I have got a nice little quirk on an old Briggs that I struggle to understand whats wrong.
This is an old 1993 Morrison I use to mow the verge. Since there is small gum nuts, hidden sticks and other things hidden in the lawn, it is the only mower I use down there.
Has a bit of a rod knock and burns 30w oil, but not 15w40 (another quirk)
It has an alloy deck so I don’t have to be as retentive about cleaning it after use.
In the 2-3 years I have had it, its seen probably 15 hours use. Had probably 5 oil changes (to flush it muck out), new air filter and cleaned twice, primer, and diaphragm and shimmed the front axle. When it started taking 5 pulls to start, it got a new plug and now it goes first crack.
So I mow tonight, first pull starts, warm up 2 minutes, throttle down half and mow.
All good, finish and go to clean it.
The quirk:
If I EVER disconnect the plug lead, it will never start again; until you take the cowl off, unbolt the coil. Don’t have to clean it or anything; just loosen the bolts, stare at it and retighten them.
There are no cracks in the lead, splits, lamination issues with the coil, its all clean, the cooling fins are clear so its not cooking, the terminal and the plug is good.
Only once hasn’t it done it – the day I replaced the plug.
Button it back together and it will go first pull. Dare to remove the plug lead and it will need it again.
Usually, I don’t disconnect the plug lead due to quirk and just sweep out the LHS back (where grass piles up). But tonight I needed to get a bit of stuff off the blade holder.
I am sort of scared I will jinx it by typing this.
Doesn’t really bother me as its literally a 5 minute job with a socket set and a business card, and I could quite easily put another coil on, but it just baffles me haha
One of my favorite mowers - bit gutless, does the basics. Has had its deck blasted by 10,000 gumnuts (sometimes end up with 1/2 a catcher full) but it never lets me down
Will probably be a bit sad the day it sends the con rod out the side - hoping it hits its 30th before it does though (Sept 2023). Probably get another 30 years out of the deck though
Considering the age of the engine could very well be a worn exhaust valve and valve guide. I have replace several over the years where customers insisted their engines need rings.
As for ignition problem it can be a bad high tension lead (HV lead, plug wire) that an internal break. Something that seen a lot on old 2 cycles coils. These leads are replaceable if you got the patience to dig out the old lead. Here I replaced several lead already this where mice have chew them in two.
