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Discussion Starter · #1 ·
I have a 8.5HP Briggs that has not been run for a least three years. I pulled the carb and thought I gave it a good cleaning. I cleaned the tank and replaced the fuel line. Engine cranked right up but has a strong surge to it. When I close the choke the surge goes away but then it starts loading up. It surges under load and with no load. There is no difference with the filter on or off. I can hold the governor arm steady and the surge goes away and the engine runs fine. Question...Is this governor related or carb related. Thanks
 

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Hi oldgrasscutter, and welcome to the group. Like your screen name.

Does it continue to run, although surging, or doe is sputter to a stop? If it stops, take a look at the gas cap, and make sure the vent is clear. If it's plugged up, gas won't flow to the carb.

Otherwise, if it sat for that long, I'm going to guess the carb is still the issue. Try cleaning it again using cleaner from a spray can, and really shoot it through all the openings. I'm a supporter of the idea of shooting cleaner in the reverse direction of the flow of the gas coming into the carb, if that makes sense. Follow up with blowing compressed air through all the carb's orifices, if you have an air compressor.

You might scroll down this page and maybe find the carb you're working on for some tips on how to disassemble and clean it.

Small Engine, Lawn Mower, Snowthrower Troubleshooting, Repairs and Safety

Hope that helps. Let us know how it goes.
 

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Most of the time its carb related, by the way, Welcome to MLF! I don't know if you replaced all the replaceable parts or just disassembled, cleaned and reassembled. You probably have blockage or a vacuum leak at a gasket. Three years, I would get a rebuild kit, completely disassemble the carb, soak the carb in a good carb cleaner like GUNK or Berrymans or similar product, blow out every orifice with compressed air and reassemble by manufacturers recommendations. Make sure you check for excessive play in the choke/throttle shafts. If they are loose with side to side play you'll need to replace them to unless the body is worn then you you would need to replace the whole carb. The shafts are usually brass and can be replaced though. Make sure you replace the base gasket as well, some kits do not have them and that could be a bad place for a vacuum leak.
Let us know how it goes!
 

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Discussion Starter · #4 ·
Thanks, This is a great forum full of some real good stuff. I've ruled out the gas cap and I guess the next step will be going back into the carb. I did not put a kit in the carb.
My concern is how well the engine runs when I hold the governor stable. It's as smooth as it gets, but let go of the arm and the surging starts back.
Anyway, thanks for the advice.
 

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No problem, let us know how it turns out, you'll be surprised what a small vacuum leak will do whether its from a leaky gasket or worn throttle shaft. We'll be watching out for your update!
 

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Discussion Starter · #6 ·
Well here is a update. I went back through the carb. I cleaned, blew and cleaned again. I was unable to get a kit anywhere local so I'll get one online.
Long story short it runs a lot better. There is still a slight surge at full throttle and it seems to hunt a lot at idle. I think to kit will get me back to normal. Thanks for the help........Oldgrasscutter....
 

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You can try richening up the carb a little (backing out the mixture screw(s)) a bit as sort of a temporary fix. It will have the same kind of affect as it does when you close the choke a little and the surge goes away. Most of the time engines like this come with a very lean setting from the factory anyway, so richening it up a little is not going to hurt it.
 

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Well here is a update. I went back through the carb. I cleaned, blew and cleaned again. I was unable to get a kit anywhere local so I'll get one online.
Long story short it runs a lot better. There is still a slight surge at full throttle and it seems to hunt a lot at idle. I think to kit will get me back to normal. Thanks for the help........Oldgrasscutter....
Thanks for the update, I'm glad the re-clean helped out a bit. I think you'll find with the kit it will help even more. Make sure you get the base gaskets if they are not included. Did the throttle and choke shafts look OK with no side to side play?
 

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Discussion Starter · #9 ·
Well, here is a update. I found a kit (new float, needle, all gaskets). Got it installed. Both throttle and choke shafts are tight. Still had a slight surge at WOT and it is still hunting at idle (from 1700 RPM to as high as 2900 RPM).
Governor is correctly adjusted. This set up a a very thin spring running along the throttle shaft from the governor to the throttle valve. I increased the tension on the spring and the high speed surge is gone. I still have the idle hunting problem. I'm getting close!!!!!!! Thanks, Oldgrasscutter
 

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Discussion Starter · #12 ·
Final update on the surging 8.5. The surging has been corrected and this baby runs like it's new!!!! Turns out it was partial problem with the carb and partial problem with the governor.

The throttle control adjustment was way out along with the idle mixture. After getting these two things back to spec's and a new kit in the carb, she's running great! Thank you,Five Points, BWD BRN 1 and Austen for the input and advice. I'm on to the next project!
 

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Good deal! :)
 

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Glad to hear it! Now, could you come over to my place, I've got a Kawasaki that's not wanting to co-operate with me.:D
 
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