Skip to main content
Collection, Preservation and Display of Old Lawn Mowers

Starting work on the Qualcast Commodore and the (usual) Ignition Problems

Enter a word or two to search the forum section and click the Search Forum button.

Hi,

Well I've made a start on my Qualcast Commodore and done some basic things including  dismantling and cleaning the carb which looks OK. I've de-coked the engine which looks ok ish and there doesn't seem to be too much piston slap. It's the good old SIF 75G unit of course. Not too sure about the exhaust valve, but I think it will run. I've fixed the stuck recoil starter and I've oiled bearings and topped up engine oil (just in case) There are lots more jobs and there will be posts on those, but as usual there is no spark currently. I have a new plug, so it isn't that and the gap is set correctly at 25thou. Looking at the Coil/Condensor/points set up, it looks a bit dodgy, but I am no expert. I have cleaned the points (although they may need to come off) and the gap is bang on at 20thou. I have checked the gap to the heel of the points and it is possibly a little lax at 4thou. Otherwise the hi-tension lead feels hard and inflexible. I suspect the condensor as the main culprit, but any guidance would be good. I do have a DMM, but I am really not an expert with it. See below for some images.

Thanks for reading

Best 

Andy

Ignition assemblyCondensorDirty pointsOpen points close upPoints with CondensorCoil assembly

 

Forums

hortimech Thu, 26/09/2019

If you have 'cleaned' the points without removing them, then you haven't cleaned them properly ;-)

I would remove and clean them using a fine abrasive (anything but sandpaper) and then refit & reset them, ensuring you do not dirty them whilst setting the gap to 20 thou.

If you still do not have a spark, then you will need to suspect a faulty condenser and/or coil.

wristpin Thu, 26/09/2019

In  no particular order. 

The plastic covering on the coil suggests that it is either from late production or a replacement. The original would possibly  have been fabric and shellac covered. You do need to take the points apart to clean them properly, I use a small carborundum slip stone. If those rocker points have been sitting around unused for a while they can partially or completely seize on their pivot, so make sure that it is free to move and that they are closing fully. I don’t think that the size of the gap between the points heal and the cam has much relevance .  

Condensers are prime candidates for time related failure. I prefer testing on a dedicated condenser tester but there’s plenty on the net about using a multimeter - preferably an analogue one rather than digital. You can use your DMM to check the coil’s primary and secondary resistances.

HT lead. As long as it has a proper wire conductor ( not carbon string) and has continuity, it’s flexibility, or lack of, is not an issue.  

hortimech Thu, 26/09/2019

No, sorry but I cannot agree with you there, you cannot clean any set of points correctly without dismantling them, otherwise you cannot ensure you remove any burning or pitting and cannot ensure they are flat and parallel to one another.

Cleaning a set of points in-situ is a botch and may or may not work.

 

wristpin Thu, 26/09/2019

No, sorry but I cannot agree with you there, you cannot clean any set of points correctly without dismantling them, otherwise you cannot ensure you remove any burning or pitting and cannot ensure they are flat and parallel to one another.

Cleaning a set of points in-situ is a botch and may or may not work.

Who are you not agreeing with? I'm with you!!

hortimech Thu, 26/09/2019

oops, either that was a senior moment or I need to go to spexsavers, somehow I saw the word 'not' in there

wristpin Thu, 26/09/2019

Not too sure about the exhaust valve, but I think it will run. 

Have you actually checked the valve clearances ?  15 thou on the exhaust and 7 on the inlet .

Why not keep all of your posts together in one thread ? Makes it easier for others to follow.

Andy B Fri, 27/09/2019

OK,

So I need to get the points off to clean them properly. No probs. I have made a small mark where the plate sits to make sure I can re-align them when I put them back on already. I think my multimeter is an analogue one in fact. I suspected the coil/condenser didn't look right and the unsightly blob of solder near the condenser may be a clue. 

Right then, that's the weekend job sorted! oh and the valve clearances...

Thanks guys.

Andy

wristpin Fri, 27/09/2019

That soldered joint was normal for the era - things were hand assembled in those days.

You can dismantle and clean the points without disturbing the stator plate but removing it may make the job easier.