

The correct spacing for the ZDZ spark plugs is 0.022".
Mike Dooley
RC Showcase

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