STUTTER/BOG AT 1/4 THROTTLE

[GRAPTOR]

OK, Here is the latest I think I have my main jet figured it ran great at full throttle. My problem now is at 1/4 throttle or when I jab the throttle I get a slight bog/stutter. If I am putting while going thru some tight trails then hit the throttle it will do this also gets worse as I ride longer ( motor gets hot).  I have changed my stock pilot jet to a 25 stock was a 22.5 and I am 3 turns out on my air mixture.  Should I go back down on the pilot? or adjust my air mixture screw in.  Thanks for any suggestions.

[h0tr0d18]

Im no jetting pro but I'd say you running rich.  I would drop back to the 22.5 unless your running in colder temps.  I have 27.5's but I ride -25 to -30 in the winter up here.  What's your stats? temp, alt, quad setup?

[GRAPTOR]

HERE IS MY CURRENT SETUP

PITTSBURGH, PA  1200FT. ASL
TEMP. WAS ABOUT 60 - 70 DEGREES
2005 RAPTOR 350
WHITE BROTHERS E2 EXHAUST
K&N FILTER
152.5 MAIN JET
25 PILOT JET
HOTCAM STAGE 1

Do you think I should go down in my main or just mess with the pilot?
My problem only appears to be at 1/4 throttle.

[BoisBlancBoy]

Most guys go with a larger main jet.  Have you tried a 155?

[GRAPTOR]

Tried a 155 it ran worse and the plug was black so I figured I was too rich.  I when to the 152.5 and it appears to run better I just have this stutter any thoughts.

[h0tr0d18]

HERE IS MY CURRENT SETUP

PITTSBURGH, PA  1200FT. ASL
TEMP. WAS ABOUT 60 - 70 DEGREES
2005 RAPTOR 350
WHITE BROTHERS E2 EXHAUST
K&N FILTER
152.5 MAIN JET
25 PILOT JET
HOTCAM STAGE 1

Do you think I should go down in my main or just mess with the pilot?
My problem only appears to be at 1/4 throttle.

If your problem is at 1/4 throttle I would try adjusting the air/fuel screw first.  It's the easiest to mess with, try to atleast get rid of the blimp and then read your plug to get a better read (throw a new one in there)

[Flynbyu]

OK, Here is the latest I think I have my main jet figured it ran great at full throttle. My problem now is at 1/4 throttle or when I jab the throttle I get a slight bog/stutter. If I am putting while going thru some tight trails then hit the throttle it will do this also gets worse as I ride longer ( motor gets hot).  I have changed my stock pilot jet to a 25 stock was a 22.5 and I am 3 turns out on my air mixture.  Should I go back down on the pilot? or adjust my air mixture screw in.  Thanks for any suggestions.

Have you tried turning the mixture screw back a half turn?

~Brian

[GRAPTOR]

Brian,
I have not tried anything yet my first thoughts were to adjust the air/mixture screw a 1/2 turn back in and see how that goes.  My other thought was to change the pilot back to the 22.5 ?? I'm going to wait until I mess with the air/mixture.  Sound good? Any suggestions would be appreciated.

Jon

[Flynbyu]

Brian,
I have not tried anything yet my first thoughts were to adjust the air/mixture screw a 1/2 turn back in and see how that goes.  My other thought was to change the pilot back to the 22.5 ?? I'm going to wait until I mess with the air/mixture.  Sound good? Any suggestions would be appreciated.

Jon

I would crank it back a half turn to see what happens first.

Your main sounds a bit small too.

I would have installed at least a 155 main with that set up. If you are jabbin' the throttle, and getting it to above 1/2 throttle when this occurs, the main jet is the problem. The main opens from 1/2 to full.

~Brian

[GRAPTOR]

I had a 155 installed an it didn't run very good the bog was more like 3/4 throttle and my plug was pretty black so I assumed that I was too rich.  Now that I changed the main jet down to a 152.5 the bog is not as drastic and the plug is more brownish/black then just black. I will post a picture of my plug tonight let me know your thoughts. Does this make any sense?

[Flynbyu]

Is your lid on or off?

~Brian

[GRAPTOR]

I was just going to post my airbox lid is on and everyone tells me they run a 155 with it off.  So I kind of figured with my problems I figured less air need less fuel so I went with a 152.5 next size down.

[h0tr0d18]

I was just going to post my airbox lid is on and everyone tells me they run a 155 with it off.  So I kind of figured with my problems I figured less air need less fuel so I went with a 152.5 next size down.

Yank that bitch off yo!!!   :grin_nod:  seriously, you'll never look back 

[Flynbyu]

Try removing the lid and see if that clears up your problem. Chances are you're not getting enough air to your engine with your mods.

Check out a high flow lid, or modifying your airbox with vents.

A great lid modification is the lid EHS Racing offers to mod your exsisting lid.

http://www.ehsracing.com/

If not, www.RockyMountainATV.com sells 2'' foam filters that snap into your drilled airbox. Pretty good add for not a lot of cash.

http://www.rockymountainatv.com/productDetail.do?navType=type&webTypeId=177&navTitle=Filters&webCatId=27&prodFamilyId=6786


~Brian

[GRAPTOR]

Brian,
Need some help this is where I am at. I just ordered the uni-filter air box vents so I will install as soon as I get them.  Now let me ask you this, while I was riding on Sunday I checked my plug it was brownish black looked ok.  After riding  I just unloaded off the trailer and ran it down to my garage and let it set I just checked it tonight and the ceremic is white ?? is that normal or am I still running lean?  From our past comments what should be my next step I am going to install the unifilters should I go back up to a 155 main? Leave at three turns out? ?? any thoughts or instructions would be helpful.

Jon