OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines briggs and stratton help

Blown Vl,

Did you take the sump cover of when you were checking the valves and remove the lifters?

Not that i think it is valve clearences but how did you check the valve clearences and what were they?? where was the piston when you made these checks. The next question is have you checked the venturi and main jet are clear. Can you please tell me do you prime the engine with fuel or is it equiped with a choke? If it has a choke does it close properly when you place the throttle in the start posistion? When you cleaned the piston and valve were they covered in thick black carbon (big pieces of dry black stuff)?

i did not remove lifters i just took valve springs out and plates and cleaned valves thats way

i used a feeler gauge to chekc valve clerances i think i did 6thou on intake valve and 8thou on exhuast. the commpression is fine though i checked it today and its blwowing my finger right off the block and sucking in very hard and when u reverse the crank it has a stopping point. yeah the valves and piston were covered in big pieces of dry black stuff (carbon?) and exhuast valve was a bit dirty and pretty burnt and intake valve i could bearly see it was that covered and i could see sunlight througth the valves lol so iclaned the seats and took valve out and cleaned them and then checked clearnces with a feeler gauge.

I am confident that your problem has nothing to do with compression, but while the subject is being discussed, if your engine has the usual B&S "Easy Spin" camshaft design, it is important to check valve clearance with the engine on top dead center. Easy Spin holds the inlet valve .010" open for something like the first half of the compression stroke, to make the engine easy to rope-start. B&S claim that it has virtually no effect at running speed because there isn't time for the gas to leak through with the valve lifted such a small amount. If you try to set valve clearance with the engine in the first part of the compression stroke, you'll end up with an enormous intake valve clearance on TDC. Some of the tappet adjusting techniques that work for car engines, don't work for B&S engines because of Easy Spin.

With regard to spark, I think you always need to check for spark with the black cord disconnected before you condemn the coil. Make sure the cord isn't touching anything anywhere along its length, too. It's probably a dead coil, but its very irritating (to me at least) to buy parts I don't need.

guess what happend today!!! i took black cord off and primed it 3 times she almost started started backfiring and blowing out black puffs then i got the starter fluid out and put some into it and took about 4 -5 pulls then it sputter then it started right up with huge black cloud and runs way bettter then before.

The black wire was the culprit!!!! something so small and all the work i did for nothing lol! ah well it was a good learning exprience. thanks everyone for all the help.

Hi Blown VI, as I have said in many posts: I only had 2 problems with my original Scotty engine.....One was called Briggs and the other....
Viva La Honda!!

Hi all,
It is so easy to overlook that tiny pathetic black wire! 1/2 the time it is either that or the points (if installed). Briggs seems to make a fairly reliable coil, but on the other hand they are pretty troublesome at times.
Regards Jay

Hi Jay, you are so spot on there mate, that little black wire can be the difference between go or no go!!

Now that you know the kill wire (black cord) is the problem, you still need to fix it. Most likely the problem is where the grounding contact on the governor base grounds the kill wire when the speed control is set to minimum - in other words the engine stop control. It is a pretty tin-pot piece of gear (in my opinion) and also is affected by the adjustment of the speed control cable. When you look at the contact and slide the speed control between max and min, you'll probably see what is wrong. (Having said all that, I've never even seen a Quantum 50 - I'm describing the smaller vertical crankshaft engines).

If your engine was a bit hard to start and then blew black smoke, it was almost certainly too rich, probably due to the amount of priming you did (pumping the primer bulb) and the use of starter fluid - it seems to have been too rich before you used the fluid and really messed it up. If you close it down properly, let it cool completely, and then use the B&S starting procedure, it should start either first or second pull. Don't prime it unless you are cold-starting it, and don't ever use starter fluid unless you are pretty sure it's broken and isn't going to start otherwise.

yeah the black wire wasnt clamped on properly after the last time i took it off and when the mower was reving the wire was shaking around and hitting the metal giving it no spark.

it only blew black smoke after the first time i started it for the first 5-10 seconds, now its fine with no more black smoke and when its cold starts in 2-3 strong pulls (wih 3 primes) then when its warmed up just takes a soft first pull(no priming).

grumpy u are right between the turtle and the rabbit on the throttle it revs like crazy but if i put it on full(rabbit) it revs normal and if i put it near the turtle it idles away. but in between it revs liek its going to blow up lol,

Engine speed should increase smoothly from 1750 rpm at idle, to its maximum which is probably 3000 rpm flat out. If it rises above maximum anywhere in between, the governor isn't working properly. It's a very simple mechanism - just an air vane beside the flywheel fan, and two springs on a tin plate. I suggest you look at it carefully, and if possible post a photograph of the tin plate and springs. Bruce is the expert - he can normally tell people what is wrong very easily.

is that at the back of the engine? what controls the engine reving? what moves as it revs up and down etc?

are u talking about this(pictures below) or the other thing behind thE fuel tank?

This is when the switch is turned to turtle:


This is when the switch is turned to Rabbit:


sorry bad phone camera
This is when the switch is turned to the middle of the 2:

The speed control lever moves one end of one of the governor springs, stretching it slightly as the speed setting increases. The other end of the spring is indirectly connected to the throttle butterfly on the carburetor. The air vane near the flywheel fan is also connected to the throttle butterfly. Essentially, the spring tries to open the throttle and the air vane tries to close it. When the speed control is set to minimum, the air vane and spring are in equilibrium at 1750 rpm. When the speed control is set to maximum, the spring is more stretched so the air vane has to push harder, and equilibrium is reached at 3000 rpm. The spring should be stretched smoothly and evenly as the speed control moves from minimum to maximum. I'll leave it to Bruce to comment on whether that is happening in your pictures - I can't see what is happening, except that the bottom of the spring is moving from right to left as you increase the speed setting, and the upper spring looks like it might not be connected.

so could the spring be streched or not on properly? it looks like it on properly

There are usually two springs pulling in opposing directions, but only one is visible in your picture. However right at the top edge of the picture I seem to see the bottom hook of the other spring, not connected to anything. Perhaps it should be connected to the center hole of the pivot-plate at the top of the picture? Dunno, I've never actually seen a Quantum XL50, and your picture only seems to show the bottom half of the governor.

You should be able to move the air vane with one finger and see the governor operate. You should also be able to see the change in operating pressure for the vane, as you advance the speed control.

If it is a two-spring governor and one spring is disconnected, the engine is likely to over-rev in a big way.

Grumpy on a quantum motor there is not air vane, it is a internal govenor that operates from the bottom of the crankcase.

If it is a two spring govenor and one is disconnected it will rev less as there is less spring tension to open up the throttle.

As for the other problem with the revs between idle and run I am not sure.

Thanks Joe, I looked at the B&S parts list and there only seems to be one spring, too, so it just isn't anything like the system I'm slightly used to. I'll leave this one to you and Bruce, as I should have done in the first place.

i found the problem the metal bracket what holds the spring at the other end had bent probably from going under a tree.