Briggs 17hp wont start and stay running

[Daquiri_briggs]

I just recently rebuilt my Briggs and Stratton, Murray mower. After getting it all back together, now it doesn't want to run. I have done all of the normal things like rebuild the carb... a few times. Check the plugs.. you know, all of that good stuff.

So, if I try to start the mower... IF it starts, it will not idle for long before dying. IF, I move the throttle all the way up, it revs up so much that it seems the engine is going to blow! I am not sure what I can do at this point. Maybe I messed something up on the linkage for the throttle? Any help would be greatly appreciated. I am currently uploading a video to YouTube and will post as soon as I can.

Any Ideas?
Model: 42a707-1237-01
Murray 46901X92b

Video should be live shortly

 

[ILENGINE]

You are having a fuel delivery problem. not sure were to go with that other than find out why you are not getting fuel. the other thing is you need to recheck, reset the static governor setting.

 

[Tinkerer200]

IF it is running wild in some instances, it is getting fuel, adjust governor, I can send you a service Manual IF you like, address below, put in proper format and remind me engine model number and what you want.

Walt Conner
wconner5 at frontier dot com

 

[Daquiri_briggs]

Thanks guys, what is the static governor vs governor? Is it the one inside the engine? I am not sure what else to check to make sure it is getting fuel, the lines are all clear and the carb has been rebuilt numerous times.

The engine will run at times, if I find that sweet spot on the throttle... but it wont idle low and if I put the throttle all the way up, it runs until I get scared it is going to blow and then I throttle it back down.

A manual would be great, I got one from Briggs but it didn't say anything about the governor or the throttle. Did you guys see the video?

 

[bertsmobile1]

Now lets take things from the top.
Was it running before you pulled it down and why did you pull it down ?
While it was apart what exactly did you do ?
What are your valve clearences ?
You would have needed to adjust them to compensate for the depth of the valve work you did.
Did you check them springs on or springs off ?
Did you touch the cam ?
Have you tried to start it with the coils disconnected from each other ?
What exctly did you do to the carby ?
The throttle linkage should come back and touch the idle stop screw if not some thing is not back together correct.
If you insist on doing videos please get some bloody light in there, hard to work out what is going on when all I can see is a shakey black blob.

Is the flywheel key intact ?
what is the compression ? it looked like the engine was spinning way too qhick of a motor with good compression.
If the valves are opening & closing at the right time and the spark is happening at the right time the engine will fire up on starting fluid, even with no carb there at all.
So that tells me valve timing / spark timming is off or not enough compression or any combination of these three.

 

[Tinkerer200]

"Have you tried to start it with the coils disconnected from each other ?"

Did you check the engine model number?

Walt Conner

 

[Daquiri_briggs]

Now let’s take things from the top.
Was it running before you pulled it down and why did you pull it down?
Pull it down, meaning rebuild it? If so, I hit a sidewalk and thought I broke my flywheel key. I didn’t, come to find out it was a broken rod, so I replaced the rod and piston. After further investigation, the sump was leaking oil, so I replaced that. It was working fine prior to this, although I think the compression was bad.

While it was apart what exactly did you do?
I replaced the following:
Flywheel key
Piston
Rod
Sump
Oil flingy thing in sump
All gaskets (Carb Included)
Replaced springs on carb screws
Replaced diaphragm and all pieces on fuel pump.
Replaced air filter and all pieces involved with that.
Replaced flywheel gear
Cleaned everything else.

What are your valve clearances?
I thought that didn’t apply to this motor. So, I don’t know that one.

You would have needed to adjust them to compensate for the depth of the valve work you did.
I took the valve “grinder gunk” and made sure they sat flush with the “block”

Did you check them springs on or springs off?
Springs where off while I was doing the work here.

Did you touch the cam?
Quite a few times :smile: . It was spinning and everything just fine, didn’t seem to have any problems there.

Have you tried to start it with the coils disconnected from each other?
I am lost on coils, maybe I am just having a brain fart right now, I will go google this and find out haha.

What exactly did you do to the carby?
I just took it apart and cleaned it, replaced gaskets and what not. Didn’t touch much of the innards except for the float, I replaced that.

The throttle linkage should come back and touch the idle stop screw if not something is not back together correct.
This is where I assumed my problem was, however I never touched the throttle linkage except to take the “wire” off.

If you insist on doing videos please get some bloody light in there, hard to work out what is going on when all I can see is a shakey black blob.

This was unnecessary, but… there are far worse videos out there. I tried to get up close so you could actually see what it was doing when it was started.

Is the flywheel key intact?
It was, but I already purchased a replacement so I installed that.


what is the compression? it looked like the engine was spinning way too quick of a motor with good compression.
How do I check this, I believe I had some problems here originally anyway?

If the valves are opening & closing at the right time and the spark is happening at the right time the engine will fire up on starting fluid, even with no carb there at all.
They are opening and closing, you can spin the cam and the pistons and valves open and close… timing on the other hand, I guess I am not 100% sure if they are correct.

So that tells me valve timing / spark timing is off or not enough compression or any combination of these three.

I guess what I dont understand from all of this is, if the timing is off, why would it start and run "fine". I can get it to start, then if I try to throttle up, it seems like it is going to blow up. If I idle down to much, it dies.

"Have you tried to start it with the coils disconnected from each other ?"

Did you check the engine model number?

Walt Conner

It is in my first post. I am not sure about the coils?

 

[Daquiri_briggs]

So, I just tore down the motor again, I have a feeling the timing "gear" needs to be fixed. Also, I wasn't sure about the compression or valves so I figured I might as well get it ready for the weekend to start working on it again.

Going to upload another video with some things I seen that will probably be apart of the issue. I tried to upload pictures, but it isn't working.

Video of it running after rebuild, just a false hope!

Video will be here of the other stuff:
https://youtu.be/75Rg5djFvig

 

[bertsmobile1]

You are falling into the novice trap by playing with too many things at once so ou get lost as to what was good and what was bad.

Now you need to understand a few things.

Firstly the throttle makes the engine go fast.
The govenor makes it go slow
Between the two is a spring.
So when thoes bob weights swing out they ill be closing off the throttle.
When they fall back in it allows the engine to go faster.

Second, valve gap is vital.
Too big and the engine will not start and will "blow" back through the carb excessively.
Too small and again it wont start and will backfire everywhere.

There is no mechanical adjustment on B & S Sidevalve engines.
If the valve gap is too small you pull out the valve and carefully grind a bit off then end of the stem with an oilstone.
Too big and you need to either dress down the valve face and / or the valve seat.
So if you recut the valve seats then there will not be enough valve clearence for the engine to run properly.
When grinding down the valve stems to restore proper clearences then you stop at the maximum gap if you are measuring the gap by holding the valve closed with your thumb.

Finally you are there, we are not. So we can only see what is actually visible in the video which is very little.
Every time you cranked the engine the throttle & choke levers moved which is very confusing, particularly if the engine was causing that to happen and it was not you moving the levers which you should not have been doing.
No matter how hard it is to see detail, you will not notice , because you are there and saw exactly what was happening.
It would have been a lot more benificial to us if the camera was sitting still on a tripod or even a milk crate

 

[ILENGINE]

A quick way to check for valve sealing is turn the flywheel to where the valves are completely closed, and put your thumb on top and try to turn the valve. If it turns it isn't sealing. From the video it appears there may be a problem with the valves not sealing properly, as well as maybe and issue with the carb needle valve leaking and allowing too much fuel to be pumped in to the engine.

Another funny thing about the old opposed twin briggs. the cylinder on the right side if you were sitting on the seat has a bad habit of egg shaping the cylinder, and also having the exhaust valve seat come out of the block.