How To

How To Get the Yamaha YZ250F and YZ250FX To Start Quickly

Tips on getting your quarter-liter four-stroke YZ to fire in a hurry.

August 29, 2022

In a Grand National Cross Country (GNCC) or any other race with a dead engine start, getting your bike to fire as quickly as possible is a huge priority. The 2019-2022 Yamaha YZ250F and 2020-2022 Yamaha YZ250FX are notoriously difficult to start, so we went to one of the best GNCC and general off-road mechanics in the business, AmPro Yamaha’s Corey MacDonald, to learn his secrets for getting the Yami to fire up fast.

The 2019-2022 Yamaha YZ250F and 2020-2022 Yamaha YZ250FX are often difficult to start, which is a huge disadvantage in a race with a dead engine start. AmPro Yamaha’s Corey MacDonald gives us a few tips on how to get the quarter-liter four-stroke YZs to start quickly and reliably. His first piece of advice is to switch to a battery with a few more cranking amps than stock, such as Antigravity Batteries’ AG-801.Shan Moore

First off, to help the YZ250F and YZ250FX start faster, MacDonald advises switching to Antigravity Batteries’ AG-801, noting that it provides a few more cranking amps than the stock battery. “I saw where Kawasaki did a big announcement when Eli Tomac rode with them saying they were using the AG-801,” MacDonald mused. “[I’m] not sure what battery [Monster Energy Yamaha] Star Racing uses, but if they run Antigravity, it’s probably the AG-801; it just fits really well in the Yamaha. Some people have tried to use their 10-cell battery, but it won’t fit in the F models. That’s why everyone picks the AG-801, but it’s a huge difference from stock.”

MacDonald told us that it’s important to set the idle to around 1,900–2,000 rpm while the bike is in gear, noting that the idle changes from when the bike is in neutral to when it’s in gear.Shan Moore

MacDonald also said it’s critical to set the idle to around 1,900–2,000 rpm while the bike is in gear. “Don’t set the idle when the bike is in neutral,” he explained. “You have to put the bike in gear, whatever gear you are starting in, because when you put the bike in gear, it actually puts a different setup into your throttle body. It’s like a ‘race mode’ and that changes when it’s in gear. If you listen to the idle, pull in your clutch, and put it in gear, you’ll notice it will actually change. So that’s where you want to set your idle at, when your bike is in gear.”

It will take some practice and trial and error, but the AmPro Yamaha technician said there is a sweet spot on the throttle opening. Opening the throttle to around 3mm of a turn is where the YZ250F and YZ250FX fire up best. Anything more than that and it will flame out, according to MacDonald.Shan Moore

The throttle setting is also critical. “The 250F is very sensitive to where your throttle is open to,” MacDonald continued. “You can just give it a slight twist; it could be a hair and that thing will fire. If you go over a hair, it will flame out and then the bike doesn’t like to start at all. A quick fix for that, if you’re in the woods and it flames out like that, [is to] hold your kill switch for five seconds. That resets everything and it will start fast again. We’ve actually tried different things. We’ll hold the kill switch and it will time out everything.

“A lot of it comes down to practicing starts, finding that sweet spot in the throttle setting [where it opens], and marking your grip. If you go to the GNCCs and look at Mike Witkowski’s bike, or any of the 250s, there will either be a notch or a piece of tape pointing where that sweet spot is on the throttle opening. You roll the throttle back to that spot and it starts. It takes a lot of trial and error, and practice starts to find it.

“That’s the biggest thing with the 250s, but once you find it, mark it and [the bike] will start every time. It’s all about trying to find that sweet spot in the throttle. Just guessing, I would say it’s most likely around 3mm [of throttle opening] at max, so start experimenting there. [If] you go anything past that, you’re going to get a flame out, for sure.”

Last of all, MacDonald, who is regarded as one of the best off-road mechanics on the East Coast, emphasizes that the clutch needs to have enough play so that even when it gets hot, there is no chance of it grabbing.Shan Moore

The amount of play in the clutch lever can make a difference as well; you don’t want it on the verge of grabbing. “You want a little bit of play, but a lot of people roll the clutch out to get it a lot more where the plates are separating,” MacDonald noted. “Paul Whibley, when we went to the starting line, even when we were waiting for them to introduce the riders, he never wanted to release the clutch when we were sitting there. Someone always had to hold the clutch [lever] in so the plates never made contact. If he had to go to the bathroom or whatever, I would hold it.

“He did not want the plates [to touch]… they would be hot and they were separated. That was when we still used a kickstarter and he could still start faster than most people who had electric start. Paul was so in tune with his motorcycle. Every day he practiced riding and practiced starts at the end of the day. It was just a thing he always did. That’s what made him such a phenomenal guy on the bike. He would also look at his throttle. You [would] always see him look down. He’d find that sweet spot every time.”