When to Rebuild Your 2-Stroke Top End

May 11, 2017 / by Laura Antenucci

Two- stroke lovers rejoice at the simplicity and low cost of rebuilding their top ends. But, are you asking yourself, when should I rebuild my top end? How do I know when it’s time to rebuild? So many people wait until it’s too late. This can make the job a lot harder and more expensive. We’re going to give you some tips to help you determine the best time to refresh your top end. As always, consult your bike’s service manual for recommended service intervals specific to your vehicle.

I don’t remember/ don’t know when my last rebuild was.

Suggested rebuild intervals are based on ideal conditions. These ideal conditions include regularly scheduled routine maintenance like air filter and spark plug replacement. If you don’t know or are unsure of the service history of your bike or ATV (maybe you just bought it from the guy down the street who may not have been the best at routine maintenance), it’s probably a good idea to put a fresh top end in so you can start from zero. Don’t forget to include an hour meter to track the time on your new top end and to plan service intervals specific to the manufacturer’s suggested routine maintenance schedule.

How you ride

A full-on race bike or quad takes much more maintenance than your weekend warrior. Many race vehicles are refreshed at strict intervals to ensure top performance. Your recreational bike won’t need to be refreshed at such a strict schedule, but it may also be a little lax on routine maintenance. Do a compression test to determine the condition of your top end. You’ll know where to go from there.

Intake Maintenance and Condition

Lax air filter maintenance can wreak havoc on your top and bottom ends. A dirty air filter starves your engine of air and can let unfiltered air in. You know that dirt and mud you’re riding through? That is now potentially in your engine and can damage the cylinder wall. When you see dirt in the intake, you’ll need to tear down the top end to check for damage. A damaged cylinder may need reconditioning or replating. The same goes for when you find your intake boot and airbox was not sealed properly. Anytime you find leaks, you’ll want to tear down and inspect for damage.

Sluggish Performance

Two-strokes are great and they can tell you when they need to be refreshed based on performance! You may notice your spark plugs fouling more often than normal or you find it’s just feels off. Doing a compression check can help determine the health of your top end. Or just simply tearing down to see what’s going on in the engine can help you determine if you need something as simple as a re-ring or going as far as refreshing the entire top end.

Grade of Fuel

Knowing the grade of fuel that fits your specific engines needs best can go a long way. Depending on the compression of your engine, you may be running fuel that is too high or too low in octane. Running fuel that is too low in octane for your engine can cause detonation.  If you do not have access to race grade fuel, it is best to always mix fresh fuel, purchased from a high-volume station. Most manufactures will recommend against a fuel containing Ethanol, those containing 10% or less are normally acceptable. Again, using fresh fuel is key, as any ethanol laced fuel tends to absorb water.

At the end of the day routine maintenance is key to keeping your bike or quad ready to ride. Your vehicle’s service manual is a great place to start to determine service intervals. Staying on top of maintenance can help you avoid unexpected, costly repairs to the top end.


Topics: featured, Powersports

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Laura Antenucci

Written by Laura Antenucci