flat spot in EVO
Thread Starter
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5th Gear
Joined: Oct 2014
Posts: 9
Likes: 0
From: Gunshine State
flat spot in EVO
Hello all,
I recently got my first HD, an 84 FLHT with 15,000 miles,
I had a shade tree shovel mechanic attempt to get it road worthy, he replaced the coil (dated 1986), plugs,wires,starter relay,ignition module,circuit breaker, oil/filter, petcock,fuel filter and rebuilt the carb (Keihin)
anyhow
I can drive it, but it has a flat spot/break up/hesitation kinda around half throttle,
slow/idle good, full throttle better than half but still sputtery
I tried to choke it when it happens in case maybe it was lean, no help, worsened
curious if anyone knows a almost certainty (as much as internet symptoms can describe)
I recently got my first HD, an 84 FLHT with 15,000 miles,
I had a shade tree shovel mechanic attempt to get it road worthy, he replaced the coil (dated 1986), plugs,wires,starter relay,ignition module,circuit breaker, oil/filter, petcock,fuel filter and rebuilt the carb (Keihin)
anyhow
I can drive it, but it has a flat spot/break up/hesitation kinda around half throttle,
slow/idle good, full throttle better than half but still sputtery
I tried to choke it when it happens in case maybe it was lean, no help, worsened
curious if anyone knows a almost certainty (as much as internet symptoms can describe)
Stellar HDF Member
Joined: Jul 2011
Posts: 2,583
Likes: 115
From: Boston, MA
Hello and welcome to the forum!
You're gonna hear this a bit and it is not awesome advice but most people will say to change to a cv carb or an s&s super-e. To be honest I have zero experience with that stock carb. Tom84, Danflstc or John jz will bee able to help so be patient.
Welcome again,
Tom
You're gonna hear this a bit and it is not awesome advice but most people will say to change to a cv carb or an s&s super-e. To be honest I have zero experience with that stock carb. Tom84, Danflstc or John jz will bee able to help so be patient.
Welcome again,
Tom
Dirt don't hurt
Joined: Jan 2011
Posts: 21,065
Likes: 4,561
From: Haslet Texas
If it is the stock carb from '86 then it is the butterfly Keihin carb and is considered by many to be junk.
Keihin also makes the cv (constant velocity) carb.
I personally like the S&S Super E.
Keihin also makes the cv (constant velocity) carb.
I personally like the S&S Super E.
Seasoned HDF Member
Joined: Jan 2012
Posts: 15,395
Likes: 19,404
From: Upstate N.Y.-Rochester Area
When I took ownership of my 1989 FLHS it had the old style carb on it. I obtained a CV style manifold and evened up all the internal casting lines and steps, and leveled the inside surface with a uniform and slightly roughened surface (IE: NOT polished more of a matte surface.), and bought a CV style carb and gave it to my indy to tweak, install and fine tune.
It was a great mod, smoother and responsive all through the power band, no MPG penalty to speak of, just a better ride.
It was a great mod, smoother and responsive all through the power band, no MPG penalty to speak of, just a better ride.
Road Master
Joined: Apr 2007
Posts: 769
Likes: 3
From: Ohio
As stated before go CV or S&S, I've always gone with CV because they were cheaper than the S&S and I know CV carbs very well now, I had a CV on my Shovelhead and after tuning it to that Shovelhead it ran great.
Road Warrior
Joined: Dec 2007
Posts: 1,666
Likes: 3
From: Styxville
+1 on this.
While you are in there, check what size jets it has in it. Too small of a slow speed jet can give mid range hiccups. The giveaway is if the idle mixture screw has to be more than about 1-3/4 turns out to give a smooth idle, you need a bigger slow jet.
Also check the accelerator pump diaphragm. They go crusty with age and mess with things. Ditto intake manifold seals.
A CV carb is maybe easier to live with, but the old Kehins work ok if set up right. Been running one on my Ironhead since 1977.
While you are in there, check what size jets it has in it. Too small of a slow speed jet can give mid range hiccups. The giveaway is if the idle mixture screw has to be more than about 1-3/4 turns out to give a smooth idle, you need a bigger slow jet.
Also check the accelerator pump diaphragm. They go crusty with age and mess with things. Ditto intake manifold seals.
A CV carb is maybe easier to live with, but the old Kehins work ok if set up right. Been running one on my Ironhead since 1977.
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Thread Starter
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5th Gear
Joined: Oct 2014
Posts: 9
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From: Gunshine State
the mechanic had the carb apart more than once, told me accelerator pump was new and different size jets were tried
once my money seeds sprout I'll put something else on, I have a 3 piece intake, I guess shovel style?
so getting a complete set/kit will be ideal
thanks all
once my money seeds sprout I'll put something else on, I have a 3 piece intake, I guess shovel style?
so getting a complete set/kit will be ideal
thanks all
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Dirt don't hurt
Joined: Jan 2011
Posts: 21,065
Likes: 4,561
From: Haslet Texas
You can probably get away for less than $100.