12 Signs You May Need to Rebuild Your Dirt Bike Engine

When is the right time to rebuild your dirt bike engine? As we all know, prevention is better than cure. If your motorcycle has got high hours on it, rebuilding today will 100% save you money and time in the long run even if the engine is still trucking along. A seized engine will cost a bucket load. And if that happens while you’re on the track, then it becomes even more expensive and it can also be a safety issue if it locks up while riding.

That said, the below list should help you diagnose when a rebuild is due before it is too late. We have listed the top 12 signs you should watch out for to determine whether your dirt bike engine needs a rebuild:

1. Trouble starting your engine

This could be due to several reasons. There might be issues with the spark plug, stale or dirty fuel, ignition or other electrical problem, cam timing might be off, worn-out valves, piston rings, or your gaskets may be leaking.

2. Low engine power

Aside from possible worn-out engine parts, a sudden lack of power could also be due to blocked injectors or carburetor jets & passages. It is also a good idea to check your air filter in case it is dirty or blocked.

3. Noisy piston

If your piston or top end starts making a rattling noise a replacement might be over due. Also check valves, cam chain, etc if you have a 4-stroke.

Complete or Top End Rebuild kits are an cheaper way to get the parts you need when rebuilding your bike.

4. Noisy bottom end

A noisy bottom end is not good. You could first check the clutch basket ensure the clutch basket and hub nut in tight. It can also be the crank, main bearings and connecting rod that are in need of replacing.

5. White Smoke

If you notice white smoke your engine could be burning coolant. That usually happens when a head gasket is leaking.

6. Blue Smoke

Smoke that is blue generally means you're burning oil. That may be because of your worn piston and rings, or your valve seals are leaking.

7. The engine is consuming oil

Your 4-stroke dirt bike may be telling you it's time for an engine rebuild if it's using more oil than usual. It may be due to worn rings, valves, or seals.

Pro tip: You can also check for clogged, pinched, or blocked crankcase breather tubes. If the breather tube is any of those three, the excess crankcase air won't be able to escape, and that may be the reason your engine consumes and burns more oil.

8. The engine oil is milky

When this happens, it usually means that coolant is leaking into the engine oil. Although small amounts of moisture in the oil is not a concern, too much of it might be a sign of a leaking water pump seal.

9. The engine is vibrating too much

Check frame bolts are tight. This has got me a few times and I thought the engine was about to explode. If the nuts are loose, re-tension. If they are all tight the vibration is still there it may be something more sinister such as a crankshaft being out of balance or a loose/worn clutch basket.

A bottom end rattle may be from a loose clutch hub nut. A slipping clutch while riding is also a sign of worn clutch plates.

10. Metal in oil

Take note of how your bike's oil looks while you're draining it. Paying attention here can save you hundreds (or thousands) of dollars. Regular oil changes are a must. You should also change your oil after an hour or less of a new engine break-in. Small metal flakes can appear during an engine break-in. And if you see larger pieces of metal, you should definitely be concerned.

11. Low compression

If you think your dirt bike is getting easy to kick over, it’s probably not because you’ve gotten stronger. 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.

12. The water pump is leaking

Most water cooled bikes have a "weep hole" located on engine case or near the water pump. If coolant starts dripping out of it, it usually means that the water pump seals and possibly the shaft need replacing.

Most of the above issues can be avoided through general servicing and regular maintenance such as replacing oil & oil filters as well as air filters. After reading the above list if you need any engine parts such as a piston kit, valves, cam chains, crankshaft, or gaskets, you can find them from the Firestorm Motorcycles.