Author Topic: Douglas 600cc Industrial engine timing  (Read 569 times)

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Offline Hapty1

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Douglas 600cc Industrial engine timing
« on: 31 May 2021 at 10:56 »
Hi All, can anyone tell me how to time magneto on my 600cc industrial truck and does anyone have a engine manual and a operating manual. Happy to pay.

Thanks,
Tony

Offline Doug

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Re: Douglas 600cc Industrial engine timing
« Reply #1 on: 01 Jun 2021 at 00:47 »
Tony,

They may have used different engines over time, but I have seen a few based on the 600EW engine. If so, I would think the timing specs for the 600EW and the subsequent F/G28~29 models would work. See this post here for the 600EW handbook page and timing diagram.

https://www.douglasmotorcycles.net/index.php?topic=6668.msg25075#msg25075

Not seen a publication for the industrial trucks, though I assume the factory must have supplied something with them.

-Doug

Offline Hapty1

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Re: Douglas 600cc Industrial engine timing
« Reply #2 on: 03 Jun 2021 at 11:35 »
Thanks Doug,

This has confused me more as I would think firing 45deg btdc is way to early. I was thinking more 4 to 6deg btdc. I have never timed a magneto before so is there something Iím not reading correctly. Donít want to break my arm if it kicks back on the hand start.

Offline cardan

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Re: Douglas 600cc Industrial engine timing
« Reply #3 on: 03 Jun 2021 at 11:56 »
Hi Tony,

The EW is seriously weird in its requirement for a spark at 45 degrees BTDC fully advanced. Perhaps it is explained by the weird heads - the tips of the plugs are quite masked from the actual cylinder. Not sure if your engine is like this?

However 4-6 degrees BTDC (fully advanced) is way too little for any engine - even a Douglas industrial truck! 35 degrees BTDC (fully advanced) might be a guess, and you should have plenty of room to adjust provided you have manual a/r on the magneto.

Cheers

Leon

Offline Doug

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Re: Douglas 600cc Industrial engine timing
« Reply #4 on: 03 Jun 2021 at 13:13 »
Agreed, Ignition timing of 35 degrees BTC is a good place to start experimenting when you lack any model specific recommendation. The longer the flame front takes to travel from the spark plug location to lighting off the majority of the charge, the more ignition advance (head start!) is required. Douglas used shrouded plug locations on both side valve and ohv to resist plug oiling, and that led to some slow ignition.

We have a model A Ford with a period Miller ohv cylinder head 'performance upgrade'. Reputed to lift the power from the factory 40hp to 60hp. When we finally got around to installing it the performance was disappointing, not much more than the factory flat head it replaced and less than high compression aftermarket flat head available for the model A like the Winfield. It turned out it needed a lot more ignition advance than expected, a lot more. Then it started to make a noticeable improvement in power. Seem there was so little turbulence in filling the cylinder (the combustion chamber was basically an extension of the cylinder bore, vertical valves, and a near vertical spark plug off to one side) that the flame propagation was glacially slow. Perhaps at higher revolutions things got mixed up more and the ignition was more efficient; it was after all a cylinder head intended for racing, not putting around on the road.

Generally though, the lower the compression (molecules not pressed together so close) and less efficient the engine, the more advance will be needed. Turbulence helps, hence the discovery that 'squish' areas in side valve head design (Riccardo?) really improved the power.

-Doug

Offline Hapty1

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Re: Douglas 600cc Industrial engine timing
« Reply #5 on: 04 Jun 2021 at 05:52 »
Cardan and Doug,

Thanks for this and what you are saying makes since. Iím not sure what the difference is from industrial engine to 600ew but there is a mark on flywheel at 35deg btdc so Iíd say you are both spot on. Iím used to later engines with overhead valves and they are usually around the 8 to 6deg btdc. At 35deg the piston is 5/16 before tdc which now sounds good to me due to side valve configuration.

Big Thanks
Tony

Offline EW-Ron

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Re: Douglas 600cc Industrial engine timing
« Reply #6 on: 04 Jun 2021 at 07:19 »
All the ohv engines I've played with have been in the 30 degrees plus mark, fully advanced.
5/16" or 3/8" wouldn't be unusual for small-ish to medium motors of any variety - sv, ohv, ohc.

5 or 6 degrees may be possible at the FULLY RETARDED mark, but even that sounds a little too little.?

And if you have a flywheel mark, you are home and hosed. ! (as they say)(and who knows where that comes from ?).

Offline graeme

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Re: Douglas 600cc Industrial engine timing
« Reply #7 on: 14 Sep 2021 at 02:36 »
"home and hosed" comes from horse racing - the horse has finished the race, and is getting hosed down back in the stable.

As for ignition timing, the recommendation for the 20s OHV Douglases is 45 degrees BTDC fully advanced - whether that is needed with modern fuels I don't know. I agree though with previous comments of starting with 35 and working from there