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Smith Motor Wheel

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Old 02-12-2016, 08:58:47 AM
Winchester Winchester is offline
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Default Smith Motor Wheel

I'm rebuilding a SMW ,rebored the cylinder and made a new piston to suit ,made new rings ,two compression and one oil scraper. I made a new inlet valve cage and valve [ atmospheric valve] and fitted a suitable compression spring. Put it all back together and set it up with an electric motor to run it in . After an hour or so still no compression ,checked everything ran it again ,no compression ........I had a think about this and I reckon that the inlet valve spring [ atmospheric] is too strong . The valve is not opening enough and I am running a partial vacuum ,hence no compression I correct. there is one way to find out but I've not got around to changing to a much weaker spring yet.
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Old 02-12-2016, 09:38:24 PM
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Junkologist Junkologist is offline
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Default Re: Smith Motor Wheel

You will definitely have a lack of compression if the intake valve will not allow air in. Can't have compression if there's no air to compress. Some air compressors unload the compressor this way by not allowing any air to be taken in.

You can check your engine out by simply removing the spark plug and turning the engine over until the piston is at BDC between the intake and compression strokes. Put the plug back in and turn the engine over. If everything is ok and there are no leaks, there will be compression as soon as the piston starts to go up the bore. If your intake valve spring is too stiff, there won't be any compression after that. The intake valve should also be making a snorting or rattling noise if it is working properly.

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