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Discussion Starter #1
Hi All,

I have a 2019 Yamaha Grizzly 90cc that was bought for my kids. I understand it's mechanically the same as the Raptor just different plastics so hoping someone here can help me out.

The ATV has been used only a handful of times and was great for the first half dozen rides but the last 2 times out, it stalls non stop. It started at the end of a long day out riding. It was slightly above freezing and it was ridden about 4 hours that day. Did great until the end of the ride then stalled out non stop all the way home. I wondered if the puddles my son was riding though eventually had an effect on the motor. I checked the air filter and it had a bit of moisture but nothing overly alarming. A bit of moisture in the airbox but nothing pooling.

I brought it into a Yamaha Dealer and they apparently looked at the carb and fuel filter etc and found nothing abnormal and said it ran fine for them.

Took it out again with my son and it stalled out non stop. Probably about 100 times total.

It did fine for the first 10 mins then started acting up. It idles fine and if you press the throttle slowly, most times it would rev up nicely but occasionally, it just bogs and dies. Applying throttle faster from idle increases its odds that it'll stall out. I pulled the air filter foam out completely (which was cleaned before today's ride) and it still stalls out the same way so not related to air filter itself.

I'm not mechanically minded so not sure what to do considering the Dealer said they found nothing wrong with it but still charged me to look it over it. Not sure what my next play should be but was a very frustrating day with this thing which has no more than 10 hours on it.

Thoughts? Could it be spark plug? Anything else that I can check myself that would be easy potential fixes before I pay someone to have a second look? It did seem to stall more while going through water even though non of the puddles were deeper than 8 inches or so.

Thanks.
 

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Welcome to the forum.

So what was temp when brought into the dealer? Cold air does affect carbs, but yet it ran fine until the end of the day is what is weird. Any funk in the gas tank filter? Is there an in line filter on those?
 

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I may be getting older, but I refuse to grow up!
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Check the gas cap vent, air in, none out. Also, drain "ALL" the gas and put in fresh.

Does that have a 'pull kill switch tether in the back? Be sure the contacts are clean.

Take a water bottle with a sprayer and with the motor running, start spraying the electrical, carb, air cleaner, etc. You may find a bare wire or loose connector.

Take it back to the Stealership and ride it around their parking lot till it fails. Then make sure they refund your money and apply it for the warranty repair.

WELCOME TO THE FORUM.
 
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Discussion Starter #4
Welcome to the forum.

So what was temp when brought into the dealer? Cold air does affect carbs, but yet it ran fine until the end of the day is what is weird. Any funk in the gas tank filter? Is there an in line filter on those?
They kept it at the shop for almost a week so not sure what the ambient temps were when they were running diagnostics but the temps have been between 40 and 50F on any given day.

Apparently there was nothing noteworthy in the fuel filters or carb based on what the tech said. I don't know my way around an engine, (which I now regret not learning in high school) so not sure what's what when I look at it, lol. Makes it all that much harder for me as I typically am the guy with answers in other hobbies.
 

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Discussion Starter #5
Check the gas cap vent, air in, none out. Also, drain "ALL" the gas and put in fresh.

Does that have a 'pull kill switch tether in the back? Be sure the contacts are clean.

Take a water bottle with a sprayer and with the motor running, start spraying the electrical, carb, air cleaner, etc. You may find a bare wire or loose connector.

Take it back to the Stealership and ride it around their parking lot till it fails. Then make sure they refund your money and apply it for the warranty repair.

WELCOME TO THE FORUM.
Can you elaborate on the gas cap check? What should I be doing to test the air flow there?

I'm not sure about pull kill switch. Not that I know of.

I just ran it up again now and it was fine for the first 10 mins. Started with choke on and after warming up I set choke to off and ran motor for about 5 mins at idle. Shifted to Neutral at that point and began pulsing throttle and could not make it stall like it was earlier. Ran it up and down the street for a few passes and was fine. Brought it back to driveway and shifted to Neutral one last time and the problem showed up again. Once it started stalling, I could repeat it every few seconds. At times, the starter would be cranking for several seconds and it wouldn't fire up. Stop, try again and same. If I waited a few more seconds it would fire up instantly again on the 4th or 5th shot but stall once I applied a bit of throttle. So weird.
 

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Discussion Starter #6
I've been reading elsewhere and the thing that makes most sense to me is that the fuel petcock could be defective and causing a slow dribble into the carb float bowl. It starts out full and runs for a bit but isn't replenishing fast enough which leads to stalling. Wait and it fills and starts and will run for a bit but cycle starts all over again.
 

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Remove the hose at the top of gas cap, try to blow through the cap. It has a one way valve, air should blow in but not out. If the ball check becomes defective air will not go into the tank and cause this issue.

Remove hose from gas tank leading to carb. Place the end from carb into a cup then turn the gas on. Fuel flowing good?
 

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Remove the hose at the top of gas cap, try to blow through the cap. It has a one way valve, air should blow in but not out. If the ball check becomes defective air will not go into the tank and cause this issue.

Remove hose from gas tank leading to carb. Place the end from carb into a cup then turn the gas on. Fuel flowing good?


I got no hose. The cap looks like this.





Am I correct in assuming the hose is end circled in red is what you’re suggesting I remove?

Is the part circled in green the in-line filter?




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Less likely the cap, maybe more likely that in line filter. Red is what you want to remove to check for flow.
 

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Discussion Starter #10
Less likely the cap, maybe more likely that in line filter. Red is what you want to remove to check for flow.


Fuel flows freely from the fuel line once petcock is turned to on position. I was really hoping to see it trickle.

How can I tell if the brass fitting that the hose connects to is partially clogged?




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Let at least 1 gallon of fuel flow freely from the hose removed from the carburetor. If it slows down at all it may be caused by the gas cap vent. Loosen the cap and see if it speeds up. See the 2 holes on the bottom (inside) of the gas cap, those are the vents. Shake the cap empty of gas, cover one hole with a finger and blow thru the other, (Yuck, you can wipe it off with a prep pad). You should not be able to blow thru. Now, try to suck thru, there should be no resistance, allowing the tank to vent. If the tank doesn't vent it creates a vacuum and eventually the fuel doesn't flow. When the motor runs bad and dies, the tank will eventually loose the vacuum and restart.

Will the RPM's increase as it shuts off?
 

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I may be getting older, but I refuse to grow up!
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Fuel flows freely from the fuel line once petcock is turned to on position. I was really hoping to see it trickle.

How can I tell if the brass fitting that the hose connects to is partially clogged?


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The brass fitting allows fuel regulated by the needle and seat, opened and closed by the float, into the float bowl. Chances there isn't a problem there.

Another possibility is dirt thru the air cleaner getting in the carburetor. Remove the air cleaner and wipe the inside of the carb boot with a white paper towel. It should be clean. Even fine dirt could plug small jets.
 

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Discussion Starter #13
The brass fitting allows fuel regulated by the needle and seat, opened and closed by the float, into the float bowl. Chances there isn't a problem there.

Another possibility is dirt thru the air cleaner getting in the carburetor. Remove the air cleaner and wipe the inside of the carb boot with a white paper towel. It should be clean. Even fine dirt could plug small jets.


Ok, will see what I’m able and comfortable to do myself. I’m stressing myself about it all though and slept very little last night. For a brand new machine, I kinda think I need to just dump it back at the dealer and let them do what needs doing to fix it. I paid full price for a working ATV.


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The dealer won't warranty dirt, and the gas cap is easy to check.
 
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