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Collection, Preservation and Display of Old Lawn Mowers

Bosch super 942 spark plug equivalent

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Hi folks,

It's been a while, but given all the spare time I've had recently I pulled out my old Ransomes Marquis and tried to start it for the first time in a couple of years, with no luck. 

My first port of call will be a new spark plug. The one currently fitted is a Bosch super 942. I can't seem to find these for sale anywhere. Can anyone recommend an alternative?

Many thanks. 
 

 

Forums

hillsider Sun, 05/04/2020

It is likely that you have other issues preventing your mower from starting like fuel or ignition issues besides the plug but you can eliminate those as you go. Meanwhile the plug you have is certainly a difficult one to cross reference for you so it may be safer if you can tell us the make and model numbers of the engine that you have on the mower i.e. Villiers, Briggs and Stratton.or even MAG / Kubota.

hsu139 Sun, 12/04/2020

Thanks for your response, hillsider. I'm concious that it could be several things, but I'm pretty sure I'm not getting a spark so I want to rule the plug out first. 

Picture of the engine with number supplied. I'm pretty sure the engine cover is stamped with 'BSA' also, though it's hard to be sure because of the dirt. 

wristpin Sun, 12/04/2020

What you have there is what is commonly known as an “F12  Sloper”. . Early ones were badged BSA and later ones Villiers.

The original Plug was a Champion N8 . The more easily obtained ones  now are either an NGK B5ES or B6ES, gapped to 30 thou.

 

hillsider Sun, 12/04/2020

Thanks wristpin for providing the answer to the spark plug question I had actually missed the reply telling us the engine type. 

hsu139 Sat, 25/04/2020

Many thanks wristpin and hillsider. Really appreciate you taking the time to answer what must be a pretty basic question for those familiar with these. 
 

Let's see how I get on with a new plug! I suspect not particularly well, but will keep my fingers crossed. 

hsu139 Sat, 02/05/2020

Fitted the new spark plug and not getting a spark, so onto the next thing...

Going to clean the points through the little window, as don't have the tool to remove the flywheel. Is it possible to get the starter cup off without removing the main central bolt? If not, how do you undo the bolt without the whole thing spinning around? Is it safe to wedge something between the fins? I'm guessing probably not. Again, any help appreciated.

wristpin Sat, 02/05/2020

You are right about the fins - easily broken. Unless you can beg or borrow a battery impact wrench to jar the nut undone a strap or band wrench around the smooth bit of the flywheel is what is needed to hold it while undoing the nut with a socket and breaker bar. 

Try cleaning the points through the port hole with a strip of wet and dry paper glued to a strip of redundant credit card and finish off by pulling a strip of clean paper through the closed points to remove any grease left by the cleaning and gap setting . Pull it through but not out, then hold the points slightly open to release it. Pulling it right out may allow the points to snap shut and trap some paper fibres, defeating the objective!

 

Chris G Sun, 03/05/2020

On a later A15 Marquis I used big wooden 45deg wedges between the engine deck and the flywheel, usual heating up of the nut etc, not advocating in case you break any fins, but it did work ok.

hsu139 Sun, 03/05/2020

Thanks again folks. 

Bit of an update: Took the cowling off and wedged an old metal pole into the fins and tried to undo the central nut. Unsurprisingly a couple of fins snapped, so had to try something different. Found an old funny shaped tool and managed to wedge it into one of the depressions in the flywheel where the studs for the clutch shoe are located (see picture). This worked tremendously well and the central bolt came out (almost too) easily.

Took off the little cover for the window and cleaned the points as advised, and reassembled everything.

I had removed the fuel line in order to properly refit it under the lugs inside the cowling, as I figured it wouldn't be possible to do this with the fuel line connected. While removing the fuel line I snapped the metal nipple off the bottom of the carb. Think it must've been pretty brittle. Was annoyed at first as I thought I would need to get a whole new carb, but on closer inspection it looks like this is a small bit that can be swapped out - so I'll be on the hunt for one of those, as well as a new fuel line (any advice on the correct diameter of fuel line would be appreciated. It's for an Amal carb, and goes into an Ewarts fuel tap).

So, given that my fuel supply was now scuppered, a proper test wasn't possible, however I just needed to know that I had a spark, so I syringed a little fuel into the spark plug hole, fitted the plug, and gave the starter a pull. To my delight it fired up momentarily!

Must say that I'm pretty delighted. It was my papa's mower that he gave to me before he died and I'm keen to at least keep it running. Perhaps one day I'll give it a proper restoration.

Thanks again for your help. No doubt I'll be back with more questions in due course!

hsu139 Sun, 03/05/2020

Yes, I dare say the seasoned restorer would've had their head in their hands if they saw me at work!

Any thoughts on the fuel line size for my Amal 379? Managed to pick up a banjo online for £5, so pretty happy about that.