Small Engine Governor Question

[Chris Lewis]

I have an early 70's Craftsman "Shredder Bagger" (chipper, model 917.285761) that has a 143.226032 engine (Tecumseh V60-70233H. Vertical shaft 6HP 4 stroke, "L Head" I believe).

Pretty good shape, not used in about 4 years.

After degunking the carburator, it starts first pull even when cold.

I had to remove the carburator/disconnect the governor
links. I don't think I buggered anything up putting it back together (ie: the links didn't get bent, they're _definately_ in the right holes).

Problem is it's running a trifle fast. I _assume_ it's supposed to be tuned to 3600 RPM. It seems to start out around 3800, and then slowly creeps up. Ie: 4000+ RPM after a few minutes.

No surging. Just smooth slow increase.

That's worrisome (the thought of those blades or a rod...).

So the assumption is that the governor either requires
adjustment or is borked.

I've gotten the Tech manual for it, but as I've not
had to fiddle with governors before, and I REALLY REALLY don't want to pull the crankcase apart to get at the internals, I was wondering if anybody might comment on the symptoms:

[If someone has the docs that say what the idle/fast
speeds on this specific model _should_ be, I'd appreciate that too!]

The governor arm (with the rod/spring linkage to the carb) is always "hard to" the "slow" side. If I gently move the arm counterclockwise (long arm towards the carb), the engine speeds up (even more). It has no travel CW (no movement right from dead vertical), and hence the governor _can't_ slow it down.

I haven't _yet_ tried to adjust the governor, I have to study the manual a bit more before that.

Does this sound like (just) an adjustment/external linkage issue, or would you think something inside borked?

I have no evidence (yet) that the internals will actually move the governor arm based on engine speed.

The governor linkage looks almost exactly identical to this:

http://www.small-engines.com/tvs.html (first one, upper left).

The only difference being that the governor clamp(? short arm) and link (long arm) is at the 6 oclock position instead of the 3 oclock position in the diagram.

[Think of the long arm as the minute hand, and the short arm as the hour ;-)]

The manual talks about swinging the clamp to 9 oclock,
but only with motors <= 5HP and made prior to 1977. It's 6HP, but I assume it was prior to 1977.

It's really not clear which way it should be from the manual, except perhaps I should be assuming that the diagram from the above link (they're from the manual) _is_ correct, and not that specific to TVM series. My carb is slightly different than the one pictured for the TVM. None of the other generator linkages come remotely close to mine.

 

[Chuck (archive)]

I have an early 70's Craftsman "Shredder Bagger" (chipper, model 917.285761) that has a 143.226032 engine (Tecumseh V60-70233H. Vertical shaft 6HP 4 stroke, "L Head" I believe).

Pretty good shape, not used in about 4 years.

After degunking the carburator, it starts first pull even when cold.

I had to remove the carburator/disconnect the governor
links. I don't think I buggered anything up putting it back together (ie: the links didn't get bent, they're _definately_ in the right holes).

Problem is it's running a trifle fast. I _assume_ it's supposed to be tuned to 3600 RPM. It seems to start out around 3800, and then slowly creeps up. Ie: 4000+ RPM after a few minutes.

No surging. Just smooth slow increase.

That's worrisome (the thought of those blades or a rod...).

So the assumption is that the governor either requires
adjustment or is borked.

I've gotten the Tech manual for it, but as I've not
had to fiddle with governors before, and I REALLY REALLY don't want to pull the crankcase apart to get at the internals, I was wondering if anybody might comment on the symptoms:

[If someone has the docs that say what the idle/fast
speeds on this specific model _should_ be, I'd appreciate that too!]

The governor arm (with the rod/spring linkage to the carb) is always "hard to" the "slow" side. If I gently move the arm counterclockwise (long arm towards the carb), the engine speeds up (even more). It has no travel CW (no movement right from dead vertical), and hence the governor _can't_ slow it down.

I haven't _yet_ tried to adjust the governor, I have to study the manual a bit more before that.

Does this sound like (just) an adjustment/external linkage issue, or would you think something inside borked?

I have no evidence (yet) that the internals will actually move the governor arm based on engine speed.

The governor linkage looks almost exactly identical to this:

http://www.small-engines.com/tvs.html (first one, upper left).

The only difference being that the governor clamp(? short arm) and link (long arm) is at the 6 oclock position instead of the 3 oclock position in the diagram.

[Think of the long arm as the minute hand, and the short arm as the hour ;-)]

The manual talks about swinging the clamp to 9 oclock,
but only with motors <= 5HP and made prior to 1977. It's 6HP, but I assume it was prior to 1977.

It's really not clear which way it should be from the manual, except perhaps I should be assuming that the diagram from the above link (they're from the manual) _is_ correct, and not that specific to TVM series. My carb is slightly different than the one pictured for the TVM. None of the other generator linkages come remotely close to mine.

Sounds like ,, when you reassembled the linkages.. something was turned 90 or 180 degrees from where it should be..

 

[Chris Lewis]

It seems much more likely it's just an adjustment problem, especially since you state that the governor is unable to move the throttle to the closed position. If you adjust it a little so it *can* close the throttle, you'll probably be all set.

I had a chance to work on it, and the situation is a little different than I thought. I adjusted the governor by the instructions in the manual (and those here - thanks!). It didn't change the motor's behaviour.

The governor _can_ pull the throttle plate all the way closed (and in fact it is closed all the way when running). When pulled all the way closed, the motor is _still_ running at over 3600 RPM.

It won't slow down to an idle either.

In other words, over 3600 RPM is the minimum speed.

The only way to slow the motor down is to starve it via the run needle.
The idle needle does nothing.

The state of the governor internals is still somewhat unknown, but, given that it runs so fast even when the throttle is closed all the way, it's probably fine.

The troubleshooting chart doesn't have symptoms that exactly match this, but, making some assumptions, this is probably due to air leaks inside the carburator - gaskets, needle seals, damaged needles, bowl seals, etc, bypassing the throttle plate.

Right?

I've bought a carb kit (various seals and replacement needles), plus the two gaskets between the carb and the engine. That, plus a more thorough cleanout should do the trick. I perhaps don't have to go this far, but, it's a useful learning experience ;-)

 

[Mark (archive)]

if the engine is running too fast with the throttle plate all the way closed, this is not a governor problem but rather a carb problem. Ther gov is trying to slow the engine down but the carb won't do it. You must have an air leak or some other problem with the carb. With the throttle plate all the way closed the engine should be at idle or less. You need to figure out hoe air and gas is getting to the eingine despite the fact that the throttle is closed.

Mark

 

[ds549]

is the round plate still on the throttleshaft inside the venturi, usually held by 2 screws.lucas.

 

[Chris Lewis]

is the round plate still on the throttleshaft inside the venturi, usually held by 2 screws.lucas.

I've not actually seen the plate (didn't have the elbow off the carb, and it's too dark looking t'other way in ;-), but I'm pretty sure it's there. Otherwise, the motor wouldn't speed up when I open up the throttle shaft.

In any event, I'll find out when I take it apart again soon.

 

[Chris Lewis]

While the engine is running, using the spray stem to localize the action, spray a small burst of WD-40 around the mounting gasket(s) area to see if it affects the engine speed. This will indicate a vacuum leak if it does. If you hold the butterfly shut on the engine and it is still revving high, you very likely have a vacuum leak between the butterfly and the engine valves. Check orientation of gaskets to see if one was placed back on incorrectly, thereby allowing air into the intake tract. Make sure mounting ears are not cracked. Start slowly blocking off the intake port of the carb with your gloved hand or a piece of cardboard, as some butterflies have a port hole in them. If this doesn't slow the engine, then you DEFINITELY have a vacuum leak, as the engine has to get it's air from somewhere to run.

I put my hand over the air filter intake, and was able to stall it. So, there wasn't an external leak. Took the carb apart, cleaned it, installed the "carb kit" and replaced the gaskets between the carb and valves.

Now it will idle. It's probable that my original problem was that the idle regulator screw (sets minimum throttle opening) was set _way_ too far in and held the throttle plate open too far, but I didn't understand the carburator well enough at the time to realize what I had to do. Now that I took the whole thing apart, I do now :-(

The engine hunts a fair bit at full speed but settles down after warmup. It hunts at idle even after warmup, and if I move it too far towards idle, it quits.

I think this will go away once it has a more formal/careful adjustment - especially the idle regulator screw. Unfortunately, the relevant Tecumseh manual doesn't appear to have anything to say about adjusting the idle regulator, other than an initial setting (one turn "back" from no longer contacting the throttle - I assume it's the full closed end of the throttle range).

I have all four screws to adjust properly (idle & run
mixture, run screw for the governor, idle regulating screw).

The governor arm is _clearly_ operating now.