Pushing a heavy mower isn’t fun, especially in a hilly yard. Most of my garden is hilly, there’s no way I could push it without the drive system.
So why is your lawn mower hard to push? The most likely reason a mower is hard to push is that the drive cable needs adjustment. Other possible causes include:
- Worn drive belt
- Damaged pulley
- Damaged trans-axle
- Worn wheels
In this post, I’ll show you how to adjust your own drive cable for free. This is an easy job and is most likely the cause of a hard-to-push mower. But I’ll also cover a few other possibilities.
If you need video help, check out “Mower self drive troubleshooting video”, it walks you through the diagnosing and repair of common mower self-drive problems including cable adjusting.
Poor cable tension – Below I’ll outline the main components of a lawnmower drive system and what they actually do. This will help your diagnosis.
As you know, your drive problem is likely poor cable tension, you’ll find the business end of this post “Adjusting drive” towards the end.
How a Mower Drive System Works
Mowers areas you know pretty simple bits of kit, the engine powers the cutting blade as it’s directly connected to the engine crankshaft, but how does the engine power get to the wheels?
Your mowers drive system comprises four main components.
- Drive belt
- Trans-axle assembly (incl. wheels)
- Drive cable
1 Crankshaft Pulley
The crankshaft pulley is dedicated to sending power to the trans-axle. It’s fitted right under your mower engine, fixed to the crankshaft, so when the engine is running the drive pulley is working. Pulleys usually have a plastic or metal shroud to help protect them from flying debris. Often the shroud comes loose, which allows grit and stones to hit the pulley causing damage.
Your pulley may or may not be visible when you turn your mower over. (always turn your mower over with carburetor side facing up – prevents gas spill and flooding)
Crank Pulley – Crank pulleys become brittle over time and a direct hit can cause them to break. This mower has lost its protective shroud which makes it a likely candidate for future crank pulley and belt issues.
2 Drive Belt
A drive belt is as its name suggests a belt that transfers engine power from the crankshaft pulley to the trans-axle. The drive belt is very similar in design to an automotive alternator belt. They are very often the cause of lots of mower drive problems. Symptoms vary, but a hard-to-push mower is high on the list.
Other symptoms include:
- Squealing noise
- Slow moving
- Slow to start moving
- Intermittently slow
- Hard to push
- Stops when hot
Drive belts are like car tires, they are expected to wear out and should be inspected at the beginning of each season. Belts will usually let you know what’s going on though, you may see cracking, peeling, or flat spots. A mower drive belt should be changed every third or fourth year depending on workload.
Drive Belts – The right belt is mission-critical, getting this wrong can cause even more problems. The missing shrouds are common and as you know it will cause debris to impact the belt and will shorten its life. Belt replacement is covered in the “Mower self drive troubleshooting video”,
Trans…..what? Is that even a real word? Mmm, I think so. A trans-axle is the name given to the complete assembly. That’s the transmission, differential, and axle combined into one compact unit. If you want to read more about lawnmower trans-axles, you can check out this post “What’s a lawnmower trans-axle?”
The trans-axle is the business end of making your mower actually move. It has a pulley fixed to the top of the assembly to receive the drive belt.
These pulleys are pretty durable but on some axles, they are made of plastic, you can guess what happens to them over time.
Anyway, the transmission component of the trans-axles unfortunately does usually wear out before the engine. Especially mowers that spent their working life laboring on a hilly yard. And the worse news is, mower manufacturers, don’t usually supply internal parts for the transmissions. However, they will sell complete transmissions. For some mowers paying for a new tranny and the labor to fit may not make economic sense.
Trans-axle – This unit has had a tough life, by the look of the dried grass, I don’t think she’s seen a lot of love.
A lawnmower trans-axle may be fitted to the front or the rear of the mower, making the mower either front or rear-wheel drive. Trans-axles are commonly lubricated at factories for life.
Leaking – Most mower transmissions are packed with grease and don’t leak. The grease is a lube for life, doesn’t require topping up.
As are the higher-end oil-filled hydrostatic transmissions. However, when the hydrostatic unit leaks, expect its replacement to be quite spendy.
Leaking units can’t be repaired.
Wear – Worn drive gears on axle and wheels. Check out “Mower wheel fitting video”.
Wear – Worn axle pins which cause a lack of drive. Pin replacement is covered in the “Mower wheel replacement video”.
4 Drive Cable
A good drive system requires control, you need the ability to progressively apply power. This is usually done by way of a control lever and a braided cable. Same type cable used on bicycle brakes. The cable pulls on a lever mounted on the transmission. The lever locks the transmission progressively, which causes the mower wheels to move.
As you can imagine, anything that prevents this lever from being fully applied will cause the mower to feel slow. This is the most common cause of a slow transmission and can fix in a snap.
Transmission lever – The cable is connected to a lever on the transmission. This lever must be fully engaged in order to have full drive power.
Adjusting The Drive System
And finally adjusting the drive system. This isn’t a difficult process, but there are a few tips you’ll need in order to get it right. It is covered in the pictures below. Your mower drive adjuster may not be identical to the one shown here, but that’s OK because the principle is the same.
Some mowers will have a tool-less adjuster, nice! makes life a ton easier. However most mowers will require tools, but not many, two vice grips or adjustable wrenches is all you need. If you’ve got some WD40, shoot it down the cable inner, you might need some eye protection, tends to splashback, Awkward? Yes, but worth the effort.
Locate cable – Locate the correct cable by operating the handlebar drive control lever.
Locate cable adjuster – Two types are common:
- An adjuster at the drive control lever bracket
- In line cable adjuster
Both types will have a lock nut, which prevents the adjuster from backing out. Simply open the lock nut by holding one nut and opening the other.
Open locknut – Back off the lock nut so as to allow plenty of room for adjustment.
Take up the slack – Adjustment is easy, our goal is to adjust the cable so that it moves further away from the drive control lever. Run it out a few turns, but wow, don’t tighten up the lock-nut just yet.
Reverse free? – This is an important step, if you over-adjust the cable, you’ll find the mower difficult (stiff) to reverse. If you have over-adjusted, not a problem, just back it off a few turns. I like to over-adjust and then back it off until I find the sweet spot, then I know I have reached max adjustment – make sense?
As a guide, with the drive lever pulled (as per pic) and mower pulled backways (engine not running here) the driven wheels (rear usually) should lock. If they don’t, you need to adjust some more.
If when dragging the mower backways, (this time the drive lever released) the driven wheels should move freely. If they don’t, back off the adjustment. This video covers it all – “Mower self drive troubleshooting video”.
Tighten locknut – When you are happy, tighten the lock-nut and you’re good to mow. Nice work you!
Is a self-propelled lawn mower hard to push? The most common cause of a hard-to-push self-propelled lawn mower is poor drive cable adjustment.