FIAMM MOD FAQ

Or

How to make your Shadow Sound like a Car!

Background:

It all started in early September. I had planned to take the bike in for it's annual Virginia State Safety Inspection when, the horns started acting up. When I bought the bike a year ago I noticed the horn button was broken and basically was just the rubber/metal part hanging out of the housing, but it still worked fine and since I always ride with gloves I never worried about getting shocked. I came home from work and got out the trusty digital volt/ohm meter and began trouble shooting. I replaced the switch with the radio shack lever switch #275-016A for $1.98 and still had horn troubles. Honda wanted some ridiculous amount for the switch housing assembly. I don't believe they sell the switch separate for the 84 VT700C. Also, pay careful attention to all the screws/parts that are removed when getting to the horn switch. That assembly is packed tight with the high-low headlight switch, turn signal switch, choke cable and the horn switch. It was quite a chore getting it off and keeping all the parts from falling out once I got it open. This is also a good time to clean out the cob-webs in the switch housing.

If I had found this earlier I may have saved myself some three hours of trouble shooting trying to find what I thought was a ground/shorting problem.

http://www.mindspring.com/~corvair/RadFAQ/horns.html

I don't endorse his FAQ I just include it here as a reference. I'd never play around with rebuilding a horn that broke, purely for safety reasons.

I also wanted something significantly LOUDER than the stock horns! So I went with the FIAMM horns. I finished this project in about 6 hours including the 3 hours of trouble shooting. I took my time, wired everything up and tested it. Disassembled it and soldered and re-tested before the final mounting. It was also my first time at taking off the gas tank, and replacing a fuse in the fuse box (don't ask). Your time will vary.

Parts List:

You will (may) need:

2 FIAMM horns (I used one high note and one low note) $11 each
1 (15A/12V) Relay (RS part #275-218C others may be substituted) $7.30?
1 Fuse assembly ( I bought the flat kind from a local auto parts store) $2.50 with additional fuse
a length of 14 gauge wire (for the feed from the fuse to the relay) $2.50
and some 16 gauge wire (from the relay to each horn). $2.50
some epoxy (I used this to mount the relay - you may choose to place it somewhere other than where I did) $3
some cable ties (see epoxy) $2
The usual soldering and electrical stuff (tape, shrink tubing, cutters, pliers, wrenches, band aides).
A volt/ohm meter (Mine happens to be a digital volt/ohm meter [DVOM], but analog would work too)

Total Cost ~ $43.97 with lever switch

Before I begin:

All the usual legal mumbo jumbo applies. If you try this and blow up something or worse, don't blame me. I am simply writing this to document what I did. It may not work for everyone and should not be attempted if you don't feel comfortable with basic electronics work and also some basic knowledge of your particular motorcycle. Please use caution. Always wear the proper protection. Please save the PBR's for AFTER the job not before!

'Nuff said.

Doing The Modification:

Start by disconnecting the battery. Remove the plastic chrome looking Honda piece that sits below the horns. Remove the old broken cheap stock horns. Note the +/- wires for the old horns. [Note: This may be determined by DVOM if no markings are present on the old horns.] Here's how I wired the new ones.

An alternative to using the old ground is running a completely separate ground from the battery up alongside the new positive feed. I didn't have enough different color wire and went with the method as stated above. I fit tested the new horns and had to drill a hole for the pin that prevents the mounting bracket from rotating once mounted to the forks. [Note: Not to scale. See pictures below. The extra hole is actually closer to the horn than the mounting hole as depicted. Use the old horn as a guide when drilling or punching the new hole's location.]

I wired the horns to the relay and tested it with a cable to the battery. Be Careful not to point the horns toward your ears or, better yet, wear hearing protection especially when trying this in a closed garage! I used crimp-on connectors onto the wires between the relay and the horn's flat spade connections. I then soldered and taped/shrink tubed the other ends to the relay. [Note: A few months later I noticed a plug in mounting block in the RS catalog for this DTDP relay. That might be easier to install although I'm not sure if it would fit with this configuration.]

I also installed an optional jumper to the horn mounting plate that acts as a ground. The (-) connection on the horn is connected to this optional plate with the included 3 inch connector wire. The other horn I connected to the original horn wire which is connected to ground. [Note: I tested the mounting crossbar on the fork to be certain it was a good ground and it was. I only did this as an extra precaution in case for some reason the forks became "ungrounded" somehow. The one horn connected to the original horn ground wire becomes the point of ground for the entire fork assembly which includes the other horn.]

Here comes the fun part. Wiring up the new 15 Amp feed from the battery. Since the new FIAMMs require a lot more current than the original stock honda horns, a new completely separate feed is recommended for this modification. I put a 15 Amp inline fuse right at the battery and ran 14 gauge wire along the wiring harness up under the tank. YES THIS DOES REQUIRE REMOVING THE FUEL TANK! I lifted the tank away from the frame and fed the wire up through with the other hand while hugging the tank to keep it from falling. I wouldn't recommend this method to anyone. It was my first try at removing the tank and I had no help and a recently filled tank which I could not empty safely so I chose this method. Please use caution when working around fuel. [Note: keep soldering irons, heat guns for shrink tubing and matches FAR AWAY while performing this step!]

Mounting the relay was also fun. In a nutshell, I used two cable ties and some 3500 lb strength epoxy and mounted it to the cross beam just behind and between the horns (See picture below).

This view is from the left side with the wheel turned all the way right. That cream glob is the relay. It is oriented with the wires pointing forward between the two horns and you can just make out the schematic which is normally on top now on the side. Be careful not to mount the relay to far back as it will impede the wheel from turning all the way to the left. That rusty stain is the left turn limiter thingy. The relay should be mounted forward of that. The cable ties went through a hole in the cross bar and were basically spread apart evenly on the relay. Epoxy was applied prior to strapping down the cable ties. It isn't going anywhere; trust me. In the picture below you can see the two cable ties just to the left of the horn on the right (as you are looking at the picture). The extra hole I drilled is hidden by the shadow if the horn.

This is when I discovered I had to slightly modify the plastic honda piece. I had to cut a small piece out of the center to allow for the relay. See the small cutout just above the "D" in HONDA?

When I got everything back together this is what it looked like:

Thank you:

My thanks to Bob Moon for scanning the pictures. Thanks to all who gave me advice about adding the dedicated power circuit for the FIAMMS rather than me learning the hard way like frying the horn button or worse. Good luck if you attempt this. It was a lot of fun. It gave me the opportunity to learn more about my bike and I finally got those louder horns. Now my motorcycle has the loudest horns of our three vehicles (the other two are compact cars!). As it turned out, when I went back for the inspection the inspector would have forgotten the horns had I not reminded him.

George Laing
glelaing@erols.com