Lawnmower Self Drive Not Working-Help And Repair

Why Has My Self Propelled Lawn Mower Drive Stopped Working?

When my lawnmower self-drive stopped working I did some research to see if it could be repaired. Over the years I’ve learned all the tips and tricks that can help get it working again.

So, why has my petrol lawnmower self-drive stopped working?

The self-propelled drive on a petrol lawnmower will have stopped working either because the drive belt has snapped or the gearbox/transmission box has worn out or it could also be that the cable is not tensioned correctly or has come loose from the transmission box, or that the cable has a break in it.

If you haven’t serviced or cleaned your lawnmower for a while it could be something as simple as the transmission box engaging lever being fouled with debris.  It could even be that the cable has overstretched or pulled through the lawnmower deck.

You might even have a lawnmower that is stuck in self-drive? Replacing a transmission box on a lawnmower isn’t the easiest of repairs so it will be worth eliminating all these things first.

How To Check My Lawnmower Self Drive

So, how do I check all these things and where do I need to look? In this article, I will cover everything I check when deciding whether to repair or replace a lawnmower self-drive. On occasions, the cheapest/best option might even be to replace the lawnmower. But let’s see if we can resolve the problem in the next few steps.

You can find lots more information and start repairing lawnmowers for profit by checking out my online training here

Let’s take a look in more detail at how to diagnose the problem

Has The Drive Belt Snapped?

Remove the spark plug. Take a look underneath the lawnmower and see if there is a drive belt still connected. It’s usually a black belt that runs from the centre above the blade to the back of the lawnmower near where the grass box fits on. If it isn’t there its because it has been pulled off.

This is usually from attempting to cut grass that’s too long. Take a look in the grass box, you may find pieces of it in there. It will have been chopped up by the blade.  If you can’t see a drive belt because there is a belt guard in the way simply remove it and have a look.

This is a simple repair, just buy a new belt and replace it.

  • Note Tip the lawnmower carburetor side up with the exhaust towards the floor. Make sure you remove the spark plug first

What does the operating cable feel like?

When you pull the self-drive lever on the handle that in turn pulls the cable does it move far? Does it feel like nothing really happens or it’s spongy?

Years ago the self-drive stopped working on my Mountfield SP 470 petrol lawnmower, I thought the self-drive was broken for weeks and did nothing about it! One day I noticed about 20 cm down the handle that the cable was attached to an adjuster.

I loosened the 10mm nut and slid the adjuster down the handle a centimetre or so then re-tightened it. This gave me more movement in the cable and less slack. The self-propel was repaired and still works 15 years later!

This would be my first suggestion as I repair a lot of lawnmowers for profit where this is the problem! If the cable doesn’t engage the transmission correctly it won’t self-drive the lawnmower.

My Youtube Videos On Self-Drive Issues

I have some videos on my youtube channel covering self-drive issues. I thought it would be useful to include them here.

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What Condition Is The Self Drive Cable In?

What condition is the self-drive cable in? Does it have a break in anywhere on the outer plastic part? If it does there is a very good chance this is the problem. I have all too often seen attempted repairs using various cable ties and wire. It doesn’t work. Ever.

If the inner cable doesn’t slide through the outer cable, it will not operate the transmission box. Take a close look at the cable where the handle folds up for storage as often the cable gets trapped and damaged during the folding down of the handle.

Has The Cable Pulled Through The Lawnmower Deck

Take a close look at where the cable runs into the lawnmower deck. Follow it down from the top and be sure it’s the correct cable as one may be a brake cable or a throttle cable. You will see a hole on the top of the lawnmower deck where the cable goes into.

If you are having difficulty starting your lawnmower feel free to check out this article

There should be a rubber/plastic part where the cable goes through. If you just see a hole where the cable goes through (perhaps because the deck is rusty) the cable will not operate correctly.

If this is the case remove the spark plug and take a look underneath to see if you can slide the missing part back through the deck.

Does The Gearbox Work Correctly.


Without the lawnmower running stand behind your lawnmower and operate the self-drive lever. When you pull the lawnmower backwards the wheels should lock and skid back over the grass.

If you do this and release the lever on the handle the wheels should spin freely again. Usually, the transmission is broken or not operating when the wheels don’t engage when trying this.

Help! My Lawnmower Is Stuck In Self Drive!

This is a real pain. Chasing your lawnmower around the garden like Norman Wisdom isn’t anyone’s idea of a great time!

If your lawnmower is stuck in self-drive it’s most likely that the cable is not operating the transmission box correctly.

There is usually a spring on the back of the transmission box and if it gets fouled with grass and twigs etc it may not work properly. Remove the spark plug and take a look underneath at the transmission box.

Operate the cable and see if everything moves freely.

How To Check The Gearbox On A Petrol Lawnmower.

This is the last resort. Be sure you have read the advice given above and attempted to resolve the problem before attempting this. If you can, remove the engine from the lawnmower.

This procedure requires the lawnmower to be turned over so we have full access to the underneath. If you cant’ remove the engine then at least remove all the fuel and oil.

Remove the blade and belt guard and clear out all the grass and debris from around the transmission box.

Note. Now would be a good time to wire bush any old grass off the lawnmower deck.

Check the cable from the transmission box is connected properly sometimes there is a plastic connector on the end of the drive cable, make sure it is fitted correctly. Undo the screws surrounding the transmission box and pry open the box. On a lot of household lawnmowers, you will see two gears.

One of those gears is a worm gear, it may be metal and it may be  plastic. The most common cause I have seen where the transmission box breaks are where a metal gear connects with a plastic worm gear and over time wears the plastic worm gear away. Spin the wheels on the lawnmower by hand and operate the cable to see the gears connect and disconnect.

I regularly repair lawnmowers for profit. You can access a playlist of over 90 videos to learn from here.

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You should feel the wheels lock up a little as the gears engage. This will give you an indication of whether everything looks to be working correctly or not.

Engage the cable and spin the wheels,  you will see the gears connect and when you release the cable they should disengage when the cable releases. The wheels should now turn freely.

Note  Make sure all springs and mechanisms are free from obstruction.

If the gears have worn and you need to replace the transmission box, look for the service ticket on your lawnmower and contact your local lawnmower dealer or take a look at the recommended products page on this website.

Often the price of a new transmission box is the reason you may decide to replace the lawnmower rather than replace it or have it repaired. Depending on the make and model of your lawnmower prices vary rapidly but undertaking this repair yourself I would advise against unless you have a good mechanical background.

Tips And Advice For Buying A New Petrol Lawnmower With A Self Propel Drive.

All self-drive mowers will likely have a problem with the drive before anything else wears out on the engine itself. Personally, unless it’s absolutely essential to have a self-drive I would avoid purchasing one.

You can see my current recommendations of self-drive lawnmowers here

A lot of keen gardeners will opt for a self-drive mower with a rear roller as this gives the nice striped look after cutting. A word of advice for anyone following me repairing lawnmowers for profit, you will often see very expensive lawnmowers with heavy rear rollers for sale on eBay and facebook marketplace.

I would avoid repairing these for profit in the beginning as many will be sold as soon as someone thinks there is a problem with the transmission.

Other common issues are poor starting lawnmowers this can often be due to a problem with the kill switch. Check out this article

I have seen and purchased almost new looking honda mowers second hand thinking I’ve grabbed a bargain only to find the self-drive is either very slow or faulty.  Imagine the work the transmission has to do to power a heavy rear roller as well as the mower itself.

Check out my recommended parts page for all your needs.

My last advice is this. If you do wish to purchase a self-propelled lawnmower check out the cost of a new gearbox on each model beforehand.

You can find lots more information and start repairing lawnmowers for profit by checking out my online training here

Happy Mowing


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