Misfire under load. 85 FLHTC

Reply Subscribe

Thread Tools

Search this Thread

Jun 16, 2013 | 09:14 PM

#31

Kickstand03303

Cruiser

Joined: Feb 2006

Posts: 141

Likes: 0

From: NH

Was it the VOES? I am having the same problem. The VOES is the oldest part on my bike.

Jun 17, 2013 | 08:59 AM

#32

JohnnyC

Outstanding HDF Member

Joined: Oct 2010

Posts: 2,706

Likes: 14

From: Near Frankenmuth, MI

Quote:

Originally Posted by Kickstand03303

Was it the VOES? I am having the same problem. The VOES is the oldest part on my bike.

The VOES is a Vacuum Operated Electronic Switch. When you open the throttle the vacuum increases and this switch activates the timing advance curve in you ignition module. The timing curve changes from idle and low speed to the proper timing for acceleration and high rpms to keep the motor and spark correctly in time with each other. When activated it ground the signal to the module to complete the circuit. Test it by applying a suction to the vacuum line and test for continuity to close. No vacuum applied and it will register open, or not allow a signal to pass.

In the early days it was a set of weights in the distributor cap of a car, or in the case of our rides it was located in the nosecone, mounted on the points plate. Back in the day you'd change the weights to alter the timing for a hot rod with a cam.

Today everything is all electronic and this function is part of the ignition module's built in functions. They still do the same function, keeping the spark in sync with the motor speed.

Last edited by JohnnyC; Jun 17, 2013 at 09:02 AM.

Jun 17, 2013 | 09:22 AM

#33

Dr.Hess

Seasoned HDF Member

Joined: Aug 2007

Posts: 8,200

Likes: 3,089

From: NW AR

Vacuum decreases when you open the throttle.

Jun 18, 2013 | 08:28 PM

#34

JohnnyC

Outstanding HDF Member

Joined: Oct 2010

Posts: 2,706

Likes: 14

From: Near Frankenmuth, MI

Quote:

Originally Posted by Dr.Hess

Vacuum decreases when you open the throttle.

Doc, I've always trusted your experience.

I will look into that information again when I have a chance. (whole lot of stuff happening right now, we were hit with a high wind and hail storm yesterday, lots of devastation, and today was all day just to get my property partially cleaned up and I have a surgery tomorrow).

I truly feel when you open the throttle it creates High Vacuum. But I'll check my facts.

Jun 18, 2013 | 09:34 PM

#35

Jackie Paper

Seasoned HDF Member

Joined: Mar 2010

Posts: 38,586

Likes: 6,435

From: Honah Lee

Quote:

Originally Posted by JohnnyC

Remember back in the good old days of points and distributors with centrifugal weights and vacuum advance to control ignition timing, going down the road at a steady 55, the vacuum advance helped fuel milage but when you opened the throttle quickly to accelerate, the butterfly opened wide and the vacuum dropped off since then the carb was wide open to atmospheric pressure and the vacuum advance dropped off preventing ping. Same with the old vacuum driven wipers. Soon as you hit a hill, they would slow down or quit. Later models before they went electric use a vacuum pump built into the fuelpump. The highest vacuum is at idle with butterfly closed. In fact this reading is a good indicator of motor condition

Last edited by Jackie Paper; Jun 18, 2013 at 09:36 PM.

Jun 14, 2014 | 01:01 PM

#36

deniro78

Stage II

Joined: Jun 2014

Posts: 2

Likes: 0

From: buffalo ny

My question is did you figure out what was causing the problem? I have the same year and the same issue,changed everything,pickup,ignition box,coil,plugs and anything else,it cuts out like it loses spark then picks back up after backfiring thru the car,I'm thinking after talking to a Harley tech that there has to be a bad connection somewhere and he suggested checkinga single wire under the gauges,the gauges plug in with one big plug and one single wire,he thinks it may be the single wire,what was causing your problem?

Jun 14, 2014 | 02:40 PM

#37

Dr.Hess

Seasoned HDF Member

Joined: Aug 2007

Posts: 8,200

Likes: 3,089

From: NW AR

My money is on the wire from the ignition pickup in the cone to the ignition module. I bet it is broken right under the cone, inside the insulation so that you'll never find it. Grab hold of the wires and pull on them. If one pulls like there is nothing inside the insulation, that's it. Do it when the motor is running and I bet it dies. Careful you don't burn yourself on the exhaust.

Jun 14, 2014 | 08:08 PM

#38

Beemervet

Ultimate HDF Member

Joined: May 2006

Posts: 6,590

Likes: 444

From: Ohio

Another thread where the OP never comes back to report the solution......

HD Forum Stories

The Best of Harley-Davidson for Lifelong Riders

7 Times Harley-Davidson Chucked Tradition Out the Window

Verdad Gallardo

7 Surprising Harley-Davidson Products that Are Not Motorcycles

Verdad Gallardo

8 Best Harley-Davidson Motorcycles Ever

Pouria Savadkouei

10 Worst Harley-Davidson Motorcycles Ever

Pouria Savadkouei

Killer Custom's Jail Break Is The Breakout That Refused to Blend In

Verdad Gallardo

Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?

Verdad Gallardo

Harley-Davidson Reveals Super Cool Cafe Racer Concept

Verdad Gallardo

Engraved Rebellion: Inside Bundnerbike's Glam Rock II

Verdad Gallardo

10 Motorcycles You Should Never Buy

Joe Kucinski

10 Things Harley-Davidson Needs to Fix in 2026

Verdad Gallardo

Jul 18, 2014 | 04:20 PM

#39

lynmark1

3rd Gear

Joined: Jun 2014

Posts: 7

Likes: 0

From: Palm Beach

intermittent sputter

1985 FLHTCU with intermittent sputters too, top end just rebuilt, butterfly carb rebuilt, new wires and spark plugs. Did notice that there is a 52 and 175 jet on this beauty, swapped ignition module and coils with presumed good used ones. Just a cough low and high range and no real power loss. No vacuum leaks. Cautiously riding but after having to lay down a few dead presidents I hope I don't hurt it by continuing to run it