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Briggs 500E series mower engine surging

#1

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nbpt100

I have one of the newer Briggs 500E series engines that will surge when the mower is being pushed. When the mower is sitting still it idles fine. I have cleaned the plastic carb twice and it has improved a bit but it will still surge when it is moving. Something about the motion is causing it. I am not sure what is the next best step. Has anyone ever seen this before? What did you do to solve it.? Thanks.


#2

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bertsmobile1

Search 500E on this site for details of how to drill out the jets.


#3

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nbpt100

Thanks, I found a good thread that describes opening the main jet to solve surging on a clean carb. These plastic carbs seem pretty easy to clean.....I will add, When using compressed air make sure you hold the ball plugs with a finger as they can shoot out and you may never find it. Also go easy on the screws as you can strip out the plastic pretty easy.

My neighbor has a similar mower with a 500E series engine and his has surged since day one. I can always tell when he is mowing his lawn from the sound.

Also, Does anyone know what RPM this engine should be set to? I can not seem to find that in the OP manual or anywhere else I have searched so far. Thanks.

It is a model 8P502-0064 F1


#4

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bertsmobile1

Every thing spins at 3,000 rpm to 3,600 rpm.
Hard to believe but this is standardized world wide
it comes from farm tractors low PTO speed is 3600 and high 5800 or there abouts

Hondas run towards the slow end around 3200 which makes he engines sound quiet and Briggs tend to the upper 3600 which makes then scream.


#5

N

nbpt100

bertsmobile1 said:
Every thing spins at 3,000 rpm to 3,600 rpm.
Hard to believe but this is standardized world wide
it comes from farm tractors low PTO speed is 3600 and high 5800 or there abouts

Hondas run towards the slow end around 3200 which makes he engines sound quiet and Briggs tend to the upper 3600 which makes then scream.
Click to expand...

I found something that says this engine is set to 1750 RPM and by the sound that seems about right. This thing would blow it self up at 3000 RPM.

I opened the main jet with a .0195" micro drill. It did help. The engine surged a lot less but would still surging when it was pushed. The rpm was more steady. I decided to go up the next available size which was .022. It seemed to make it a bit worse losing a bit of ground. It is still better than before I modified the jet but I think it was overall better at the .0195. It is not surging a lot it just seems more like the engine is missing here and there. Again more so when the mower is being pushed. When it is sitting still it runs so much better.

Could it be something with the Governor as well?

I will check the plug tomorrow and see if it looks like it is now running rich.


#6

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bertsmobile1

1750, if it is a speed from a manual would be the min idle speed as set with the throttle stop.
The cheaper the engine the faster they idle.


#7

N

nbpt100

These are the new entry level lawn mower engines made by Briggs. No throttle control. 1750 RPM is the only info in writing I could find. It sounds good right around 1750rpm. I could go a bit faster but nothing near 3000 rpm.

I ran it again this morning and it starts right up on one pull. It idles nice. Once it heats up I am getting a bit of a surge and/or skipping. I pulled the plug and it seems ok. Not too rich. Certainly not too lean. I changed it and the skipping has been greatly reduced but still a bit of surging when it is pushed.
Now I am thinking I could perhaps open it a hair more....i.e. .001 to .002". But I want to wait before I do that and just see how it goes.

I noticed is the manual specs the spark gap at .020". This is not an auto choke engine, Or a "Ready Start" as Briggs brands them. They are the only engines I have seen from Briggs with that small of a gap. The RC12YC plugs come with a .030 gap. I assume this is done to help with easier starts but from my experience on the ready starts they run just fine with a .030 gap. I'm not convinced if changing to a .020 gap that will impact surging or even skipping.


#8

B

bertsmobile1

nbpt100 said:
These are the new entry level lawn mower engines made by Briggs. No throttle control. 1750 RPM is the only info in writing I could find. It sounds good right around 1750rpm. I could go a bit faster but nothing near 3000 rpm.

I ran it again this morning and it starts right up on one pull. It idles nice. Once it heats up I am getting a bit of a surge and/or skipping. I pulled the plug and it seems ok. Not too rich. Certainly not too lean. I changed it and the skipping has been greatly reduced but still a bit of surging when it is pushed.
Now I am thinking I could perhaps open it a hair more....i.e. .001 to .002". But I want to wait before I do that and just see how it goes.

I noticed is the manual specs the spark gap at .020". This is not an auto choke engine, Or a "Ready Start" as Briggs brands them. They are the only engines I have seen from Briggs with that small of a gap. The RC12YC plugs come with a .030 gap. I assume this is done to help with easier starts but from my experience on the ready starts they run just fine with a .030 gap. I'm not convinced if changing to a .020 gap that will impact surging or even skipping.
Click to expand...

Change the gap.
The new engines are very sensitive to plugs & plug gaps.
The old engines were not all that fussy and would not really car if they were fitted with a resistor plug or a plain one.
The new engines do.

And just so you know, 500e is not your model number, it is a name , like intek or quattro.
You engine is a 120000 series engine ( 175cc ) .
Somewhere on the engine will be a 120000 number like 122R02-0126-H1 or 122T07-5308-B1
On newer engines it is on the decal with a bar code , under the bar code and electroetched into the side of the crankcase sort of behind the carb
Earlier models have it stamped into the rocker cover and if it has a metal heat shield over the muffler it is stamped into that.
If you search for service information on the 120000 series engines you will have more luck.


#9

N

nbpt100

Sorry for any confusion.

Actually it is a 08P502 0064 F1
It is relay a 450E series engine. Similar to the 500E design....... 125cc vs. 140cc.

I got a bit confused as i just worked on a 500E.

This is the type with a plastic Carb and no throttle control.

Right here for those with interest:

https://www.briggsandstratton.com/e...g/engines/lawn-mower-engines/500e-series.html


#10

B

bertsmobile1

Note the engine speeds
Could not find a 500e spec sheet but I do not have access to the Briggs portal where that information is .
These are the later fixed speed engines found on mowers that do not have a throttle, just a bail.
I seriously doubt that a mower spinning at 1750 would actually cut grass.

https://www.smallenginesuppliers.com/shop/html/pages/products/briggs_vertical_shaft_engines4309.html
https://www.smallenginesuppliers.com/shop/html/pages/products/briggs_vertical_shaft_engines4299.html


#11

N

nbpt100

bertsmobile1 said:
Note the engine speeds
Could not find a 500e spec sheet but I do not have access to the Briggs portal where that information is .
These are the later fixed speed engines found on mowers that do not have a throttle, just a bail.
I seriously doubt that a mower spinning at 1750 would actually cut grass.

https://www.smallenginesuppliers.com/shop/html/pages/products/briggs_vertical_shaft_engines4309.html
https://www.smallenginesuppliers.com/shop/html/pages/products/briggs_vertical_shaft_engines4299.html
Click to expand...

Thanks for the info. I guess my inductive tach is not working properly. It does jump around a bit. I will have to dig out my optical tach and pick up the blade speed to get an accurate reading.
1750 rpm does sound pretty slow.
Thanks again for the help.


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