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General Forestry => General Board => Topic started by: ljohnsaw on May 06, 2019, 11:02:54 PM

Title: Rebuilding an old carb off a Briggs & Stratton engine...
Post by: ljohnsaw on May 06, 2019, 11:02:54 PM
I posted this winch elsewhere:

(http://forestryforum.com/gallery/albums/userpics/30640/Yarder_2.jpg?easyrotate_cache=1551734971)
 
Its got an old Briggs & Stratton engine - 12-14hp?  The carb was leaking from the main jet adjusting screw on the bottom side of the bowl so I figured I pull the carb and clean it up.  To pull the carb apart, you need to pull a brass tube that goes diagonal from the main jet needle up to the top of the carb.  Only problem is the brass threads have pretty much fused with the pot metal of the bowl.  

I was able to finagle the carb apart and found the next problem.  The brass pin that holds the float in place is also fused.  I have to get that off to change the gasket.  I put it back together (a few times now) and now it seems the float valve is not sealing up - gas leaking out.  I tested by blowing in gas line fitting and it works fine that way.  I had some spare valve needle thingys but still leaks gas.  I did clean it up with carb cleaner so there shouldn't be gunk on the valve seat.  Maybe the gunk was what helped it seal... ::)

Anyhow, I would like to track down a carb kit or make new gaskets but I have to get it apart correctly.  Any choice ways to get it apart without damage?
Title: Re: Rebuilding an old carb off a Briggs & Stratton engine...
Post by: Steve Crook on May 07, 2019, 12:01:47 AM
I ran in to one of those carbs years ago. the brass tube that goes through the carb broke and I had to drill it out. the remainder of the tube had to be removed with a tap. I Had to make a special tap because it is a goofy thread pattern. Like 3/8 34 or something like that.I believe that the replacement tube was available from briggs.
If that is what you have leave a message to me and you can have the tap. i think I may remember where it is. if not it is no big deal to make another. 
Title: Re: Rebuilding an old carb off a Briggs & Stratton engine...
Post by: Old Greenhorn on May 07, 2019, 06:04:02 AM
I have had a few of these over the years, always a pain when they start to corrode. On more than one occasion I have found pin holes in the float causing it to sink and keep the needle valve open. Tough to notice if you are not looking for it. I always have trouble making these run clean and neat. The gaskets always seem to leak from someplace.
 Good luck.
Title: Re: Rebuilding an old carb off a Briggs & Stratton engine...
Post by: Corley5 on May 07, 2019, 08:55:18 AM
Might be time for a Chonda ??? :)
Title: Re: Rebuilding an old carb off a Briggs & Stratton engine...
Post by: luap on May 07, 2019, 09:37:34 AM
You have a couple of options. This carburetor comes in two sizes with the relative same shape. Your best option is to replace the carb. I Save Tractors sells them, and they are available on Amazon. Jacks small engines have rebuild kits. You could also install a gas line shut off valve and just remember to turn on-off as needed. besides the needle seat, the other problem with these carbs is the wear on the throttle shaft leaks air affecting the fuel air ratio. They sell new bushings for the throttle shaft but the throttle shaft is usually worn also. These few items alone almost equal the price of an amazon carb.
Title: Re: Rebuilding an old carb off a Briggs & Stratton engine...
Post by: sawguy21 on May 07, 2019, 11:48:24 AM
Those carbs tend to leak where the brass nozzle seats against the upper carb body. Sometimes it can be cured by grinding the threads off the old nozzle and dabbing valve lapping compund on the taper, work the nozzle back and forth with a screwdriver. In your case I would replace the carburetor with an aftermarket, the price of a new OEM will scare you.
Title: Re: Rebuilding an old carb off a Briggs & Stratton engine...
Post by: ljohnsaw on May 07, 2019, 02:59:41 PM
Yeah, I'm thinking a replacement carb.  It was running good until I messed around with it - the engine is fine.  Now the problem.  The carb has no numbers on it and the engine has multiple layers of black and yellow paint obscuring everything but an embossed B & S.  I can make out the faint outline of the B&S sticker on the top of the shroud.  So I've got nothing to do a look up.  :-\

(http://forestryforum.com/gallery/albums/userpics/30640/Yarder_4_-_carb.JPG?easyrotate_cache=1557255531)
 
On the plus side, the outside of the carb is really clean...  On the other side of the engine is the gas tank (about 1 gallon) and it has a glass bowl water separator with a shutoff valve.  This is an updraft carb, but has a side intake.  What would you call it?  Steve Crook, did yours look like this?  Did you have a carb number?
Title: Re: Rebuilding an old carb off a Briggs & Stratton engine...
Post by: Steve Crook on May 07, 2019, 04:04:36 PM
     I  do not recall having #s on mine but it is a two-piece flo-jet carb.
You do need to remove what the book calls the nozzle to separate the two halves. that is the angled brass tube.running up through the carb.
It was mentioned about the throttle shaft having excess play. that was a problem on mine. it required making bushings drilling and installing.
          
Title: Re: Rebuilding an old carb off a Briggs & Stratton engine...
Post by: ljohnsaw on May 07, 2019, 04:30:58 PM
Problem is I can NOT get the cross tube out.  It is corroded in place for all eternity.  I got a hit on another forum (garden tractors) to use ISaveTractors.com and a medium or large Flojet carb.  Turns out mine is the medium one.  Since this engine is circa 1972, I figure it could use a new carb so I just ordered one.  They also had a 10% off your first order so shipping was basically free.  Now I know I shouldn't have any problems with this when I use it this summer.
Title: Re: Rebuilding an old carb off a Briggs & Stratton engine...
Post by: hamish on May 07, 2019, 04:55:12 PM
Heat is your friend, the brass and the composition of the body with expand and contract at different rates.  A simple heat gun with allow you take it apart easily.

You can buy an aftermarket updraft carb for most likely less than $30 USD.
Title: Re: Rebuilding an old carb off a Briggs & Stratton engine...
Post by: luap on May 08, 2019, 04:29:50 PM
Yeah, I'm thinking a replacement carb.  It was running good until I messed around with it - the engine is fine.  Now the problem.  The carb has no numbers on it and the engine has multiple layers of black and yellow paint obscuring everything but an embossed B & S.  I can make out the faint outline of the B&S sticker on the top of the shroud.  So I've got nothing to do a look up.  :-\

(http://forestryforum.com/gallery/albums/userpics/30640/Yarder_4_-_carb.JPG?easyrotate_cache=1557255531)
 
On the plus side, the outside of the carb is really clean...  On the other side of the engine is the gas tank (about 1 gallon) and it has a glass bowl water separator with a shutoff valve.  This is an updraft carb, but has a side intake.  What would you call it?  Steve Crook, did yours look like this?  Did you have a carb number?
Every post war Briggs engine I have seen has three series of numbers-Model, type and code stamped in the sheet metal fly wheel housing, typically filled  in with paint. With the series number you can just find it on Jacks small engines or small engines parts  warehouse.