CV Performance Motorcycle Blog

Harley MAP Sensor problems

2018-11-22T19:18:00-06:00

Manifold Absolute Pressure or MAP sensors are a major component on fuel injected and later carbureted Harley motorcycles. MAP sensors are used on most modern engines to monitor manifold pressure (vacuum), sending that information back to the electronic control module (ECM). The ECM then determines the correct amount of spark advance and for fuel injection also determines the pulse and amount of fuel based on the MAP and other engine conditions. Other sensors also play a role in engine management on fuel injected models.

When your Harley MAP sensor fails or begins to malfunction the ECM will begin to make inaccurate changes to ignition timing and fuel management, resulting in various poor running conditions. These conditions may include:

Poor fuel economy (MPG).
The ECM may incorrectly read low vacuum and assume the engine is under high load, resulting in providing too much fuel and overly advanced timing.
Sluggish or lack of power.
If the ECM believes the vacuum is high or under low load it will reduce the amount of fuel and retard spark timing. This would result in poor performance when the MAP sensor fails to notify the ECM of an increase in load.
Rough Idle.
Insufficient fuel injection (supply or pulse width) can produce a rough idle.
Hesitation.
When starting from a stop or rolling on the throttle, you may experience a hesitation or stall if the ECM receives the wrong signal from the MAP.
Hard starting.
An overly rich or lean mixture caused by faulty data from the MAP sensor will make starting difficult. On a fuel injected Harley if you suddenly need to add throttle to start the engine, this is a common sign of a failing MAP sensor.
Check Engine Light or trouble code.
A check engine light will appear if the sensor fails or if certain trouble codes have been recorded based on different malfunctions. Trouble codes may not always be recorded by all intermittent failures.

It is also important to check the orange boot seal or o-ring that mates the MAP sensor to the intake manifold. A poor seal not only produces a vacuum leak but may also appear as a sensor failure.

While some sites or articles may suggest different methods of testing a MAP sensor, this can be difficult if the fault is only occurring intermittently. If other faults have been ruled out or trouble codes already indicate related faults, replacement of the MAP sensor is recommended.

Note that MAP sensors found on 2008-later Touring and Sportster models do not use an analog sensor and therefore cannot reliably be bench tested with a common digital multimeter. Digital MAP sensors require an oscilloscope or specialized scan tool designed to read wave forms. Always consult a qualified technician.

Replacement is straight forward for analog MAP sensors, simply remove the screws that hold the sensor clip, then remove the MAP sensor from the intake manifold. When installing the new sensor always use the new orange seal included and make sure it is firmly seated to avoid vacuum leaks.

Replacing a digital MAP sensor is simple but may also require calibration of the ECM. Digital MAP sensors are also prone to damage by faulty wiring, static discharge, or other conditions. For this reason it is always advisable to have a qualified technician install a digital MAP sensor since most electronic sensors are not warrantied for damage once installed.

Common Trouble Codes for MAP sensor failures

P0106 - MAP Sensor Rate of Range Error (04-06 Carburetor)
P0107 - Map Sensor Failed Open/Low (04-06 Carburetor)
P0107 - Map Sensor Open/Low (EFI)
P0108 - Map Sensor Failed High (04-06 Carburetor)
P0108 - Map Sensor High (EFI)

P0108 can also indicate a failed sensor seal at the manifold.

See our list of Fuel Injection Parts and Oxygen Sensors including other ignition and fuel management system components.

Trouble codes may vary on newer models. Always refer to the factory service manual or consult a qualified service technician.

Common Carburetor Fuel Leaks

2016-05-08T15:13:00-05:00

One of the more common questions we get concerns either the overwhelming smell of gas coming from the carburetor or fuel leaking out of the bowl or overflow. Both conditions are typically caused by a stuck or worn float needle valve.

The float needle valve is responsible for regulating the flow of fuel into the float bowl. When the tip of the valve becomes worn or debris prevents the closing of the valve, fuel flows continuously into the bowl thus flooding the engine. Under severe conditions gas may soak the air filter or overflow out of the carburetor and onto the ground while parked.

Worn or stuck float valves are very common following prolonged storage or when gasoline has been allowed to sit inside the carburetor and begins to lacquer with age. Another common cause is the use of fuel containing any Ethanol. Many states now include anywhere from 5-15% Ethanol which can be detrimental to certain rubber parts over time.

If the fuel in your state or region contains more than 10% Ethanol you may need to replace certain soft parts more often, including the float needle valve and the accelerator pump diaphragm.

The parts discussed above, Float valve and Accelerator Pump Diaphragm, can be found in the CV carburetor Renewal Kit.

Avoid Ethanol

Never use E85 (aka FlexFuel) in a carbureted motorcycle. E85 pump fuel contains 85% + Ethanol and will begin to damage parts in the carburetor that were never designed for this type of fuel.

We always recommend replacing the float needle valve every 2-3 years or immediately following any prolonged storage where a fuel stabilizer was not used. If you used a high content Ethanol fuel be prepared to replace this part much sooner.

Flooding

One major concern following a stuck/worn float valve and flooding is the resulting damage that can occur to your engine. Fuel that is allowed to overflow or flood back into the intake will wash down the walls of the cylinders. This not only increases the possibility of piston ring wear but the contaminated oil is unable to lubricate bearings or other critical parts properly. If you suspect that a bad float valve or similar condition has been allowing unburned gas to flow into the engine then we recommend an oil change while fixing the original cause.

Float Valve Types

Just a note on the types of float needle valves. There are 2 types; 3 sided and 4 sided. both work the same despite years of rumors that the 3 sided valves should not be used. Back around 1992 Harley-Davidson released a bulletin warning not to use a 3 sided valve in the newer CV carburetors. This was actually in reference to an early style 3 sided valve that had been used on the earlier Keihin butterfly carburetors. Unfortunately the motor company never put out an update when they and others began making 3 sided valves that were compatible with the CV carburetor, so rumors still circulate today about not using this style valve (yes 24 years later). The below pictured float valves are both compatible in a Harley CV carburetor.

We sell both our own 4 sided valve along with rebuild kits from our suppliers that contain the 3 sided valve. Both will work equally however, if you still only want to use a 4 sided valve we have them available here:
cv-performance.com/float-fuel-valve-4-sided

ALWAYS reset your float bowl level after installing a new float valve.

For a complete list of replacement carburetor gaskets visit:
cv-performance.com/gaskets

The Cure for the Common CV?

2016-03-28T22:24:00-05:00

The other day a Harley magazine advertisement caught my eye entitled The Cure for the Common CV. The "adicle" (Advertisement that mimics an article) started by asking if your stock CV carburetor on your Harley is worn out or in need of a major rebuild, with the intention of selling their brand of aftermarket carburetor as a replacement.

I thought I'd share my own insights and clear up some common misunderstandings about the stock Harley carburetor. Let me first preface this by saying I have nothing against the advertiser (to remain nameless) whose ad I am referencing, and over the years I have recommended them for certain non-stock and race applications.

Let's start with the title, "The Cure for the Common CV". The only thing common about the Harley CV carburetor would be that over 3 million Harley's were outfitted with these versatile carbs from the factory.

The CV carburetor's ability to adapt to changing engine conditions all while keeping up with emission standards allowed Harley motorcycles to continue using this carburetor virtually unchanged from 1989 to 2006.

Unlike aftermarket carburetors using throttle controlled slides or butterfly valves, the Harley CV made by Keihin uses a vacuum actuated slide. The unique design constantly changes the size of the venturi (throat) based on manifold vacuum while simultaneously metering the air/fuel delivery. All of this occurs independent of the throttle unlike the "common" aftermarket carburetors. The name "CV" is derived from the design which maintains a Constant Velocity of flow which describes these carburetors perfectly.

Based on the above, I would say the CV carburetor is anything but common.

Throwing out the baby with the bath water
The ad recommends replacement of the CV carb if it is worn or running poorly and lists the benefits of their aftermarket brand. In regards to a CV carburetor being worn, the majority of parts that could become worn are few and are easier to replace as opposed to installing a new carburetor. Poor running conditions are easily overcome with simple upgrades and part replacements. Other performance improvements are also available that will awaken the CV carburetor beyond it's undeserving mild mannered reputation.

Before replacing your stock CV carburetor, be aware that doing so is a violation or illegal in some states. Other local regulations could require you to maintain the factory stock carburetor for emission testing or when transferring ownership. Keep this in mind before deciding to replace the otherwise perfectly good carburetor - already capable of delivering plenty of performance on it's own.

When to choose aftermarket over stock
While the Harley CV can become a performance carburetor with the right tuning and components, there are circumstances where stepping up to an aftermarket carburetor may be necessary. This includes racing or big bore builds that stretch the original CV beyond its limit. Jetting and tuning can adapt the original carburetor all the way up to a 95" big bore or slightly higher with some modifications, including high revving Buell models or bikes with wild cams.

Engine displacements 100 inches and higher or racing applications lend themselves to aftermarket carburetors where daily driving and gas mileage are less of a concern. That is not to say that you cannot use one of those carburetors on your daily stock ride, but the hidden performance in the CV carb you already have may surprise you. For years builders have opted for the larger aftermarket carburetors with the belief that bigger is better. Recent trends at shows and meets have seen builders and riders getting back to the tried and true CV carburetor.

Many have regretted giving up this reliable component which has since created a new demand and premium for them. Just be weary of the knock-off CV carbs out there which can be spotted by their lack of Harley branding cast into the body. These copies may have parts that are not interchangeable leaving you high and dry when it comes time to find replacement parts.

I may be a bit biased when it comes to the CV carburetor and my passion for their effective design. I've been rebuilding, tuning and dedicated to improving their performance since Harley began using them in 1988. To me they are anything but common.

Ken - CVP

Harley O2 Sensors now available

2016-02-27T02:26:00-06:00

Oxygen sensors for Harley-Davidson^® models are now in stock.

O2 Sensors for Harley Big Twins, Sportsters, and V Rods.

We now carry a full line of O2 Sensors for all Harley models. High quality sensors precision made for outstanding performance and manufactured to meet or exceed OEM specifications.

Update: Oxygen Sensors are now available for Harley Milwaukee Eight M8 models, Buell, Indian, and Triumph motorcycles.

Shed the winter blues and get your Harley ready for spring

2016-01-15T01:49:00-06:00

Winter may still have a firm grip on parts of the country but riding season is just around the corner. Carburetor accelerator pump diaphragms and float needle valves typically suffer following a winter's hibernation or prolonged exposure to fuel additives.

Now is the perfect time to start getting your bike in shape for your spring riding. We recommend cleaning out your fuel system if your bike has been in storage or not in regular service over the winter. This includes cleaning out the fuel valve filter, draining the tank of any old fuel or stabilzer, and for carburetor models a thorough flush and replacement of soft parts that have been sitting in old lacquered gas.

Those who have stored their Harley (and other equipment) over the winter typically use a fuel stabilzer added to the fuel system to prevent the gas from turning to lacquer and rust from forming in the tank. Flushing out the old gas, stabilizer, and any sludge will guarantee your bike runs great when you start running it hard in the spring. Allowing the old gas and junk to run through the system can lead to clogged jets and passages on a carbureted bike, or congested injectors on EFI models.

Drain the fuel tank and dispose of the old fuel properly.
Remove the fuel petcock valve from under the tank and clean the screen.
Inspect the fuel hose, replace if there are any signs of cracks or swelling. Replace the clamps if necessary.
Check the vacuum hoses and connections between the petcock or VOES where applicable.
Carburetor models:
- Drain the float bowl.
- Replace the accelerator pump diaphragm or clean if stored with stabilizer.
- Replace the float valve if old or suspected of being worn.

Following your cleaning, run some high octane premium pump gas. Avoid gas that uses additives such as Ethanol, especially any that uses more than 5% Ethanol.

Those in warmer western and southern locations may not have needed to winterize, but prolonged periods of non-use during the winter will still benefit from this same spring maintenance. Flushing out the fuel system before the spring riding season will help guarantee trouble free riding down the road.

While you're at it check and replace your spark plugs and plug wires. New plugs are fairly inexpensive and can be replaced within minutes.

View all parts for your Harley.

Harley Carburetor Tuning 101: The 88 Sportster Needle

2014-05-31T01:26:00-05:00

Harley tuners, mechanics, and those doing their own wrenching have long known about using the 1988 Sportster needle for tuning the Harley CV carburetor.

History
Harley Davidson motorcycles have a long history of carburetors used on their models over the years, but none as popular as the CV carburetor. Introduced in 1988 on Sportster models to replace the Keihin "butterfly" carburetor, the CV also from Keihin introduced a vacuum actuated slide and needle to regulate fuel delivery. As engine loads change the slide moves up or down allowing the suspended needle to meter fuel passing around it from a nozzle (needle jet). This innovative fuel metering system not only handles the air/fuel mixture throughout the mid range, but also provides a constantly changing venturi or throat size, hence the name CV or constant velocity.

The original CV carburetor in 1988 lacked an accelerator pump commonly used on most carburetors. To compensate for the lack of an accelerator pump and to eliminate lean flat spots, the factory produced the N65C needle whose length, diameter, and taper positions were designed to alleviate the off idle hesitation.

In 1989 an accelerator pump was added to the CV carburetor as all other models began to adopt the new carburetor, and the CV carb remained virtually unchanged until retired in 2006. The 88 needle (or N65C, HD #27094-88) became very popular after tuners and mechanics discovered its usefulness in tuning other models needing a richer off-idle and mid range mixture required with exhaust or intake upgrades. The N65C became a staple for tuners and is still used today even by Harley dealerships. Similar needles pulled from Buell variations and other special uses were used such as the N65B, NOKK, and NOKT however the N65C remained the most popular.

The 88 Needle Lives Again
Shortly after Harley Davidson discontinued use of the CV carburetor on factory models in 2006, the factory began discontinuing older components including the N65C needle. Having insight into these parts becoming obsolete, CV Performance began producing our own N65C "Sportster" needle (fits Big Twins too) to meet the needs of those wanting to continue using them. Based on the original specs from Keihin, the N65 needle was added to our line of velocity needles using our unique precision CNC machining process and billet aluminum material.

How Harley-Davidson V-Twin engines are made

2014-05-06T01:15:00-05:00

Here is an interesting video of how the v-twin engine is made in the Harley Davidson factory.

It's amazing how easy this assembly seems when produced on an assembly line. Anyone who has ever built or rebuilt a Harley engine in their garage can appreciate how much more difficult this is when using standard shop tools and your bare hands.

Harley Brake Pad Replacement

2014-03-31T02:47:00-05:00

An often overlooked item when preparing for the spring riding season are brakes. Replacing your Harley brake pads will assure you have the stopping power for whatever the road throws at you.

Well maintained motorcycle brakes, especially on a heavy Harley-Davidson ® are crucial. At the first sign of major wear you should always service your brakes. Installing new brake pads can be a simple procedure when following the instructions in your service manual and is accomplished with basic tools.

Be sure to "bed-in" new brake pads after installation for proper break in. Check out the following video that describes this break in process.

Brake Pad Bed-In Instructions

There are a variety of brake pad types for your Harley and while all can be a vast improvement over old worn pads, each can have characteristics for different needs.

Organic Brake Pads are ideal for all conditions while being easy on polished rotors.

Sintered Metalic brakes tend to have a longer life and provide excellent stopping power.

Kevlar/Metallic Pads are a great all around brake pad - last longer than OE's, easy on rotors, and provided as original equipment replacements by many shops.

CV Performance carries these varieties of Harley brake pads for most models.

Always consult your factory service manual or seek the help of a qualified service technician if unsure about installing any part.

NGK spark plugs now available

2014-01-28T01:46:00-06:00

CVP now stocks NGK spark plugs for many Harley models, including early models. This includes both the popular standard nickle plugs and performance Iridium plugs.

For early models or those using point ignitions we recommend a standard plug. Iridium plugs are best suited for bikes with electronic ignitions due to their fixed gap.*

We have used NGK plugs on our bikes for years and feel they provide outstanding performance for V-twins.

* Note: never attempt to gap Iridium spark plugs as this will damage the electrode.

Welcome to CV Performance's blog

2012-02-12T01:36:00-06:00

Let's kick this page off with a brief introduction. My name is Ken, owner of CV Performance. I started CVP because as much as I love to ride, I have just as much passion for improving the ride. I've had a life-long obsession with carburetor's and intakes, so much so that I eventually turned that into CV Performance.

The Harley CV carburetor from Keihin was the staple carburetor for the motor company from 1988 until 2006 with little to no changes. With 18 years of production and an estimated 2 million + CV carburetor equipped models still on the road I suspect we will be seeing them around for a long time. The same core design carburetor is still in production use today on several ATV's due to it's performance characteristics and ease of tuning.

Through these pages and my products I hope to share with other Harley enthusiasts how myself and others are able to make every ride even better. Stay tuned.