Hi, i found an old 79' lawnmower, anyways, it has a B&S 10hp horizontal shaft engine (cast iron sob) Took it home took the head off, cleaned the head and cover, opened the valves and cleaned with the wire wheel on a drill, got all the carbon out, cleaned out the cyl...looked good, took carb off and cleaned it, cleaned tank and plug, put it together and realized the points or coil were bad. So it sat for about 4 months because i had a real project ive been working on. (oh yeah, sat for at least 10 years in a field before this)

today i got the wild hair to work on it, so i bought a new coil, got the magnetron kit to do away with the points, put oil in her, cranked and cranked and finally got it fired up!

Well, it ran really bad and backfiring constantly so i adjusted the carb and now its going to run as good as its going to run but its still randomly backfireing out of the exhaust. I thinking either the valves arent quite seated right or the carb need cleaned even more. Im going to take the carb apart and cleaned it good here in a bit, any suggestions thought.

Cant believe it, 30 years and the engine is barely smoking :)

One more thing, I just went to a junk yard and found more engine than ive ever seen in my life, ultimatly im wanting to get a 10 or so hp side shaft engine with electric start, im using it for a 10 speed mountain bike project,

my question is is there any advantage or disadvantages to this cast iron block (other than the weighting a fruckin ton) and any advice on the backfiring?

sh*t, i forgot the most important part, the crank has a little slop (like free spin) just barely, and it has a little bit of a knock when you turn it back and fourth, but NO knock when its running. I assume the crank bearings are worn. Again, being a cast iron 79 block would it be worth tearing it down and fixing it or getting a new engine (i can get them for around 20 bux or less... BUT i just spen 60 bux on ignition on this engine.

Made back when they made engines to last instead of to sale like they do now.YEAH,I'd jump on it.

Oh yeah sounds like the valves isn't seating good.Might just the valve cleance

Hearye Hearye repair_guy
I am from that same world. Cast iron will outlast all this aluminum junk.It just can't stand the pressure.

well, i took the head off yet again and cleared out all the soot, and wire wheeled the valved and the head where they meet and they are nice and shiney, but i guess that doesnt mean they are seating fully. That and i took all the jets and everything out and cleaned the carb up. Still doing it.

One thing, i know how to adjust the idle and needle valve, but i didnt know what the third one was for, idle mixture i realize now, so do i just turn it untill the idle is perfect?



Anything i can do to the valves? I imagine i could try some lapping compound or maybe the seats are getting bad?

so do i just turn it untill the idle is perfect?***Basicly,turn the screw in until barely seated.Then turn out 1-1/2 turn and go from there.

Remove valve cover underneath carb and check clearance on exhaust valve to tappet or bottom end of valve at top dead center, both valves closed and piston at top,use a feeler guage, on a cast iron cylinder the exhaust is a mininum of .014 and a maximum of .016 on models 5,6,8,n,9,14,19,190000,200000 series.My guess is your exhaust is worn under .014 thousandths, remove valve and file off a few thousandths,but dont get it over .016 with both valves closed and piston at top dead center.
My two cents worth,how about those gas prices.
http:www.smallenginetrblshtng.com/alternative-fuel-source.php (http://www.smallenginetrblshtng.com/alternative-fuel-source.php)

hey thanks for that info! I may try that tomarrow if i can find a feeler gauge laying around


"My two cents worth,how about those gas prices.
http:www.smallenginetrblshtng.com/alternative-fuel-source.php"

wtf is that?

ok, the valve clearanced for my engine are actually

Intake .007-.009
Exhaust .017-.019

And mine were:
Intake .010
Exhaust .021

What should I do/ would that cause any of my problems?

alright i went out and tore the engine down, the wrist pin has alot of play and the rod bearing has just a hair. I dont think im going to do an overhaul yet, so im just going to clean everything and paint it chevy orange and aluminum on the cyl head. Im going to use silicon for the oil pan and the front cover. Hopefully it will seal good.

Still like to know why it backfired so much, im thinking it is the carb still, the valves looked real good. When it ran, and you hold the rpm steady at low rpm, it fired probably 1 out of 5 rotations :rolleyes: But still reved up good when you gassed it.

I didnt realize the cams have as big of duration as they do, i dont think it was just worn down flat but its possible, (didnt look or feel like it).

All pretty now
http://www.t-mobilepictures.com/photos/photo09/9f/a0/856f002b9a9e.jpg

Bump on the clearance issue, is that enough to need to fix? would that effect anything? id kinda like to fix the engine up agian after letting it sit for a year o wow, actually its a year exactly, how weird.

yes, having the clearence that much might be the main part of the backfiring issue