Ask Me Help Desk - Problematic push lawn mower

Hello,

I need your insight.
I have Noma - Briggs & Stratton 3.5 HP 148 CC model Brute push mower.

In the fall I run the mower until it is dry of fuel and replace with new fuel in the spring.

Today was my planned initial mowing of the season. The only way I was able to start the motor was by putting a screwdriver in the carburator to keep the plastic plate (butterfly?)open. Initially it idled very roughly and the gasoline smell was awfull along with a fair amount of grey smoke coming out of the exhaust. At one point it finally started to idle properly without the screwdriver in place. But when I attempted to put the air filter back on it died or if I tried to actually mow it would lose its idle and die.

This mower is at least 15 years old, but I love it because its light and does a good job.

I am not very adept at these types of repair, so I would appreciate your explanations/suggestions in a 'Repairs for Dummies' type of language.

Thanking you in advance for your time and help.

Regards

Richard

Are you sure the air filter isn't clogged?

Get the model and code numbers off the blower housing. They are usually stamped in and are very difficult to see and we'll look it up online. You can do the legwork too at Home - Briggs & Stratton

I think I know the engine your talking about. It has a gas tank below the carb and it's mounted on the opposite side of the muffler, but a tube goes to the other side. It has a white plastic choke and a very poor linkage setup. It has a foam pankake like somewhat rectangular air cleaner with a semi-circle out of it.

Quote:

Originally Posted by KeepItSimpleStupid

Get the model and code numbers off the blower housing. They are usually stamped in and are very difficult to see and we'll look it up online. You can do the legwork too at Home - Briggs & Stratton

I think I know the engine your talking about. It has a gas tank below the carb and it's mounted on the opposite side of the muffler, but a tube goes to the other side. It has a white plastic choke and a very poor linkage setup. It has a foam pankake like somewhat rectangular air cleaner with a semi-circle out of it.

KISS, thanks for the reply.

Yes, I tried to get more info on the model , but unfortunately with time the stamping has gotten to where I can only guess at some of markings.

However, your description of the model is dead on. By the way, I did not know that the plastic piece was a choke. That is the piece that I am holding open with a screw driver and it enables the mower to at least start, though idle very roughly and at lower rpms than when it's operating normally.

As concerns the air filter, I gather that the problem may be when I try to mount the filter back in it's proper position and need place the screw through the carburator it must kill the air/gas ration and it dies.

Your suggestions would be appreciated.

Thanks

The first thing you want to do is clean and degrease everything including the rotating plate. Use a degreaser and possibly Wd-40. Make sure the choke moves freely too. You might need carb cleaner here. Lubercate with a lithium based grease such as Luberplate.

Now move the throttle to full on (choke) and the choke should close. Move the throttle toward idle and it should open.

Adjustments are the tab that moves the choke and repositioning the throttle cable within the clamp on the side of the engine. Throttle should move from idle to choke and the choke close at one extreme and should release shortly in the opposite direction.

The problem is that the plate that moves the choke wobbles over time and this causes problems with the choke operating properly. It tends to hang up. Real solution is to replace the plate assy.

In the choke position the choke should be free to move on its own. It will open because of engine vacuum when the engine starts.

The erratic engine idle is probably due to an O ring on the tube that goes across the engine. It's letting too much air in.

I've got two of these engines that I use very rarely, so I do have to fiddle just a little. In my case the choke normally doesn't close. I need to replace the plates too.

Be careful installing the screw through the air cleaner.

Quote:

Originally Posted by KeepItSimpleStupid

The first thing you want to do is clean and degrease everything including the rotating plate. Use a degreaser and possibly Wd-40. Make sure the choke moves freely too. You might need carb cleaner here. Lubercate with a lithium based grease such as Luberplate.

Now move the throttle to full on (choke) and the choke should close. Move the throttle toward idle and it should open.

Adjustments are the tab that moves the choke and repositioning the throttle cable within the clamp on the side of the engine. Throttle should move from idle to choke and the choke close at one extreme and should release shortly in the opposite direction.

The problem is that the plate that moves the choke wobbles over time and this causes problems with the choke operating properly. It tends to hang up. Real solution is to replace the plate assy.

In the choke position the choke should be free to move on its own. It will open because of engine vacuum when the engine starts.

The erratic engine idle is probably due to an O ring on the tube that goes across the engine. It’s letting too much air in.

I’ve got two of these engines that I use very rarely, so I do have to fiddle just a little. In my case the choke normally doesn’t close. I need to replace the plates too.

Be careful installing the screw through the air cleaner.

K.I.S.S. the carb cleaner seemed to have done the trick, thank you !
I find that it still is a bit smokey though the idle seems fine.
Do I need to adjust the screw located underneath the carb. Is this is to adjust the air/fuel mixture?
Thanks again for your help

Richard

I can't remember if there are one or two screws. Usually there are two. One for low speed and one for high. The larger one is for high speed. So, you can have an engine that idles nice and has poor high speed performance.