800 special stumbling idle

[zeke83 2]

I have a 1970 800 special with a 8hp briggs that has had a problem with the idle and sometime while mowing. The motor revs up and down at low and high rpm, but gets better when there is a load on the engine....mower deck running.

It just started to do it one day, so i drained the gas and put in fresh 93 octane. It smoothed out for a while. But it started to do it again. Now it is starting hard and will not idle down low like it used to.

I pulled the fuel line off and plenty of gas is coming though, so the filter is not clogged. Its getting plenty of spark, and the air filter is clean.

The only thing I can think of is that there is something in the fuel pump. The muffler came loose one day and melted the pulse line to the pump. I took it apart, but did not see any blockage

This is not just a little problem, because even the wife came out of the house and asked why it was running like that haha

Thanks for the help

[zieg72 209]

There is something in the carb that is causing that to happen. Sometimes you can clear it by applying full choke to a full throttle and just before it dies unchoke it. I have to do that to mine every so often,

[zeke83 2]

Thanks zieg, but I did try that already with no help

Something else I should add is if I hold the throttle on the carb, it will run fine. Otherwise you can watch it bob open and close.

[Fordiesel69 271]

The gov is hunting because the engine is natuarally falling in RPM so the gov opens the throttle. The gov gear is VERY sensitive!

You have a carb issue. Or you have an intake air leak.

[MarkPalmer 81]

This is the common symptom of blockage in the main jet nozzle or debris on the jet needle. The detergents in the 93 octane was able to clear it for a little while, but it started blocking again. The carb needs to be removed and taken apart for a good thorough cleaning.

-Mark-

[zeke83 2]

Thanks guys

I'll clean her out tonight and hopefully fixes the problem.

[DeWayne 1]

The governor is the problem. Look on the lower block on the muffler side and you will see a lever that attaches to the linkage. Use a break down diagram and you will see where the spring(s) will go. Some BS use one while others use more depending on engine function. Some may have a long thin spring going from said level to the carb linkage. Examine diagram(s) carefully.

[Fordiesel69 271]

If 93 octane solved the prob temporarily, the GOV is not the issue. But yes, your springs need to be correct, and cannot be disconnected or broken.

[zeke83 2]

Where can I find a diagram?

[TT-(Moderator) 1,162]

Unless I missed it, was an attempt made to adjust the mixture screws?

Sometimes just a little twist in either direction will make a huge difference.

[DeWayne 1]

Diagrams of parts layouts are in great supply on the net. You do need correct reference to your model number usually found on the cover of the engine. It's stamped in the housing in many cases near the spark plug. Look up the information and do a Google for a diagram using that info. It's worked for me in the past.

[zeke83 2]

Unless I missed it, was an attempt made to adjust the mixture screws?

Sometimes just a little twist in either direction will make a huge difference.

If the mixture screw is on the bottom of the carb next to the air intake, then yes I did. Tried many small and large adjustments, but nothing helped