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Author Topic: Wondering if anyone can help  (Read 4193 times)

Jamesengland

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Wondering if anyone can help
« on: May 03, 2018, 06:20:59 PM »
Hello all. Iíve discovered the wonderful world of stationary engines recently and have a Petter A1 and a Lister D petrol engines. Iím having a hell of a time getting the Lister to run. I noticed today that the valve timing seems to be incorrect..thatís if a book I have is correct. The inlet valve opened at approx 12 degrees after TDC. The book says that the inlet valve should open at 12 degrees before TDC and the exhaust valve should open 44 degrees before BDC.

Is this correct, does anyone know please? Iíve set the crank to TDC and got the cam of the push rod assembly pointing upwards between the two feet of the cam followers....all done correctly...but the inlet valve opens at 12 degrees AFTER TDC.

Thanks for any help

dieselspanner

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Re: Wondering if anyone can help
« Reply #1 on: May 03, 2018, 08:04:15 PM »
Hi James, and welcome....

The first thing that occurs to me, 'Are you rotating it the right way?'

Not so foolish a thought, ask me and several others that regularly post on here..............

At TDC on most single cylinder engines the inlet and exhaust valves should change over, as you 'rock' the crank back and forth over 15 degrees or so, you will feel this with two fingers (of the same hand!) on the rockers or, if they are exposed, the cam followers. This is the start of the four stroke cycle, suck, squeeze, bang, blow.

Cheers Stef
Tighten 'til it strips, weld nut to chassis, peen stud, adjust with angle grinder.

BruceM

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Re: Wondering if anyone can help
« Reply #2 on: May 03, 2018, 08:25:27 PM »
Great diagnosis, Stef! 

Jamesengland

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Re: Wondering if anyone can help
« Reply #3 on: May 04, 2018, 06:43:07 AM »
Thanks for that. Yep, rotating the correct way! The Ďsuckí stage begins when the valve starts to open at about 10 degrees AFTER TDC. Next TDC is the top of the compression stroke and both valves are closed When the piston reaches TDC

I looked at the timing gear yesterday and it seems to me as if itís not actually adjustable. I put the piston to TDC. Then put the lobe of the cam equally between the feet of the cam followers, lobe pointing up. Then engaged the forked arm with the square peg on the crankshaft. The inlet valve STILL starts to open at 10 degrees after TDC! I just donít see how the valv timing can be adjusted.....???

mikenash

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Re: Wondering if anyone can help
« Reply #4 on: May 04, 2018, 07:34:56 AM »
FWIW when i bought a Lister that I was told "had been running when it was put in the shed . . . " it turned out the cam idler gear had been removed at some point and the cam was 90 degrees out.  Yours might be a tooth or two out - just a thought.  Good luck

Jamesengland

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Re: Wondering if anyone can help
« Reply #5 on: May 04, 2018, 07:48:07 AM »
Yes, the book mentioned being a tooth out. But, from what I can see, there are no teeth involved...... the square peg on the crankshaft engages with the forked drive of the cam and thatís it. No teeth or gears mesh in order to drive the cams. From what Iíve read, the lobe of the cam should be facing up, between the two cam followers, the piston should be at TDC and thatís it. No teeth, no cogs and no adjustment seems to be possible???

dieselspanner

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Re: Wondering if anyone can help
« Reply #6 on: May 04, 2018, 08:15:45 AM »
OK,

The only experience I have of a D type is a swift glance at a few web sites but.....

You say there are no gears and the cam is a direct drive from the crank, however in  a four stroke engine the cam runs at half the rpm of the crank, to provide the timing events over the four strokes.

Looking at this

https://www.google.fr/search?q=lister+d+type+parts+list&rlz=1CAACAH_enFR734FR735&tbm=isch&source=iu&ictx=1&fir=US1TFAlPgBWKYM%253A%252C6IAhu6h96oKKxM%252C_&usg=__jbmRGJ50Yq_a35CeSqJURhxqFk4%3D&sa=X&ved=0ahUKEwjMhp78vevaAhUQKVAKHa5RC8gQ9QEIVzAD#imgrc=US1TFAlPgBWKYM:

There's an idler gear arrangement shown, I'd say further digging and checking of timing is your next move

If the misalignment of the cam was 45 or 90 degrees out I'd suspect the square drive depending on whether it'd before or after the reduction provided by the idler gear, but an error of 12 degrees before to 12 after = 25 degrees, this wouldn't tie in with a square driv,  and smacks of the set up being a couple of teeth out

At least you know you're not going backwards!

Cheers Stef







Tighten 'til it strips, weld nut to chassis, peen stud, adjust with angle grinder.

dieselspanner

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Re: Wondering if anyone can help
« Reply #7 on: May 04, 2018, 08:19:30 AM »
Oops!

My mistake, the drawing shows a reduction gear and not a idler gear,

It's only 9 am here and I've not had breakfast yet!

Cheers Stef
Tighten 'til it strips, weld nut to chassis, peen stud, adjust with angle grinder.

Jamesengland

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Re: Wondering if anyone can help
« Reply #8 on: May 04, 2018, 08:36:15 AM »
Yes...the toothed cog is just the cranking assembly that the cranking handle turns

mikenash

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Re: Wondering if anyone can help
« Reply #9 on: May 04, 2018, 08:49:53 AM »
Y'know, looking at those pics, maybe the gear on the crank is half the size of the gear that drives the cam stuff? does that give us the two-to-one?  I thought that dog assy for the starter was at right-angles to the plane of the cam & the crank?  If there are two gears meshing for that reduction, then maybe they are meshed wrong?  Kind of hard to read those drawings.  Good luck

BruceM

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Re: Wondering if anyone can help
« Reply #10 on: May 04, 2018, 09:28:06 AM »
Check the current exhaust timing- is it also out roughly 25 degrees in the same direction?


dieselspanner

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Re: Wondering if anyone can help
« Reply #11 on: May 04, 2018, 10:21:04 AM »
Ok,

After waking the dog, a couple of Lidl's breakfast bars, with tea I think I've got it..........


http://craigmarshall.org.uk/sites/default/files/images/Book%2068%20-%20Plate%204.jpg

Yes the reduction gear, driven by the starting handle rotates the crank to fire the motor, look at the link above and you'll see there's a single cam with a double follower that works both the inlet and exhausts, A pound to a pinch of, there's you're problem.

Counting the teeth on the crank sprocket (and hoping the drawing is correct) I'd say you'd be one tooth out - 360 divided by 14 = 24, or 12 degrees either side of TDC

I've seen this single cam, double follower system somewhere in the past , JAP lawnmower engines maybe, and I think this arrangement has name, but like lots of things it escapes me, I'll probably remember next time I get to the top of the stairs and have the usual brain fart.....

Fancy a pint on the outcome?

Cheers Stef
Tighten 'til it strips, weld nut to chassis, peen stud, adjust with angle grinder.

Jamesengland

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Re: Wondering if anyone can help
« Reply #12 on: May 04, 2018, 05:32:22 PM »
Yep...that gear turns the crank via the handle. But thatís all it does. It just turns the crankshaft. Itís the crankshaft itself that operates the cam via the square peg locating into the fork that turns the cam. To me, it looks as if the valve timing on this engine cannot actually be changed at all. It appears to be set permanently....if the cam lobe is pointing up and the piston is at TDC, thatís it.

BruceM

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Re: Wondering if anyone can help
« Reply #13 on: May 04, 2018, 06:13:22 PM »
There's no way to make a mechanical only 4 cycle engine without a 2:1 reduction to the cam.  Check the exhaust timing to confirm it's shifted 24 degrees also, please.


Jamesengland

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Re: Wondering if anyone can help
« Reply #14 on: May 04, 2018, 10:40:39 PM »
You are correct. There is a reduction gear. But still no way of adjusting timing