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Valve Timing 21 Jan 2021 19:48 #218206

  • wee-allis
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If you have set the points to open at TDC instead of 8deg advanced, then you are asking it to run constantly retarded. Bit like me I guess.
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Valve Timing 21 Jan 2021 20:00 #218207

  • grandad
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What's the firing order on this engine?
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Valve Timing 21 Jan 2021 22:42 #218208

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Hi mamoth, governor 'interfears' with the engine revs. They are governed to 2200 rpm from meory but if you are pulling a heavy weight or even driving along and come to a hill it then opens up the carby and away you go. Surprisingly this has worked perfectly all of the time I have run the tractor. IT did required so sensitive adjustment of the spring tension but I have that all sorted.
Grandad firing order on this one is 1-2-4-3. So as I have been winding the engine over from the drive lug nit on the end of the cranshaft I can watch the valves open and close all in the correct sequence. It took a couple of times through the complete revolution but then it all made sense as to the order of things and that order was consistant for each cylinder.
Yes Steve, I (me) must be retarded. Once I get the chance to clean up all the parts again and refit the covers I will start with setting the spark timing properly and at the 8'BTDC. I found that the letter "M" on the flywheel stands for 'magneto' and is the timing mark for the spark. So either tomorrow or Saturday I will be onto that stage.
The weirdest thing is that it has always burst into life with the least amount of starter motor and the one and only year I hooked it up to the sled at Macksville I was asked if I was running water in the rear tyres which I wasn;t. It pulled that good, you could even see the torque flex in the rear tyres as it hooked into the job. All of this with bad spark timing done by me!
Cheers Cobba & Cobbarette
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Valve Timing 21 Jan 2021 22:52 #218209

  • PDU
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Hmmmm, if it ain't broke, and it runs strong, why fix it?

Leave it alone and go find another job to do . . . :whistle:

The eternal lazy bastard??? :blush:

NB Edit after cobba's following comment . . . I assume you have tried twisting the distributor accordingly? Does it have a distributor?!? :unsure: ;)
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Last edit: by PDU.

Valve Timing 22 Jan 2021 08:21 #218216

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I agree PDU but the bloody thing is not running strong now and is sounding and driving with a miss fire and lack of go.
Cheers Cobba & Cobbarette
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Valve Timing 22 Jan 2021 12:01 #218219

  • jon_d
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and lack of go.


Set the timing right and see what happens. 8* retarded is quite a lot. The piston is over the top and on its way down. The exhaust valve are starting to open and the flame escapes

Retarded engines run hot. (esp the exhaust manifold) Was it hot?

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Valve Timing 22 Jan 2021 22:12 #218228

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Ok, this is where I am at by the end of the day. Tappets rechecked yet again. Timing cover back on as is the generator and fan. Rocker cover back on and then went to the spark timing. As by the manual I rotated the engine ove until the "M" mark showed up which is the 8'BTDC. I got my test light out and connected it to the battery so if I touched the probe on the points the light lit up. Then I loosened the locking clamp and backed the dissy way back then slowly rotated it in the right direction until the light flickered then went out.
This is where it is suppose to be, 8' BTDC.
Going by an uneducated guess the way it was certainly was not right as it was firing after TDC.
Got lawn duties again in the morning then back to fitting the radiator and topping it up, throw the plugs in and connect the leads and 'have a go ya mug'.
Cheers Cobba & Cobbarette
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Valve Timing 23 Jan 2021 05:40 #218234

  • Mrsmackpaul
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Do you use a timing light at all ?

Paul
Your better to die trying than live on your knees begging
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Valve Timing 23 Jan 2021 09:36 #218236

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Then I loosened the locking clamp and backed the dissy way back then slowly rotated it in the right direction until the light flickered then went out.
This is where it is suppose to be, 8' BTDC.
Going by an uneducated guess the way it was certainly was not right as it was firing after TDC.


Just some ramblings... ;) ;)

This method is known as "static" ie, setting it with out the engine running. It's a good start. But to do it properly, the engine must be running and with a timing light.

The spark timing is set when the light goes out. The light going out reflects when the current in the primary coil (12V winding) stops flowing. This triggers a 'breakdown in flux" which then generates the HV pulse in the secondary HV coil.

The HV voltage will increase to a point where the air/fuel mix across the plug breaks down (ionizes) and sparks.

If the gap is to large, or the air fuel is to 'dry', then the spark voltage has to be higher to ionize. If the coil voltage cannot reach the required ionization voltage, the engine will miss. If something else (eg HV wire) breaks down, the engine will miss.

If the rotor rotates off the brass probe n the cap before ionization, the engine will miss. (aka play in the shaft)
If the rotor moves off the cap, during ionisation, the spark will be short and a full burn/ignition may not happen. (aka miss)

If the HV lead or something else breaks down at a lower ionization voltage, the engine will miss.

If the dwell is set wrong, the LV coil will not saturate and therefor the HV ionization voltage will be low and possibly not trigger a spark. (or a weak spark)

If the plates holding the points, or the rubbing block opening the points is moving about, the dwell will change. (see above for impact.)

Vacuum timing advance impacts dwell. If it's faulty or not set right it can change the dwell at different RPM's.

You want the dwell set such that maximum HV is generated at high revs. Which would mean a longer dwell at idle... but not to long becuase then the mechanical timing components come into play.
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Valve Timing 23 Jan 2021 10:58 #218238

  • wouldyou
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Cobba,
For static timing turn the distributor body forward in rotor direction and then back until points begin to open, this allows for play in the drive.
I may have misunderstood your method but think you are finding points closing.
David.
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