My 129 loses power while mowing (for at least the first hour)

three4rd · #1 08-25-2017, 08:13 PM

Hi,

Perhaps it's more due to an area of grass/weeds that is a bit thicker than other parts of my lawn (although I've been mowing the same stuff for years), but what has been happening is that, first of all, the tractor starts a bit hard. The ACR system should be working cause I checked and the springs are attached. Anyway, once it starts, it doesn't sound right - as though the power strokes are not as close together as they should be. I have to run at higher throttle than usual. Then, when I start mowing, the engine slows way down as I start going through the higher grass. I have to go on the brake, let the RPM come back up, then can go again. All this necessitates mowing at a much slower pace than usual. Sometimes it seems like it's almost going to stall. However, once I'm going for close to an hour - everything seems fine and the engine sounds normal, and I can back off the throttle a bit. Granted that the rest of lawn - after the first hour - is not as thick as the first section I mow, but still, something just doesn't seem right.

Any thoughts or suggestions appreciated. The engine is undoubtedly due for overhaul since it does take a good amount of oil, and so could that be the main problem? I've done some carburetor adjustments but that didn't seem to really help.

Thanks,
Keith

dale c. · #2 08-25-2017, 08:58 PM

check the points run a piece of emery cloth through them till they clean up then gap them at .020

john hall · #3 08-25-2017, 09:36 PM

After listening to all the preaching here on OCC, I started setting the points by the book with an ohm meter and it makes a difference cranking as well as running. Do yourself a favor and look up setting the timing (static) in the service manual section or search the forums for how to. The hard part is finding the timing mark if it is rusty--its a little aggravating but well worth it in my opinion.

Terry C · #4 08-25-2017, 10:47 PM

Quote:

Originally Posted by three4rd

Hi,

Perhaps it's more due to an area of grass/weeds that is a bit thicker than other parts of my lawn (although I've been mowing the same stuff for years), but what has been happening is that, first of all, the tractor starts a bit hard. The ACR system should be working cause I checked and the springs are attached. Anyway, once it starts, it doesn't sound right - as though the power strokes are not as close together as they should be. I have to run at higher throttle than usual. Then, when I start mowing, the engine slows way down as I start going through the higher grass. I have to go on the brake, let the RPM come back up, then can go again. All this necessitates mowing at a much slower pace than usual. Sometimes it seems like it's almost going to stall. However, once I'm going for close to an hour - everything seems fine and the engine sounds normal, and I can back off the throttle a bit. Granted that the rest of lawn - after the first hour - is not as thick as the first section I mow, but still, something just doesn't seem right.

Any thoughts or suggestions appreciated. The engine is undoubtedly due for overhaul since it does take a good amount of oil, and so could that be the main problem? I've done some carburetor adjustments but that didn't seem to really help.

Thanks,
Keith

Why do you back off the throttle when the engine seems better. Run that thing full bore anytime you mow. Once I engage that clutch I go to full throttle and never back off till I'm done. Trust me you won't hurt it.
If it's using lots of oil obviously you need a rebuild. Burning oil leaves deposits so maybe you should pull the head and scrape the carbon out, flatten the head and put a new gasket in. Might buy you a little time. Just a suggestion.

three4rd · #5 08-25-2017, 10:51 PM

Quote:

Originally Posted by john hall

After listening to all the preaching here on OCC, I started setting the points by the book with an ohm meter and it makes a difference cranking as well as running. Do yourself a favor and look up setting the timing (static) in the service manual section or search the forums for how to. The hard part is finding the timing mark if it is rusty--its a little aggravating but well worth it in my opinion.

I'd gladly do it if I had any idea how to! I know I replaced the points awhile back as part of a total electrical system overhaul, but I'd need a refresher on where they are first of all, and needless to say I don't have a timing light. Thanks anyway. I'm sure your suggestion is great.

three4rd · #6 08-25-2017, 10:52 PM

Quote:

Originally Posted by Terry C

Why do you back off the throttle when the engine seems better. Run that thing full bore anytime you mow. Once I engage that clutch I go to full throttle and never back off till I'm done. Trust me you won't hurt it.
If it's using lots of oil obviously you need a rebuild. Burning oil leaves deposits so maybe you should pull the head and scrape the carbon out, flatten the head and put a new gasket in. Might buy you a little time. Just a suggestion.

OK...so how do I go about 'pulling the head'? My dad overhauled the engine many years ago, but I wasn't involved in the work at all to see how it was done. Let me guess...I start by taking out the spark plug...and then... ???

three4rd · #7 08-25-2017, 10:53 PM

Quote:

Originally Posted by Terry C

Why do you back off the throttle when the engine seems better. Run that thing full bore anytime you mow. Once I engage that clutch I go to full throttle and never back off till I'm done. Trust me you won't hurt it.
If it's using lots of oil obviously you need a rebuild. Burning oil leaves deposits so maybe you should pull the head and scrape the carbon out, flatten the head and put a new gasket in. Might buy you a little time. Just a suggestion.

I know they are supposed to be run full throttle, but I've always been afraid that it's taxing the engine pretty hard at that full RPM.

three4rd · #8 08-25-2017, 10:55 PM

Quote:

Originally Posted by dale c.

check the points run a piece of emery cloth through them till they clean up then gap them at .020

If the points and timing, etc. are responsible for the loss of power, why does the engine run better after I'm mowing for about an hour? Wouldn't a messed-up timing cause a constant problem?

john hall · #9 08-26-2017, 07:37 AM

Quote:

Originally Posted by three4rd

I'd gladly do it if I had any idea how to! I know I replaced the points awhile back as part of a total electrical system overhaul, but I'd need a refresher on where they are first of all, and needless to say I don't have a timing light. Thanks anyway. I'm sure your suggestion is great.

Go here http://www.onlycubcadets.net/forum/s...ead.php?t=4646
Then to page 8.2, read section on static timing. Note that on page 8.3 it tells the timing is the same for battery and magneto ignition systems.

three4rd · #10 08-26-2017, 11:41 AM

I'll check out the manual. I'm pretty sure I still have the feeler gauge for gapping the points - diid it when I helped to overhaul the electrical system several years ago.