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Question Posted By: hammerhead1 on 4-16-2008
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| Make of Bike: |
harley |
| Model of Bike |
fxst |
| Year of Bike |
2005 |
| Engine Size |
95 in |
| Other info on Bike |
88 tc w/ big bore kit,585 andrews cams w/ gears,adjustable push rods,twin tech ign.,ported and polished heads,rejetted carb
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| What's your question? |
under hard acceleration bike hesitates
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| Details: |
under hard acceleration at any rpm or speed while already in motion if i hammer it to wide open throttle, bike hesitates or coughs then goes;was told possible main jet clog,or bad acclerator pump. anyone had this prob or know what to do to correct it? |
Answers:
- Hesitations are usually traced down to the accelerator pump. With your engine the added volume in the intake ports and the camshaft profile should also be taken into consideration.
Instant response comes from velocity in the intake system. It's what makes the carburetor respond. You add a larger volume in the ports and you decrease the velocity...until you reach a higher rpm range. You add a camshaft profile that opens the intake sooner and you get reversion before you get vacuum.
Accelerator pumps add (fuel)weight to the fuel/air mixture to counteract against reversion. Opening the throttle to a wide-open position in a butterfly- throttled carburetor loses most of the vacuum in the intake port. That's why H-D went to a CV (constant velocity) carburetor with a reactive slide. That reactive slide works the same way vacuum secondaries do in a spread-bore 4-barrel Quadrajet. Small primary butterflies and large secondary butterflies regulated by a secondary vacuum-regulated throttle plate. You stomp on the gas peddle and until there's enough vacuum in the manifold...the vacuum regulated secondary throttle plate won't open.
There's a good chance you might have a crack in the CV diaphram in your carburetor. Remember, CVs are picky about their vacuum. You go changin' shit around and they get real touchy!
Try starting with a little more fuel from your accelerator pump, and check your VOES. By: 47Knuckle-Dragger on: 4-16-2008
Reads: 2017
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