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Discussion Starter #1
Helppppp!
My 04 grizzly 660 wont take mid range throttle. It idles great, will do wheelies. Hates mid range throttle ⅛-½ throttle. Backfires though the intake

✅Stator - 6VAC on each phase at idle an pulsar coil an direction sensing coil is good. Charging at 13.--
✅ cleaned carb, ran though ultrasonic cleaner X2 an followed by carb cleaner. Seems like all ports are clear
  • new diaphragm for plunger needle doesn't seem to affect it.
  • float height just under 13mm (12.8 ish)
✅compression - 130 psi (Too Low??) Everything I've seen says minimum of 160 psi but it runs like a champ an idles great?
✅ Valve Clearance, Intake & Exhaust all is well
✅ cleaned filter in tank, no inline filter
✅ New 50 Cal CDI Box
✅ Fresh Gas - Premium No Ethanol
✅ New sparkplug - NGK, .033 gap
✅ Sprayed starting fluid around air box, an intake fittings an noticed no rise in RPMs, so I belive intake boots are good.
✅ New air filter

100% stock except 27" tires, stock air box setup, stock exhaust
Low mile machine less than 600 miles
I'm at a loss of words could really use some help big time! Er might consider selling it ?

Getting really desperate here.
 

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130 is low. Using this method is difficult for some. The engine needs to be crank fast enough to close the compression release.
The newer models have the compression spec'ed to the to a range of 93-142 for the 708 and 60-77 for the 686(700)

Did you OEM CDI fail? Might try putting the OEM back in.
Is the reverse light blinking during the mid-range issue?
Carb is most likely the problem. I'm not a carb guy hopefully member dezz will stop in.

97114
 

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Discussion Starter #3
Yes, I've seen reverse light flashing? What's that about? An I considered a bad OEM CDI an ordered the 50 cal cdi because I couldn't find any other issues other than possibly the CDI, or compression both of which were uncertain. Because everything I've read says minimum of 160, but it seems to run, wouldn't expect getting wheels up or idle if compression were an issue.
 

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Discussion Starter #4
An, everyone suggested the carb so I put a different oem carb on it an an still doing same thing unfortunately.
 

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Does it run good up to about 20 m.p.h.?
Then fall on its face?
Like a de-tuned engine?
If so that flashing light is about a rev limiter de-tuning the engine around 20 m.p.h., generally this kicks in around 20 m.p.h. in forward diff lock and in reverse around 10 m.p.h. or so.
 

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Yes, I've seen reverse light flashing? What's that about? --------------------
It means that reverse sensor is bad. It causes the rev-limiter to kick in. Can be tested be grounding the wire to the frame.
 

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Discussion Starter #7
No, like 3mph it begins to backfire if I run the mixture screw all the way out it is border line oook. But eventually will fall on its face. When I make it home this afternoon I'll get a video of what its doing.
 

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Was it acting like this before your carb cleaning? I would think your carb should be nice and clean after 2X through the ultrasonic. I see that you also tried a different carb and had the same issues. Does the engine "stumble/cough" between about 5-10 mph and then just take off like crazy if you push it through that RPM range?

Just a suggestion here and it's something easy to check, have you checked what the actual fuel level in the carb is? Even though the float measurement is correct, it doesn't necessarily mean that the fuel level is where it should be. I had similar issues with a stubborn carb a few years ago and tried forever to remedy the issue with the fuel screw without success. Might be worth a quick check and only takes a few minutes and then you can eliminate it as an issue.

I used the exact method noted in the manual and here's my measurement and this was the fuel level - way too low. Mine was popping and backfiring through the intake too because it was starved for fuel as it transitioned from the pilot jet to the needle jet circuit. Once I got the fuel level up to the correct height (4.5mm above the mating surface of the bowl) it ran like crazy!

97118
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If you are just revving the engine in neutral or park the reverse light may flash - mine does this. It is signifiying that the RPMs are too high to shift into gear.
 

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Discussion Starter #11
Attached is a video of it running an symptoms I'm running into. Below is a picture of fuel level with clear hose. Appearing to be at approx 4.5 mm above the mating surface.

97122
 

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Put your hand over the intake and try it again. Or use something to partially block or close the intake off.
See it if revs up at that point.
 

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Discussion Starter #13
So, I did it an it actually runs better nearly perfect. Then I removed my hand an blew carb off the intake of the motor. I'm guessing air/fuel ratio is off an needs jetting?
 

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........
 

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Yes it's an indication that your engine is going very lean. Try pulling on the choke next time
 

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Discussion Starter #16
Okay, well with an adjustment to the float. An a new needle an seat because old one was leaking this is where I'm at. ???‍♂?‍♂??
Thanks everyone for their input! I'm thinking a jet needs to be bigger but I'm unsure which one?
Idles great, pulls wheels up but wont run at ¼ throttle. ????

 

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I would try two size bigger then you presently have on your main jet.
 

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Discussion Starter #18
Okay, I dont have larger jets so I just purchased a DynoJet kit ?stage 1. Will serve me when I put exhaust an snorkel kit on as well. I'm just slightly confused everything is stock? Unless compression is causing this difficulty. 2 days out hopefully this will solve it ? I'll definitely report my findings after I receive it!
 

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Don't know if you already did this, but

while the bike's idling, spray some carb cleaner around your carb, and inlet boot. Listen closely for any changes in idle. Just trying to make 100% sure you have NO VACUUM LEAKS.
 

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Discussion Starter #20
Yes, I have that was my thought too just bad rubber boot er.... but no luck, checked from intake all the way to air box.
 
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