Why is My Yamaha ATV Thumping on Startup?

If you hear a thumping sound when starting up a Yamaha Grizzly 700 ATV, what you’re experiencing might be the primary clutch in need of some re-greasing.

Partzilla’s Yamaha ATV expert John Talley hosts live Q&A sessions on our YouTube channel every Friday at 3pm Eastern. In this session, John was asked what could be causing a 2008 Yamaha Grizzly 700 to make a thumping noise on startup.

Yamaha Grizzly thumping noise grease clutch

Yamaha Grizzly Thumping Noise Q&A

I have a 2008 Yamaha Grizzly 700 and when I start it up at cold, it makes a little thumping sound in or around the clutch drive belt case. It’ll stop when I throttle it or after it warms for a few minutes. It’s not really bad, but I can hear it when I throttle it. Just wondering if the belt could be stretched a little and maybe slapping on the case. It doesn’t sound normal. What could it be?

John Talley: What you’re describing is probably the weights. They’re just little round hoops that are inside of the drive clutch. They more or less ride in a bed of grease, and over time all of the different deposits, and maybe you’ve got some water in there, start to turn that grease into plaster. And when it’s cold, those weights just get thrown around because the grease hasn’t really heated up to become grease again. So it sounds like that’s what’s happening to yours. Now, we did a video that shows you how to repack the Grizzly 700 primary clutch. So if you would, take a look at that and I walk you through it. It’s a messy job but you’ll be amazed how much smoother the clutch will engage once you get all that crud cleaned out of there, and pack it with the correct amount of Yamaha Ultramatic Grease.