Briggs governor & carb question

[Steve Kraus]

I have a generator with an 8 HP Briggs & Stratton engine about 15 years old and hardly used. I have two problems.

I seem to be unable to completely eliminate gas seepage from where the two halves of the carb meet. In this last attempt I tried polishing away any nicks, and using a new gasket with Permatex on both sides. Still have some seepage. I don't know what else I can do. Fortunately it's a very small amount and wouldn't prevent me from running it if I need to.

The other issue I'm having is that it's not holding speed very well as I test it with varying loads. And I think it's because I've done something wrong with the springs.

Here's the basic setup:

The governor arm emerging from the engine is connected by a wire rod to the throttle near the top of the carb. A spring attached to the end of the gov arm pulls downward and the speed adjust screw controls how hard that spring pulls. Adjusting that move the plastic block in the metal plate (the ?? in the photo). Not sure the point of that but maybe it's used in other engine applications.

In this side view I've moved the plate away a bit and you can see the spring referred to above. Here's the part I can't remember. There is a fine wire spring wrapped around the throttle rod. The top end is bent into a hook shape that presumable must loop around the throttle shaft. But where does the bottom (bent into a small hook shape) go? To the gov arm? To some part of the plate shown? If the top does indeed go around the throttle valve shaft it can't be exerting any force there but I guess it could be pulling on the governor arm. I'm not sure how that makes it more senstive to speed regulation but it's there for a reason. Anyone know for sure how this should be?

[jacko]

[Steve Kraus]

Ah that's interesting; thanks. The float and valve seemed to work ok when I tested it but maybe I need to bend the little tab on the float so the valve closes sooner.

[trainfan1]

Adjust the float, & replace/renew the valve & seat as needed.

Adjust under load to 3600 rpm. Adjust the fuel mixture valve first, then the governor.

Rob

[Steve Kraus]

Yeah that I've done. I'm looking at the frequency of the output and it dips when I apply loads. If I adjust and bring it back up to 60 Hz then it goes higher when the load is removed.

[Meat Plow]

If it's not frequency compensated the frequency is going to dip under load. How much does it dip? How are you monitoring?

[Don Young]

Some governor linkages have small springs that do nothing except keep the slack out of the linkage. This seems to mainly be to prevent wear at the pivots from vibration.

All simple governors such as those will allow the speed, frequency and voltage to vary somewhat with load. Some instructions say to set the governor for around 125-130 volts with no load and the voltage generally will not drop below about 105-110 volts at full load. The frequency is less important as it is not accurate enough for clocks to keep good time anyway and motors tolerate 55-65 Hertz without any problems.

You can sometimes increase the governor sensitivity to keep the speed closer by changing the linkage, but you are likely to cause surging at some load point if you do. Remember that the only way the governor knows to increase the fuel at full load is because the speed has dropped somewhat. If it gives enough fuel to bring the speed fully back to where it was, then it will cut the fuel back to where it was. These governors do not sense load so they can only work on speed variations.

Hope this helps. Don Young

[trainfan1]

It seems you've solved your problem.

Are you running synchronous motors with security application issues?

If not, then you are being too critical. The engine should run at 3600

+/- 10% throughout the LOAD range.

Rob

[Steve Kraus]

Maybe a Hz or two with a couple of kW load. (It's rated 4.4 kW, 6 kW peak.)

DMM on the generator output.

I know the regulation isn't going to be as tight as a utility but I recall it used to be much better and in any case I still need to know where to attach the bottom end of that fine spring. I would presume it's there for a reason and maybe finer regulation is part of it.

[Steve Kraus]

Perhaps but I recall it as being better in the past and since I've got a governor-related spring that I'm not sure where it should be hooked up it's not unreasonable to think these are related. Or at least I should get it back to where it should be before deciding 'ok, this is as good as it gets.'

[Stormin Mormon]

The spring that regulates the governor is a very precisely made spring. If it gets a trace of rust or corrosion, it doesn't do its job. I'd suggest to find, purchase, install another OEM spring for that governor.

I took a small engine repair course years ago, that was one of the things that was taught. When a small engine varies in speed, that's called "hunting" and it's generally a bad governor spring.

[Steve Kraus]

Wow...that could well be the case here because if it's hooked up the way that seems obvious (around both ends of the linkage) it's not exerting any force that would affect anything so maybe it is just for vibration control. Thanks.

[Steve Kraus]

Interesting; thanks.