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Small Air Cooled Gasoline Engines Briggs & Stratton, Clinton, Lauson, Maytag, Nelson, Wisconsin and other small air cooled engines. Sub forums for mowers, scooters and powered eqipment.

Small Air Cooled Gasoline Engines

Briggs Stratton Model 8


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  #1  
Old 03-24-2019, 09:06:04 PM
Grit Grit is offline
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Default Briggs Stratton Model 8

I知 working on a Briggs and Stratton Engine Model 8.

I started it up last night and noticed a couple things that I have questions about and hoping someone can help me out with.

I知 noticing the muffler is turning red hot.
Fuel is coming up thru the gas cap and gas tank bolts on top.
The carb seems to be leaking from the needle valve. I noticed the threads in the carb look like they are damaged ( probably from a screwdriver)

I知 assuming I値l need a new carb assembly if the threads are damaged but a thought I壇 ask these questions. I知 getting into restoring these small engines to keep me busy. So I知 sorry if these are stupid questions.
Thanks in advance!!!!
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  #2  
Old 03-24-2019, 10:11:15 PM
radiodoc radiodoc is offline
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Default Re: Briggs Stratton model 8

The muffler may be partly restricted not allowing the exhaust gases to freely escape. May need to replace the gas cap or check and replace it's gasket. As for the leaking around the needle valve, the packing may need to be replaced. Others on here may be more familiar with this engine and can better help you. Allie
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  #3  
Old 03-24-2019, 10:57:03 PM
K-Tron K-Tron is offline
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Default Re: Briggs Stratton model 8

If your engine has the tank I think it has, the two bolts which hold the tank in place are self tapping. It is possible that someone tightened them to the point that the threads are now stripped. If the threads are good, back the bolts out and use something like loctite 567 thread sealant and re-assemble. Your muffler could be glowing red hot because it is wrong, too restrictive or the valve timing is off. When setting the valves on a model 8, you will have to carefully grind the stem of the valve down for proper clearance. If the clearance is excessive, either replace the valve of cut the seat deeper. If the clearances are too far off from factory the engine can hold in heat too long. There is no such thing as a stupid question when it comes to antique engines. You have come to the right place.

Chris
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Old 03-25-2019, 12:05:56 AM
Grit Grit is offline
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Default Re: Briggs Stratton model 8

The muffler was turning red so I took off the muffler and started the engine. You were able to see flashes don稚 really want to say flames. I was going to replace the muffler.

The gas cap could be replaced. The bolts are not self tapping just regular bolts. I can try the loctite.

The carb leaking seems to be my biggest problem.

I値l check the valve, I cleaned everything but I didn稚 remove the valves.

I appreciate the suggestions, keep地 coming.
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Old 03-25-2019, 08:03:20 AM
Ed Radtke Ed Radtke is offline
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Default Re: Briggs Stratton model 8

check to see that the points plunger isnt worn down causing late ignition timing.also set points to .020".a wide gap will cause late timing.
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Old 03-25-2019, 09:26:19 AM
Andy Williams Andy Williams is offline
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Default Re: Briggs Stratton model 8

about the muffler i think some mufflers just do that they way they are made we had an old tiller with a b&s vertical shaft engine and when running fast it always got red, not really noticeable in day, it ran for years like that. it shouldn't at idle or slow speed. also i've seen tractors that the pipe or muffler was red at night sometimes see a flame coming out.
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Old 03-25-2019, 02:05:56 PM
batrider batrider is offline
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Default Re: Briggs Stratton model 8

My 1968 generator has a Model 8 engine running at 3600 rpm and I noticed that the muffler would get red hot - visible at night especially. I was able to adjust the carb mixture slightly (richer) so it didn't do that.
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Old 03-25-2019, 05:07:17 PM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: Briggs Stratton model 8

Recap" Major causes of a 'hot' muffler -
1) worn valve and or seat - improper seating of the exhaust valve. Have a look at the guide too
2) improper valve clearance.
3) ignition timing not set correctly Point gap .020" Plug gap .025"
4) blocked cooling fins. Make sure there is no debris around the valve area
5) restricted or worn muffler. By worn I mean that the muffler body is eroded to the point where it is very thin. Be sure to use one of the tubular mufflers, not the round ones with a bunch of 1/16" holes in the face
6) be sure you do not have the carburetor set too lean. Too lean and you will burn the exhaust valve and may damage the piston. Start and warm engine. Set on high speed and back out high speed mixture screw until the engine either begins to double stroke (miss) or smoke black. Turn in mixture screw until either the engine just runs smoothly, or the black smoke stops. Alternative, set mixture for best running and then back out the mixture screw 1/8th turn. If there is an idle mixture screw, set for best idle
7) make sure to replace the gaskets and gas cap. If you have the carb that attaches to the tank, take a fine file and dress the top of the tank so it is flat. If the tank bolts ate tightenned up too much, they may pull the threads out of the tank, making it hard to seal.
8) Make sure the fuel adjuster packing is in good shape. if it leaks, the carb may suck air past the adjuster causing a lean condition. If you cannot get a new packing from B&S, you can use a graphite impregnated packing from a good plumbing supply.
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Old 03-25-2019, 09:16:41 PM
Grit Grit is offline
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Default Re: Briggs Stratton model 8

- I値l check the valves
- I値l check the gaps
- In going to purchase a new muffler, the one that is currently on the motor is pretty worn.
- I cleaned the carb and installed a carb rebuild kit but like I said before when I noticed gas dripping from the needle valve I really stopped running the engine. You mentioned the packing are you saying I use the packaging around the needle valve????
- this might be helpful for everyone to one the motor starts right up with the choke closed but as soon as I open the choke the motor starts dying out. Also on bottom of the carb near the needle valve there is a small hole I noticed smoke coming from that hole. Normal?????

I really appreciate all the help.
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Old 03-25-2019, 11:33:35 PM
EvilDr235 EvilDr235 is offline
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Default Re: Briggs Stratton model 8

If I were you I would find a Factory Briggs service manual to guide you in your quest. I have found over the years that a factory manual has the best information. I have found most aftermarket manuals do not have enough information pertaining to a single model of engine. In aftermarket manuals they try to squeeze info on a dozen different model engines in the small book. eBay has manuals and Briggs books listed on the site all the time. And most modern manuals have more current info not related to the antique stuff we work on. Most repair parts are available. Gaskets, carbs, carb kits, tuneup parts, mufflers, rods, pistons, seals, rings and valves can be found on eBay or from dealers on this site. If you plan on keeping your engine, it's a good idea to pick up a parts engine or two.
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Old 03-29-2019, 02:52:38 PM
Ogrebeast64 Ogrebeast64 is offline
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Default Re: Briggs Stratton model 8

Shoot me your email via PM. I have a Model 8 and a PDF file manual that covers all types of the model 8 I can send to you.

https://www.youtube.com/watch?v=F3O9...y&index=6&t=0s
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Old 05-27-2019, 12:14:51 AM
Grit Grit is offline
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Default Re: Briggs Stratton model 8

Sorry it’s been awhile, finally got back to working on the engine. Finally got the engine running but I have a hell of a leak from the carb
( underneath ) I’ve rebuilt the carb ( Briggs & Stratton parts ) including the float, adjusted everything. I hear people say make sure the float is adjusted ( done ) and the nozzle is tight ( done ). What am I missing????
This carb has been gone over several times. Anything else??? I seen somewhere on line I wish I can remember where this person said you should use the metal tubing for the gas line instead of rubber hosing. Is this true??
I need help, thank you !!
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Old 06-02-2019, 01:41:54 PM
Ogrebeast64 Ogrebeast64 is offline
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Default Re: Briggs Stratton model 8

I shot the manual I have to you. On my model 8, someone had packed horse hair all around the main needle jet, as well as on the sediment bowl shutoff valve. Needless to say, it all disintegrated when taken apart for cleaning and rebuild. Fortunately, the rebuild kit I got for the small Flo-Jet carby also included new packing for the main needle valve.

EDIT: Also on mine, if I try to use full choke, it results in an immediately flooded engine. Also using the standard initial settings, the engine ran FAR too rich and flooded out. I think I have the mixture screw now set about a half a turn open and it runs fine, without spewing gas out the weep hole on the bottom. My main needle valve did have a leak, but I slowly tightened the nut around it until it stopped leaking. BTW, the copper tubing is better for the fuel line from the tank.
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Old 06-02-2019, 10:22:59 PM
Grit Grit is offline
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Default Re: Briggs Stratton model 8

Got the manual, thank you!!! Seems like mine runs good and doesn’t leak when the choke is closed. I’ll get the copper tubing on mine, can’t hurt. So basically it sounds like a flooding issue than a leak issue.
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