This is for entertainment purposes.Consult a professional mechanic before modifying your motorcycle.
Click pics for larger image.
This modification should apply to most all V twin cruisers made by most manufactures.The specific motorcycle I am working on is a 2001 Yamaha XVS650A, AKA V Star 650 Classic.I am adding an aftermarket tachometer I bought from ebay.It's made by Dynamic Biking Innovations.It's a knock off of Drag Specialties tach.The tach only goes to 8000 rpm.Most V twin cruisers do not rev that high.A few do,refer to an owner's manual or a factory service manual, if you're interested in knowing your max rpm.This paticular write up will pertain to all V Star 650 models and they are rev limited to 7200rpm, if I'm not mistaken.This mod should take about 1.5 to 2.5 hours depending on knowledge of motorcycle systems and mechainics.
Parts and Supply List
DBI tachometer from Ebay
Radio Shack Quick Disconnects Adapter Set Item # 6403064<----Get this specific item #.
Wire ties-small black
3x .250 female spade terminals-I used uninsulated for soldering.
1x .250 ring terminal-I used uninsulated for soldering.
I had everything except the tach and Radio Shack disconnects.I have $70 in them.
Metric wrench set 8mm,10mm,12mm,14mm
Small adjustable wrench-8 inch is what I used.
Metric Allen key set
Pliars or Channel lock pliars
Soldering iron with solder
BBQ lighter for shrink tubing
Flat head/end/blade screw driver
JIS screw driver-Japanese Industrial Standard screw driver-Looks like a philips head but it isn't.Using a philips screw driver makes the screw heads more prone to stripping out. These can be found cheap on the internet from $3 and up.All Japanese motorcycles use JIS screws,not philips screws.
3 feet of 1/4 inch gas hose
5 Gallon fuel container/jug
Couple rags would be nice.
Lets get this started.First thing is to remove the seats.On stock V Star the rear seat is removed first and then the front seat.There is a 14mm acorn nut behind the rear seat holding it on.Remove the nut and washer.Lift the back of the seat up and slide it back and up.It should come right off.Make sure not to loose the metal spacer bushing,for the lack of a better term.I put the bushing,washer,and nut back on the bike to keep from getting caught on the seat stud. If the seat stud unscrewd,don't worry about it.It'll go back together just the same.Now move onto the front seat.There's one 14mm bolt holding the back down on the front seat,remove it.To remover the seat lift up while pulling back.It may help to gently wiggle the seat while lifting and pulling back.Put the bolt back in the fender to keep from loosing it and set the seats in a place they won't be in the way and get damaged.
Disconnecting the Battery
Now disconnect the battery negative cable.Open the right side frame cover by removing the 10mm bolt and pulling it straight out and up.If the bike still has the plastic battery cover, pull the front edge back enough to get the 10mm bolt off the negative battery cable,and pull the battery cable away from the battery terminal.Ignore my fat finger in this pic.The big black negative battery cable is to the right of my finger.
Removing the Fuel Tank
Now move on to removing the fuel tank.If the tank is full, it can easily be drained into a 5 gallon fuel container.Locate the fuel valve (AKA petcock) on the left side of the tank,and turn it to off.Slide the hose clamp up the hose using pliars.Now twist and pull the hose off the fuel valve.To drain the tank,put one end of the 3 foot piece of 1/4 inch tubing on the fuel valve and slide the other end of the tubing into the spout of the 5 gallon fuel container.Now open the fuel valve to the reserve setting, so all the fuel can drain out into the fuel container.Pay attention to the fuel level in the container.Make sure it doesn't over flow and run every where.If the 5 gallon fuel container is empty,it should hold a full tank of fuel.Once the tank has drained,turn the fuel valve to off,cap the fuel container,move it out and away from the work area.Electricity and fuel do not mix well.Move up to the top of the tank, and remove the three allen screws holding on the dash.They are 4mm if I remember correctly.Be careful not to loose the washers and metal spacers.I put them in a ziploc bag.Once all the screws are out,lift the dash straight up a couple inches,and reach under it and disconnect the two electrical connectors.Use channel lock pliars to unscrew the speedometer cable nut.It's the long round rough nut on the speedometer cable.It shouldn't be on very tight.Once it's loose,romove the dash and put it in a safe place where it won't get damaged or knocked over.The connectors and speedometer cable need to be pushed just below the cut out in the tank to make it easier to remove the tank.Look under the rear of the tank, on both sides.There are two 12mm bolts,pne on each side, holding the tank on,remove them.The left bolt holds down the choke cable and knob.I just let it hang down the side of the engine, with a rag wrapped around it to prevent scratching the chrome.Lift the rear of the tank while pulling it back.It helps to wiggle it from side to side to loosen the tank from the rubber grommets, that hold the front of the tank to the frame.If the rubber grommets come off,they simply slide back on the frame mounts.Set the tank up some where safe to protect the paint and keep it from getting dinged up.Sorry I don't have pics of this, but it's pretty simple to do this, and most have probably already done it.
Removing the Airbox
The air box has to be removed to gain access to the front coil.Locate the hose on the back of the airbox,squeeze the clamp with your fingers,and slide it back down the hose.Pull the hose off the airbox barb.One the right side of the air box is the airfilter housing duct.Loosen the JIS screw holding the clamping band.No need to remove the screw.Wiggle the duct off the air box port.Under the frame on the left side,there are to band clamps holding the airbox to the carbs,loosen,do not remove,the JIS screws.Grab the airbox at the front and back,wiggle it while pulling up.Cover the carbs with a rag so nothing can get into the carbs.
Installing the Tachometer
Remove the tach and hardware from the box and get an idea where to mount the tach. Anywhere around the handle bar mounts is the best place.The tach should have enough wiring to reach the front ignition coil for hook up.The way I set my tach up requires no fuse, because the ignition circuit is already fuse protected.
I decided to mount my tach right of center, between my handle bar clamps.The space to the left of the tach is reserved for my charging station and GPS mount.
This is how the tach should be mounted in the clamp to isolate as much vibration as possible.It's better to let it move a little than for it to take all the hard impacts the front end gets on rough roads.
Now it's time to wire the tach.I used uninsulated crimp connectors and soldered them on.Then I covered them with shrink wrap.I did the tach connectors on the work bench and didn't get any pics.I have included the wiring diagram, and I will explain why I wired the tach this way,other than being cheap.The tach needs power and the backlight needs power,so I wired the blue and red wire together.Since the dash lights are on while the bike is on,so will the tach light.The green wire is the tach pick up, and connects to the coil negative wire.The black tach ground wire must be a direct chassis ground, and it gets grounded with the coil to the frame.
This is how I ran my wires.I wanted the tach to appear as close to factory as possible, or at least look like something Yamaha would have sold as an accessory for the V Star.I ran the wiring down the right side of the frame folowing the cables and other wiring,to the front cylinder ignition coil.
The front ignition coil has the wires connected to it with the clear covers over the terminals.Make a note of where the wires are connected or take a picture.
Now remove both wires by pulling the connectors straight back.Do not pull by the wires.It's ok to grip the connectors using the clear covers.I used pliars to grab the connectors, and not the clear covers.I also,remove the JIS screw between the connectors.
Now it's time to get to work.The negative wiring terminal (gray wire) on the V Star presents a small problem.The connector is .190 and all of the new connectors and adapters are .250.I must remedy that by changing the V Star's negative coil connector to a .250 connector.Cut off the .190 connector as close as possible to the connector.Then I soldered and shrink wrapped a .250 onto the negative (gray) wire.Carefully snip the clear cover close to the wire on both sides,it can be slid up the wire and reused to protect the connectors.Don't worry about the .250 connector fitting the .190 coil terminal.They will connect tightly and work well.The positive side of the coil is already a .250 connector.
Finished negative coil wire connector.
Now it's time to wire in the new tach to the coil.First thing is to attach the black ground wire, and make the coil soild enough to install the spade adapters and wires.Bolt down the black ground wire with the coil JIS screw.Make sure the wire is pointing straight back.
Get these two adapters out of the Radio Shack pack.
Plug the red and black wire connector onto the long straight adapter terminal and plug the red and blue wire connector onto the short angled adapter terminal.
Now plug the adapter wiring on to the lower positive coil terminal.It will be close to the head cover but shouldn't touch.If it does,flip the adapter over.No need to remove the wires from it.
Now do the same thing on the other side.Plug the gray negative wire connector onto the long straight adapter terminal.Then plug the green wire connector onto the short angled adapter terminal.Now plug the adapter onto the coil upper negative terminal.You should have something that looks similar to this when done.
Wire tie the wires to the harness.Don't crank down on them, just enough to keep the wiring from flopping around.Reassemble the motorcycle in reverse order,and connect the battery last.Reinstall the frame side cover and fill the gas tank.If all goes well,it looks like this.
Reassembly is the reverse order of disassembly.Take care to make sure the airbox is completely seated onto the carbs.Do not over tighten the airbox band clamps.Over tightening may cause the box to slide off the carbs.
I checked my tach with a timing light that had a built in digital tach.This tach was almost spot on.It was 25 rpm +/- from being spot on.More than close enough for my needs.
One thing to note:Wiring the tach light to the coil makes the back light flicker a little at idle.As soon as the rpm comes up the flicker goes away.To eliminate this,you can trace down the wire for the front marker lights, headlight,or tail light, and connect the tach light wire there.It will require cutting the motorcycle wiring and adding in the tach light wire,unless you know how to unpin connectors, and install new wire terminal on the wires.I know how to do it and I have done it.I prefer not to do it and it's difficult to explain through page text.I did it this way to make things simple for the new people to wrenching and riding.
On a scale of 1 to 5,I rate this a 1.5.
1 for me would be changing spark plugs,air filter, and doing a full oil change.