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Briggs Commercial V-twin surging

#1

L

loneryder

I've got a 3 yr old Ferris iz700 with the Briggs Commercial 27 hp engine. The engine model # etched on the valve cover is 497877. I has 95 hrs of operation. About 91 hrs I changed the oil/filter and airfilter. I used HDEO syn 5-40. Since then it's started surging and smell like it's running rich. With the blades engaged, it seems to run ok. Shut the blades down and it surges and smells rich. I ran some fuel system cleaner thru it and the gas I use is Costco's tier 1 with that Starbright enzyme treatment in the cans. It's fresh gas. Up to now it's been a great engine/mower.
Any ideas or thoughts before I take it to the shop?
Thanks.


#2

L

loneryder

I'm sorry. The engine # is 49T877-0019-G1. Blame my old eyes on this one.


#3

Douglasdzaster

Douglasdzaster

Drain the bowl under the carburetor. If it has sat up for anytime there could be a little water in it or trash. Water will make it surge. It’s also possible to get a tank of bad gas anywhere. I always buy gas at the busiest place where they sell a lot of gas then I know it’s fresh.It’s worth draining the carburetor since it’s easy to do. Could be a blockage somewhere also. If it has a fuel filter check it. Check the vent on the gas cap by loosing it and see if the surging stops. Could also be the spark plugs not firing correctly. When’s the last time they were replaced? Make sure the gap is in spec with the manual.


#4

M

MParr

So, you have around 100 hours on the machine.
Has the fuel filter been changed?
Have the spark plugs been changed?
It’s also time to change the hydrostatic filters and fluid.
As mentioned above, drain the carburetor bowl.


#5

B

bertsmobile1

Unless you are at the top of the Rockeys or use it for pushing snow that oil is a touch on the thin side
You know when it is too thin cause you get a bit of oil smoke on start up that goes away after a couple of minutes.
Surging happens because the air:fuel ratio gets too lean
If it only happens at start up but get better when the blades are on then it is the pilot / idle circuit in the carb
So either something is preventing enough fuel getting into the engine or air is getting in after the fuel is added


#6

L

loneryder

bertsmobile1 said:
Unless you are at the top of the Rockeys or use it for pushing snow that oil is a touch on the thin side
You know when it is too thin cause you get a bit of oil smoke on start up that goes away after a couple of minutes.
Surging happens because the air:fuel ratio gets too lean
If it only happens at start up but get better when the blades are on then it is the pilot / idle circuit in the carb
So either something is preventing enough fuel getting into the engine or air is getting in after the fuel is added
Click to expand...
Thanks. I was worried the oil might be too heavy. Book calls for nothing more than a 30wt.


#7

L

loneryder

MParr said:
So, you have around 100 hours on the machine.
Has the fuel filter been changed?
Have the spark plugs been changed?
It’s also time to change the hydrostatic filters and fluid.
As mentioned above, drain the carburetor bowl.
Click to expand...
Only the Hydrogear fluid and filters. Should I go ahead and change the fuel filter and plugs? Plugs look ok and I re set the gap.


#8

M

MParr

loneryder said:
Only the Hydrogear fluid and filters. Should I go ahead and change the fuel filter and plugs? Plugs look ok and I re set the gap.
Click to expand...
Absolutely! I’ve had the best luck with Kohler brand fuel filters. This is my go to for mowers with fuel pumps.

Amazon.com: KOHLER 24 050 13-S1 Engine Fuel Filter 15 Micron With 1/4-Inch Inside Diameter : Automotive

Buy KOHLER 24 050 13-S1 Engine Fuel Filter 15 Micron With 1/4-Inch Inside Diameter: Fuel Filters - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com


#9

L

loneryder

Here's an update. My local repair guy sold me a small bottle of Motor Medic (I think). He said to run it thru the engine and let it sit overnight. He said if that didn't do it, nothing would. Said be careful because it would burn my hands. Changing the plugs and fuel filter didn't help the surging. I put the whole bottle in the tank and ran it for a while and let it sit overnight. No real change. Did it for another day/night and low and middle idle came back but high speed still surged. Did it for another day/night and shazaam, all idles are smooth.
Here's what I don't get: I fill my gas cans at Costco and use the blue enzyme stuff in each can. I use the gas within a month. You can't get fresher gas than Costco as they go through 3-15 tankers a day. I gave up on Stabil. And still I have these carb problems.
Thanks for all your suggestions.


#10

Douglasdzaster

Douglasdzaster

loneryder said:
Here's an update. My local repair guy sold me a small bottle of Motor Medic (I think). He said to run it thru the engine and let it sit overnight. He said if that didn't do it, nothing would. Said be careful because it would burn my hands. Changing the plugs and fuel filter didn't help the surging. I put the whole bottle in the tank and ran it for a while and let it sit overnight. No real change. Did it for another day/night and low and middle idle came back but high speed still surged. Did it for another day/night and shazaam, all idles are smooth.
Here's what I don't get: I fill my gas cans at Costco and use the blue enzyme stuff in each can. I use the gas within a month. You can't get fresher gas than Costco as they go through 3-15 tankers a day. I gave up on Stabil. And still I have these carb problems.
Thanks for all your suggestions.
Click to expand...
It’s possible Costco got a bad load it happens. Or the fuel you got came from the bottom of their tank. Did your guy check the fuel? Just wondering. Glad your up and running again. I just recently switched from Stabil to Star Tron myself. Time will tell.


#11

L

loneryder

That product is called Fuel Medic.


#12

L

loneryder

Douglasdzaster said:
It’s possible Costco got a bad load it happens. Or the fuel you got came from the bottom of their tank. Did your guy check the fuel? Just wondering. Glad your up and running again. I just recently switched from Stabil to Star Tron myself. Time will tell.
Click to expand...
This Costco is one of the smaller ones. They only go thru 3-5 tankers a day. I asked the attendant. I guess it's possible but I doubt it. Same pumping went into my truck. I know that doesn't mean much. On Stabil I had the same mower crap out twice. First time it had corn starch in the bowl. Second time it was so bad it required a new carb. That mower doesn't get used much but it always has additive in it. I think I'm going to start using premium. My local dealer recommends it. He said at all the training classes they ask about what fuel to use and the manufacturers tell them that the engines are designed to run on 87 but they prefer you run at least 91.


#13

S

slomo

What I've noticed in Oklahoma, Costco, Homeland and Sam's Club get their gas furmulated weirdly. Meaning they use MKE I think the pump says. My stuff ran weird on these fuels. They alter the formula to get the price down for their members. Long story short, go to 7-11 or any other "real" gas station.

Far as the OP oil goes, that 5w-40 is too thin for summer mowing. Bert caught it. Use plain old tried and true SAE30 oil.

slomo


#14

Douglasdzaster

Douglasdzaster

loneryder said:
This Costco is one of the smaller ones. They only go thru 3-5 tankers a day. I asked the attendant. I guess it's possible but I doubt it. Same pumping went into my truck. I know that doesn't mean much. On Stabil I had the same mower crap out twice. First time it had corn starch in the bowl. Second time it was so bad it required a new carb. That mower doesn't get used much but it always has additive in it. I think I'm going to start using premium. My local dealer recommends it. He said at all the training classes they ask about what fuel to use and the manufacturers tell them that the engines are designed to run on 87 but they prefer you run at least 91.
Click to expand...
Yep when I pulled out my pressure washer that had been sitting a couple of months and it wouldn’t start and I had to clean the crud out of the carburetor. I switched to none ethanol fuel and Star Tron. It’s like Stabil just stopped working or the fuel is getting worse.


#15

Scrubcadet10

Scrubcadet10

i've been using star tron for several years...i also use it in the ATV at the hunting lease, that sits for a week between starts... occasionally 2 weeks. It fires up with the touch of the button now, instead of cranking for about 3 or 4 seconds now.


#16

S

slomo

Douglasdzaster said:
I switched to none ethanol fuel
Click to expand...
Great move going to non ethanol fuel. Think the fuel is getting worse. Getting diluted with other "chemicals" to cut the price down. Probably oil field junk that's being resold and mixed in.

slomo


#17

B

bertsmobile1

Fuel is a bigger lottery than the lottery is.
So many things can make it go off which will be particular to almost anything from the time of day, humidity, dew point, etc etc etc .
Try to keep your fuel tank either full to the top or totally empty when the mower is not in use


#18

L

loneryder

The problem with regular (no alcohol) gas is the only source in my area doesn't pump very much so it's sitting a long time. It's at a BP station but it's not BP gas.


#19

Douglasdzaster

Douglasdzaster

loneryder said:
The problem with regular (no alcohol) gas is the only source in my area doesn't pump very much so it's sitting a long time. It's at a BP station but it's not BP gas.
Click to expand...
I’m very fortunate. They stay super busy where I go and now there’s a new one open next to them also with none ethanol and both sell a lot as they are on the way to the lake which is handy. I read where a lot of people can’t get none ethanol at all.


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