Tecumseh H60 no spark - help

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jonnyhall
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Tecumseh H60 no spark - help

Hi, I have purchased a Atco B20 with a Tecumseh H60 engine, but there is no spark.

model is h60 75448m

I have changed the coil, points, condenser & spark plug. Its timed to 80" before TDC with 20" points gap.

The magnets are good on the flywheel

The magneto plates are a little rusty and I have wire brushed them off so they are now much better.

When I spin the flywheel I can feel a pulse when holding the spark plug but its not enough to produce a spark across the spark plug...

I don't really know where to go now... any advice?

Thanks

Jon

wristpin
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Not sure about your 80” TDC.

Not sure about your 80” TDC.  Should be 50 thou”. / 0.050” Before Top Dead Centre. To do it really accurately you need the cylinder head off.  Just in case you have converted distance into degrees , it’s not a straight linear transposition as it has to take in the crankpin angle. I’ve long forgotten it but you will find it on the net.

Make sure that the points are set to 20 thou and spotlessly clean - in the case of new ones ensure that you have removed any preservative and pull a piece of clean card through to remove any dirt from your feeler gauge. 

EDIT

Added later

https://www.dropbox.com/s/sinz5e6rh8dtuut/Tecumseh%20medium%20frame%20en...

 

jonnyhall
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Hi wristpin, thanks for your

Hi wristpin, thanks for your feedback. All the documentation I can find says the timing is 80 thou before tdc. Where do you get 50 from?

eg.
https://www.allotment-garden.org/rotavator-manuals/Techumseh-L-Head-Engi...

wristpin
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From the Tecumseh workshop

From the Tecumseh workshop manual . I’ll scan and post the relevant spec page later today.

wristpin
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This is what I have but your

This is what I have but your link is more modern. However, as your engine is points ignition these specs should apply - I think.

https://www.dropbox.com/s/sinz5e6rh8dtuut/Tecumseh%20medium%20frame%20en...

 

jonnyhall
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ahh right, thanks, i'll have

ahh right, thanks, i'll have a look now. ;-)

jonnyhall
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ok Thanks Wristpin, I can see

ok Thanks Wristpin, I can see what you are saying, I'll give it a go, as cant hur't. Is there anywhere that you know of where I can find the exact settings for the engine numbers stamped on my engine?

which is.... h60 75448m 1278d

Thanks for your help.

Jon

 

wristpin
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Unfortunately when Tecumseh

Unfortunately when Tecumseh withdrew from the engine manufacture they closed their UK operation in Staines. As yours has points ignition it will be a fairly early build H60 and the spec pages that I posted should be OK for it. As you say that you have new coil, points and condenser it should just be a matter of careful, clean and accurate assembly.  Set the points first than the timing.  I will have a look to see whether I have anything that will interpret your engine numbers but Tecumseh were never very good of distributing and updating such information - even to their dealers.

 

 

Straitcut
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As a new member I have a

As a new member I have a similar "no spark" problem.

My Atco Royale B20 ( 60 years Diamond Jubilee insignia) has given excellent service with no trouble over the past 20 years. This year - no spark. After normal checks  in removing the flywheel I find that the insulated terminal wired to one of the points shows a short to earth (<1 ohm), when the points are either open or closed even when disconnected from the on/off switch lead. Does this indicate that the coil is n/u?  Perhaps the next stage is to take off the whole magneto assembly. I have previously checked the points gap etc. If coil is N/U what can I do?  Mower is too good to lose.

wristpin
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First, does your engine have

First, does your engine have a kill wire going from the external points terminal block to an external stop switch. If so check for a faulty switch or chafed kill wire.

Then I suggest disconnecting the condenser and coil wires from the points block and separate them . You can then recheck the points for the permanent grounding that you report. You can also then check the resistance on both the primary and secondary coil windings.

I have the luxury of a dedicated condenser tester but I believe that it’s possible to do so with a digital multimeter but I’ve never done that, you may find the procedure on line. It’s far more likely that the condenser will have failed than the coil. I believe that some  people test by charging  the condenser with a 9v ( PP3?) battery and then discharge it to it’s casing - NOT through the multimeter !

jonnyhall
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Thanks again Wristpin, I got

Thanks again Wristpin, I got it running. 50thou was no good, I could not get the adjustment on the stator plate when timed to 50. So I went back to 80thou, and as you say very carefully put it ll back together again. I noticed that the points spring was possibly fouling on the points locking screw (it was twisting as I tightened up the nut holding on the wires) so give it a little tweak. To me the spark still seems weak, but there is a defo improvement, and anyway it started up first pull.... Happy days.

Thanks for your help

Jon

wristpin
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Any spark that runs it is a

Any spark that runs it is a good’un.

I'm surprised that it wouldn’t set up at 50 thou ; can only assume that they  made some running changes to the geometry of the ignition cam ring. Usually when that happens there will be a  before and after serial number note but there doesn’t seem to be any sign of one.

 

 

DJD
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How I very roughly test any

How I very roughly test any capacitor, all I need is my quality old fashioned moving coil multi meter.

I turn it to the very highest ohms setting firstly and connect the test prods to the capacitor, doesn't matter which way around, but do take notice how.

I then re-set the meter to the very lowest dc voltage setting, but I then swap the leads around, forget this and needle will hit the low end stop!

If cap. is in good condition, you should see needle rise quite highly up scale, then slowly return to zero as you continue holding the prods on, only takes a few seconds.

This very simple method which I've not seen advised anywhere else yet I sort of invented as far as I know, about thirty years ago.

It's a case of simply charging and discharging the cap, if it won't work with such tiny voltages and amperages, it's a good guess it won't work at the high voltages required in the ordinary magneto low tension circuit.

Try it at your own risk, but my meter is the original one I used when I thought this up. and still going well.

Straitcut
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Thanks Wristpin (and also DJD

Thanks Wristpin (and also DJD ).

On my Atco B20 magneto I have taken all the steps suggested, and the 2 wires emerging from the coil are not shorting to ground as I previously thought. They have a resistance of 0.7 ohm, which does seem low, but I do not know the gauge of the Cu wire gauge or its length  within the coil.

Using the condenser test with a multimeter the capacitor shows a residual voltage that slowly reduces over 10 seconds or so, the capacitor seems to pass the test. Further investigation of the problem maybe needed.

Somewhere on another post I saw a coil resistance quoted to be somewhat higher than 0.7 ohm. What can one expect the resistance of the coil to be? 

wristpin
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After my first reply I did

After my first reply I did have a look for the primary and secondary resistance figures but to no avail . I’ve got one other possible source and will look later. I may even have a coil to measure.

jonnyhall
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Update - So after getting the

Update - So after getting the H60 engine running ok, I decided to swap out the points & condenser out for a SIG-01 electronic ignition Module. It cost me £10 on ebay (although I could have paid £24 from a couple of sellers). I had my doubts it would work, but amazingly it does!

I mounted the module onto the heat shield with a self tapping screw to ensure its got a good ground.

It makes having to faf around with the points and getting the timing spot on a thing of the past, wish I had known about these modules when I started the restoration.

;-)