Questioni have a 1986 honda goldwing aspencade,the problem started last spring with a hesitation when taking off from a stoplight.i then removed the carbs ,cleaned them ,removed pilotscrew caps and ajusted pilots.cold starting and idle improved ,but i still had a hesitation off idle.since them i have replaced the following parts spark plugs and caps,wires ,all fuel lines and filters ,2 more carb cleanesplus new kits ,i had problems with the stator so i replaced the stator plus a new stator harness from electric conections.i have tested every ignition part on the bike and they are all in spec.i fired it up and hesitation off idle.the bike will accelerate fine with the choke on or if i apply vacuum to the air cut off valve with a hand held vacuum pump. i removed carbs again,replaced air cut off valve ,checked reed valves ,replaced o ring between reed valve case and air box,and raised float level in carbs.ifired it up and same thing it will not accelerate unless the choke is on or vacuum applied to air cut off valve,i also ran a compression check,185 on all 4.pilot screws are at 3.5 turns out ,its idles good but will not accelerate,diapharms look good ,i held them up to light and tried to find pin holes but did not see any.if you can help me with this please reply. gary robinson
AnswerHi Gary,
Compression looks very good. Air-cut off valves reduce/eliminate de-acceleration backfing. Try adjusting air-fuel screws again.
Compare your carb cleaning work to the following files: something may have been missed during the cleanings.
Carb Cleaning 101
The elements of internal combustion engines are: correct fuel/air ratio, spark at right time, adequate cylinder compression.
There are many passageways and openings to check and clean. All are important in function and when obstructed or not working properly, have subtle to radical effects on engine performance. Vacuum leaks and carburetor synchronization also have effects on performance and should be inspected and adjusted following the below procedures.
Carb Cleaning
Warning: Remove all rubber parts before you begin. These parts usually include vacuum diaphragms, needle valves, orings, hoses, and other parts. Spray cleaners will damage these parts. Do not disassemble individual carbs from the carb bracket.
Air & Fuel Passageways: Trace and learn individual fuel and air circuits from beginning to end. Machines can only drill straight through the cast passageways. To change direction, another angled passageway must be drilled. The union is plugged with a brass or bronze bead. Inspect and clean each passageway with spray cleaner, brushes/pipe cleaners/etc, and compressed air. Remove any discoloration and debris. Look for spray cleaner to exit from one or more passageways.
Jet Cleaning: Inspect jets by holding to light and look through them. You should see an unobstructed round hole. Clean the jets with one or more of the following: jet cleaning wires, soak solutions, carb spray cleaners and compressed air. Re-inspect jets after cleaning and install when clear of obstructions. Some main jets have paper-like gaskets. Most have metal spacers between the jet and the emulsion tube. Some screw directly into a brass emulsion tube which is machined for a 7mm wrench at its float chamber exposed base.
Inlet Fuel Valve: Inspect the needle valve & spring. Press down the tiny metal rod that protrudes from the butt or float end of the needle valve. The spring should move freely and return the rod to its location. Check the needle valve's seat area for a groove or other wear. It should appear highly polished. Some needle valve seats are rubber and wear may not be visible. Inspect the needle valve jet seat. You can clean the jet seat with Q-tips and semi-chrome polish if necessary.
Carb Body Castings: Blow air through the atmospheric vent holes located on the dome of each float bowl chamber. Air should exit via hoses or brass nipples. Inspect the emulsion tubes and passageways (cast towers that jets thread into) for discoloration and debris. Clean interior emulsion towers with a soft bristle gun cleaning brush. Clean the Venturi's (main carb bore).
Needle Jets & Jet Needles: Clean the needle jets, jet needles, and passageway or tower that needle jet screws into. Clean the emulsion tube (pipe between needle jet and main jet) (Main Jet may screw into emulsion tube). Jet needles are part of the throttle slides. See below…
Throttle Slides: There are several types of throttle slides: Mechanical linkage, vacuum, diaphragm, and cable. Disassembling the jet needle from the slide is not always required for cleaning. If you have vacuum piston type throttle slides (large diameter solid metal slide), avoid cleaning the lubrication from sides and caps. If piston type check cap vents and passageways with air. Clean if necessary and re-lube. If you have rubber vacuum throttle diaphragms, inspect for dry-rot, defects, and tears by gently stretching rubber away from center. Do this until all areas around diaphragm have been inspected. Replace any defective part as described above. Clean carb body areas around diaphragm including air passageways and air jets. Diaphragms have a locator loop or tab fabricated into their sealing edge. Observe this locator upon reassembly. Avoid pinching the diaphragm when reinstalling caps.
Fuel Screws: Fuel screws have sharp tapered ends. Carefully turn one fuel screw in while counting the turns until it seats lightly. Warning: These screws are very easily damaged if over tightened into their seats. Record amount of "turns-in" and remove the fuel screw, spring, washer, and oring. The fuel screw is part of the enrichment (choke) circuit...clean passageways as described above. When carbs are assembled, spray low PSI compressed air into diaphragm air vents located at intake side of carbs. Throttle slides should rise, then fall when air is removed. Lightly lube external moving linkages. Reinstall carbs and follow through with carburetor synchronization.
Throttle Cables: Lubricate cables periodically. If cables are disconnected from carbs or removed for replacement, etc . . . remember cable routing and ensure proper reinstallation routing. Avoid bread-tying, sharp bends, and pinching cables. Adjust cables so throttle grip has about 5mm of play or throttle slides or butterfly valves may not open completely (full throttle)(wide full open).
Float Bowls: Inspect float bowls for sediment, gum or varnish, crystallization, and defects. Clean all pipes, tubes, passageways, and embedded jets with cleaners and compressed air. Remove and clean the drain screw and area. Inspect bowl gasket and replace if necessary. Clean and inspect overflow pipes and tubes, look for vertical cracks.
Floats: There are several types of float materials: plastic, brass, black composite, tin, and others. Handle floats carefully. Avoid bending, twisting, denting, or other means of mishandling. Most floats are adjustable by bending a small metal tab near the float axle end. Do not change the float adjuster tab unless tuning fuel service levels. Clean metal floats by soaking or spray cleaners, if necessary. Replace other type floats if cleaning is necessary. Clean the float axle or pin.
Synchronization: This is a fine adjustment performed usually and preferably with the carbs installed and the engine running. The unusual part is performed with gauged wire with the carbs on the work bench. Carburetor synchronizing balances Venturi vacuum at the exhaust side of each carburetor, resulting with smooth idling and optimized performance at all throttle openings. Synchronization is checked using a set of gauges which are either air vacuum type or liquid mercury type. The gauges are connected to vacuum ports on the intake manifolds via nipple tubes or if sealed with screws, sync gauge adapters will be needed. With the engine running at temperature, and with a fan or means of forced convection aimed onto the engine, the carbs fuel screws and idle are adjusted, then the synchronization is adjusted via adjustment screws on the carbs. A reserve fuel tank is recommended for convenience of accessing carbs during this procedure. See gauge instructions and repair manuals for detailed use of synchronization gauges.
Notes: While carbs are apart, record the jet sizes. Look for a very small number imprinted on the body of the jets. It should be the same number for all. If you have dial or veneer calipers, measure and record float heights. Perform measurements with floats just touching needle valves, though not depressing the needle valve rods. Replace fuel and vacuum hoses. Be sure to use fuel rated hose for fuel. Install or replace in-line fuel filters. It's a good time to remove and clean interior petcock fuel filters. Inspect carb manifolds for dry-rotting, inspect all clamps and air ducts. Inspect, clean, lube, and/or replace air filter(s).
Top Honda GL1000 Carb Rebuilding Mistakes
Here's a partial list of problems encountered by amateurs when rebuilding GL1000 carbs. Often, I'm called upon to resolve botched rebuilds by incompetent mechanics, current or previous owners, brothers-in-laws and neighbors. Avoid these mistakes if you tackle a rebuild yourself.
1. Overestimating your own mechanical aptitude, patience and attention span. This is not rocket science, but it does require a fair amount of planning, calm concentration and methodical execution. Interruptions are death for amateur carb rebuilders. Get all your necessary supplies in advance and block out your entire Saturday.
2. Not doing a valve adjust and compression test. These MUST be addressed before doing ANY carb tuning. There is no point chasing carb gremlins unless you have good compression.
3. Failure to perfect all ignition issues before tackling carb work. There is no point chasing carb gremlins unless you have perfect ignition.
4. Commencing work without access to a good workshop manual. The official Honda manual is best. Others are adequate. Be aware of the infamous "Air Jet Mix-up Problem" with Clymer Manuals. See my Tech Tip covering this for details.
5. Deciding that it's OK to re-use old rubber parts. This false economy will likely doom you to misery. When the internal O-rings harden they also shrink. This can allow fuel to by-pass the jets and float valve seats. Needless to say, this leads to over-rich and flooding problems.
6. Ditto for float bowl gaskets. Oddly, one of the functions of the fuel bowl gasket is to help form a "channel" from the idle mixture adjustment port to the idle mixture nozzle. When the fuel bowl gasket gets tired, split, torn, overly compressed, etc. this "channel" can get compromised and idle performance deteriorates.
7. Insufficient cleanliness. Work area should be well lit and surgically clean. The external surfaces of the carbs should be thoroughly degreased before you crack them open.
8. Failure to use bodacious quantities of compressed air. There is no substitute for 125# psi! These carbs are blessed with a myriad of internal air and fuel passageways that must be blown clean.
9. Failure to pre-soak internal components to facilitate disassembly. I use PB Blaster.
10. Breaking float pivot pin bosses when removing float pins. I use a small pick awl and tap with a toy brass hammer (really!) after pre-soaking per #9 above. If you look carefully, you will notice that one end of the pin should have a slightly beveled tip. This is the end you should tap on. Place the entire assembly on a shop rag or towel on the bench so that the entire rack will "float" across the workbench when you gently tap the pin. If it doesn't immediately begin to move, try tapping from the other side. If it still fails to move, try more solvent and a longer wait before re-trying. If it doesn't budge on try #2, try a gentle application of heat from a pinpoint "torch." If this fails, sacrifice the float and pin and remove with a miniature hacksaw or Dremel. This hurts, but it's not nearly as painful as replacing the entire carb body!
11. Incomplete disassembly. You're wasting your time if you don't address all of these:
a. Fuel inlet screen. These are located under each float valve seat. Usually can be removed with a small pick, cleaned and re-used. If they need replacement, they are only available from Honda as part of the float valve needle and seat assembly.
b. Main Nozzle / Primary Needle Jet. These perforated brass emulsion tubes are located beneath the primary and secondary main fuel jets. They are necessary to pre-mix the fuel into a "froth" to promote proper air/fuel mixing. To remove, they are pushed out from the carb bore side. (I use a wooden dowel). Take care because they are easily damaged. These tubes contain many small orifices that are typically clogged in carbs that have sat for long periods with fuel in the bowls. If these orifices are blocked, the air circuits can't provide sufficient air and chronic richness is the result.
c. Idle Jet…a small rubber "bung" passage plug between the 2 main fuel jets provides access to the idle fuel jet. This jet has an impossibly small orifice and must be removed for cleaning and inspection. This orifice and all the associated passages must be clear for each carb or your idle will be corrupted.
d. Circular aluminum "puck." This is about the size of a large aspirin tablet and is located beneath the bowl gasket in the main carb body. It's necessary to cover the access point used in the manufacturing process to create by-pass transfer ports for the idle circuit. It's mandatory that you remove these to clean the hidden passages. Usually, compressed air applied thought the idle mixture adjustment screw hole will pop them out (and cause them to fly across the room!). Sometimes, they are really stuck and solvents are necessary (apply through the idle mixture adjustment screw hole). Occasionally, heat is necessary to free them. Sometimes they won't budge and it's necessary to remove them with brute force. In these cases, I "install" a sheet metal screw into the puck to provide the purchase necessary to remove. Unfortunately, the pucks aren't available from Honda, so if you need replacements, you will need access to a stash of salvage parts.
e. Carb Top assembly. CV slide, spring and cap must be disassembled, inspected, cleaned, polished and re-cleaned. Same goes for the slide bore in the carb. See Tech Tip Section ("Special Tuning Tips for '77 GL1000s + Carb Top Service") for more details on this.
f. Primary and Secondary Air Jets. These are located under the kidney-shaped plate on the top of the carbs (under the cap). These sometimes develop a fungus-like coating on lightly used bikes that will cause all sorts of over-rich problems.
g. Idle mixture adjustment screw
12. Using aftermarket float valve needle and seat assemblies. These are notorious for leaking. Inspect carefully and reuse the original parts. Make sure the seats have Keihin logo marks and "1.0" flow rating mark…otherwise, they are aftermarket. The only way to go is OEM Honda. These are pricey, but easily last 25 years and 100,000+ miles. If there is any doubt regarding their condition, order new OEM float valve needle and seat assemblies from Honda!
13. Air Jet Mix-up problem. The primary and secondary air jets are located under the kidney-shaped plate on the top of the carbs (under the cap). These can be reversed with bad results. Worse, the Clymer manual has misinformation about their correct orientation. See the "Air Jet Mix-up Problem" Tech Tip in this section for more details on this.
14. Installing main fuel jets upside down. The primary main and secondary main fuel jets can be installed upside down. Not a catastrophic problem. The correct orientation is with the actual orifice oriented "up" (installed position).
15. Failure to align floats. Prior to setting the float height, you should check each float carefully to make sure that it is square, plumb and that the pivot is true. I use a precision right angle device and lots of visual inspection. Adjust each float as necessary. This is a critical step. Unless the geometry of each float is identical, you won't get consistent mixtures across all 4 cylinders. Poorly aligned floats can "foul" on adjacent structures and cause chronic fuel starvation or flooding. I take an additional step...I weigh all four floats to make sure they are evenly matched. On my scale, clean floats weigh 12 grams. I throw out any outliers than vary by more than 1 gram. The plastic floats used on GL1000s aren't prone to saturation like old-fashioned floats, but weight-matching is a good idea nonetheless.
16. Failure to check and set float height properly. The correct spec is 21mm. This is measured from the bottom edge of the float to the raised lip adjacent to the carb body fuel bowl gasket surface. Be sure the spring loaded "tip" of the float valve is contacted but not depressed when you take your measurement. The best way to accomplish this is to set the rack up (on end) on your bench and tilt it slightly away from vertical so that it rests against something sturdy (I use my bench vise). Then measure the floats on the lower pair of carbs. Adjust the "tang" as necessary to get the measurement to exactly 21mm. Also, when the measurement is correctly set, the bottom edge of the float should be exactly parallel to the carb body along the entire length of the float…not just at one point of measurement. When satisfied with the first pair, flip the carbs over and repeat for the other two.
17. Failure to check for air and fuel leaks within the plenum passages.
18. Failure to check for air leaks within intake manifolds.
19. Failure to use all new fuel and vacuum hoses.
20. Failure to rebuild the air cut-off valve.
21. Failure to service the choke linkage. The choke butterflies operate via spring pressure, not direct mechanical linkage. Any binding in the linkage will result in problems like inability to get full choke on 1 or more carbs or failure of choke butterflies to release correctly. This is a frequent cause of hard starting and over-rich problems.
22. Failure to check / set fast idle free play (between transfer link on plenum and fast idle ramp on carb #4)
23. Failure to implement the "Off Idle Fix." See details below in Tech Tip section. Probably the single best "improvement" you can make on an early GL1000 ('75-'77)
24. Failure to service the fuel tank, replace external filter, and fuel hoses. Easiest way to contaminate your freshly cleaned carbs.
25. Failure to flush debris from the fuel pump. Another easy way to contaminate your freshly cleaned carbs.
26. Failure to synchronize carbs once they have been re-installed.
