# [SOLVED] Briggs and Stratton Intek V twin sputtering under load



## Badger7

Help. I'm having issues with my Briggs and Stratton 20 hp V twin running rough under load. The details of the engine are as follows.

Purchased 2002 (Scotts mower)
150 hours
Model 406777
Type 0128 E1
Code 020409YG

This engine has been well maintained but has had a backfiring problem I since the first year I owned it. I never did anything to address the backfire, but now I wonder if it is related to the more severe issues I'm having now. The engine starts fine and runs well at high speed when just driving, but any time the mower deck is on, it runs rough (sounds like it misses). It also seems to have a slight and occasional miss at idle when it is cold. Things I have checked or changed are as follows.

New Air filter
New spark plugs (helped the problem, but didn't solve it)
Cleaned carb
Checked coils/wires with spark gap tester (spark jumps .250" gap)
Set valve clearance
Checked flywheel key (seemed straight, but I did not pull it)
check fuel delivery, everything seems good there.
Checked compression (126 psi one side, 140 on other), I thought this was okay.

After changing the spark plugs, the mower was usable again, missing only occasionally. I did notice that one of the plugs was full of soot and the other was not. I used the mower after changing the plugs and it got progressively worse, running rough under load, and belching black smoke under load. After using for only a few hours, the new plugs were black, with one full of soot again. I change the plugs again, and it runs a little better again. The cylinder with the excessive soot build up is the cylinder with the higher compression pressure. 

Thanks in advance for any help you can provide is solving this issue.


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## Badger7

*Re: Briggs and Stratton Intek V twin sputtering under load*

Although I didn't get help here, I thought I would share the solution in hopes of helping someone else. The problem was in the carb. The carb is a Nikki and the "jet" is located in a strange spot. This two barrel carb has only one jet and it is located at the bottom of the fuel bowl where fuel from the bowl first get pulled from the bowl. The issue I had is that there is an o-ring seal down stream of the jet that sits in fuel 100% of the time. This oring was deteriorated and the seal had failed. Under heavy fuel draw, fuel from the bowl was bypassing the jet and the carb was running rich. Briggs changed this design on later model years.


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## Basementgeek

*Re: Briggs and Stratton Intek V twin sputtering under load*

Thanks for letting us know. Much appreciated.

BG


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