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ianbruin

Qualcast rotavator, suffolk engine? no spark

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Just got myself a rotavator, believe its a qualcast culti super with a 98cc suffolk engine. I'm hoping someone will be able to confirm this.

 

It was last used about 4 years ago and was then left outside down the back of a shed. Engine is free, spins with good compression but not getting any spark.

Replaced the point and tried with a different spark plug but still no spark. Any advise on what I should be looking at next would be very much appreciated

 

Thanks

 

Ian

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That’s a bit of a mess in the carb and governor department!  Have you checked for a spark straight off the end of the plug lead with the cap removed? Also , with no sign of a recoil unit , how are you spinning the engine? May be just not fast enough, or is the clue in that drill lying on the ground? May still not be fast enough.

Can’t see from the images but is there a wire from the magneto to an insulated terminal on the carb. If there is, that is the kill wire and it may be shorting out.  When you were in the mag replacing the points did you notice a condenser ? If there’s no separate condenser it may have the later pattern coil incorporateing a condenser  and the whole unit may have failed  but before going that route check that the plug lead is firmly screwed into the coil .

An image of the mag with the flywheel removed will be useful.

Edited by Wristpin

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Hi Wristpin

 

There is a recoil unit I had removed it to clean everything up. The Carb I have stripped down cleaned the jets and replaced the gasket I can blow through all the jets and its has stopped leaking now. I had been putting the recoil back on each time to test but have tried to use the drill as a quicker way to test. I will try it with the recoil back on tonight and see if I get a spark.

As this machine is used I am unsure if it is all wired up right there is a cable from the magneto to the points, the ht lead from the bottom of the magneto to the spark plug, a cable from the points to the throttle. There was also a broken cable from one side of the magneto the other side which I had to replace. Ill take some more pictures of behind the fly wheel tonight. I have wondered if I had order the wrong points as we were only guessing what engine we had.

 

Thank you for all the information so far.

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The lead that you describe as going to the throttle is the “ kill / stop” wire and could be the cause of your loss of spark. Make sure that  it is not earthing out . You don’t mention a condenser so you probably have a coil incorporating one.  

I am fairly certain that your engine is an early A98. - aluminium crankcase, 98cc - as the later ones  and the 112cc and 114 cc aluminium engines that followed had electronic ignition - no points.

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I have taken some pictures from inside the flywheel.

The brown wire in the picture is the kill /stop wire, the original black wire was split when we got the rotavator so we have replaced this. The blue wire in the picture was red but we replaced this to make sure it was not a bad cable causing the issue. The silver section of the flywheel is still magnetic not sure if this would require or even if it can be adjusted? Put the recoil back on tonight and tested again but no spark. I have tried with the kill switch connected and totally disconnected same out come. Having a closer look at the coil it looks like it may have been hot at some point you can just make it out in the picture.

Is there anyway I can test the coil? does it look like everything is in the correct place?

Thanks again

 

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It looks ok as far as the relationship of the components goes . Please confirm that you have tried for a spark straight off the end of the HT lead without the plug cap and that you’ve cleaned  any protective coating off the contact faces of your new points, set the points to the correct gap ( 18 thou.? ) **, recleaned them after setting and that they are opening just before the piston reaches top dead centre.

Unless  an external voltage has been applied to the coil it is unlikely to have overheated but if you have a multimeter you can check for continuity and resistance of the low and high tension windings of the coil but unfortuately I don’t have any figures for what those readings should be.

**the correct gap  figure is usually cast into the outer face of the flywheel or even stamped into the removable cover that gives access to the points. 

This may be of assistance.  https://www.dropbox.com/s/gbq4bdj2cto80gv/Suffolk A98 Magneto and carburettor0001.pdf?dl=0

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Thank you for the PDF that is the first one I have actually seen that is the same look as the engine I am working on and does confirm that all the parts are in the correct place.

 

I gave it a pull with the plug cap removed but got no spark. Took points out and gave a good clean, put back in set to 18 thou, which is also written on the inspection cover. Took out the coil to take a picture of the back as this is where it looks potentially damaged. When I took the coil out the HT lead fell out so was not connected properly, secured this and put everything back together. Went to tighten crankshaft nut and bang snapped the thread, on inspection it did have a rust line into it so I looks like it has been weak all through my testing I have just been lucky until now. I have uploaded the pics of the back of the coil.

 

I have not given up with this engine I am just going to try and source a replacement crankshaft before I can try and get to the bottom of no spark. Or another engine and I can swap parts around as required.

 

Thanks for your help this far

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That's what's best described as a bit of a B****r! PM sent.

Meanwhile here's a pic of the back of a brand new coil. As you will see the potting material is decidedly lumpy. it's just some form of resin / epoxy poured in over the coil and condenser and allowed to find its own level.

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Had some time today to have a proper look at the crankshaft. Cut a flat surface where the thread had snapped and very carefully drilled into the crankshaft gradually increasing insize.

Threaded the hole and inserted an m10 nut covered in thread lock. Cut the head of the bolt and put everything back together just to make sure I had cut the nut to the correct size.

having come this far, gave it a little pull and to my surprise I had a spark. Put some fuel in and and found a small leak from the tap on the bottom of the tank, put an o ring in the tap and sorted the leak. Tried to start but it was not having it, a quick adjustment to the carb settings one more pull and it started and ran brilliantly. I just need to spend a bit more time now cleaning it up and working out what springs and little bits i might be missing from the governor setup and I will have it at the allotment next week chewing through anything that gets in the way.

 

Wristpin thank you so much for all your help with trying to the find why I had no spark. If your ever York way for what ever reason give me a shout ill buy you a few beers

 

I have cut the thread down some more since taking this picture.

 

 

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