1999 hp 500 carb jetting
07-17-2021 | 09:25 AM
#1
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Joined: Apr 2008
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From: sandown, nh
1999 hp 500 carb jetting
I just replaced my carbs on my stock HP 500s due to age. I put Holly HP 830 Carbs on, anybody have any recommendations for jetting/air bleeds/squirter’s and set up. thank you in advance
07-23-2021 | 05:04 AM
#2
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Joined: Sep 2009
Posts: 419
Likes: 14
From: Lake Winnipesaukee, NH
I hope you have wideband AFR. It makes all this way easier.
You need widebands, jet kits, some reusable fuel bowl gaskets, and a vacuum gauge.
Air bleeds and squirters are later.
But, put them on. Check that the throttle blades open all the way. And check where the secondaries open. Is the carb mechanical secondary?
Set up idle mix, then add 1/8 turn to idle to compensate for idle in gear. You could set idle in gear with your boat tied to a dock or steered by someone you trust. But that's another step and I found that if I just fattened the idle a bit my engine became docile at the dock.
Now it's time to make some runs to half or 2/3 throttle. Check for AFR, if it's safe got to wide open.
You want 12.5 to 12.8 AFR.
If it's wrong below secondary, change the primary jets. If it's wrong above secondary BY A DIFFERENT AMOUNT, change the secondary jets.
If it's rich use smaller jets to lean it out, if it's lean use larger jets to richen it up.
If stumbles or surges find the vacuum port and get idle vacuum in gear. Change to a power valve that is half the vacuum value. Your carb probably came from the builder with a 6.5 power valve.
You need widebands, jet kits, some reusable fuel bowl gaskets, and a vacuum gauge.
Air bleeds and squirters are later.
But, put them on. Check that the throttle blades open all the way. And check where the secondaries open. Is the carb mechanical secondary?
Set up idle mix, then add 1/8 turn to idle to compensate for idle in gear. You could set idle in gear with your boat tied to a dock or steered by someone you trust. But that's another step and I found that if I just fattened the idle a bit my engine became docile at the dock.
Now it's time to make some runs to half or 2/3 throttle. Check for AFR, if it's safe got to wide open.
You want 12.5 to 12.8 AFR.
If it's wrong below secondary, change the primary jets. If it's wrong above secondary BY A DIFFERENT AMOUNT, change the secondary jets.
If it's rich use smaller jets to lean it out, if it's lean use larger jets to richen it up.
If stumbles or surges find the vacuum port and get idle vacuum in gear. Change to a power valve that is half the vacuum value. Your carb probably came from the builder with a 6.5 power valve.
