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Hi all. I just bought a 07 griz 660 with 250 hrs on it. It's been sitting quite a while. When I test drove it, it ran great. I brought it home that night and it ran great then also. The next day I come home from work super excited to get it into the woods but now it backfires and wants to cut out when I give it throttle, it will idle all day but once I push the throttle half way or more it wants to cut out.

I'm guessing it's not the spark plug but the carburetor. Correct? Is the carb hard to remove and clean? Please help, thank you in advance!
 

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Grizzled
2014 Yamaha Grizzly 700 EPS
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Welcome to GC.

I'll let the more knowledgable 660 carb guys respond to your question. Someone should be along soon to respond directly to your question.

However, with a new-to-you-bike, first things I would be doing is changing the spark plug, cleaning/oiling air filter and changing all fluids right away. This is not intended to address your issue, but for you to know where all that stands moving forward.
 
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jkbrooks15- My guess it that the carb is going to need some cleaning and at a minimum the main jet. If it idles okay then I'd say that the low speed circuit is okay (may still need it to run at optimum). When your at mid throttle and above your looking at the main jet and slide needle. Generally speaking it's going to be the main jet that needs cleaning or replacing. You may be able to just pull off the side cover off and gain access to the float bowl bolt (very bottom of float bowl) and remove the main jet (think it's like a 6mm socket) clean and go try it. If you have to pull the entire carb off I would make sure to clean everything (needle and valve seat (float bowl), needle and main jet & idle jet.
 

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Welcome from Colorado.
I'm betting your bike has 2500 miles if not more, 10 mph x 250 hours.
If it sat for a time, there is probably crap in the tank that has got into the carb.
I would plan on removing the carb which is a bitch requiring you remove the gas tank to get the heat shield off under the tank.
I remove the front rack, front fenders, tank cover then the tank to get at the carb.
If you do all this, plan to adjust the valve lash too, while you are close to the valve covers, and adjust the valves to the wide side of the lash range. The information on valve lash is on the air box lid.
I would spray out the bowl and clean the jet, adjust the valves, install a new spark plug, clean the air filter and replace the old gas with new after cleaning the tank.
Let us know what you decide.
 
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Discussion Starter #5
Thank you all for the words of wisdom and the quick responses. I would like to try to clean the main jet, where is it in the attached photo? That would make sense since it is acting up once the throttle is half way pressed. I agree with crap being in the tank after sitting, when I bought it he was running it on the reserve position, which just allows the bottom junk into the carb. I do plan on replacing all fluids and spark plug. If I have to rip that carb out which does sound like a long process then that will be the best time. Do you know of an additive to the gas that might help the carb/spark ??
 

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You don't see the jets from outside the carburetor. You need to remove the float bowl to see the jets and internals.

If it sat for a while, the carb is going to need a cleaning. Remove the carburetor and take it a part. A can of carburetor/brake cleaner and compressed air should work fine for you. If you have lots of green varnish in the carb, a soaking carburetor cleaner solution will be required.
If it were mine, I would also drain the fuel tank and remove the fuel petcock valve and inspect it's filters. Make sure they are still intact.
 
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Just wanna ride!!
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Sea foam is a good additive for cleaning jets and injectors. You’ll still need to do as suggested above. Check YouTube for vids on carb cleaning. One carb is pretty much like another once you’ve messed with a few. If you remove any screws, count the turns of each and make a note of them for reassembly.
 

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Okbear made a good point. You'll need to count the number of turns the pilot needle is out from seated position. You do this by screwing it in and counting the number of turns it takes to bottom it out. Then you can remove it completely from the carb. There will be a small spring that will come out with it, so make sure you do not lose it.
 

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jkbrooks15- My bad, been awhile since I've been in my carb (13 years) on the 660. There is NO bolt on the bottom of the float bowl to gain access. The whole bottom of the float bowl must be removed (4 screws).
Looks like you'll have to tear into it. Once their you'll have to clean the entire thing as their is probably a varnish (old gas) build up on all the jets and adjustment screws (pay attention to what dezz said).
In the future it will help if you completely shut the fuel petcock off after riding and then just let it idle and die after most of the gas is used in the float bowl. That will help prevent any varnish build up in the future. Good luck.
 

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Thanks for reminding me. I can’t believe I actually forgot.

That’s actually funny. My wife just said it’s that I’m not a spring chicken anymore.
 

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Discussion Starter #15
I was told it was an 07 when I bought it but I haven't investigated to make sure.

I was able to get to the carb today and drop the bowl. Now I'm shocked it even ran, the amount of deposits in there was pretty amazing. I knew it was going to be bad when I tried draining the bowl using the drain screw line yesterday and no gas came out. Anyway, I'm going to buy a new fuel cock and I guess a carb repair kit just to get new/fresh parts. Hopefully soon so I can get it up and going, dying to ride it!
 

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Yamaha sold 660's and 700's in '07' and '08'.
 
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