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Discussion Starter · #1 ·
Hello all,
2011 Grizz 450 Stock no mods. 142 ft elevation
Working on the Grizzly for a friend, looking for some help. It sat for a year or more in his shed. Trying to troubleshoot on the cheap since he's on a low budget. Can't for the life of me get her right. Haven't ridden only troubleshooting in garage. Compression seems looow at ~95 I did get a 120psi reading once. Compression didn't go up much when adding oil in cylinder. I modded my Blaster leakdown tester to attempt a leak test but she wouldn't hold. The main issue is when at operating temp, it runs like crap. It will rev high then drop rpms and want to stall. When I hit throttle (quick acceleration) it sputters bad and will not rev.

Symptoms:
Hard start cold. Need choke and throttle but she will fire up no issue.
Will not hold idle until warm but when I blurp throttle rpm's will raise for a bit and then eventually drop and cut out if not on throttle. There is no air filter or guide at the moment I'm ordering parts.
When fully warm/hot it will sputter bad on quick acceleration over 1/4 throttle in neutral also. will not idle.
Also sputter when slow acceleration at higher rpm but before limiter. neutral. There is no air filter

This to me seems like a fuel issue but I've check, triple checked carb jets, float height. Intake boot seems ok, no cracks and sealed. I'm leaning toward top end/valve issue.


Things I've done.
New Plug
Adjusted valves to spec
Flushed tank and cleaned petcock. fuel delivery is good.
New 93 octane
Oil and filter change
Seafoam treatment
Carb clean x5.
New "jet kit" stock - amazon. (but does the same with oem jets.)
A/F screw 2 1/2 out.

Anything else I can try?

Thank you!!
 

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Try putting the air filter in. believe it or not, it'll affect the fuel mixture a fair amount. it's probably too lean? It's a free test anyway. Different animal, but I know a lot of polaris machines won't run for beans without the filter in place AND the airbox lid.
 

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Still doing the same with air filter in.
It will rev when cool but when fully warm it's like the rev limiter on about half throttle and above in neutral. It wont go anywhere when in gear.
Once warm, what does it do when you make very fine changes to the choke lever? Does it get worse, or better?
 

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Discussion Starter · #7 ·
Does an assortment of things. Need choke and throttle when cold to start and maintain running until warm. will not idle.
When Warm, it will surge and rev high for a ~1 min or so, sometimes I will pull choke to bring rpm's down then it will fail to idle and stall if I don't continue to use throttle. But if on choke and throttle it will sputter and will not rev past 1/2 throttle.
Carb is clean been in this thing too many times.

Thanks!
 

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Discussion Starter · #8 ·
I will note more on what the choke does when warm and post soon.
Can the diaphragm on the side of carb cause these issues? it looks fine but unsure.
The needle diaphragm looks good... no cracks and seals fine.
 

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I agree it sounds like more than just carb issues. I'd look at the full intake tract between carb and engine for air leaks, if you haven't already. Looks like you set the pilot screw to 2.5 turns out, and I'm assuming that is factory service manual recommendation. What clip position did you set for the needle? Are all the right o-rings in place where needed in the carburetor? Have a good look at the parts diagram as a sanity check.
 

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I had the same problem with my 2007 grizzly 450 and was never able to fix it. I was seriously thinking about just buying a brand new carb. My carb was on and off several times, there is so many very small holes in that carb. The fuel these days will gum up the carb and the smallest particle will foul it up.
 

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Sorry for the delay I've been busy. Thank you for all the replies.

I went through the carb again probably 3 more times adjusted the air fuel screw same results. Below is a video of what it's doing. It's sputters bad from half throttle.

https://youtu.be/1Lv6kE5QvkU
Items 4 through 6, which the needle attaches to...does that slide up and down easy with only the resistance of the spring?
Yamaha ATV Parts 2011 GRIZZLY 450 4WD - YFM45FGAGR CARBURETOR Diagram

I also wouldn't rule out something electrical either. Know anyone else with a 450 nearby?
 

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Discussion Starter · #14 ·
@tythomps yes needle slides freely with resistance of the spring. I've rechecked this a bunch. diaphragm looks good and pliable.
No one I know of has a grizz 450 but the owner has a new kodiak 700 though.
Checked compression again tonight and nothing over 120.
Could timing cause this issue? The valves have been checked and adjusted to within spec. I haven't had the cover off to check chain yet but I did check tensioner and looks good.

How about coil, stator, pick up? I needed to order a multi-meter because mine took a crap. I will test the resistance but I read that the stator may still be bad even if it checks out?

Ugh the Grizz has me on the ropes.

Thanks for the help here much appreciated!
 

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@tythomps yes needle slides freely with resistance of the spring. I've rechecked this a bunch. diaphragm looks good and pliable.
No one I know of has a grizz 450 but the owner has a new kodiak 700 though.
Checked compression again tonight and nothing over 120.
Could timing cause this issue? The valves have been checked and adjusted to within spec. I haven't had the cover off to check chain yet but I did check tensioner and looks good.

How about coil, stator, pick up? I needed to order a multi-meter because mine took a crap. I will test the resistance but I read that the stator may still be bad even if it checks out?

Ugh the Grizz has me on the ropes.

Thanks for the help here much appreciated!
Hopefully other guys with more experience can weigh in. Especially on the compression number. Only remaining thing I'd say is get yourself a new multimeter, and then go through all the troubleshooting and diagnostic sections in the factory service manual. I'd not bother with the carb again until you check those other things. And if all it did was set for a while, I don't see how the timing could have changed.

My same year 450 has 2400 miles on it now and runs PERFECT
 

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@bigjohnson Ok so I had a better listen to it with headphones today. To me it sounds like it is running good at idle and what you start getting on the throttle it sounds normal too. But then once the rpm pick up, it almost sounds like it is hitting the diff lock or reverse rev limiter. You said the thing sat for a while....have you checked EVERYWHERE to make sure a mouse or something didn't chew and cross some wires up? Does holding the override button in change anything?

And yes, mine is a little cold blooded too, needs choke to start up and keep running when cold, takes a minute or more to be able to idle on its own without choke.
 

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Discussion Starter · #17 ·
Yeah she run fine if I'm on the throttle up to about a quarter, above that when warm it gets hairy and that's the sputtering you here. She won't idle for crap either I've adjusted everything, air screw, float height, idle adjustment. The wiring does seem like it's been messed with on the right side of the Quad underneath the top frame gas tank. 1 wire goes to the LCD has no effect the other one is connected. I don't see any other wiring issues I did put some Dielectric grease in all the fittings.

Like I said I ordered a multimeter that arrived today I'll check resistance on components tonight if I have time. I also ordered a Dynojet kit. I'm grasping at this point.
Thanks for all the input so far I really appreciate it. Let me know if you have any other Clues.
 

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I'll recount a problem with a Kawa 300 Bayou I own that has a similar problem, this quad would sit for years at a time between uses & does the same as yours, I would strip the carb, replace parts, sonic clean it, pull my hair out, turn to the bottle, nothing worked until one day after an aggressive sonic clean I looked under the plastic rack in the cleaner & found something that looked like a tiny piece of chewing gum substance, the pennies dropped, some carbs have fixed jets that are used in between the idle & the intermediate systems & if they block up the carb drops it's bundle, most guys blow jet holes out from the float area, but this just blows crap towards the tiny jet holes, won't come out, you gotta blow it out from inside the venturi area(have a look with the throttle plate wide open for the tiny holes) for this you need a special air gun that blows at right angles instead of the end, so solder up the end of your air gun & drill same sized hole in the tube 90 deg. to the tube at the end, now you can blow straight down that POS jet hole & hopefully dislodge the crap in there, take ALL jets needles etc off carb & use some carb clean to loosen stuff, worked for me, worth a go, also check the diaphragm for tears by holding it to the light & stretching the rubber. :grin2:
 
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Yeah she run fine if I'm on the throttle up to about a quarter, above that when warm it gets hairy and that's the sputtering you here. She won't idle for crap either I've adjusted everything, air screw, float height, idle adjustment. The wiring does seem like it's been messed with on the right side of the Quad underneath the top frame gas tank. 1 wire goes to the LCD has no effect the other one is connected. I don't see any other wiring issues I did put some Dielectric grease in all the fittings.

Like I said I ordered a multimeter that arrived today I'll check resistance on components tonight if I have time. I also ordered a Dynojet kit. I'm grasping at this point.
Thanks for all the input so far I really appreciate it. Let me know if you have any other Clues.
I'm just as stumped as before. Only remaining thought is you keep using term air screw, but on these carbs they are actually a pilot screw. Difference being that you turn the screw out to richen the mixture, opposite of an air screw.
 
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