Antique Engines and Old Iron
[Home] - [HELP] - [Forums] - [Groups] - [Classified Ads] - [Subscribe] - [Books] - [Sponsors] -

Go Back   SmokStak > SmokStak® Antique Engine Community > Small Air Cooled Gasoline Engines > Garden Tractors and Mowers
Forgot Password? Join Us!

Notices

Garden Tractors and Mowers Vintage lawn and garden tractors, mowers, snow blowers, snowmobiles and other old machinery that is driven by small air cooled engines.

Garden Tractors and Mowers

Briggs and Stratton 3.5Hp Problem


this thread has 8 replies and has been viewed 21067 times

Reply
 
Thread Tools Display Modes
  #1  
Old 05-08-2010, 04:26:35 PM
petesoldsaw petesoldsaw is offline
Registered
 
Join Date: Aug 2008
Location: British Columbia,Canada
Posts: 141
Thanks: 0
Thanked 9 Times in 8 Posts
Default Briggs and Stratton 3.5Hp Problem

Hello Fellas
I have a problem with my mower,it has a 3.5Hp Briggs and Stratton engine.It was surging,reving high then low,high then low.So I thought it was the throttle spring,I got one from the dealer hooked it up and had the same problem.So I cleaned the fuel tank out,rinsed the carb out with fuel,replaced the carb diaphram and fuel tank gasket and also a new primer bulb.Same problem.I shortened the the stiff wire cable that comes from the governor to the control on the handle bar that adjusts the speed from slow to fast so that it is a little more acurate than it was as the original one broke awhile back and replced with another one.Anyway I still have the same problem.With the air filter off and the screw that holds the air filter cover on in the carb I watched as the throttle that is in between the carb anf intake just goes back and forth revs up then down uop then down.Any ideas fellas ?I would sure appreciate it.Tried you tube for a video but they stop and start all the time and they are hard to follow.I have high speedinterenet don't know why it dows that either.
Many Thanks
Lawrence
Reply With Quote
Sponsored Links
  #2  
Old 05-08-2010, 10:59:34 PM
Ken Karrow Ken Karrow is offline
Subscriber
 
Join Date: Aug 2009
Location: West Central Missouri
Posts: 1,066
Thanks: 735
Thanked 535 Times in 362 Posts
Default Re: Briggs and Stratton 3.5Hp Problem

Try pulling the blower housing and checking for something binding but not completely stopping movement of the air vane governor, particulary if this is the first use of the season and worked OK last year. Spider web, leaf, etc. Ken
Reply With Quote
  #3  
Old 05-10-2010, 09:59:23 AM
petesoldsaw petesoldsaw is offline
Registered
 
Join Date: Aug 2008
Location: British Columbia,Canada
Posts: 141
Thanks: 0
Thanked 9 Times in 8 Posts
Default Re: Briggs and Stratton 3.5Hp Problem

Hello Ken
All is clear of the wind vane no debris at all.I think the replacement spring may not have been the right one i was sold or the throttle wire from the lever on the handle is too long.I don't see any idle screws on that carb either.I just don't want to pay that shop rate if i can fix the problem myself.
Lawrence
Reply With Quote
  #4  
Old 05-10-2010, 10:16:23 AM
Bill Sherlock Bill Sherlock is offline
Subscriber
 
Join Date: Nov 2004
Location: Maymont, Saskatchewan, Canada
Posts: 2,879
Thanks: 778
Thanked 1,605 Times in 745 Posts
Default Re: Briggs and Stratton 3.5Hp Problem

Lawrence,

What model of Briggs engine do you have? Might have a manual here that would give me an idea what carb your engine has. Think it could be that one of the passages for fuel might be plugged.

Regarding the problem viewing videos on your computer, could be your hard drive is running low on disk space? On our old computer quite often the picture and sound aren't synchronized and one catches up to the other near the end of the video. We've had problems with the telephone lines in the past as well which effected the efficiency of the high speed internet.

Bill
Reply With Quote
  #5  
Old 05-10-2010, 11:55:44 AM
petesoldsaw petesoldsaw is offline
Registered
 
Join Date: Aug 2008
Location: British Columbia,Canada
Posts: 141
Thanks: 0
Thanked 9 Times in 8 Posts
Default Re: Briggs and Stratton 3.5Hp Problem

Hello Biil
Good to hear from you again and just at the right time,LOL!
It is a Model 95902 Type 310701 Code 94092105 3.5 Hp
Briggs and Stratton.I think I have cleaned it properly.I sprayed carb cleaner in the carbin every passage nook and cranny and that was done when I had it off the fuel tank.Bill,if I move the little plastic piece that is situated between the intake and the carb throat it runs great I can move it left or right and it well rev right up to full or I can move it the othere way and it will idle just fine.But leave it for the throttle spring whiuch is attached to the above mentioned part and also to the govenor pklate forget it,it will not respond properly.surely mechanics don't have to fiddle with that spring to get the right tension on it.I am stumped and frustrated for sure.I guess to sum up it is getting full fuel from the carb it seems to be a govenor throttle spring problem.
Many Thanks
Lawrence
Reply With Quote
  #6  
Old 05-10-2010, 02:06:47 PM
Bill Sherlock Bill Sherlock is offline
Subscriber
 
Join Date: Nov 2004
Location: Maymont, Saskatchewan, Canada
Posts: 2,879
Thanks: 778
Thanked 1,605 Times in 745 Posts
Default Re: Briggs and Stratton 3.5Hp Problem

Lawrence,

OK, found my parts list that I downloaded from the Briggs & Stratton site. I see that's a one piece plastic suction carb. Not many parts to it! I note the diaphragm is a two piece unit. Is it possible you have them stacked the wrong way? Also did you have the throttle shaft (think it's plastic) out of the carb? If so is it possible it may have been facing the wrong angle when the throttle disk (butterfly) was reinstalled?

There's a couple of screens in the carb, one on the bottom of the pickup tube and a cylindrical one. Might not hurt to check those again. Did you notice any white powdery corrosion when you had the carb off the tank earlier? If so, that's from ethanol gas. I've found that regular carb cleaner doesn't dissolve that so if any got into carb passages or on the screens may still be blocked or partially blocked. I've had good luck soaking or spraying the carb or parts with CLR and then rinsing with water, and blow drying with compressed air. Maybe wouldn't hurt to follow that up with your carb cleaner and/or WD-40.

My Briggs service manual is older than your model of engine so I don't have any linkage info to show governor or throttle linkage diagrams.

Off hand, think I'd be suspicious of the butterfly position in relation to how it fits in the barrel or venturi of the carb.

Bill
Reply With Quote
  #7  
Old 05-10-2010, 05:34:30 PM
petesoldsaw petesoldsaw is offline
Registered
 
Join Date: Aug 2008
Location: British Columbia,Canada
Posts: 141
Thanks: 0
Thanked 9 Times in 8 Posts
Default Re: Briggs and Stratton 3.5Hp Problem

Hello Bill
I have had the carb apart and it is clean as a whistle,no blockages,no dirt.I did not remove the white plastic piece that controls the the butterfly valve.I watched a YouTube video and in segment the fella talks about a spring between the diaphram and the carb body.I don't remember that spring being under the diaphram,i think it went through the diaphram and the gasket.I'm completely baffled!
Lawrence
Reply With Quote
  #8  
Old 05-10-2010, 08:37:08 PM
Bill Sherlock Bill Sherlock is offline
Subscriber
 
Join Date: Nov 2004
Location: Maymont, Saskatchewan, Canada
Posts: 2,879
Thanks: 778
Thanked 1,605 Times in 745 Posts
Default Re: Briggs and Stratton 3.5Hp Problem

Lawrence,

Your carb kit should have consisted of the diaphragm and gasket, a screen about 1/2" X 3/4" and a spring about 1/4" X 9/16". The stiffer diaphragm (gasket) is placed on top of the flimsy diaphragm and should be next to the mounting flange of the carb. The screen is placed over the round main jet tube. The spring fits over a round boss in the half moon looking recess and will be above the diaphragm when the carb is assembled on the gas tank.

I should mention there is a "O" ring in the carb intake opening on the engine that needs to be lubricated before the carb is reinstalled. If it isn't lubricated, there could be a chance that the "O" ring could be dislodged and sucked into the engine and likely blown out the exhaust. Could that could have happened in your case??

I took a picture of the throttle linkage and spring of a similar carb on a B & S Sprint engine that I mounted on an old John Deere push mower. It's too big of a file to download from my laptop but could email it to you if you want.

Bill
Reply With Quote
  #9  
Old 05-11-2010, 02:49:34 PM
petesoldsaw petesoldsaw is offline
Registered
 
Join Date: Aug 2008
Location: British Columbia,Canada
Posts: 141
Thanks: 0
Thanked 9 Times in 8 Posts
Default Re: Briggs and Stratton 3.5Hp Problem

Thanks Bill,I got your email !
Lawrence
Reply With Quote
Reply

Bookmarks


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

F o r u m Jump

Similar Threads Chosen at Random
Thread Thread Starter F o r u m Replies Last Post
Briggs and Stratton starting problem nitro74cs Small Air Cooled Gasoline Engines 7 05-20-2009 05:47:12 PM
14HP Briggs & Stratton starting problem, please help! Danny J Small Air Cooled Gasoline Engines 5 04-16-2009 10:01:29 AM
Briggs and Stratton WMB cearles Small Air Cooled Gasoline Engines 15 05-14-2006 10:51:07 PM
Briggs & Stratton Al Steppich Antique Engine Archives 1 03-22-2003 10:02:32 PM
Briggs & Stratton Problem John Edwards Generators & Electric Motors General Discussion 3 03-15-2003 08:31:30 PM


Use "Ctrl" mouse wheel to change screen size.
All times are GMT -4. The time now is 01:15:41 AM.

Smokstak and Enginads site search!


All use is subject to our TERMS OF SERVICE
SMOKSTAK® is a Registered Trade Mark - A Community of Antique Engine Enthusiasts
Copyright © 2000 - 2019 by Harry Matthews P.O. Box 5612 - Sarasota, FL 34277