Homemade 4 Stroke, Opposed Twin Glow Plug Engine - Why Won't It Start?

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clemley

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Thank you for these comments.

I have noticed that various components of the engine (eg. the valves) rust very quickly. I assumed it was the methanol rather than the nitro but nitro makes sense. It's ferocious how quickly rust forms.

Anyway, next project is going to be a single cylinder, gasoline, spark ignition engine, when I get around to it.
 

bluejets

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The nitro residue is nitric acid.

Chinese make a 1/4" spark plug if you have the need to convert your existing engine.
There are a few off-the-shelf small CDI units you could use but rather expensive. (here in Aus at least)
Then there are many roll your own, one of which I put a write up in here using the CDI unit from a pocket rocket motorcycle.
Cost there all up is around AU$20.00. 1/4"spark plug around the AU$15.00 mark.
 

AndrewW

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Hi. I recently made my first Farmboy hit and miss engine and had all sorts of problems trying to get it to run.
My YouTube video explains some of the fault finding I followed.
I hope this might help you:

By the way, I tried using methanol initially and couldn't believe the rust build up in the cylinder. Searching on the internet suggests that it burns forming carbon dioxide and water! I quickly switched to Coleman fuel.
Good luck!
Andrew
 

bluejets

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bluejets, I'd like to know more about these spark plugs & ignition system whenever you are ready to share/

Around 2 years ago the Chinese plugs came up at DLE mob in Australia and the bloke there gave me a good price when I ordered 24.
Now with the virus, things get difficult to buy here and no longer stocked.
There is Rcexl who have both the 1/4"/32tpi plugs and the small CDI units.
Also Rimfire V2 is another type.

Ignition system using the mini motorcycle parts writeup ......
Model engine CDI easy and cheap

There was also a fairly simple multispark ignition originally posted by Doc .
I looked up many details on this as not much info was supplied and found it to be an older circuit he had revived.
I did a couple of small changes and wrote the effects here.
Uses a BA Ford ignition coil with all the extra bits stripped off.
Works well on a single 18650 lipo cell.
https://www.homemodelenginemachinist.com/threads/pdfs-l-cheapo-ignition.31916/

Doc had his running on a twin.


 
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Nerd1000

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Hi. I recently made my first Farmboy hit and miss engine and had all sorts of problems trying to get it to run.
My YouTube video explains some of the fault finding I followed.
I hope this might help you:

By the way, I tried using methanol initially and couldn't believe the rust build up in the cylinder. Searching on the internet suggests that it burns forming carbon dioxide and water! I quickly switched to Coleman fuel.
Good luck!
Andrew

Pretty much every fuel burns to carbon dioxide and water! Coleman fuel is certainly no exception, being a mix of hydrocarbons similar to octane, C8H10. For every molecule of octane you burn, you will make eight molecules of carbon dioxide and five of water.

The real issue with methanol is that it is hydroscopic, so it absorbs extra water from the air over time. As some residual fuel is usually left inside the engine after shutdown, there may be residual water hanging around with it, which is of course not good news where corrosion is concerned.

4-strokes will probably benefit from a 'PCV' system, basically a tube and non return valve that routes any crankcase vapours into the intake. This way leftover fuel and water in the blowby gases will not be allowed to accumulate in the crankcase, so long as the engine is warmed up sufficiently each time it is run. This also has the happy additional benefits of helping the piston rings seal and reducing pollution, which is why you're unlikely to find any production engine that lacks one these days.
 

AndrewW

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Pretty much every fuel burns to carbon dioxide and water! Coleman fuel is certainly no exception, being a mix of hydrocarbons similar to octane, C8H10. For every molecule of octane you burn, you will make eight molecules of carbon dioxide and five of water.

The real issue with methanol is that it is hydroscopic, so it absorbs extra water from the air over time. As some residual fuel is usually left inside the engine after shutdown, there may be residual water hanging around with it, which is of course not good news where corrosion is concerned.

4-strokes will probably benefit from a 'PCV' system, basically a tube and non return valve that routes any crankcase vapours into the intake. This way leftover fuel and water in the blowby gases will not be allowed to accumulate in the crankcase, so long as the engine is warmed up sufficiently each time it is run. This also has the happy additional benefits of helping the piston rings seal and reducing pollution, which is why you're unlikely to find any production engine that lacks one these days.
Very interesting!
 
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