QuestionI'm having a few strange problems with my 1986 Yamaha Virago 750. I've been out of the country for over 2 months and the last time I rode my bike was the day before I left. At that time it worked fine. While I was gone I was told that it began to slowly leak gasoline which I thought was caused by the fuel selector being accidentally left in the PRIME position. However it still leaks gas which drips out at the bottom of the gearbox, just under where the clutch cable goes in. Also the clutch feels weird and alternately works and doesn't work. Finally...this may or may not be related but its very hard to start the bike and the starter constantly makes a bad noise like the starter gear isn't engaging the flywheel or something. THats a mouthful...got any ideas?
AnswerHi Dan,
The gas in the float bowls has varnished (more specifically-the needle valve springs likely varnishd) and is causing the fuel to free flow into the airbox and crankcase. Gas has thinned the engine oil is making clutch operation improper. Oil seals cannot hold the pressure of the added gas with the oil and the thinned mix easily escapes past seals.
The carbs will need thoroughly cleaned. I recommend replacing the needle valves and seats. They tend to varnish more easily after first time, and may not clean well.
Change the oil and filter now, and again after the carbs are finished. I think the clutch will survive once life giving oil is replaced.
Viragos are known for that scary loud grinding starter noise. There's a fix in the from of shims.
Send me an email and I'll return all the necessary repair and informaion files to get her running properly again. My email addy is: mshively1@woh.rr.com
See sample files below. I send many files, so emailing is necessary.
Respectfully,
Mark Shively
Dayton, Ohio
Carb Cleaning 101
By M. Shively
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 101
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).
Virago CARB CLEANING
It won't start or idle, runs rough, spits gas into the air filter, leaks and overall poor performance.
Things you need:
clean work surface that will not be disturbed
large jug of diesel fuel
carb cleaner, one can should do
carb cleaner - spray type- two cans are best
clean rags
magnifying glass -my old eyes can't read the jet numbers!!
small container to catch drained gas
toothbrush or similar brush
garbage bag ties (thin wire is used to clean pilot holes)
standard set of tools
compressed air source - can of air from Radio Shack or a computer store works well
typical manual such as Clymers, Haynes or factory.
1. Most carburetor problems range from high to low probability in this order:
• Contamination
• Improper adjustment
• Component failure
2. Contamination
Fuel and air flow into and mix together in the carburetor, a process critically dependent upon the dimensions of all the ports, channels, jets, passages, chambers, etc., therein. Any contamination, any foreign substance, can compromise any component's function, resulting in lousy running at some or all stages of operation.
Gasoline itself remains a major source of contamination! In fact, unless stabilized, gasoline tends to gum up and ultimately form hard varnish over periods of long storage. The resulting sludge and crud can close down orifices, clog valves, etc. causing all sorts of mayhem. For preventive maintenance, always use fresh gasoline; when storage appears inevitable, treat the gas with a fuel stabilizer like "STABIL," available at your friendly local auto supply store..
Moisture in the fuel is the most common source of contamination. Water may enter the fuel tank from condensation alone.. Water in the float bowl can cause high-speed "missing," as the carburetor drinks from the main jet, where the heavier fluid settles. Adding "fuel treatment" fluids to the tank help minimize this problem; draining the float bowl (as described later) occasionally is a good idea also.
Solid waste can honk up a carburetor as well, either through fuel or air ingestion. A tiny piece of dirt can hold a float valve open, draining an entire gasoline tank through the drain tube. For preventive maintenance, an in-line gasoline filter available over-the-counter at your favorite auto store is a good idea. I use in-line fuel filters on all my bikes.
Try the simplest, easiest, most obvious solutions first. Shut off your fuel petcock. Stick the carburetor drain tube, extending from the spout under the carburetor float bowl, into a suitable container. With a Phillips-head screwdriver, open the drain screw on the side of the float bowl, draining the carburetor. Remove the drain screw you want to open the hole large enough for passing pieces of dirt. Observe the discharge on a clean white cloth - any dirt present? Open the tank petcock for a few seconds, until an uninterrupted flow issues from tank, through the carb to the drain tube, then shut her down. Any foreign material? Keep flushing the carburetor as long as garbage comes out.. When finished, close the drain screw, open the tank petcock, re-route the drain tube properly, and start the engine! If you've led a clean, righteous life, your problem may be solved! If problems persist, read on.
3. Chemical Warfare
The next easiest possible solution: add some miracle fluid to your tank, a fluid whose "millions of tiny scrubbers" solve all your problems as you ride. A host of "carburetor and fuel injector cleaners" repose on dealers' shelves; mix this stuff according to your tank capacity (I favor a solvent-rich mix, exceeding the concentration recommended by the manufacturers). With a little bit of luck, you may dissolve and incinerate the irritant as you ride, merrily, along. I've had good luck with Chev Techron fuel injector cleaner and WynnTune carb cleaner. I normally run some through my bike each spring just to keep the carbs cleaned.
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Spray carb cleaner is available at Wally Mart and Canadian Tire. I usually have serveral cans on my work bench.
I've had great results with diesel fuel as a pre-soak to clean carbs. I had a set of carbs from an 83 Goldwing Aspencade that had been sitting for years. I dumped the whole complete set into a tub of diesel fuel and let them soak for a week
The results were very good. Most of the grime, dirt and most of the varnished gas in the carbs had disappeared!! I let the carbs drain for a few hours then began the dismantling process.
PART 1: Shut off fuel petcock. Drain carburetor into container. Remove fuel line at carburetor input. Insert carburetor cleaner spray can nozzle into carburetor fuel inlet port. Spray the HELL out of IT, until pure carb cleaner flows into container. You may need a full can of carb cleaner to get good results. Reconnect the fuel line and cycle the float bowl with gasoline as before; shut the drain screw and giver 'er a try.
PART 2: After spraying carb cleaner directly into the float chamber as above, connect a length of fuel line to the carburetor. Insert the fuel line into the hose of your Wet-or-Dry Shop-Vac. Restrict the vacuum cleaner hose opening with your hand, providing maximum pressure differential to the fuel line and let 'er roar! After a minute or so, restore machine to operational configuration and see if everything is all better (don't forget closing the drain screw!).
* "Going a little farther, PART 2: WARNING: DON'T EVEN THINK ABOUT USING A VACUUM CLEANER AROUND YOUR BIKE IF THERE IS THE SLIGHTEST POSSIBILITY OF ELECTRIC-SPARK IGNITON OF FLAMABLES. CHECK YOUR VACUUM CLEANER MANUAL."
You may want to try one more trick before you monkey further with the carburetor. Yamaha makes a dynamite carb cleaner. Mixed three parts of gasoline to one part concentrate (I think, but read the can) and poured directly into the carburetor through the fuel line, this stuff gets your carb squeaky clean. Be sure to drain this elixir COMPLETELY when finished.
PART 3: You've completed Parts 1 and 2, but problems persist. Shut off tank petcock. Drain carburetor. Loosen hose clamps on both engine and airbox sides of carburetor mixture/air hoses. Looking into the engine, rotate carburetor clockwise as far as possible without excessive binding (mind the choke cable connection!). From the left side, take a long Phillips-head screwdriver and loosen the four screws holding the float bowl; remove the float bowl and the idle adjustment control bracket. Squirt the carburetor cleaner with abandon into the pilot jet, main jet, around the float valve; wherever you can reach. Don't neglect the float bowl! The well, the bottom part, of the float bowl provides a hideaway for trash. Purge well! Further, this partial disassembly provides an opportunity for removing anything on the interior float bowl surface, a source of potential future problems. When finished, button 'er up, righten up the carb and tighten the fore and aft hose clamps, close the dump screw, and turn on the fuel petcock. Any luck? If not, we've gone just about as far in the cleaning department as possible without carb removal and disassembly. Advance (or retreat?) to the next section!
This is a dirty float bowl from my CB650, evident by the gas varnish on the bottom of the bowl. Sorry for the poor pic, but the protusion in the middle of the float bowl has to been cleaned. Spray carb cleaner down the hole and air blow it dry.
Cleaning sticky carb sliders is a question I'm often asked. Don't spray carb cleaner near the carb sliders. The cleaner will eat the rubber diaphram on the end of the slider. Remove the slider and use a toothbrush soaked in cleaner. Use the brush to clean the brass area on the slider and the contact area in the carb throat. Make sure to remove any residue of carb cleaner. Replacing the rubber diaprahms is EXPENSIVE.
Some older carbs like my Honda 81 CB650 Custom have pressed in pilot/starter jets. They are not removeable according to Clymer/Haynes manuals. They can be removed if you use caution. Grip the jet with vise grips and gently rotate and pull. The vise grips may ruin the jets so have replacements available. An easier method is to drill them. The crap that packs in it is beyond soaking and chemicals. The heating and A/C supply houses have a jet drill with a 1/4 hex end on it to allow chucking it into a drill. Wonder why? A device called a pin vise will also allow you to chuck the jet and spin it while you hold the drill still. Sometimes this is easier if you don't have the hex end drills. Light feed rate, high spindle speed, clear jets often. Then flush with chemical. The numbering system is relative to the number of cc's the jet will flow in a given time frame. If you are reluctant to use the drill method, use a fine wire (from a garbage bag tie) and poke it in the hole.
4. Adjustment
If starting/idling/backfiring on throttle let-off problems surface, pilot screw adjustment may solve them. A small flat-blade screwdriver, inserted into the pilot/air screw slot at the bottom of the carb body, "bottoms" the pilot /air screw (not too tightly; over-torqueing can bugger the screw tip and/or seat/jet). Withdraw the screw to the initial starting (or, as computer nerds might say, "default") position (2-1/8 turns on the Kawi KZ750). If excessive backfiring on throttle let-off occurs, back the screw out further, fuel-enriching the idle mixture. Generally speaking, a too-rich (fuel-wise) mixture does no harm; a too-lean mixture can cause problems, like valve-burning. I etched a file mark on the carb corresponding to the pilot screw slot orientation when I found the optimum position for my machine. You may need to adjust idle speed for the slowest smooth idle after setting the pilot/air screw. No set of carbs are identical. On my 84 Z750 is 2 1/8 turns on my KZ655 is 3.5 turns.
SCREW IN - Makes it leaner
SCREW OUT - Makes it richer
Some problems result from improper float level setting; you may check the float chamber fluid level without removing and disassembling the carb. Park on a level surface. Connect a clear flexible hose to the dump spout on the float bowl, or connect a clear hose extension to the dump tube. Make a "U" with the tube, its transparent section held against the carburetor at its intersection with the float bowl. Open the drain screw and observe the fuel level height after it settles relative to the intersection between the carburetor body and the float bowl. The Keihin CVK32 tolerance is 0.5 mm +/- 1.0mm above the intersection. If the fuel level deviates from the specification, you're about to see what the carburetor inside looks like; adjustment involves bending the float valve tang. Don't forget to close the drain screw when finished with this check!
If the quick-and-dirty cleaning routine comes up short, and/or the float level needs adjusting, you must disassemble your carburetor. Remove the carbs following the instructions in your repair manual. I use an old broom handle as a wedge to push the carbs away from the intake/out boots.
Carburetor disassembly appears pretty straightforward; take off the four top screws, removing cap, diaphragm, spring, spring seat, needle. Remove four float bowl screws, removing idle adjustment cable bracket, float bowl; remove pilot screw, spring, and whatever else you find in that hole; remove pilot jet, main jet, air bleed pipe; punch needle jet with your finger from the carb air intake passage and remove. Punch out float pin; lift float and float valve from carb. Time for a good cleaning of all metal (and plastic) parts. Clean ONLY one carb at a time - DO NOT INTERHCHANGE THE PARTS !!!
Most major auto part stores sell carb cleaner in bulk ( 2 liter cans) The Yamaha carb cleaner, sold in about quart-sized cans of concentrate, may be a lifetime supply, but it's worth the ten bucks or so it costs. I have used a five-dollar parts cleaner kit, purchased form my local discount auto parts store, consisting of a solvent bucket complete with bailed parts basket. Dump all the parts to be cleaned in the basket, slosh 'em around, and leave 'em for awhile. I believe the carburetor body needs cleaning, too; dunk it, making sure the fuel intake port and float valve passages get plenty soaked. Be sure all orifices of all parts are thoroughly cleaned, including the tiny holes in the air bleed pipe. I use the wire from a garbage bag tie to clean the holes. Do not soak rubber parts in carb cleaner for a long period of time. Carb cleaner can eat rubber!!! After a good soaking (overnight is best) I use a can of compressed air to blow all the holes, nooks and crannies in the carb clean. Check the float bowel gasket for wear and tear, replace if necessary.
SAFETY NOTE: Getting any solvent, even gasoline, on your bare skin is NOT a good idea; be careful. When finished, drain the parts and do whatever the solvent supplier says, like "air dry" or "rinse in water."
Carburetor reassembly is basically the opposite of disassembly; drop the needle jet in, small end first, followed by the air tube (when assembled correctly, the needle jet protrudes into the air passage). Hook the float valve on the float tang, carefully drop the float valve onto its seat, and insert the float pivot pin. Specified float height on the Keihin CVK32 is 17 mm, about 43/64ths of an inch, I think, if no metric scale appears. Note: Measurement of float height is facilitated by holding the carb at about a 30-degree angle, taking some load off the contact between the tang and the float valve pin. The measurement is made when the tang TOUCHES the pin with the float valve seated; not when the pin and its spring are COMPRESSED. Bending the tang ever so slightly adjusts float height. (After reassembly and installation, check the float bowl fuel level with a clear flexible tube as previously described.)
Reinstalling the carb, position the carburetor so you can connect the choke cable plunger cap FIRST! Otherwise, you'll be mucho cramped for space, attempting manipulation of that jewel; setting the choke lever "on" assists connection. Careful when you're jacking the carburetor around subsequently in the installation process, that you don't yank the choke connection from its purchase. You'll never have a better shot at this connection than at the start of installation. Reconnect everything; fuel line, air breather tube, and throttle cable. Fit the carb intake and output ends into their respective hoses; save the hose clamps for last because you may want to rotate the carb, giving you better access to the throttle bracket screw; the bracket forks a stud on the carburetor body, held in position by a single screw. Open the throttle butterfly, thread the throttle cable through the slot, and drop the end disc into its hole. Align the carb and tighten the hose clamps. Turn on the fuel petcock (remember:ddrain screw closed!) and fire her up! Having performed these procedures properly, you've pretty well eliminated the carburetor as your source of problems. Check that gaskets (o-rings) hold with no leaks present.
6. Parts Failure
Every component deserves inspection throughout all procedures discussed. Check that float valve "needle" and seat! A likely source of crummy idling, starting, etc. Anything bashed, scored, bent and so on needs repair or replacement. Common sense prevails. Do all parts function correctly, slide easily and seat tightly where they should? Make it happen! Check the end of the float needle, If it has a rubber end make sure it's intact. I've had great success getting carb parts from Partsnmore and Sirius Consolidated Inc
7. Summary and Conclusion
Fuel contamination remains a carburetor's worst enemy; prevented by dry, fresh and/or stabilized gasoline and in-line filters. "Better living through chemistry" may clean your carburetor without removal and disassembly. Mind the basic carburetor adjustments, check component condition, and here's wishing you many maintenance- and trouble-free miles!
Virago Starter Problem
We Virago owners all know about the starter problems with these bikes (It's usually not the starter, it's the FLYWHEEL!!)(Yamaha calls it a "rotor") And it happens to all the older Viragos 535,750 and 920 !! This auction is for a flywheel re-machining service that we perform. What we do is after the auction, you send us your flywheel and we will service it and send it back to you with a set of re-machined teeth with nice sharp edges and it will be shipped within 3 business days !!
Everyone is very happy with this service !! Take a look at your flywheel teeth before you spend big bucks on a new or used flywheel (If they're rounded-off at the inner edges, that's your problem ) (Also look at the gear that engages the flywheel-if it's teeth are rounded-off, you'll need one of these too)(you can get this from Yamaha - it's called the #2 idler).
This is not the only problem with the Virago starter, but if your flywheel is damaged (teeth smoothed, or rounded-off, then you need this service). The shim kit sold on E-bay is highly recommended in addition (not instead of) because they address 2 different short-comings of the starting system. The shim kit sold by dwsparrish@hotmail.com (on E-bay)is the original and one of the 2 proven successful fix for the starter drive mechanism (this is the other) .
The problem is normally the flywheel teeth have been ground to an angle or are rounded-off because the starter drive gear is already spinning when it engages the flywheel teeth (which means that it grinds a little metal off the flywheel each time you use the starter) and it causes the starter gear to slip across the flywheel teeth and to grind, not engage at all, or else crank for a split second and then just spin.(Which ruins a perfectly fine bike or else gives a 500-700.00 repair bill)
The bad news is that a new flywheel from Yamaha is very expensive!! (Bad news for bike owners, but Yamaha knows what we need). And the salvage yard guys only chuckle and tell you that they haven't seen a good used Virago flywheel in years !! (BEWARE OF SALVAGE YARDS THAT DON'T HAVE EXPERIENCE WITH THESE FLYWHEELS, OR DON'T KNOW A GOOD ONE FROM A BAD ONE!!)
I run a small motorcycle repair shop in Pennsylvania and I have had more than one Virago owner with this problem and I wanted to give them a little help without costing $500.00 and our flywheel re-machining service works very well for Virago owners. PLUS, IT'S A LOT LOWER-PRICED THAN A NEW ONE AT BIG MONEY OR A USED ONE FROM A SALVAGE YARD THAT WON'T LAST TILL THE END OF THE SEASON !! This auction is for a flywheel re-machining service for the Yamaha Virago 535,750, and 920. They work well because it gives the starter drive gear a new sharp surface to engage and it helps take away the grinding and slipping starter that either won't engage or kicks out after a split-second of cranking.
These have saved quite a few Virago owners a few bucks. At the auction end, I will E-mail you with our address to send it to and ask for your payment option.(the machining takes 2-3 business days) I have excellent feed-back, so bid with confidence that this is a true-to-life product that will help your starting problems.
Payment can be made with Pay-Pal , or you can mail a money-order along with the flywheel. The item will usually be in the mail in 2-3 business days. Shipping is 14.95 east of the Mississippi, or 17.95 west of the Mississippi because of the weight of this item. Thanks and happy bidding !!! IF YOU HAVE ANY MORE QUESTIONS ABOUT THESE STARTER SYSTEMS, FEEL FREE TO CONTACT ME AT SHOESVW@CS.COM)
