I would suspect a worn belt.
With the age of the machine, the pulleys have probably worn some amount too, increasing the slop in the belt.
Can you adjust the belt tighter than spec's?

I actually have been wondering exactly that; the clutching idler pulley is set about halfway out on its track and it could certainly be pushed all the way out, thought it would be set where the brake/clutch pedal is well forward of upright. Might make sense to try that? It really does seem loose. Saw a post elsewhere on checking the drive belt tension, I think, that it should move freely by hand with brake/clutch engaged but not when released? Or maybe it was the other way around. Belt seems ok but it IS old. Wondering if it's ever been changed at all. I will take a closer look at again it tomorrow eve when I have a chance next and maybe try that to see if it solves the problem. Then put a belt change on the list of things to do, anyway, if it does. Unless there is no harm in running it that way?

This post was edited by kssue on Sat, May 11, 13 at 2:06

Does your owner's manual give you any adjustment information?

rcbe, yes, it does; I have already adjusted the belt to manual specs: it instructs to depress brake/clutch, set parking brake on third notch, loosen clutching idler pulley and slide outward to tighten belt; release pedal to check position (should be straight up and down), depress again and set parking brake, tighten pulley, and re-check position. The pulley is about in the middle of its range of motion back and forth on the adjustment track when the pedal is upright as specified but this setting did not improve performance much. My first adjustment all the way out to the side away from the engine pulley caused the pedal to be forward at about a 45 degree angle, so readjusted to specs. So wondering if I should just tighten it all the way and see if it helps the drive issue, which would seem to point to a loose belt ?

I wouldn't tighten it "all the way", at least not to start.
Tighten it "more" and see if performance improves.

Makes sense. I did have that thought since "all the way" limits the range of motion in the pedal. I will try it tonight and see if it helps. Will follow up to let you know. Thanks.

Made the adjustments Sat night but now I can't get the dang thing started to see if it helped; something's amiss. Looks like I may need to start a new thread to figure it out but just to throw it out here since it's the same machine and MIGHT be related:

First off, the starter gear has to be manually engaged to the flywheel by turning it til it rises up to the flywheel teeth before turning the key to crank the starter, because something inside is not making it come up to engage the flywheel when you turn the key. Usually it will turn the engine over just fine from there but the engine will not fire up until you move the throttle to RUN from CHOKE. But it DOES fire slowly at first, then runs. So now all of a sudden, it is barely firing (a couple pops at most) and then the starter gear drops down and spins (ie does not turn the engine flywheel) as soon as it starts to fire, making me think it is not firing enough times to catch and run.

So next question: does this sound like a starter problem (it has started the engine just fine several times so far this season), or possibly not enough current from the battery to the starter (battery has been put on a charger a couple times and may also be due for bi-annual replacement), or a fuel/air system problem? It seems to be getting fuel just fine; pulled and cleaned the plug and the wire head contact (which was rusty inside) to be sure it was getting good spark. So could also be the wire itself. The plug was somewhat fouled which also makes me wonder about ANOTHER oddity just recently noticed; hubby thinks it may be throwing oil when running because I have topped the oil off several times this season and it's always low next time out. But no sign of leaks underneath anywhere. WTH. It does not seem to be burning oil; no smoke when it runs. I have already run it several times this season and other than the drive issue haven't had any trouble til now...

On the starting issue my gut feeling is the starter and/or the battery needs replacement again. Obviously the starter is not working right but it HAS been functional enough as described to get it running until I can afford a new one. OK, shoot me down now...

I am really just trying to get an idea of the likely culprit(s) to start on so I don't end up replacing everything before I solve the problem (unless that's needed). And then when I can get it started i can return to the original issue of drive power. grr.

I suggest downloading the IPL for your engine from the Briggs website.
It's educational, at a minimum.

Your starter drive isn't engaging properly.
This could be caused by a couple reasons.
The starter has to "spin up" fast for the drive to move into the "engage position".
IF the battery is very low, starter motor bad, drive parts "gummy or burrs" or the drive being simply bad could cause this.
I don't know how easy it is to get to, but you could try cleaning/lubing the drive mechanism. (spray in some WD-40 or similar?)
The drive itself isn't too expensive.
Google-
Briggs 490421

Are you talking about the starter drive? I have replaced a couple parts on two different starters; this one is fairly new and had to replace the gear once already. The vendor sent me the gear for no charge but had to figure out how to change it myself. Thank goodness for Google. But it was h**l getting retainer on the cap (or whatever it is called) off the top because I lacked the proper tool. But did suspect there was something going on with it when it failed to move up into engage.

The starter is conveniently on the side of the engine; shroud's been off since I began having starting problems a couple seasons ago so maybe it IS a dirt issue. I have tried WD-40 in the past on a different starter so that is certainly an easy option to try. Basically the shaft just spins very rapidly when you turn the switch; I really think it's getting enough current but might look into that too. I will take a look at the starter diagram again; if the driver is not too expensive it might be worth wrestling with it to replace.

What does IPL mean? I do have the engine service manual and parts diagrams and lists that I downloaded from Briggs a couple years ago so likely already have it. They are what have enabled me to work on this mower at all since I'm not exactly engine or even mower literate. Very useful and informative. PL= Parts List?

Illustrated Parts List

Duh. The "I" simply escaped me.

Good news. A few shots of WD-40 alternated with cranking the starter did free up the starter drive and the gear started popping up on its own, and eventually stayed up long enough to crank the engine sufficiently to start. So booyah there.

And, back to the original issue, adjusting the belt a little tighter than specs DID improve the drive performance, significantly. May tighten it a little more since it was still struggling little on moderate inclines but a definite improvement from previously. Thanks for the pointers and advice.

[BTW Bill, do you have KS relatives? There are some well-known Kapauns around here...]

Mine are out of NDAK, by way of Bohemia.
Maybe a few generations farther back?
Not the most common name-

I assume you are talking about Chaplain Kapaun?

Yes, Father Emil Kapaun I think...my hubby went to Kapaun HS in Wichita, named for him I think, before it became coed with the girls' school Mt Carmel. I know, it ISN'T a common name but I don't know the family history that well myself. I'm sure hubby's family does, lol...there is a Kapaun descendant living in AZ, a friend of ours, too. Small world, eh! You've GOTTA be related somehow... :) Thanks again for your help.

A school named after me:)

LOL yep...it's the Kapaun Mt Carmel (KMC) Crusaders...14 of my 20 nieces and nephews went there! Along with their parents... :D

This post was edited by kssue on Tue, May 14, 13 at 10:49