First off, credit goes to tremor38 (Dean) at kawasakiforums.com for coming up with this ingenious design, here's a link to his original post. Also, inspiration came from planetklx.com as well.

Background: After a spill, the KLX250S can be a bear to get started again. This is usually due to flooding. This issue is made worse if there's a pumper carb installed. While opening the throttle, there's an extra squirt of fuel introduced. A hot start system can be viewed as the opposite of a choke system. Instead of providing an overly rich mixture, it provides an overly lean mixture by introducing an alternate path for fresh air into the intake port.  Many traditional hot start systems on dirt bikes were of a mechanical type (since those bikes don't have a battery in their electrical system). This system uses an electrically-controlled air valve.

Parts list:

•  Delco Remy EGR Solenoid Control Valve P/N 1997240 (got mine off ebay for $4.99 + shipping)
•  Engine Stop Switch for KLX400R, Kawasaki P/N 27010-0070 ($17.61 at ronayers.com) - this is a SPST N.O. switch
•  EGR Solenoid Connector, 93-97 LT1 ($11.00 from tpiparts.net) (photo)
•  Dorman Male Connector: BRASS-TITE!; 1/8" NPT for 1/4" Hose, P/N 43276 Qty: 2 (found locally at Advance Auto Parts for $2.29) (photo)
•  Watts 1/8" Female Pipe to Female Pipe Elbow (found locally at Lowe's for $1.97) (photo)

Consumables:

•  epoxy
•  JB Weld
•  heat shrink tubing
•  wire splices - bullet type, Qty: 3
•  thread selant
•  self adhering velcro
•  1/4" I.D. fuel grade tubing
•  hookup wire
•  electrical tape
•  "piggyback" splices, Qty: 2
•  small piece of 3/8" I.D. hose (cut and used a small piece of the smog system hose)
•  hose clamps

Notable tools needed:

•  1/8" pipe thread tap
•  1/8" pipe thread die
•  5/16" drill bit

Valve preparation

Since I received the valve used off of ebay, the first thing that I did was to perform a bench test to determine the correct polarity of the hookup wires, to see if the valve was in working order and to analyze its operation. It turns out that the gray wire is where 12V should be connected and GND goes to the black wire.  I also found that the valve isn't "air tight" in all directions. The side air port won't hold a vacuum, it bleeds air from the top air port. The top air port does hold a vacuum, therefore this is the port that should be connected to the engine intake.

Modification of the valve started with cutting off the mounting flanges. Next was to thread the top air port. Remove the blue gasket and trim down the lip on the air port with a utility knife. This allows the 1/8" pipe thread die to be started. Carefully cut a thread on the top air port.

Next assemble one of the brass nipples to the brass elbow -- use a light coat of thread sealant and tighten the two together.  Now mix a small amount of epoxy and lightly coat the newly cut threads on the top air port. Assemble the brass fitting to the top air port, align the two ports and let dry.

Installing nipple into intake port

This next procedure isn't for the faint of heart. If you're lucky enough to have a carburetor with an unused vacuum port, then this step isn't necessary. If you have removed the smog system from the bike and you have the stock Keihin CVK34, then there's an unused port available on the carb. Both of the commonly used Mikunis (TM34-8012 and TM36-68) do not have a vacuum port.  Therefore, you'll need to install a nipple into the intake port.

Find your center and drill a 5/16" hole into the intake port. Cleanliness is key here, be sure to stuff a clean rag into the intake port. I also coated the drill bit with grease to help catch the shavings.  I also kept a shop-vac handy and vacuumed up after drilling, tapping and removing the rag.

Next, use a 1/8" NPT tap and tap some threads. I coated the tap with grease too to help catch the shavings.

Now mix up some JB Weld and lightly coat the threads of the nipple.  Screw the nipple in and stop once the back side is flush with the inside wall of the intake port.

Installing the switch and wiring harness

Find a spot on the left hand side of the handlebars for the switch. You'll want to be able to push both the start button (on the right side) and the hot start button simultaneously. 

The KLX400R switch has an "ENGINE KILL" label which I peeled off.  I cut off the two pin connector and spliced on two lengths of hookup wire and sheathed the new wires in a piece of heatshrink tubing.  Make sure the wire is long enough to route along the main wiring harness all the way back to the area behind the seat.

The switch will provide a path for GND to the solenoid.  Under and behind the seat is a convenient GND wire (black with a yellow stripe). I used one of the piggyback splices to tap into this wire.

Note: my left hand console isn't stock - I replaced it with an alternate switch that is narrower and shallower, provides an off function for the headlamp and eliminates the turn signal switch (my bike doesn't have any turn signals).

Mounting the solenoid, finishing the wiring and hooking up the hoses

I mounted the solenoid with the previously referred to top at the bottom using some self adhering velcro on the right side of the airbox. Conveniently there a small recess here for it to fit into.  Even more convenient is the nearby switched 12V power. Follow the rear brake light switch up to the connector. On the harness side of that connecter, use a piggyback splice to tap into the brown wire to connect the solenoid's gray wire. 

In the same location connect the other side of the handlebar switch wiring harness with a bullet splice to the solenoid's black wire. I wrapped the splices up in electrical tape for some extra protection.

Now route and hook up the hoses. Run one hose from the brass nipple on the solenoid to the brass nipple on the intake port. The other hose runs from the side port of the solenoid to the unused port on the airbox (unused due to the smog system being removed). The problem here is that the airbox port accepts a 3/8" I.D. hose. My fix was to use a small piece of the 3/8" hose from the smog system to connect to this port and then insert the 1/4" I.D. hose into it -- it fits together very snugly.  This port on the airbox is on the clean side of the air filter -- good.

Then added clamps to the hose on the vacuum side tube to ensure that there are no air leaks.

Testing

Turn on the ignition switch and touch the solenoid. Push the hot start button on the handlebar and you should be able to feel the solenoid activate.

Start the bike and let it warm up completely. If you push the button now, then the engine should falter as the overly lean fuel mixture is introduced.  Without dumping the bike, it system can be further tested if there is a pumper carb installed.  Kill the engine and twist the throttle half a dozen times and try starting the bike. It should be difficult to start if it starts at all. Now push in the hot start switch and hit the engine start button, it should start right up in a revolution or two.

Won't be long until I'm able to test the system in a real life situation.  I'll try to remember to update this page then.

Wednesday, October 22, 2008