S3 Thunderbolt Converting from EFI to Carburetor

The advent of electronics has brought about many changes in all industries across the board with greater and more precise control however, to some of us not all of these changes are for the better. I know that electronic control is about the only way vehicles are going to meet the government’s expectations of pollution control, the people’s expectations of greater miles per the ever expensive gallon of fuel, and in the right hands a riders expectations of unreal performance. But for some of us the electronic control ain’t always the way to go. I thought it was a good idea when the electronic ignition first came along and I no longer had to deal with setting points (I can still set them but I’m lazy). In the simpler form there weren’t the myriad of peripheral sensors and multitude of settings, just a black box and cam position sensor and that suited me just fine. Personal opinion out of the way there are some communist states in America that will get bent out of shape if you convert from EFI to carbureted so you better check before you proceed. If you happen to live in one of those states then I truly feel for you for your options are few; Be happy with what you’ve got and learn to live with it, Get an older machine, or MOVE. But for the rest of us who ain’t electronic geeks, have a thing for the carby, and live in one of the few remaining free states then greetings brothers and sisters.

The S3 Thunderbolt/Lightning crossbreed

I must apologize for the lack of disassembly pictures but Mike got a bit over zealous and started the tear down before I got there so I’ll do the best I can to keep you in step.

First the negative cable from the battery was disconnected then the positive then the battery was removed. The seat, air cleaner stuff and the rear fairing was removed. Then on to the fuel tank, NOTE: make sure fuel line pressure is relieved before removing fuel tank! we removed the hold down on the rear of the tank then disconnected the fuel pump and removed the fuel line (after pressure was released) and took off the tank. The tank was set aside and we will deal with the fuel pump later. We got slack in the throttle cables and removed them from the throttle body. we disconnected the throttle position sensor, and injectors, then removed intake manifold. We installed the intake manifold for the 42mm Mikuni HSR.

We are replacing the 2 X 12 pin Electronic Control Module with an 8-pin ignition module with the idea of upgrading to the Crane HI-4E later (also an 8 pin). I spent a few hours going over the manuals and the different wiring diagrams mapping out the wiring using the Deutsch DT connectors that come stock. I like these connectors for the environmental resistance and ease of disassembly. The Deutsch website has excellent references on installation.

VOES

The sensors have one of two ways to be dealt with: disconnect and remove the sensor then cap off the terminals leaving the harness wiring intact (easy way) or (since I was doing surgery anyway) remove the sensor, connector and associated wiring up to any splice. I removed the braiding from the wiring harness from the dash connectors to the battery box. The harness that went behind the battery box and toward the swingarm was left intact and the wires to the unused sensors were clipped as close as possible to the wrapping. I also removed the braiding from the Ignition/Starter Relay Block to the part where the forward braiding was removed. The tape was then removed from the harness where the braiding was removed. It looked like the bike was hemorrhaging wires.

All splices that were made are soldered and shrink tube was used over the splice to make them weather/fuel resistant. The Violet/Yellow wire from the Throttle Position Sensor is used to replace the Violet/White lead that would normally be used for the V.O.E.S. We kept the O2 sensor on the exhaust manifold for now and will replace it later for the input on a K&N air/fuel ratio monitor. The Speed Sensor (easy to spot it has three heavy wires twisted together from the front all the way down to the tail) was retained since we kept the electronic speedometer instead of swapping out a mechanical one.

The clock was removed, as the K&N fuel/air monitor will occupy the space in the dash.

Stock coil and connector

click on image for larger diagram

To have a working tachometer the pink lead from the tachometer was clipped and spliced into the Blue/Orange lead for the coil.

The Ignition/Starter Relay Block was next. First the White/Black lead was pulled from the block and the female spade connector was clipped. The insulator was trimmed back and a male Deutsch DT pin was crimped on. This was inserted into pin position 1 of a male Deutsch DT 8-pin connector for the Ignition Module and checked against the new ignition module connector for proper routing. That was the easy part. I clipped the Gray/Orange lead that goes to the ignition power switch leaving about 5” of wire connected to the block. CAUTION; make sure it is the one going to the ignition switch and NOT the one going to the fuse block). I trimmed back the insulation and crimped on a 3/16” female spade connector. I could not find the connector that is made to fit this style block locally so I removed the plastic collar from a common 3/16” female spade and with a pin punch pushed out the center slightly to grab the block as the replacement would. This connector is then inserted into the Ignition/Starter Relay Block where the White/Black lead connector was pulled. The other clipped end of the Gray/Orange ignition power switch lead is then spliced into the power (Gray) wire.

8-pin ignition module installed

Now we moved on to the meat: the ignition module. The Electronic Control Module is unplugged and removed from the chassis and replaced by the 8-pin ignition module. Both of the Deutsch DT 12-pin connectors (Gray and Black) are pulled apart. The pins were removed with the wires of the unused sensor connectors and the sensor wiring was set aside. The female pins for the Cam Position Sensor (Red/White, Black/White, and Green/White) were removed and replaced by males and then

Manufactured Choke Bracket

Cleaned out fuel tank

inserted into the 8-pin connector, checking the pin position against the ignition module for placement. The Coil Front Primary (Blue/Orange) pin was pulled and replaced by a male and inserted into the 8-pin block were the Pink coil lead would go. There are two Ground Black leads (both were be used), I replaced the female pin with a male pin on the shortest and insert in 8-pin block at its proper position. I removed the remaining Black wire and replaced the female pin with a male pin and let it dangle (this was used for the V.O.E.S. later). I retrieved the Violet/Yellow wire from the Throttle Position Sensor and installed a male pin on the end and inserted it in the 8-pin connector where the Violet/White V.O.E.S. lead would go. The Rear Primary Yellow/Blue had its female pin removed and replaced by a male pin and then inserted into the unused position in the 8-pin block. The 8-pin male connector was then hooked up to the ignition module and rechecked for proper wire position.

A 2-pin male Deutsch DT connector was then used for the V.O.E.S. a second male pin was connected to the free end of the Violet/Yellow wire and
inserted into the 2-pin connector with the free back wire.

I re-checked all connections for integrity and placement re-enforced sleeves were then added to the new connector installs. The wiring harness was then bundled with electrical tape then split plastic conduit was added and then the harness was secured against the frame. I made sure that the wiring was away from hot or moving engine components as well as not interfering

Completed wiring harness

Mikuni 42mm HSR installed

with the movement or placement of chassis parts. I then installed a Mikuni 42 mm HSR onto the new intake manifold without the air cleaner (at this point). I had to manufacture a bracket for the choke out of sheet steel. I hooked up the throttle cables and VOES and temporarily hooked up a carburated M2 fuel tank. I then re-installed the battery and turned on the gas, it took a few seconds for the fuel bowl to fill on the carburetor. I twisted the throttle a few times and when I saw fuel jetting down the throat I pulled the choke out turned on the key and hit the ignition. She fired right up. After a small victory celebration (something wet for the throat and something dry for the head) I moved on.

I pulled the DDFI tank out and started to drain the old fuel in a gas can when I noticed gelling had taken place. The gas had sat too long in the tank and de-stabilized resulting in translucent snot looking globs floating in the old gas. I chucked the old fuel (about 1/2 gal into our waste chemical drum and thoroughly cleaned out the tank. I removed the inlet ring, vent and rubber then removed the fuel pump. We ran into a re-occurring issue with the Buell body parts. With the exception of the engine, frame, swingarm and a few brackets the Buell is largely plastic. Plastic has allot of fine qualities; it is lighter than metal, it has a better memory than

Tank preped

Nut installed in tank

most metals (which means it has a tendency to pop back to form is not overly stressed), and if compatible material is used, can be easy to repair. The key word is compatable in metallurgy the term is similar or dis-similar.  Mating surfaces of dis-similsr metals (and plastics) can produce either positive or negative results. Bi-metal strips (with different thermal co-efficients) are used in thermostats as the metal bends to one side or the other as the temperature changes (an example of a positive effect). The other side of the coin is that  pre-mature (galvanic) corrosion can occur which can result in the mating surfaces failing.  With plastics similarity is determined by chemical make-up and each require it's own bonding agents that work only with that chemical make-up (try repairing a PVC pipe with model glue and you will understand this principal). The point I am trying to make is unless you know exactly which plastic you are working with repairs can be very dicey. Now let's complicate matters by mating a metal surface with a plastic surface, and make it worse by having the joint hold fluid (so that any bonding agient or fastner must be resistant to that fluid). Plastics do not hold a thread worth a hoot, so often the plastic is sandwiched between metal to maintain integrity.

When bonding or sealing agents are used strength of bond and fluid resistance are the primary concern. Now that you have insight into my brain I show you my solution to the problem of securing the Pingel Petcock to the plastic DDFI Buell tank. After the tank was gutted and cleaned I assessed the situation; two holes in the tank about 4" apart, one has to be sealed off and the other has to accept the 7/8 UNF 14 thread of the Pingle DDFI to petcock adapter. The only adapter Pingle makes for DDFI to Carby is for the Harley-Davidson Delphi System with metal fuel tanks and not the Buell Dephi system for the plastic tanks. Apparently the Buell system has a small thread size so I could not use the thin nut or rubberized washers from the old fuel pump (as I anticipated). First I tried to get a 7/8 UNF 14 nut in stainless but no go the local dealer only had it in steel. I took the 7/8 nut to the grinding bench

Fabricated parts with Pingle DDFI  carburetor adapter

 and shaved off about 1/3 then undercut one corner to catch the inside of the tank. Then I fabricated a bracket out of 1/8" plate steel to seal off the unwanted hole, provide rigidity to the plastic, and a mounting surface for the adapter. I then turned to the tank. I felt that there was going to be an unacceptable amount of the 7/8 nut protruding into the tank which would allow too much water to build up in the tank so I cut the hole in the tank to allow the nut to drop down flush with the plate. The undercut lip of the nut catches the tank on the inside and provides some grab.

The surfaces of the tank that was to get the bonding agient (JB WELD) were thoroughly cleaned and scuffed to roughen the surface. The nut had bond applied then installed through the inside of the tank, then the plate had bond applied and set in place. The adapter had teflon tape wrapped on threads and screwed into the nut then torqued down. The whole works was set up to cure overnight.

While Mark and I were searching for parts in the shop we ran across the Thunderbolt's front shroud. I thought the X1 add on was a style choice of Marks but it turns out the S3 was laid down resulting in damage to the shroud and instead of fixing it Mark went with plan B. He said he would like it fixed and reinstalled so while I was waiting on parts I decided to press on to body work. The right turn signal and mirror were history but the shroud only had a small crack at the base of the mirror on the left hand side. I used JB weld and some window screen mesh as backing on the crack, after it cured  only a small white scar was visible.

The Thunderbolt is finished

When I remounted the headlight assembly I noticed that the most of the adjusting screws and clips were missing. This meant a floppy headlight in the cradle so more parts to order. Under the old parts manual the entire headlight assembly has to be ordered (which is costly) under the new parts numbers the clips and adjusting screws can be ordered separately (at much less cost). When I re-mounted the shroud I noticed that the top spreader bar on the shroud frame was bent in slightly (1-1/2") so I bent it back out with some low heat and a pry bar. I snapped on the shroud and another small victory celebration ensued.