Briggs 18.5 hp Wont Run

[kkjfjns2014]

.003 intake
.005 Ex

Intake is the main one to get set at .003-.005. go for .003 because the ACR (Automatic compression release) is on the intake cam lobe of the valve
BUT
You say the engine cranks fast which indicates that the valve lash may not be the main problem YET. (but can be easily checked)
You can see you tube videos of how to do such for your Model Briggs))

You say in post #7 when it's cranking fast you see gas blowing back up into the carb throat. seeing gas blowing back is normal on that Model engine when the engine does not start and it's getting too much gas into the carb float due to flooding.

The reason you see a spit back of gas is the ACR momentarily blows excess gas back into the carb throat and then sucks it back just before TDC for a run. (sounds strange but true)
Pull the spark plug and see if it's wet. dry it off and re-install then
turn off the gas supply to the carb set the throttle to high rpms, no choke and crank engine and it will probably start and run for little while. If you then see it doing same thing again the carb bowl is getting too full. Note that I did not say it's the needle/seat. If it's a Nikki carb the little rubber gasket in the very top of the carb above the plastic piece is bad (it seals above/before the needle/seat or the needle/seat is bad.

It was a couple different Chinese carbs that don't seem to work. My dad pulled the nikki carb off because it wasn't running right. I got it and pulled it apart and seems like it's in ok shape. I'm going to try to clean it really good and see if it'll work. Are you talking about the circle gasket that has all the little passages on it?

 

[kkjfjns2014]

.003 intake
.005 Ex

Intake is the main one to get set at .003-.005. go for .003 because the ACR (compression release is on the intake valve
BUT
You say the engine cranks fast which indicates that the valve lash may not be the main problem YET.

You say in post #7 when it's cranking fast you see gas blowing back up into the carb throat. seeing gas blowing back is normal on that Model engine when the engine does not start and it's getting too much gas into the carb float due to flooding.

The reason you see a spit back of gas is the ACR (Automatic compression release) momentarily blows excess gas back into the carb throat and then sucks it back just before TDC for a run. (sounds strange but true)

Doubtful it's a valve lash issue if that model engine is cranking fast.

Most likely the engine has weak ignition, flooding or wrong or bad spark plug or weak magneto.

You seem to indicate that it was doing the same thing before you replaced the carb so I would think about ignition.

 

[Forest#2]

Yes and the two little o rings , itty bitty one that goes around the jet and some have a o ring in the bottom of the bowl.

You can normally get a kit for your carb for about $9 that has all these parts plus other parts. (on fleece bay or otherwise)
Post u[p a part number for the carb you are currently working on and maybe we can then point you towards a kit.
Usually if a Nikki is old and you pull it apart it likes to have new gaskets and o rings when it goes back together.
I have taken parts like the rubber gasket and o rings from the New cheap clones that were not running smooth and make a real Nikki operate ok, but one size does not fit all when the Nikki's are in the loop, different bowls and some difference inside and the jet might be a different size so you are rolling the dice trying to take 2 or 3 and make one.
I have had to return some Amazon Nikki's that would not run correctly.

The Old Walbro LMT carb's are usually to most user friendly on those engines. Briggs used them few years ago before they went to the Nikki and Ruxing carb.
Here is a link to a used LMT on fleece bay. Also here is a link that shows how to repair both types of carbs. Walbro LMT and Nikki plus others
https://outdoorpowerinfo.com/repairs/

Link to view a used Walbro LMT that is a direct replacement bolt on for your Nikki. (with a 30 day warranty)They say it runs good.

Carburetor for Briggs & Stratton 696179 Original Walbro LMT Replaces Nikki Carb | eBay

Find many great new & used options and get the best deals for Carburetor for Briggs & Stratton 696179 Original Walbro LMT Replaces Nikki Carb at the best online prices at eBay! Free shipping for many products!

www.ebay.com

 

[kkjfjns2014]

Thank you for all that information I really appreciate it. I think I'll try the gaskets from the clone carb first and it still won't work good I'll order a kit.

The numbers on it are:
697203
G02703
5X19 C

Yes and the two little o rings , itty bitty one that goes around the jet and some have a o ring in the bottom of the bowl.

You can normally get a kit for your carb for about $9 that has all these parts plus other parts. (on fleece bay or otherwise)
Post u[p a part number for the carb you are currently working on and maybe we can then point you towards a kit.
Usually if a Nikki is old and you pull it apart it likes to have new gaskets and o rings when it goes back together.
I have taken parts like the rubber gasket and o rings from the New cheap clones that were not running smooth and make a real Nikki operate ok, but one size does not fit all when the Nikki's are in the loop, different bowls and some difference inside and the jet might be a different size so you are rolling the dice trying to take 2 or 3 and make one.
I have had to return some Amazon Nikki's that would not run correctly.

The Old Walbro LMT carb's are usually to most user friendly on those engines. Briggs used them few years ago before they went to the Nikki and Ruxing carb.
Here is a link to a used LMT on fleece bay. Also here is a link that shows how to repair both types of carbs. Walbro LMT and Nikki plus others
https://outdoorpowerinfo.com/repairs/

Link to view a used Walbro LMT that is a direct replacement bolt on for your Nikki. (with a 30 day warranty)They say it runs good.

Carburetor for Briggs & Stratton 696179 Original Walbro LMT Replaces Nikki Carb | eBay

Find many great new & used options and get the best deals for Carburetor for Briggs & Stratton 696179 Original Walbro LMT Replaces Nikki Carb at the best online prices at eBay! Free shipping for many products!

www.ebay.com

 

[kkjfjns2014]

Thank you for all that information I really appreciate it. I think I'll try the gaskets from the clone carb first and it still won't work good I'll order a kit.

The numbers on it are:
697203
G02703
5X19 C

Thank you for all that information I really appreciate it. I think I'll try the gaskets from the clone carb first and it still won't work good I'll order a kit.

The numbers on it are:
697203
G02703
5X19 C

 

[Forest#2]

Review that link I sent about carb repairing. Very good do and don't info in that link.

 

[kkjfjns2014]

Review that link I sent about carb repairing. Very good do and don't info in that link.

That's an awesome and detailed guide. Thank you for sharing!

 

[DaveTN]

After getting the fuel shutoff working properly, why not do
a Gasoline IV line and as ILENGINE said the fuel level may
drop below gravity feed and starve the engine for fuel. It
should run on an elevated portable tank or another push
mower gas tank and see if it continues to run ok. And Welcome
to the LMF!

 

[doug9694]

Hello all, I have a 2006 briggs and stratton 18.5 HP [31N707] engine that came off a craftsman. We put it on a small ariens zero turn. It worked very well for awhile, then got it where it wouldn't run unless the choke was on. Eventually it quit running all together. After this my dad parked it and it sat for 2 years.

I decided to try and fix it for him this year. There was water in the gas, so I took that tank off and drained it and dried it in the sun for a few days. I put it back on put in fresh gas. I also replaced the carb and all fuel lines and vacuum lines and filters. I put the choke on and started it and it ran for about 10 seconds, I took the choke off and now it's back to not running at all again. Tried tinkering with the air/fuel mix a bit, still no luck. If you feed it gas directly into the carb it will run. It has good spark, everything else seems to be functioning, I have no idea what else to do. I'm about to pull my hair put. Any advice on next steps would be greatly appreciated. Thank you.

Could be the fuel shut off solenoid if it has one.

 

[smallenginerepairs]

Hello all, I have a 2006 briggs and stratton 18.5 HP [31N707] engine that came off a craftsman. We put it on a small ariens zero turn. It worked very well for awhile, then got it where it wouldn't run unless the choke was on. Eventually it quit running all together. After this my dad parked it and it sat for 2 years.

I decided to try and fix it for him this year. There was water in the gas, so I took that tank off and drained it and dried it in the sun for a few days. I put it back on put in fresh gas. I also replaced the carb and all fuel lines and vacuum lines and filters. I put the choke on and started it and it ran for about 10 seconds, I took the choke off and now it's back to not running at all again. Tried tinkering with the air/fuel mix a bit, still no luck. If you feed it gas directly into the carb it will run. It has good spark, everything else seems to be functioning, I have no idea what else to do. I'm about to pull my hair put. Any advice on next steps would be greatly appreciated. Thank you.

you have fuel restriction. check your fuel pump, and make sure when cranking your getting a good fuel supply. If you're getting good fuel supply it's the carb. Many aftermarket carbs are made in China, and they do not have qualoty control. They do not check carbs before they are sold, so a brand new carb can have a manufacture flaw.