Yamaha YFZ450 Starting Problems: Intake Smoke

Got a Yamaha ATV that won't start and smokes from the intake? You could have a timing problem on your hands, which means you may have to pull the valve cover and do a little digging. 

Our resident Yamaha ATV expert John Talley does live Q&A sessions on our YouTube channel every Friday at 3pm Eastern. In this edition, John was asked by one of our viewers about a starting problem with a YFZ40 that was smoking from the intake upon cranking it. 

Yamaha YFZ450 starting problems intake smoke

Yamaha ATV Starting Problems

My YFZ450R won’t turn on. It smokes from the intake when I try to crank it. Any ideas? 

John Talley: It almost sounds like it jumped timing to me. I think I’d start with that first. Take off your inspection caps at the crankshaft, bring it around to top dead center, maybe pull your valve cover and let’s make sure she didn’t jump time. That’s what it sounds like to me. If it’s spitting back through and she doesn’t want to start, she may have jumped a tooth. 

As John mentioned, bringing the engine to top dead center and checking the timing is a possible solution to our viewer's starting problem. In the video below, John did a complete engine rebuild for a Yamaha YFZ450 ATV, which includes a segment on how to remove the valve cover and find top dead center. 

 Buy valve train parts

 Buy Yamaha ATV starter motor

Watch the video below to see how to remove the valve cover and find TDC on a Yamaha YFZ450R.

Besides checking the timing, there are other ways to troubleshoot starting problems with a Yamaha YFZ450. In the video below, John takes you through some simple tests to diagnose ATV starting problems, including testing the battery, the main fuse, the starter relay and the starter motor.

Watch the video below to see how to troubleshoot starting problems with a Yamaha YFZ450R.

Want to see more live repair questions answered? See more motorcycle and ATV repair questions answered here.  

 
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