Hit & Miss Engine – Help Needed

[Blue HeelerParticipant @blueheeler]

Have Spark now !!!
Thanks again one and all, now have a really good spark using 4 x 1.5v AA batteries giving me 6v in total.
I can't get the engine to fire and start, any suggestions would be appreciated to get it firing.
I'm not 100% how to set the timing on these engines.
It has spark now, has fuel so what should I be looking for?

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Blue Heeler on 28/07/2023 00:38:36:

Posted by Michael Gilligan on 27/07/2023 07:06:57:

.

Thanks for the photos

The basic spec is [usefully] already translated

… but now we know that it’s a

Dongsheng pulse igniter

and can start searching for more info.

MichaelG

[JasonBModerator @jasonb]

Was it purely the voltage increase that did it? Or a battery holder/wiring issue.

Time it to fire at or just before TDC. Cam is probably part of the larger gear so any timing adjustment will be by rotating small gear on the crankshaft if it just has a grub screw to hold it. If keyed to the shaft then you need to slip a gear out of mesh and remesh in the required position.

Too much fuel is often a problem, you only want to crack the needle open a little

[Blue HeelerParticipant @blueheeler]

Thanks @JasonB Jason really appreciate all the posts trying to help me mate.

I've had my wife in the shed now multiple times to test having the spark plug resting next to the spark plug hole with the 3 x 1.5v AA batteries and there's no, zilch, nada, nothing. As soon as I switch over to the 4 x 1.5vAA battery pack instantly there's a really good spark across the gap which has me utterly baffled as I've watched so many YT vids of other owners running their same engines with the 3 battery pack as supplied with the engine (like what I received) but when I emailed the company they said the engine needs a minimum of 6v to fire.

Next hurdle is the timing.

I'm starting to doubt myself now, so to double check this is TDC isn't it !

**LINK**

Am I incorrect that I adjust the firing (timing?) by adjusting this brass piece that slides on that rail that pushes down on the switch to make contact?

**LINK**

Once again….appreciate the posts.

[Michael GilliganParticipant @michaelgilligan61133]

As you have already ‘emailed the company’ … I guess it was unnecessary to translate this:

.

.

but I’ve posted it here in case anyone feels like trying an ‘image search’

… Google didn’t get far with: Dongsheng pulse igniter

MichaelG.

[JasonBModerator @jasonb]

Valve timing adjusted as I said by the gears, I see you have a grub screw on the crankshaft gear so easy enough to alter if needed. Yes that is TDC

Ignition timing as you say by moving the brass arm that actuates the contacts.

[noel shelleyParticipant @noelshelley55608]

Without correct valve and spark events the engine will not run. Remove the spark plug and put a wood or plastic rod down the hole so you can find the piston position. There are 2 TDCs in a 4 stroke cycle engine. Watch the valves. When the inlet and exhaust are both closed and the piston at the top of the stroke this is the compression stroke and about 1/8" before this TDC is when the spark happens. Putting your finger over the spark plug hole you will feel the compression – no compression and it will not run. The valve timing ! As the piston rises from BDC the exhaust valve must be open, closing as the piston reaches TDC, at the same time the inlet valve must open to admit the air/fuel mixture. As the piston approaches BDC the inlet valve will close, followed by compression again. Make sure you have a small clearance on the valves may be 5 thou or 0.1mm

I do not know this engine so the above is basic principles but should put you in the ball park. Good luck. Noel.

[Howard LewisParticipant @howardlewis46836]

As Noel says, the valve timings will be very approximately

Inlet opens about 5 degrees btdc, closes about 5 degres abdc (Allows for inertia of the gas column )

Exhaust opens about tdc or maybe upto 5 degrees btdc, closes about 5 degrees abdc (as above – gas inertia)

Overlap tends to be more important in high speed, high performance engines.

Ignition should be just a few degrees btdc, (Less for a slow revving engine ) to allow time for the ignition process to get under way. Exact timing will depend upon mixture strength and engine speed. Weak mixtures burn more slowly.

Suggest that you set the valve events first, and then adjust ignition timing to optimise performance.

Do not over advance, this produces excessive cylinder pressures, and can adversely affect perfornace and fuel consumption; not to mention over stressing bearings, con rods etc.

HTH

Howard

[JasonBModerator @jasonb]

These engines have an atmospheric inlet so you can't do much to alter the timing on that, just the exhaust. Inlet will typically open after TDC as it needs the vacuum created in the combustion chamber to open the valve against it's light spring.

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