8HP Briggs Questions


Old 04-07-05, 01:59 PM
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8HP Briggs Questions

Well, i had a few questions for all of you, and was hoping for some help. I scanned the entire board and could not find answers to my problem. Here it goes.


-Mid 70s Briggs & Stratton 8HP ex Pump engine
-19000 series
-Horizontal Drive
-Carb is a 2 piece "medium" flo-jet, gravity fed
-Rewind Start

Mods & Use, is to be used for a race kart. ItalKart knockoff frame , intake has been ported and polished as well as exhaust port. Single stage header, Cylinder honed ,RedLine synthetic race Kart oil,rebuilt and cleaned carb plus a K&N filter. The head has been taken off, the piston removed and cleaned and the cylinder honed. The velves look to be in good shape and the seats show no signs of wear or pitting.

Upcoming mods include switching to methanol, Deck milling the head, boring .020 over, wiseco piston, blueprinting the flo-jet & a compcams camshaft.


#1: the carb tends to leak fuel while sitting , not a lot, but a slow drip.The loak speeds up a little bit too while running. I dissasembled the carb and the needle is in mint condition, and the seat is just the same. Float height is also bang on. The only thing i can think of is the needle not seating properly that would cause this, but it looks great. I dont wanna go and spend $40 on a kit to not have it work.

#2 I can get the idle perfect, and SLOWLY open the throttle to about 25% open and the it will "putt" hard , blow black smoke and nearly stall. I cannot open the throttle any more without it dieing. Ive spend about 2 hours and 2 tanks of gas adjusting the idle/air screw and the high sped screw, and 25% open is the best i can get out of it.

I am very knowledgable with motors small and large alike, and can almost do any mechanical repair myself. Any help would bne much appreciated.

PS: The motor is under NO load, has a new plug in it, new oil, torn down and cleaned carb and fresh gas. The only thing i havent done is check the timing, and the condition of the points.
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Old 04-08-05, 01:33 AM
cheese's Avatar
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Join Date: Jul 2001
Location: USA
Posts: 16,817
Sounds like a good carb cleaning and rebuild should solve both problems. You might have to soak it in a bath type cleaner.
Old 04-08-05, 03:19 AM
puey61's Avatar
Join Date: Apr 2004
Location: Upstate New York
Posts: 3,224
These carbs are notorious for weeping. Usually the only fix is to soak the carb AND replace the needle & seat. Is the seat a screw-fit or press-fit? If I were you, i'd find an alcohol-ready Tillotson HR carburetor. This will be better suited for what you are doing.
Old 04-08-05, 04:45 AM
Join Date: Jan 2005
Location: Texas
Posts: 478
Check the float. If hollow check to see if it has gas in it.
Old 04-08-05, 07:26 AM
Join Date: Jan 2005
Posts: 80

I had same weeping problem with my 8HP Brigggs carb. I had to adjust float to put a little more pressure on the valve. Not much, just a touch.

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