QuestionI have recently revived a 1978 Honda Hawk 400 Type II. It had been sitting for about a decade. The usual; cleaned and set carbs/fuel system in general, new battery, cleaned all connections and grounds, had everything working extremely well (surprisingly well). I changed the oil today to take it out on its maiden voyage into the sunlight. It started immediately upon pushing the elec. start button (as it has every time since the assembly) but wouldn't idle, then died. I have started the bike about twenty times since the resurrection (start, check something, shut off - start, ride into the back yard & back, shut off - etc.# and have never had this happen. Upon trying to restart, nothing - no try - no backfire - nothing. I checked the fuel, it was fine. I checked the spark plugs, looked good, but when I grounded them against the motor and turned the motor over, they spark healthy for just a moment and then as the the engine cranks the spark fades and disappears. This can be repeated with shutting the switch off then switching it back on, push starter button and watch the spark fade over the course of just a few revolutions of the motor. I have checked the plug connection where the three yellow wires come out of the motor and connect under the lefthand side cover, this looks good. I have checked the ground for the coil and the CDI, both grounds check. I don't want to start doing something stupid from ignorance that will either damage the bike further or give me false result or even waste the time put into it. I am not well versed in these bikes. Please use language an idiot can understand, I am hard to offend, but easy to confound. If I have not provided enough information or if you need other questions answered to make a complete answer, great just let me know I'll do my very best. I really like the bike and was really excited to hear it fire up and run so well. Also, if there are parts to be replaced #CDI, Coil, Stator, whatever# please let me know where I would be able to purchase these items, my local Honda dealers #all 3 of them) either 1.tell me my bike doesn't exist and therefore they "really can't help me with it" or 2.tell me that everything on the bike is obsolete and therefore they "really can't help me with it". Frustration getting the best of me, please help and thank you very much in advance, I appreciate all the help I can get!
AnswerLOL... I hoped it would be a "Honda" manual... here is the extracts for the ignition system....
Pulse generator test 50-170 ohms Blue/yellow to Green wires
Alternator charging coil measuer between all three yellow wires .6 to 1.1 ohms between leads
Ignition coil primary windings .1 to .3 ohms Rebel 450 .55 to .65 all others.
Ignition coil secondary windings 7,200 to 8,800 ohms Rebel 450, 7,400 to 11,100 all others
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Found this on the web...
http://motoservicemanuals.blogspot.com/2009/03/honda-cb-400-service-manual.html
Quentin.... Sounds like you got a good start on rehabbing the bike, but the early CB400Ts were notorious for CDI issues.
Note that the CDI is self-powered, so a battery isn't required to make sparks, just to turn the motor over and supply a source for lighting and load for the charging system.
The system is turned OFF through the ignition switch and the KILL switch. Both of these switches GROUND the ignition system, rather than to open a circuit. So, if you disconnect both switches, you eliminate the possible sources of unintended grounding. If you know how to jump start the starter motor crossing the two big posts with a screwdriver to activate the starter motor, do that and check for spark at the same time. If spark is steady, then one of the switches is causing grounding of the ignition.
If "fading" spark persists, you must understand that the initial signals to the ignition system come from the pulse generator coils, which are part of the stator. These are the usual suspects in ignition problems. The pulse generators create a timing signal to the CDI box, plus a charge coil powers the system up. Losing either part of the equation= no spark/weak spark.
http://www.electrosport.com/technical-resources/known-issues/common-tech-issue?m...
http://www.electrosport.com/technical-resources/technical-articles/motorcycle-st...
Test the ignition coil at the secondary leads (plug caps disconnected) with an ohm meter to see what that reading is. Normally they are down around 10k-25k ohms or so, but never ZERO or infinity. Check each spark plug cap for 5k ohm reading. Test the primary small wires on the coil for ohms readings around 1 ohm.
Wiring diagrams at: http://www.oldmanhonda.com/MC/WiringDiagrams/MCwiring.php#class
http://www.ricksmotorsportelectrics.com/ shows rebuilt stators for $350.
Pulse generator coils are usually in the 5 ohm range or less. I don't have specifics handy on the CB400T. A shop manual is a wise investment when owning these bikes. Get an OEM manual at www.helminc.com or a dealer or Ebay.
Bill Silver
