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Discussion Starter #1 (Edited)
First post, but I did search the forum for well over an hour looking for someone that's had my exact problem... No dice.

I recently purchased a used 2008 700 Special Edition Grizzly. It's got 5,600 miles and about 850 hours. The guy told me it's been "gone through", and when I changed all the fluids, that did appear to be the case. It even had a new belt and CV shaft.

I took it for It's first ride today, and was disappointed to have issues shortly into the ride: It ran spectacularly in the lower throttle positions, up to about 25 to 30 miles an hour. When I pushed it beyond 1/2 throttle and 30+ MPH, it would start to sputter, backfire, and die. Sometimes when I let off the gas, it would compression start itself and carry on as normal, other times I would have to come to a complete stop, put it in park, and restart the engine. It would again run just fine, if I kept the throttle below 1/2.

It occurred at varying altitudes, and both when the engine was quite hot climbing a hill, but also running quite cool going downhill. The problem was not consistent, it would run like a dog for 30 minutes, and then the machine seemed to run as hard as it must have when it was new. Then two hours later, the problem would return. Rinse and repeat.

I got service on top of one of the mountains ( 9700 ft) and read about the neutral safety switch. I watched the display several times when I experienced this problem, the reverse light never flashed.

Hoping someone else has had a similar issue, and knows the resolution. A little frustrating.

Thanks!
 

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Grizzled
2014 Yamaha Grizzly 700 EPS
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First, get yourself a new spark plug making sure it is the proper one by NGK. You would be surprised how many times that fixes similar running issues.
 

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Welcome from Colorado.
X-2 on a new plug and.....
If the bike sat stored the gas might have gone sour. Or there is dirt, goo, gelled gas interrupting/blocking the gas flow in the tank causing irregular fuel pressure from the pump.
If it runs good at low speed always, I suggest adding a little sea foam to the partial tank now and take'r out and blow the cobs out, with a new plug...and you might want to get a couple plugs if you're burning crappy gas out.
If she starts to clear up, and the tank get low, I would add a gallon of gas with injector cleaner, not too much, and keep going to see if its getting better. If so run what you can on that day and at the end add a little more gas to dilute the injector cleaner and run the engine to get diluted gas to the injector. This stuff is said to be a little corrosive on rubber part, I'm not sure if this is true so error on the side of caution.
It also helps if you can go out for a long day for this, then on the next ride, hopefully another long day to use most of a tank of gas, top'r' off and add more injector cleaner and see what happens.
There may be to much goo in the tank to do this in a couple days, so you might have to drain the tank and clean.
Also :)
A buddy here let his son-in-law use his griz for a day, and the kid topped of the tank when he got back not knowing the yellow can was for diesel fuel.
He added a gallon or so, so the next time out the bike ran like crap and smoked. It would start but not run right, and we went through a few new plugs before we realized the problem, drained the tank and added gas.
You never know what the last guy did, let us know what happens.
 

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First, get yourself a new spark plug making sure it is the proper one by NGK. You would be surprised how many times that fixes similar running issues.
Yeah. Do this, run recommended octane fuel (not higher), and run fuel injector cleanout through it for a tank or two.
 

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Discussion Starter #5
A bit of an update: I replaced the spark plug with the NGK spec plug. I also pulled out the spark arrestor to make sure it wasn't fouled or clogged, it looked okay. I put in some fresh fuel as well, so hopefully a couple different things that will help.

After a 50 mile ride last Saturday, the engine did not use any oil, or fuel dilute the oil. I don't think compression or piston ring wear appears to be an issue.

I can't replicate the problem in my neighborhood without the police coming, so I'm going to take it out Wednesday night for a 25-mile ride. Will update whether or not this fixes it.

The only other thing I can think of, short of fuel pump, is that I may have been a little too liberal with the air filter oil.
 

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Filter oil is like grease and I don't think the oil is your problem.
 

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Discussion Starter #7
A bit of an update:

With a new plug and another 1.5 gallons of fresh gas (88 octane ethanol free) added to whatever was in it when I bought it, I took it out for a 35 mile ride yesterday.

Overall, it ran somewhat better. I did have the bog and die issue for about 15 minutes, but now it would only die over 35 MPH, and past 2/3 throttle. It mostly occurred on top of the mountain (7000 feet) and when going downhill.

That was the only episode, so definitely an improvement over last ride, but still frustrating. When it ran, it ran good.... Had it up to 56 MPH at one point, which is as fast as I care to go on dirt.

Any recommendations to get to 100% reliable? Keep running it and blowing out the cobwebs? When it dies, it smells as if it is running rich.
 

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Grizzled
2014 Yamaha Grizzly 700 EPS
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Not burning oil is obviously a good thing. Also appears as you cleaned the air filter and re-oiled. You might also want to look into the Pod-mod for your year to make sure the previous owner(s) didn't richen the fuel. I would continue to run that fresh fuel through it and make sure to have some injector cleaner in there too.

There is also the simple fact that you will be running slightly rich at altitude. Both myself and Ridgway, along with multiple other users on here at GC, deal with that too.
 

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I mentioned adding sea foam, this is to break up or dissolve any gel in the tank from bad gas, to prevent you from removing the gas tank to drain and rinse. Its old enough to have dirt accumulated in there if the previous owner was not careful re-fueling in the dust on the trail. I've seen guys open the tank without knocking of the dirt around the opening, and others carefully clean that area before opening the tank, who knows what's in your tank.
As its getting better you're on the right track.
Maybe fresh gas only will be the trick, but a little sea foam will not hurt and I suggest not treating a full tank, but maybe a couple gallons at a time for 35 mile runs.
Then I suggested injector cleaner after the sea foam, this was for the injector nozzle and to keep the plug fouling to a minimum.
I figured once the fuel tank and line are clear, your next task would be to adjust the valves if needed. I was going one step at a time, so keep us up to date with you progress.
As for die over 35 m.p.h., I think you have more than one problem. These are low compression engines and you are running at high elevation so the engine will not produce its max output as rated at sea level in your best case situation.
As we are going in the right direction, I suggest you add a signature to your account here. This is where you can list all mods to the bike, tires are a big deal up here in the mountains, and this information shows up in every post you make. This feature is very important for those asking for help and wanting the best reply possible. Just writing in a post only show that one time, so the signature keeps everyone offering information up to date on what you current have.
As for your bike, I think you have a minor timing problem, so if there is bad gas in the tank, that's two problems. Then as you work to run the bad gas out of the system, you might be fouling the new plug while all this time your engine valves might be out of adjustment causing lower than best possibly compression to an engine already limited to high power out-put.
THEN, if you are running tires taller than 23.5"s actual diameter (the stock tire diameter) without c.v.t. mods, you are really feeling the effects of several problems, not just one or two.
I have helped a few in these mountains, so if we were going for a ride I would suggest having a couple gallons in the tank treated with sea foam for a 30ish mile hard run. Around here that would take about an hour.
Then out on the trail we would add a couple more gallons and treat this with injector cleaner for a hard ride back to the trailers. And I would suggest you have a new plug in the machine just in case :)
Then somewhere along the way we would measure your exact roll-out, the stock roll-out for your bike was 74"s. Tire cause a drag to the drive system, and the taller the tire, the higher the drag. Some here believe its the weight of the taller tire causing the problem, but weight is not the biggest problem, which is easy to prove.
We would go out and do a couple plug readings to know what's going on with the gas, and learn if the valves might be a problem.
Let us know what you do next.
 
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