Q. How should I break in my new engine or cylinder kit?
First off, you will probably never get everyone to agree on a break-in procedure. It can be a topic of great debate. That said, here are some of my opinions regarding engine break-in :
- If the scooter is stock, hopefully you've already done a PDI including unsealing the carburetor if necessary. Whether your engine is stock or modified, have the carburetor ready with jetting somewhere in a range that you believe will be appropriate. It's hard to know without tuning, but hopefully you'll end up with something close enough to work for a few miles.
- Have tools handy to adjust the idle mixture and speed before the engine is started. If accessing the screws requires removing body panels, have a plan that allows you to ride right after adjusting. I often leave off any non-essential panels such as side fairings and just make sure the seat bucket and all wires, cables, etc... are secure.
- Start the scooter and let it warm up for maybe 5 minutes. As it warms up, adjust the idle speed and mixture screws so that you get a smooth idle and the engine isn't trying to cut out. It doesn't need to be perfect at this point. When it's good enough, secure whatever you need to in order to ride.
- Take the scooter out on the road, track, large parking lot, or wherever it's safe to ride it with minimal traffic. You'll be riding in a strange manner, so it's not a good idea to have any traffic behind you.
- Begin by giving it about 1/2 throttle for a few seconds, then letting it decelerate on it's own. Repeat this a few times.
- Do the same thing, but now at 3/4 throttle a few times.
- Use wide open throttle (WOT) for a few seconds now, again letting off and letting the scooter decelerate on it's own. Repeat a few times.
- With a new engine or cylinder kit and no real carb tuning done I'd head back at this point, or I would have turned around about halfway through the process to head toward home. If you are riding after this, vary throttle position so you don't hold one speed or RPM for very long.
From there I would work on getting the tune dialed in with WOT passes and different jets. Give it at least 20 miles of varied throttle riding before riding it however you usually would.
For four-strokes, I change the old oil after the installation of a cylinder kit so you drain out any debris that may have made it's way into the crankcase. If the scooter is new, the oil should be changed as part of the PDI process. Then I'd change the oil after about 20 miles. Again around 100-200 miles. Again by 500 miles. Then I stay with my usual 500 mile oil change intervals. Stick with conventional non-synthetic for the first 500 miles, or more if you'd like. At very least use it for the first oil change. Some don't change oil as often, some use synthetic from the start... again everyone has their own preferences. Magnetic drain plugs are good for break-in (and full time use). They can really show you how much metal is worked off and you can also see how it tapers off on subsequent oil changes.
Some prefer to use richer pre-mix ratios for breaking in two-stroke engines, or they may add a cap full or 2T oil to their tank for oil injected models. I use the same pre-mix ratios that I normally use. For two-strokes I also use the same synthetic oil for break-in that I use any other time.
You may wish to check the head bolt torque after your first rides and tuning as well. Sometimes it doesn't change, but sometimes the gaskets will compress after the engine has been ran for a bit. For four-strokes, check the valve clearances while you've got the valve cover off.
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