Why?
Staying on top of engine rebuilds is important to ensure your dirt bike continues to perform as it should while also preventing major engine failure that can cause costly damage or worst case an accident while out on the track or trail. All manufacturers will provide a rebuilding schedule in the owner’s manual of when you should be rebuilding the top and bottom end of your bike and we always recommend sticking to the numbers given. Dirt bikes are high performance machines requiring unique maintenance intervals and unlike a car, they are generally ridden hard and ridden in some treacherous conditions!
Rebuild times provided by your manufacturer are a guide as there are plenty of variables involved in our chosen sport. These include riding conditions, how the bike is ridden, air filter maintenance, the quality of oil used and more! All of these if abused can drastically reduce the lifetime of your engine and in turn make rebuilds more frequent, so it is extremely important to carry outyour routine maintenance to stick to those rebuild times as much as you can.
Two Strokes:
Usually, there are a few ways to tell when a two-stroke needs to be rebuilt - a noticeable loss of power, lack of compression or it has reached a certain amount of hours where a rebuild would be appropriate. It’s also important to keep in mind that if you’re running your two-stroke on the lean side, it may need more frequent rebuild intervals.
When rebuilding the top end the general time frame is every 25 hours however like we said earlier every bike is unique and rebuild times also vary with engine sizes. A KTM 50 or a fire breathing CR500 will have totally different rebuild times so we always recommend checking your owner's manual for the most accurate intervals!
The bottom end of a two-stroke can usually last around 70-80 hours before rebuilding. It’s always advised that when you rebuild the bottom end to also rebuild the top end. Tell tail signs of a bottom end about to let go is a rattly, noisy engine or heavy vibration through your handlebars or again lack of power and drop in compression.
Four Strokes:
A four-stroke has slightly different intervals between rebuilds, the top end is generally rebuilt at the 25-30 hour mark if you’re a regular racer, and more importantly on a 250F, which is typically ridden more aggressively. On a 450, or if you’re riding the bike under an ‘easy’ load, then rebuilding the top end between 30-40 hours will be adequate. Again these are just a guide and you should always follow your owner's manual.
The bottom end on a four-stroke engine can typically see 100 hours of life, however, to be on the safe side, most riders will rebuild it at approximately the 80-hour mark or sooner. Again, when you’re rebuilding the bottom end, always rebuild the top end and throw in a new piston at the same time. It’s also always advised to check your valve clearances every time you tear the engine down.
Takeaways:
Check your owner's manual for the accurate service intervals between rebuilds for your bike! Stay on top of other routine maintenance items like oil changes and clean air filters to get the most out of your dirt bike. However, when rebuilding your bike it is a perfect opportunity to give it a birthday by replacing coolant, spark plugs, air filters, engine oil, oil filter, and muffler packing to keep your bike in the best running condition. When rebuilding your engine make sure you replace your gaskets and o-rings or head gaskets in your cylinder head because there's nothing worse than having to do it all again because of a gasket or o-ring.
FAQs
Four Strokes:
How often should you rebuild a 450? ›
If you're a regular racer, and especially if you're riding a 250 four-stroke, then you'll want to rebuild your new top-end between the 25-30 hour mark. If you're riding a 450, or riding the bike under an easy load majority of the time, then you'll want to rebuild the top-end between 30-40 hours.
How long do dirt bike engines last? ›
4-stroke engines generally last for a maximum of 500 hours if they are well-cared for and ridden casually, and if they're used for racing or heavy-duty off-roading they'll wear out more quickly. Many riders consider anything over 100 hours to be at risk for breakdown.
How do I know if my dirt bike needs a top-end rebuild? ›
If your compression is low the top end will need checking. Common causes are a worn piston, rings, cylinder, or valves or shims. Low compression or hard to start can be signs of worn valves.
When should I rebuild my engine? ›
The usual reasons for rebuilding an engine are loss of compression, excessive oil consumption, or excessive oil clearances. The symptoms of loss of compression are extended cranking (hard to start), lack of power, or a misfire (running rough).
How often does a 2 stroke dirt bike need to be rebuilt? ›
Dirt bikes come in many different types and sizes and are used in a wide variety of uses that radically affect rebuild times. For example: Race-prepped 2-strokes suggest rebuilds in the 10s of hours. Generally 2-strokes need top-end rebuilds more frequently than 4-strokes.
Is 150 hours a lot for a dirt bike? ›
If you're a dirt bike enthusiast who casually drives the motorcycle from time to time, 100 hours is considered high hours. But, of course, this still depends on many factors like maintenance and use.
How many hours does a KTM 450 last? ›
I think a good 350/450 with a good quick local rider will be fine for 100 hours based on what I have seen both in the UK and Australia. Even a 250f with an intermediate vet rider would be hard-pushed to need a top end before that. i had a 22 ktm 350sxf and it had to get a new top end twice by the time i hit 62hrs...
What lasts longer 2 stroke or 4 stroke? ›
While 4-stroke engines perform well and generally last longer than 2-stroke engines, 2-stroke engines are faster and lighter than 4-stroke engines. The 2-stroke engine is more powerful, but a 4-stroke is more fuel-efficient.
Is 500 miles on a dirt bike a lot? ›
Generally speaking, 500 miles is not a lot on a used motorcycle. Some bikes like touring models are built to last over 100,000 miles, and even bikes with low mileage like dirt bikes can last about 20,000 miles. In the grand scheme of things, 500 miles isn't a lot of mileage on a bike.
When you are using all OEM parts, which includes all new bearings throughout the engine, a cylinder head (reconditioned or new), new valvetrain, new crank, new piston, new cam chain and tensioner, and a freshly honed cylinder, the cost comes out to be between $1300 and $1500.
How many hours till a dirt bike needs a rebuild? ›
If you have a two-stroke engine, you know you need to rebuild your bottom end when you notice you're not getting the amount of power you used to or when you've reached between 70 and 80 riding hours. For four-stroke engines, rebuild your top end between 80 and 100 hours of riding use.
How long does a dirt bike piston last? ›
Piston replacement intervals are typically outlined in your machine's factory service manual. Using dirt bikes as an example, many manufacturers outline a piston and ring replacement schedule of every six races or 15-30 hours for a four-stroke, depending on the machine.
How many hours will a 450 last? ›
The key is frequent oil changes and a clean air filter. A well maintained 450 ridden by a fast motocross guy will easily go 60 hours on a topend (piston,rings, timing chain).
