While not a radio subject I thought if SC can run stories on fixing hair dryers, washing machines and cat feeders this column can handle a lawnmower.
Also I'm still not back to working on radios, you need a break sometimes from a hobby to get re-freshed.
The story started off with something simple and has ended up as a two-part thing.
Why? Well I thought I had fixed the problem only to look like real goose. To find out read on!

I'll send the usual PDF to Brad and you can read the first part on an unfinished story!

Fred.

Fixing ignition on a Subaru engine - Part 1
Fixing ignition on a Subaru engine - Part 2
Fixing ignition on a Subaru engine - Part 3

Hi Fred, not quite on subject but I used to own a chainsaw that ran beautifully at home.
But failed to start in the bush.
After numerous attempts I vowed that the only way it would be successful was if I showed the saw photos of home whilst in the bush.
Didn't work, but still started every time and went well at home!
JJ

I could try showing this piece of **** a photo of the scrap heap!
No, better still I'll put it ON the scrap heap!
When you can read the story I'll reckon you will agree!
Fred.

G'day Fred,

I tried uploading the article however the pages are blank. I'll try again tonight as I have to scoot into work now.

Hi Brad, I checked back on my send attachment within outlook at my end.
The attachment opens up ok within that.
Fred.

chainsaw that ran beautifully at home. But failed to start in the bush.

So, a saw in the home is worth two in the bush?

Now that's the sort of diverse entertainment one gets here. You never know what turns up next to add to the DIY. It could be a chainsaw, last week an offsite lawn mower for disaster repair, recently a transmission fault on the ride on & I ended up taking the teeth off one sprocket & machining the centre out of a new one to sort that out, currently the new bench in shed one, has a high pressure washer spread out all over it as the pump decided to chuck a wobbly.

Bit annoying as it only went into service Dec 1992. Bad as the ride on that gear had only done about 400Hours.

I bought new electric chainsaw abt 2017 to match the Honda inverter, but also be able to run off mains, for odd pruning jobs etc. No battery as they just cannot last the time needed. The advantage is that all it needs is oil for the chain, is light and it does not stall during the climb up a ladder like the petrol one. Petrol one is getting on. Bought around 1976. It still starts in the bush.

One trap with Briggs & Stratton should it break the flywheel key; Is if you replace it with a steel one instead of aluminium, the motor will never run. If you mix your own two stroke fuel, using motor oil is a disaster. It will pick up water & send the fuel white: Incombustible. It also forms soot which will kill the spark by shorting the gap.

This has to be a proper BIA two-stroke oil.

When my boys were teenagers they were into off-road 2 stroke bikes. They used a synthetic oil that gave the exhaust an almost floral odour, not unpleasant. And yes, it didn't soot up the plugs or the mufflers.

Both boys still ride, despite being in their 40s with wives and kids.

My last petrol chainsaw gave me the odd ratio of 40:1 instead of either 25:1 or 50:1, which made life a bit harder for someone who ain't that good at maths. I even resorted to making up a table once at home when I had a calculator handy but the piece of paper didn't survive amongst the pool of oil in the bottom of the carrying case. Whilst I did get by, it was just too hard to remember how much oil to use. When the diaphragm for the tiny little fuel pump gave way I was going to take it to a place to get it replaced but have since run into two battery operated saws, both Dewalt and they destroy just as good as a petrol saw of the same size. The small 18V one has a 20cm bar which is good for cutting medium-sized campfire wood one-handed (not recommended for beginners to chainsaws) and the big 54V one has a 50cm bar and it will cut through just about anything but it is big and heavy like a Husky.

Both saws come on all my camping trips these days and I didn't go electric to go on some climate crusade but to enjoy the benefits of 'no leaks or smell' in the back of the car. The lube job some from standard chain oil but there is no fuel to mix.

The first part of Fred's article is now uploaded.

Fred, don't you just hate failures after all that work?

Reminds me of a Morris 1100 engine-gearbox rebuild where I destroyed a flywheel puller and two sledgehammers trying to get that flywheel off. Engine had thrown a rod through the crankcase and gearbox casing. Flywheel key was half-sheared.

In most cases the two stroke oil has ratio's on the bottle. Most of my life was chemistry so mixing it, is not an issue. The ratio does affect how it runs due to the resultant fuel viscosity related to jetting. However, from my experience with the Australian heat 50:1 is too weak & the 1976 one runs 25:1 and is still going. You should be able to find the oil data on the WEB or based on Cairns Axiom, read the manual, as its often in there.

With small branches and tops, on down timber and with a Farm I get a lot of that; I find that the fastest and most reliable unit is an axe.
Especially on bad fire risk days, which is when the firewood normally lands on a boundary fence.

Guys, the engine is a write off now that I have pulled it apart.
I needed to go to Specsavers as my view that the chain wheel was loose was wrong.
That was squinting down the chain void.
The chain has just derailed again.
With the crankcase cover finally off its clear that the chain can de-rail at certain times from wear and tear.
Thís engine is worn and torn!
I'll do a part 2 to wrap up the story and memory trip back to the olden "engine mechnic" days.

Thanks to Brad for sorting the tech issues with the first PDF.

I'll do a PDF tomorrow and you can all laugh at the hi-jinks required to pull off the shaft coupling.

Cheers, Fred.

Chains can have two things go wrong - stretching and worn teeth on the sprockets. I'd say if that engine is an old 'un then there'll be a bit of both. There is a lot of pressure on cam shafts. I remember the fibre gear drive stripping itself like a porn star in my Torana's trusty 202 some 25 years ago. $460 later I had it back, ready for another 500,000km.

Timing chains & driving chains can be of different mechanical construction The 1951 TE20-D had its checked in 2019 and the Ute the last time it chewed out the crankshaft oil seal and the front cover had to come off. The Ag bike always stretched the hell out of chains working in the mud.

Where there is a long chain driving overhead cams, you can have a nightmare as some have rubbing blocks and no hydraulic tensioner. In one car I had it I believe a slack chain was responsible for cracking the head at the journal. If the guides are worn and the chain slack they can jump the sprockets. The ride on here was a slightly different issue it wore the tensioning and stretched the chain but ultimately, that combined with a sprocket with hardly any teeth, caused in to jam in the forward direction.

I would note that the drive socket is on a spline to keep it in alignment with the driven gear (diff) When changing those chains and the chainsaw one. You count the links not measure the chain length.

I've sent the part 2 PDF to Brad to attach to the thread.

Yes, the whole problem is overall wear and the fact the engine was never serviced.
Those little engines have no strainers or filters, if the oil is not drained and changed it runs in a soup of abrasive particles.
That something that most people do not understand.
The chain and guides are fairly worn but servicable with a new tensioner.
While I don't have any data or new parts to compare with, I believe the killer is the tension spring.
It's just lost its tension and the tensioner arm can be forced back by chain flexing too easily.
There is no hydraulic device in a simple engine like this to restrain the chain, the spring and guides are the only support.
Penny pinching design based on a strict service regime.
I was brought up mainly on two strokes or four stroke with gear train cam drives, those things last forever.
Long chains have to be maintained and looked after.

Fred.