The Mower Bench

[GardenKit]

9 hours ago, Sawchip said:

What have you found with Champion plugs ..some get confused with the heat ratings between the 2 brands but is there another thing you find ?

Its just that most of the spark plug failures that I come across are on Champion plugs. Some manufactures still fit Champion as standard bust the majority use NGK.

[agg221]

Any ideas on this one?

 

I have an old Westwood 1200 ride-on with a Briggs & Stratton 12hp engine. It has always been annoying in one way or another - I think in 5yrs of using it I haven't yet been able to walk up to it, start up, cut the grass and put it away without something going wrong, however it's what I have.

 

It semi-seized last year and the pull start packed up so it didn't get any use until around May, when it finally got fixed and serviced with new oil, plug etc. The battery packed up on the next cut and I finally got round to sorting it the Sunday before last. It took a bit of turning over but spluttered into life in the end and then ran fine until it ran dry.

 

Yesterday I fuelled it up and now it flatly refuses to start. It is spluttering, popping and backfiring through the carb. I stuck some carb cleaner through which did no good but did produce bigger flames when it backfires  It then rained so I gave up until this evening when I pulled the flywheel to see if the key had sheared - it hasn't.

 

So, I have fuel, air, mix, spark, some compression (can't measure this), oil at the right level and no leaks but ignition timing appears completely wrong, despite the flywheel being set right and there being no sign that the coil has moved (plenty of rust showing no signs of disturbance).

 

Any ideas welcome!

 

Alec

Edited September 18, 2017 by agg221

[lurkalot]

Turn it backwards by hand and see if there's any compression, otherwise you won't feel the compression properly because of the decompressor.  They also have a habit of one the valve seats coming out, so something else you could check.

[agg221]

2 hours ago, lurkalot said:

Turn it backwards by hand and see if there's any compression, otherwise you won't feel the compression properly because of the decompressor.  They also have a habit of one the valve seats coming out, so something else you could check.

Cheers - where do I uncover the valves on this one? It doesn't appear to be OHV. I can post a picture if it helps.

 

Alec

[lurkalot]

48 minutes ago, agg221 said:

Cheers - where do I uncover the valves on this one? It doesn't appear to be OHV. I can post a picture if it helps.

 

Alec

Unfortunately it's a head and carb off job to do the valves on this side valve engine.  The valve springs and retainers are behind the breather assy which is behind the carb.  That said, if the compression is there you probably don't need to go down that route, although it probably wouldn't hurt to check that it has tappet clearance on such an old engine. 

[tree-fancier123]

I had a honda that wouldnt start even after spraying easystart - had to dismantle the carb and blow out, as per downloaded service manual - maybe see if there is a cheap new carb on ebay, perhaps you can google up a Briggs service manual pdf

[agg221]

23 hours ago, lurkalot said:

Turn it backwards by hand and see if there's any compression, otherwise you won't feel the compression properly because of the decompressor.  They also have a habit of one the valve seats coming out, so something else you could check.

You were right - it's the valve seat. I tapped it back in, it started on the first half-crank and ran smoothly for about 30 seconds, when it promptly spat the valve seat back out again.

 

What's the best way to secure it (I'm guessing one of the Hermatite instant gaskets)?

 

Alec

[lurkalot]

58 minutes ago, agg221 said:

You were right - it's the valve seat. I tapped it back in, it started on the first half-crank and ran smoothly for about 30 seconds, when it promptly spat the valve seat back out again.

 

What's the best way to secure it (I'm guessing one of the Hermatite instant gaskets)?

 

Alec

No don't use any sealant or anything, just run around the aluminium block just outside the valve seat with a center punch or a small pin punch, and gently peen it back in.  This should secure it sufficiently.   It's a pretty common problem with the sidevalve Briggs.  When done look for a build up of grass and debris under the Cowling.  If this clogs up then it'll over heat often causing the seats to come out.  done

 

Hopefully it'll keep running for you.

Edited September 19, 2017 by lurkalot
Missed a bit of info.

[agg221]

1 hour ago, lurkalot said:

No don't use any sealant or anything, just run around the aluminium block just outside the valve seat with a center punch or a small pin punch, and gently peen it back in.  This should secure it sufficiently.   It's a pretty common problem with the sidevalve Briggs.  When done look for a build up of grass and debris under the Cowling.  If this clogs up then it'll over heat often causing the seats to come out.  done

 

Hopefully it'll keep running for you.

Ah, 'punching up' as I know it from clock repair (where it's generally regarded as bodging). No debris under the cowling, all pretty clean in there all things considered but I was working it pretty hard when it ran out of fuel. I'll keep an eye on it and see how it goes. To be honest, part of me would rather it died in a catastrophic, terminal fashion as that would justify getting a replacement but on the other hand I have a tendency to try to keep these things running when possible and maybe it has a few years left.

 

Alec

Edited September 19, 2017 by agg221

[lurkalot]

38 minutes ago, agg221 said:

Ah, 'punching up' as I know it from clock repair (where it's generally regarded as bodging).

Yep it is regarded as a bodge job, but unless you want to take the engine on a trip to a engine preconditioner and have a new seat made and fitted then this is a workaround that does work quite well in the past.  Just don't over do the peening.  Try to shift some of the aluminium over the edge of the seat if possible,  I find a small(ish) pin punch better for this job tbh.