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thumpin hard

hesistation after hotcam install??

4 posts in this topic

i am guessing this stupid vacuum slide is the culprit..maybe a needle change? my 650l has been opened up etc..dynojetted by a local shop..i went from a 150 to a 160 main..and from a 152 to a 155 idle jet after doing the cam..runs strong..but if you let off after hard accelleration and hold the throttle it seems to lose fuel..dies out for a second..somtimes in complete off throttle it will die. it pops on decell also..it is fine if you let off slowly,but if you quickly cecrease to half of less it will act as if you hit the kill swittch and turn it on again..i am almost at sea level..any ideas of slide replacement or needle? how about an edelbrock carb? i dont want to fork out 500 clams unless it is gonna make it lots better..i would appreciate any help!

thanks!

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Sounds like you just need to tune your carb for your setup. I have a 650R so I'm not much help on exact jet specs. Look up fuel screw tuning for fine tuning your carb. See below for jetting/tuning guidelines.

_____________________

Here is what I have found so far about the black magic of carb tuning. I'm sure other people will pipe in here to help out if I state something wrong. Start with #1 and work your way to #5:

1. Hard to start, may need choke when warm - Lean, get bigger pilot jet

2. Adjust fuel screw per forum directions for idle to throttle on bog. (See #3 if Fuel screw does not work or adjust properly - You bike must idle down when turning the screw in too far AND out too far. If not, then the pilot jet is too big or small as per fuel screw tuning directions.)

3. Idle to throttle-on bog - lean condition, fatten up main and/or pilot jets

4. Full throttle transition rolling-off hesitation - Main jet too big. Feels like you have the throttle pinned and soon as you let off the bike stumbles then comes back in about 1 second

5. Mid throttle burbles but previous stated conditions are ok - Needle Tuning mid-low throttle to 3/4-7/8 throttle range, Fuel screw contributes more at low throttle ranges. May need to play with Main jet at +/- 1 size for fine tuning with needle adustments.

____________________________

Uncorked from stock - see other threads. Jets sizing below builds on uncorked settings

Air box & header mods need bigger main jets over just uncorked (+2 sizes or so)

Cams addition to airbox & Header may need another slight bump in Main Jet (+1 or +2) over just header and airbox mods.

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Sounds like you just need to tune your carb for your setup. I have a 650R so I'm not much help on exact jet specs. Look up fuel screw tuning for fine tuning your carb. See below for jetting/tuning guidelines.

_____________________

Here is what I have found so far about the black magic of carb tuning. I'm sure other people will pipe in here to help out if I state something wrong. Start with #1 and work your way to #5:

1. Hard to start, may need choke when warm - Lean, get bigger pilot jet

2. Adjust fuel screw per forum directions for idle to throttle on bog. (See #3 if Fuel screw does not work or adjust properly - You bike must idle down when turning the screw in too far AND out too far. If not, then the pilot jet is too big or small as per fuel screw tuning directions.)

3. Idle to throttle-on bog - lean condition, fatten up main and/or pilot jets

4. Full throttle transition rolling-off hesitation - Main jet too big. Feels like you have the throttle pinned and soon as you let off the bike stumbles then comes back in about 1 second

5. Mid throttle burbles but previous stated conditions are ok - Needle Tuning mid-low throttle to 3/4-7/8 throttle range, Fuel screw contributes more at low throttle ranges. May need to play with Main jet at +/- 1 size for fine tuning with needle adustments.

____________________________

Uncorked from stock - see other threads. Jets sizing below builds on uncorked settings

Air box & header mods need bigger main jets over just uncorked (+2 sizes or so)

Cams addition to airbox & Header may need another slight bump in Main Jet (+1 or +2) over just header and airbox mods.

i argued with the shop about there dyno tuning..said it seemed like it was not right..the last thing i was going to try was to bring the main from 160 back to 155....i will let you all know! thanks!

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