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Discussion Starter · #1 ·
From what I've gathered the factory settings for the air/fuel screws are generally somewhere around 2.5/3 turns out from seated. I'm very confused on this.... with my screws at those positions my bike idles ok, but does not rev right at all. It cannot hold an rpm level for any amount of time either... it will begin to sputter and backfire. And no, it isn't my reverse sensor or my parking brake sensor... checked (bypassed) them. I have my floats set right and the fuel level is EXACTLY 3mm. I have cleaned the carbs very well and am positive there are no obstructions. My needle valves are not sticking. I have to turn my srews out (counterclockwise) 8 1/4 turns in order to get good throttle response. My bike is stock... no modifications. The air/fuel screws are nearly at the end of the threads and there is no resistance from the springs at all by the time the bike seems to run right. :3question:
 

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Discussion Starter · #3 ·
Thanks for the reply, but I've got a new plug in and tried the one of my other 2 extras... no good. Air filter shouldn't be it... does it with or without a filter. Tried driving a couple hundred feet on the bike.... throttle response at higher rpm's seems good..... low rpm scooting though results in chugging and sputtering. When gassed the bike will hesitate, then rpms will start to climb. Checked the plug and it doesn't really look like it's running too rich... not real black. At 3 turns it looks lean. The choke is not stuck. I've checked that. I'm really clueless as to what might be up?
 

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After a certain point (and for the Mikuni BSR I can't remember what it is) the fuel screws can't flow any more regardless of how far you back them out. The range of adjustability is really between .75 and 4 turns, anything higher or lower and you're really not doing much.

I have no idea what modifications you're running if any and that along with existing jetting with have a signficant impact on your issues with these jets.

If you're too lean at 3 turns out then you need to get bigger pilot jets. Stock is 22.5, you'll probably want 25's unless you're at sea level with the airbox lid removed or have no airbox and routinely ride in very low temperatures then you'll want 27.5's.
 

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Discussion Starter · #5 ·
The 4 wheeler is completely stock so I can't see why it would need an adjustment to the jets. I had a dealer tech mention that maybe it could be the synchronization screws. There's no way to adjust and check them is there? There's no possibility that it could be electrical is there. I don't think so, but I just thought I'd ask. What are the symptoms of a bad CDI box?
 

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You said the bike is totaly stock. Do you have the lid and snorkel on when it does this? Just checking the basics. Mine was leaking around the air box lid and had very similiar symptons. It would also do it when I tried to take the snorkel off.
 

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I'm having the same problem with my stock 05. I just tried starting it after about 3 months of sitting and it will not idle and also back fires, dumped all the fuel, changed spark plug and still runs like crap. It ran perfect when I put it away.
 

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on my 01 raptor 660, i bought the mechanical book and the settings are 3 turns out for the left(main carb) and 2 turns out for the right carb (seconday)
 

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Im having th same problem im running stock jets with a k&n air filter and a h&f exhaust i know i need bigger jets but i dont know what size i should get any help?
Old post, but Get a dynojet stage 2 kit and run a 146/148 if your under 3000 ft elevation.
 

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what should i run my fuel screws at with the 146/148
Dynojets instructions will tell you to cut the little rubber tabs that stick out in to the air stream off, and to set the fuel screws 3 turns out from fully seated. There are two little rubber flaps that stick off the main center rib in the rubber snorkel on the end that gets clamped to the lid. They are a pretty big air restriction since they are flat and stick clear out. Take an exacto knife or a razor blade and cut them off. That way you just have the center rib down the middle for support.

Also make sure your getting a genuine Dynojet kit. There are knock off kits that are junk. 6 Sigma Racing is one that comes to mind. There are rebranded dynojet kits out there that are fine as well. I had a Moose Jet kit and it was a Stage 2 kit but with a nice plastic hard case for the parts. I believe FMF was the same way. Getting a stage 2 kit gets you a pair of aftermarket carb needles. The only way to get them now days is in a Stage 2 kit.
 

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Im having th same problem im running stock jets with a k&n air filter and a h&f exhaust i know i need bigger jets but i dont know what size i should get any help?
No, you have a completely different problem - you have modified your intake and exhaust but have not re-jetted accordingly... his quad is box stock.

Do you still have the stock airbox intact or have you removed, cut, holed or in any way modified the airbox, snorkel or lid? If modded, follow 03Limited's suggestions. If stock, just try turning your fuel screws out 1/4 to 1/2 turn and raise your needles a notch.
 

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No, you have a completely different problem - you have modified your intake and exhaust but have not re-jetted accordingly... his quad is box stock.

Do you still have the stock airbox intact or have you removed, cut, holed or in any way modified the airbox, snorkel or lid? If modded, follow 03Limited's suggestions. If stock, just try turning your fuel screws out 1/4 to 1/2 turn and raise your needles a notch.
How do you raise your needles?
 

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How do you raise your needles?
Pull the "e"clip snap-rings out of the groove they are in, and move them up or down to lean or richen the air/fuel, and this will effect the 1/4 to 3/4 rev range.
Both needles must be in the same position.
All settings will be the same in both carbs, with the exception that the right main jet will Always be one size larger than the left.
Both pilots the same, both fuel screws set to the same number of turns counter clockwise(2.5 to 3 is ballpark).
 
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