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Original Post: Riding Mower Lack of Power

slimshaky Member

I have a Simplicity Regent (2690437) riding lawnmower with a 20hp briggs intek v-twin engine. It is currently displaying a lack of power and the engine does not sound like it is running smoothly. In regards to the power, pressing on the accelerator pedal results in the mower moving forward more slowly than it used to. I'm not an expert in engine noises, but the engine is perhaps making a bit of a pinging or misfiring noise.

So far this season, I have changed the oil, changed the spark plugs, and replaced a worn drive belt. However, none of these seemed to make a difference to the lack of power. I did also confirm that both plugs are sparking, although I am not a great judge of how strong the spark is.

Pilot Dane Group Moderator

Are both cylinders firing?

When you replaced the spark plugs what did the old ones look like?

slimshaky Member

How do I know if both cylinders are firing?

The ends of both plugs were black and at least one of them looked to have some oil on it. I did decide to check the oil level at that time, and it was within the ideal zone.

BFHFixit

Make sure your choke is operating correctly.

slimshaky Member

In terms of the choke, I can confirm that opening and closing it does make a difference in engine operation, as I do have to adjust it every time that I do a cold start on the mower. Am I correct in assuming that this would be a good indicator that it is working properly?

Pilot Dane Group Moderator

Is the exhaust smoking? If so, and with the oil-covered spark plug, I would put a blown head gasket on the list of potential causes.

slimshaky Member

I think it does smoke a bit when I first start the mower but not after that.

Pilot Dane Group Moderator

Check for sparks at both cylinders. If both have a spark I would look for other signs you might have a blown head gasket. If that's it, it's a pretty inexpensive repair.

geogrubb Member

I don't see where it was ever confirmed the engine was running on both cylinders. Start it and remove one spark plug wire. If the engine tempo changes/starts to miss, then that cylinder is firing. Then try it on the other cylinder. Have a good one.

Geo

slimshaky Member

Thanks for the detailed instructions. I have now confirmed that the engine is running on both cylinders.

slimshaky Member

Is there something that I should check with the head gasket next? I will say that I am not noticing a constant smoking like I saw in several videos that demonstrated symptoms of a failed head gasket.

Pilot Dane Group Moderator

Do some reading online. There are many different symptoms like smoke, fouling spark plugs, oil on spark plugs, more than the usual amount of oil blown up into air filter housing.

I don't recall you mentioning changing the air filter. Have you done that? A clogged air filter can rob power.

slimshaky Member

The air filter looks a little dusty, but not too bad by my eye. I fired up the mower, let it run for a minute, and then removed the air filter. It made no difference in terms of how the engine runs.

slimshaky Member

Someone that I know recommended doing a compression test. I did that earlier today and found that the left cylinder (as I sit in the driver seat) has 140psi. The right cylinder has 130psi. Does that sound reasonable for this type of engine? I don't think I previously mentioned this, so the engine number is 406577.

cheese Forum Topic Moderator

Those numbers are great. What color is the smoke? Have you checked the valves and their adjustments?

slimshaky Member

I double-checked again to be certain on the smoke item. When I first start the mower, there is a decently strong exhaust smell, but no smoke at this point. Perhaps this is pretty normal.

I have not looked at the valves. Do you have a recommended video or instructions for that?

cheese Forum Topic Moderator

I'd start by removing the valve covers and making sure the push rods and rocker arms are in place and not loose.

slimshaky Member

This is another demonstration of my ignorance on this topic, but after investigating further, it turns out that the noise that I was hearing and thought was coming from the engine is actually coming from the transmission area. After doing some further research, I am looking into changing the transmission oil.

In addition, I have noticed that there is another belt that has the beginning of a tear in it. I'm planning on replacing it. The part number is 1728008 with a description of "V-BELT, Drive Belt, Aramid/Kevlar". I don't know if this is normal, but I also notice that it is quite loose.

Obviously, the noise from the transmission doesn't explain the oil that I saw on my spark plug earlier, but perhaps it is the source of the mower's reduced power.

slimshaky Member

You folks probably already know this, but maybe it will be helpful for someone else to read. The belt is the transmission drive belt. It appears that this is loose when the parking brake is on, but then tightens up when you release the parking brake.

To read the rest of the thread, look here: https://www.doityourself.com/forum/outdoor-gasoline-electric-powered-equipment-small-engines/594241-riding-mower-lack-power.html

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