Briggs & stratton motors

[MrFluffy]

Someone has given me a old sit and ride tractor for a modest sum telling me it was in use but one day when he went to start it, it chewed its ring gear up and "just needed a new ring gear". Its fitted with a 11hp sidevalve aluminium Briggs and stratton engine with a vertical crankshaft.

Turned out to have a techmusen starter with the wrong pinion to suit the briggs motor so replaced ring gear with alarm bells sounding quietly in head, and machined briggs pinion to techmusen starter. Lots more fettling, plug, carb, mag gap etc and it still wont fire up so head off, bore scored really deeply, with scores running the length of the piston stroke, and as I crank it I can see oil passing the rings at bdc.
Dress it as best I can, lap the valves in, reassemble and compression test it, and it has 40psi, but still refuses to fire even with petrol down the plug hole...
Would have thought 40psi of pressure would have let it at least fire up, even if it was crap.

Now, I know I can get a +.030" piston in a engine recon kit for it from the states for a reasonable price, but there is no liner on the cylinder and the piston runs directly in the aluminium crankcase material! whats the life expectancy of a engine like that? Can it be measured in years, or is a more valid unit how long it lasts compared to a packet of wine gums?

Also, does anyone know if there is enough casting thickness to use the cast iron liner from the IC series motors in one, I don't fancy having to spend the first week of each year rebuilding the mower engine when I can improve it a little now and do the job properly...

B*ggering mower, 4 nights work and its still not sorted out.
What it needs is a nice motorbike engine...

 

[Justme]

What it needs is a nice motorbike engine...

many a true word spoke in jest

40psi sounds very low petrol cars are more like 160-200psi



Justme

 

[MrFluffy]

They have some funny cam grind (called easycrank or something nonsense) that lifts the inlet open slightly at cranking speeds so they can cheap out on the startermotor, which always skews the numbers.
Online stuff says anything over 50psi should be fine...

If this is in the wrong place sorry guys, i wasnt sure if it was so ot to be in here, or should be in tools/techniques...

 

[Justme]

Ah like the decomp lever on a diesel

 

[MrFluffy]

Sort of, but its not some mechanism you can disengage, its done by the shape of the cam, only snaps the valve open for a short duration, so at cranking speed it releases the pressure, but higher rpm it isnt open long enough to cause problems.

Yes I did think the valve had stuck open till I got my head around it...

 

[snowcat]

B*ggering mower, 4 nights work and its still not sorted out.
What it needs is a nice motorbike engine...

What it need's is a Honda lump, Rather than the B&Scrapem, Have you tried the old oil down the plug trick, before comprestion test???

 

[MrFluffy]

no, but just a visual on the bore scratches says its long past its sell by date. It can blow my finger off the plug hole a bit tho, which usually means something will start, no matter how sick and ailing.
I'd love a honda gx160 or the like, fit, change oil every year and forget, but Im absolutely broke at the moment with everything going on for our new place, and Im already getting grief from mrs f for buying the mower in the first place. I think paying for a honda donk would be the straw that broke the camels back.
The piston + liner option if possible is the bestest/cheapest way out with the weakness of the dollar and if I import it and don't get hit for import tax, I already have the tooling to bore/hone it myself. I just dont see the point of boring out a piston to run on a unplated aluminium bore and stuffing it again within a year of use...

If someone says "yeah did that liner thing, its fine" that'd be good, or "the motor will go for 200 hrs runtime before its worn out again". Even "no, you bore into the finned area before you get clearance for the ic liner" would be good. I cant be the only one who's thought about it...

However someone just emailed me that the problem could be the techmusen starter not spinning it fast enough when under compression and it did seem to struggle when the engine got near tdc on the start of the power stroke so just "won" a b&s starter. Picked up a old renault master starter and considered machining the pinion to fit that instead too but its too physically big to jam under the flywheel

I hate the design of this engine, even the 1950's french bernard in my push along mower is better built than this. Ive just been on ebay looking at suitable bike engines again...

 

[shenion]

B&S engine are good if they are maintained well.

I have a 12hp on my riding mower. I picked up 2 riders, one with bad tranny, other with bad engine.

The bad engine they had let the oil run low. As the smaller B&S engines (less than 18HP) have no oil pump ,just a sling gear, they destroy themselves on lo oil or too much oil. Funny, the engine still ran, knocked like hell with the couterbalance support broken and parts all over the bottom. With low oil, the upper journal on vertical engines starve.

Sleeveless alum blocks are common these days (most sportbikes are that way to save weight.) They use a a nickel plating to give a hard surface (called something like Nikesiil). They will last a long time but if abused they will wear out quickly. They can not be rebored without replating.

Be careful on starters. The second mower I had had a real noisy starter. He threw in another. Turns out both were the wrong one. The one from my dead egine is 14 tooth, the tw others were 16-tooth and did not mesh properly. Seems a common issue as B&S have both alum and steel ring gears. They take 2 different starters.

The first rider came with the blown engine but was complete with a bagger and was free. I kept an aye on craigs list and picked up the second one cheap. It had a bad tranny; they fail often as they will break the sliding clips if you shift them while moving.

Keep an eye out for something with the same or larger engine. Most are now OHV type. Freecycle and other forums would be good.

Tecumsech seem to be over rated on power.

Koler engines are good as they have a real oiling system

A Honda is best bit don't expect to get one cheap.

All within the 12-17HP range seem to have the same shaft size and mounting. Should be an easy swap.

 

[drivewasher]

Is there a spark? b&S are renown for the plunger sticking in it's bore that pushes the points open, it's only fibre be careful getting it out.
They do have a compression release on a valve (inlet irc) also the bolt that secures the air filter has to be in the threads in the carb with or without the filter on as it wont pull fuel in

 

[shenion]

Points? How old are we talking here. I don't think B&S has used points in over 20 years.

 

[snowcat]

yep he could be correct with the starter not chucking it round quick enough, Iv know it when the battery's get bad, Must be one without a recoil then....so too slow speed could be the issue, Id expect it to start TBH, even if it was blowing everything from the top to the sump, even when there completely shaged there start, but have zero power...

Good luck on it, rather you than me, I too share your loathing for B&S engines..

 

[shenion]

Yes, the B&S are magneto, so they have very little spark at low speed. My dad's 17HP will not start if the batt is low as it does not turn fast enough.

On some B&S engines thre is a small clip on the campshaft that opens the exhaust during the compression stroke. Makes for easier starting. Is supposed to flip out of the way, but can bend and stick (does not sound like the problem if it is turning slow.) But it does make compression tests useless.

I'd look for a 12HP OHV or just a newer model. The 12HP on mine has worked well and has a vibration damper.

I doubt you will find a motorcycle engine that will run on its side

 

[MrFluffy]

Hmm I put a plug in it, and put a second on the lead and laid it on the head so I could see it under compression spin speeds, but its still firing a surprisingly blue spark (surprising because i expect some pants yellow spark on a mower engine).
Have to just wait and see when the starter arrives. If it fires up but uses as much oil as petrol Ill take it from there.

Its not old enough to have the lifter on the exhaust valve, they moved it from the ex to the inlet because it was burning the valves or something. Its new enough to have the mag fired electronic ignition too so no points issues.
I wont find a bike engine that has a vertical crank, but I have a spare axle diff, and Ill weld up one side to make a 90deg conversion for the drive if I get one. Desperately trying not to turn lawn project into Yet Another Unfinished Project though.

This belongs to a member of the turbo site I help run, gives me bad ideas, he's running a prop from the shaftie GT 750 motor to the lawn tractor axle, no good for a cutting deck too though. A quick ferret in the sheds last night revealed a xl125 honda 125 4 stroke single, though mrs f canned the idea as whatever goes in has to be electric start so she can start it... :-

 

[snowcat]

. A quick ferret in the sheds last night revealed a xl125 honda 125 4 stroke single, though mrs f canned the idea as whatever goes in has to be electric start so she can start it... :-
]

I used to have a Mountfield mower with a 6.5Hp (I think) briggs, the trouble was the Mrs not haveing the best machanical mind could never start it, although it had an ellectric start, It needed primeing, then chokeing for the right time to start, get it wrong and it would crank till the batery was dead or flood, Last year Bought a lawnflight with a 6.5 honda, She starts this on the recoil first pull everytime, never needs choke, even a 5yr old could start it...

 

[whycanismellburning]

Are you guys trying to find the fastest method of cutting the grass or is it the road tax advoidence scheme coming into play?!!

Do you lawnmover race?

 

[shenion]

Are you guys trying to find the fastest method of cutting the grass or is it the road tax advoidence scheme coming into play?!!

Do you lawnmover race?

In my case, I have a bad back. Any repetitive side-side work causes real pain. Can lift an 80lb back of concrete no problem. Rake leaves for 10 minutes and I have to spend a day in bed with icepack/painkillers.

With the rider and bagger, I just mow over the leaves (you get about 30'), stop dump buckets of leaves in bags, move on. Whole job takes 40 minutes instead of hours; no raking or bending over picking up leaves. My lot is all dense oak/hickory trees; in the fall there is 6" of leaves everywhere. Takes months of weekends to do by hand (neighbor across street just did small area in front of house; 90+ 30 gal refuse bags.)

Also have a trailer hitch, great to save my back moving the 5x10' trailer around (has to be pushed around as not enough room in driveway to turn around.)

Yes, it is overkill for a 1/3 acre lot with over half not mowed. But cost me a total of $170.US. Worth the back savings.

Top speed on mine is about 8MPH, geared way down.

 

[whycanismellburning]

Fair enough! that does make a lot of sense.... Would it not be better with something like a litter picker? (basically a big hoover on wheels See here)

 

[shenion]

Those would require a tractor anyway . This works great. 1st time I used it, it even sucked up all the dead grass between the fescue. The push mower would leave a lot there.

It also chops up the leaves. I did my front with 10 leaf bags. Normally takes about 30+. Does save money as buying 100 leaf bags gets expensive every year

 

[whycanismellburning]

What's the difference between a leaf bag and a rubbish bag?

 

[shenion]

Leaf bags are made of paper. Need to be so they can be recycled with the lawn waste (they will refuse pickup of any plastic bags.)