Will Dirt Bike Start Without Oil? (Don’t do it!)


Dirt bike

Your Dirt bike is pretty tough, but it won’t run for very long without engine oil.

A dirt bike will start without engine oil, however doing so risks severe engine damage to bearings, piston and cylinder.

In this post you’ll learn why engine oil is so important. I’ll also cover the top 3 reasons a dirt bike won’t start and what you can do to fix it.

Engine Oil

A 2 stroke or 4 stroke dirt bike engine will start without oil but will cause major engine failure. Some higher end bikes may be fitted with a low oil level fail safe sensor, which prevents engine starting.

Oil is the one fluid your dike can’t live without. Your bike will start without oil, but doing so risks destroying the motor.

As your engine operates, it creates friction which becomes heat. If engine heat isn’t managed, it simply becomes so great that the metal components like bearings, rings, piston and cylinder fuse together and seize.

Oil is the main player when it comes to managing engine heat. Fresh oil is important as it coats components and making them super slippery. Bearings and rings ride on a film of oil instead of metal on metal.

Without oil the metal on metal friction would kill your motor within minutes.

But oil does more than cool and lubricate, detergents in the oil help keep your engine internals free from contaminates associated with combustion. Detergents break down harmful acids and carbon deposits.

Old Oil

Engine oil is the one fluid you’ve got to get right. The type, quality and quantity is important.

Using the recommended oil in your motor is best advice, as your engine maker has likely tested the engine and determined the optimum grade oil for performance and longevity.

Old oil loses it’s ability to cool, it becomes diluted by gas and overcome by harmful acids. Changing your engine oil regularly is the one maintenance job that pays off big-time, oil is cheap, an engine rebuild isn’t.

Oil Quantity

And finally quantity, having too little oil in the motor causes the oil to over heat and reduce its ability work. Almost as bad is having too much oil in the engine, which is a very common occurrence.

Too much oil reduces crankcase splash and the oil can become aerated, which has the effect of reducing oil coverage on crucial components.

2 Stroke & 4 Stroke Engines

Dirt bike engines come in 2 flavours, two stroke and four stroke, both need oil.

A four stroke uses engine oil the same way as a car, but in addition a four stroke dirt bike engine oil works even harder as the engine oil also lubricates the transmission.

A 2 stroke does engine lubrication differently, it mixes specially formulated 2 stroke oil with the gas to manage engine friction. The ratios are very precise and must be respected, mixing too much or too little oil can and cause some serious engine damage.

Incorrect two stroke mix can also prevent your engine from starting. Too much oil can foul the plug, too little and the engines risks damage.

Two stroke dirt bike transmissions are lubricated separately using transmission oil.

Checking Oil

Checking the oil is a 5 minute job. You’ll need a clean rag, funnel and some top up oil. Some dirt bikes make this really easy, they fitted a sight glass on the crankcase cover. The oil level should be at the very top of the glass.

The following guide is for a regular dipstick style:

  • Park the bike on level ground
  • Allow engine cool if running
  • Locate dipstick
  • Clean around dipstick
  • Remove stick and clean
  • Reseat dipstick without threading in
  • A reading in the hatched area is ok, but at the top mark is best.

Top Dirt Bike No Start Reasons

There may be many reasons why your dirt bike won’t start but oil generally won’t be the cause, unless your engine has actually seized. For the purpose of this guide, we’ll assume your engine isn’t.

Firsts off you’ll need oil in the motor, your engine not starting might just be a blessing in disguise.

Here we’ll list all the easy to check stuff before we get into the top 3 causes of dirt bike no starts.

Check the following:

  • Choke on or primed
  • Gas in tank and petcock on
  • Spark plug wire firmly on
  • Air filter clean and air way clear

The top 3 reasons a dirt bike won’t start include:

  1. Old gas in the tank
  2. Gummed carburettor
  3. Contaminated spark plug

1 Old Gas

Bad gas is a persistent issue and that’s because dirt bikes are left idle more than not. Old gas goes stale, regular after 3 months and blended after about a month.

How to fix it?

If you suspect your gas is old, go ahead and drain the gas tank and the carburettor gas bowl. Fill with fresh gas and crank her over, job done.

2 Gummed Carburettor

This is a little more work. It too is caused by old gas, but the difference the gas has evaporated and left behind a sticky gum that blocks up the pilot and main jets. The jets feed gas to the engine and with these guys blocked, you’re going nowhere.

How to fix?

You’ll need to remove the carburettor, dismantle and clean thoroughly, either in an ultrasonic tank or using carb cleaner. You’ll notice the difference with a clean carb but you will likely need to tune the AFR afterwards, it’s not difficult.

Contaminated Spark Plug

A fouled plug is common too, as you know too much gas can flood the plug. A wet or oily plug won’t generate a spark strong enough to ignite the fuel mix.

How to fix it ?

Try waiting twenty minutes, cranking it over with choke off and throttle held wide open. This helps dry out the cylinder.

Removed the plug, check the plug gap as per spec, a closed gap won’t spark. An oily plug will need to be removed and cleaned, or better, replaced.

John Cunningham

John Cunningham is an certified mechanic and writer on ATVFixed.com. I’ve been a mechanic for over twenty years, I use my knowledge and experience to write articles that help fellow gear-heads with all aspects of ATV ownership, from maintenance, repair to troubleshooting.

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