Need Help with a Briggs and Stratton engine

WesternSaw · May 14, 2010

I am posting this thread in this forum so that it may get the attention of you engine Gurus,I know it is not the appropriate place,so please don't get too pissed off!.
Here's the problem.I have a push lawnmower powered by a Briggs and Stratton Classic 3.5 HP engine.It has the basic white plastic carb with no idle screws or anything.I have thoroughly cleaned the carb,I mean thoroughly.I am big into detail.replaced everything like i think it should go back together,BUT I think I may have put the one little spring in the wrong way.In my search to discover what the problem was with it I went to YouTube and found a fella on there taking apart the exact same carb.As he takes apart the carb he is removing the diaphragm off of the carb and stops to point out that there is a little spring that sits just under the diaphragm next to the carb underside.Does this seem to be the right place for this spring?If so I think that I may have put it in the wrong place in reassembling the carb,thus the poor running of the engine.Fella in the video say's that this spring under the diaphragm acts as the fuel pump from the engines vibrations.
Thanks in Advance
Lawrence
http://www.youtube.com/watch?v=Gg4OWXW520k

JasonBmac · May 14, 2010

Check out this site:

http://outdoorpowerinfo.com/repairs/

Last picture here http://outdoorpowerinfo.com/repairs/briggs_pulsa-prime_carb.asp indicates that the spring goes on the carb side of the diaphragm.

J

WesternSaw · May 14, 2010

JasonBMac

Your the man! Thanks for that link.I will do a reassemble and see what happens.
Lawrence

Fish · May 14, 2010

You need to replace the diaphragm, the little rubber flappers get curly and do not function correctly.

$2 at any mower shop.

WesternSaw · May 14, 2010

Hi Fish and Thanks!

I did that as well as the gasket.Also put a new governor spring on.It stills seems to be hunting for the right speed when you move the handlebar throttle lever.It will only stay at a certain RPM though, any movement with the handlebar mounted throttle lever towards high or towards low and it starts to hunt for the correct speed and will not stay there.I'm thinking as well as placing the carb spring under the diaphram maybe I need to shorten the wire cable from the handlebar throttle lever to the governor.What do you fellas think?
Lawrence

bullittman281 · May 14, 2010

Hello,
I'm familiar with the carb you describe. Make sure it gets a new diaphragm as this is what dies and causes them to run bad, normally rich which makes the governor hunt. The little spring should go between the carb bottom and the diaphragm. Those carbs are very simple and in my travels give little problems except the diaphragms are totally crap. Make sure its clean and assembled correct and you should be good to go.

Bullittman

twiztedsix · May 14, 2010

make sure the screen on the pick up tube is really clean as well.

Rookie1 · May 14, 2010

Fish said:
You need to replace the diaphragm, the little rubber flappers get curly and do not function correctly.

$2 at any mower shop.

Ooh Ooh Ooh! I want to add my 2 cents. The mower shop I deal with told me this trick so I cant claim all the glory,Im not that kinda guy anyway. As stated the diaphram curls and doesnt pump well. if you look at the diaphram you will see where its thin near the spring hole. Take a razor knife and straight edge and score the aluminum base so the diaphram has something to bite on. That way it will last alot longer. I believe if you dont it will do the same thing again. Wow Im glad I was able share that. :cheers:

WesternSaw · May 14, 2010

bullitman281

Thanks very much for the information!I try and get running better this weekend.
Lawrence

WesternSaw · May 14, 2010

twiztedsix

Thanks for the information you have provided!
Lawrence

WesternSaw · May 14, 2010

Rookie1

Thanks Rookie1 That's seems like a hell of an idea!For lack of a better description I will say that the carb bottom should be somewhat knurled,if that's right word.

Lawrence

chainsawland · May 14, 2010

I think everyone covered most of the likely causes, but I'm curious if you drained out and cleaned the gas tank?

Those Briggs are famous for water and dirt accumulating in the bottom of the gas tank under the fuel pickup.

WesternSaw · May 14, 2010

Chainsawland

Thanks for the heads up on the fuel tank,that was the first thing I did when I pulled the carb off.
Lawrence

Rookie1 · May 14, 2010

petesoldsaw said:
Thanks Rookie1 That's seems like a hell of an idea!For lack of a better description I will say that the carb bottom should be somewhat knurled,if that's right word.

Lawrence

That things as smooth as a babies bottom. You are right the surface should be textured somehow. I took one apart and put back together three times before asking mower shop. Felt like a big fool. :dizzy:

Glad I was able to pass it on. :clap:

WesternSaw · May 18, 2010

Aaaagggghhhh!

Okay here's where it stands with the engine so far.The carb is cleaned immaculately,all screens jets passages etc.!The air vain and surrounding are flywheel etc. is free of all debris and spotless.I have double checked the diaphragm and gasket ,the diaphragm is lying flat not bent up and the gasket is fine.Both of these are in the correct position.The little spring that I had worried about, the one that goes on the boss and lies between the carb bottom and the diaphragm, is in it's right place.This spring acts like a fuel pump.
The throttle wire that goes from the governor to the remote throttle on the side handle bar is working.Meaning it works the governor from the remote from slow idle to fast.BUT.It's still not running right.If I operate the throttle valve by my finger switching it from slow to high on the the little plastic wing that controls the throttle valve it runs like a top.All I can think of is that the spring that connects the little white plastic throttle valve to the governor is A. not the right one that I should have been given at the parts store or B. I have somehow stretched it BUT,I don't think so.What an ordeal!
Lawrence

AUSSIE1 · May 18, 2010

I've got the OEM Briggs manual Lawrence.
If you need any pages emailed let me know.
A model no of the motor would help.

AKDriveSprocket · May 18, 2010

A lot of the time when you have governor hunting you have a problem with the low circuit on the carb. If all else fails loosen the governor and move just a bit. All linkage and springs need to be in place and not bent. Water under a welsh plug will do this all so.

Fish · May 18, 2010

To increase your rpms, you need to grab this bracket and pull it forward
to increase the spring tension. It gets bent back by mowing into/under low shrubs, and Brigg's official way of adjustment is bending it back here.

P.S. : BTW, I normally don't go to these great lengths, well maybe I do,
but this new Saw Dr. threat has me worried about my job and paycheck
here on A.S., I am thinking of a name change too.

Something to get the respect of those down under may help.............
Maybe Dr.Bill-fishypuss?

Maybe I should start agreeing with the Aussies more........

But everyone knows their beer is terribly weak, couldn't give a nun a buzz.....

I hear it is better than Canadian. Canadians have the coldest beer, but why
wouldn't they????

Sorry, I am digressing....

It may be a long night, the moon is waxxing "digress", and I am a creature
of nature.

I am in a fragile, but volatile mood.......

WesternSaw · May 18, 2010

Honestly you fellas are the best!

I mean come on,where in the heck can you ask advice like I do on this site and get such good response from a bunch a fellas you have never laid eyes on.Okay, I have met three fellas so far and they are all great.

Now on to business!
Aussie1 It's a Briggs and Stratton Classic Model 95902 Type 310701 Code 94092105 I think it's made in the USA.It's about 14 years old.

AK DriveSprocket-Not sure what a low circuit is on a carb,or a welsh plug.This carb has no idle screws,it's just a plain jane plastic carb very,very basic.

Fish-Not too sure who Saw Dr is.How is he threatening you and your job/paycheck please fill me in.My friend in Nova Scotia speaks highly of you.
I Thank You for the pictures you provided and the time you took to do this,also the information you provided for me.The carb you pictured I don't think is the same as mine.I will try to take a picture in the next hour or so and post it up. Hmmm, if I could get one of the family members to hold the camera I could try and take a video.
Many Thanks to all of you who have replied to my questions!
Lawrence

Fish · May 18, 2010

If your model numbers are correct, it is the same carb.

Tension to that spring will increase your rpms

Need Help with a Briggs and Stratton engine

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