Topic: cb400f 1975 redish faded side plates ruby red tank and a clue

[Redline it]

10500 mile ride before rust got the chance to grow.

from what i can see, everything was tight, in place, except for that brake caliper hanging from it's line, water/dust shield over the disc, it was gone.

slowly has some stubborn electronics come back to life-turn signals, horn, brake lights and high beam, and the dash lights. turn signal relay was swapped out. and new battery.

starter motor runs excellent in the fresh painted frame. harness and fuses show no signs of lacking ability.

only 1 time watching only 1 and 2 spark plugs, produced a single weak spark followed by 4 to 10 slighty stronger sparks before they stopped.

couple days later, after some deep thought and small checks, led to a notion, with key on, kill switch in the run position, was an insulated screwdriver used to first simply open 2&3 points in low light for a hopeful sign of a spark, nothing.

then 1&4 when opened got a bright blue, only long spark. the clue. so 10 minutes the same test revealed not just a bright blue spark at the point break, but anywhere the screwdriver got close to a ground while holding the points open, points base and crank shaft shot out long splatters of sparks. not loud, but what looked like dragging a positive wire on a near dead battery negative post or shorting the battery to see if it has what it takes to work. is something shorted or not making contact with ground?

it's a mystery to me, completely. continuity, power, it's all the same not sinking in. ohms and microferads-what?

[Redline it]

Hoping it wasn't too complex of a description, if so I can summarize it:.. points and are energized. Only no spark at the plugs. Any idea where to start, thanks.

[newday777]

I worked on a friend's K4 750 last summer that he rode to my shop(weak on power).
I found weak/no spark on 2/3 plugs. He brought new coils and plugs along with carb kits(I just used the bowl gaskets and cleaned the carbs well). I chased it down to being a bad condenser.
Are you running aftermarket points and condensers? They are known to fail quickly. New points plate assemblies are available from Honda.

[69cb750]

then 1&4 when opened got a bright blue, only long spark. the clue. so 10 minutes the same test revealed not just a bright blue spark at the point break, but anywhere the screwdriver got close to a ground while holding the points open, points base and crank shaft shot out long splatters of sparks. not loud, but what looked like dragging a positive wire on a near dead battery negative post or shorting the battery to see if it has what it takes to work. is something shorted or not making contact with ground?

Lots of points sparks is probably bad condensors, buy Honda or Japan made, after market are junk.

[Scootch]

Make sure plug wires, caps, coil is/are good and good connections. I would recommend real solid conductor center conductor plug wires. You can make them yourself. I just made a set to replace the graphite suppression wires and screw on plug caps. Questionable connectivity. Ordered solid conductor plug wire, crimp on connectors/caps and crimp tool. Solid connections. One less thing to be intermittent.

[MauiK3]

Yes, the caps that go on the plugs often have too high resistance, good to replace them.

[newday777]

Make sure plug wires, caps, coil is/are good and good connections. I would recommend real solid conductor center conductor plug wires. You can make them yourself. I just made a set to replace the graphite suppression wires and screw on plug caps. Questionable connectivity. Ordered solid conductor plug wire, crimp on connectors/caps and crimp tool. Solid connections. One less thing to be intermittent.

The plug wires are molded into the coils

[Redline it]

I worked on a friend's K4 750 last summer that he rode to my shop(weak on power).
I found weak/no spark on 2/3 plugs. He brought new coils and plugs along with carb kits(I just used the bowl gaskets and cleaned the carbs well). I chased it down to being a bad condenser.
Are you running aftermarket points and condensers? They are known to fail quickly. New points plate assemblies are available from Honda.

i'm not sure what they are, nipon denso points and they both with a center pit, i cut that off. condensers,i've been going through the list here, and i'm abit stubborn to think all for plugs, caps or wires failed at once. but i did have a spare rectifier and going further down the tubes put that on and hit the starter and the points were sparking wildly in time with what the points should be doing other than arcing,they were in time so i stoped,oh and 1 the only one i was trying was sparking also. after a few minutes i tried it again and maybe a couple rounds of sparks then the sparks quit. like they have been doing since trying.the bike was rusty so there was moisture running around, not to stray with chattin, afew weeks ago i was gonna go get a battery for this bike, by my other 400f had a dead battery, so i jumped it like i always have with a non running car battery, only i for the first time in 40 yrs connected the cablebackwards. i knew it did something but i charged the bike battery for 1/2 hour starting with 50amps and then ended up 20 mins on the 10 amps (yea i know that's too much, so i takeoff and the bike is running like a monster in power. a mile later as i squeeze between cars in the number 3 lane, the banner drops and im all hand full of throttle, and it dies.so i kick it and it fires up, i get gas and then make it to the store and it dies, the store didn't have batteries.so ended up pushing it 2 miles at night with traffic zinging by. it took 2 hours. ok so that rectifier is bad after the 40 yrs, but it's plug wires and caps are still original. and without knowing off hand what is not good other than everything including the jump starts, there's something wrong that i get occasional ignition and then it disappears fast. so i read these and the other ignition troubles and solutions, i gotta get a better multi meter. i got spare everything but i should trace the problem before i know of the order in which to try by maybe a known good part. 

[Redline it]

update on this 400f 1975;
i mentioned on these unorganized post that process of elimination continues with no certainty yet of a running bike. thanks for the help so far, the lack of spark at the plugs were my inexperience of the clutch saftey switch working on another 400f, that i've riden for over 40 years. and only by luck one night it came out of nowhere, to try and pull the clutch lever while trying to start it, and i grumbled.

the cam spray bars i haven't been convinced they're producing what they're intended to do. after like 4 or 5 second spurts of running motor, only 2 attempts, the appearance of the valves hasn't changed and i thought i seen dripping on both sides of motor so i had hope. and that seemed to have vanished. so i took the oil pan off to check if the screen pick up was functioning. after 2 days of no oil in an exposed lower gearbox, pan off, i pulled the oil pick up screen and it had a cup of oil or 1/2 in it that dumped while pulling it off? so i checked the screen and put it back on, and the oil pan also. now full on oil, i'll try to get a good prime on the pump from a large drill in reverse turning the motor over in the run direction  at the alternator nut, with the plugs out. i'm hoping that's a reverse threaded nut. . appreciate the tips so far.

[Redline it]

update on this 400f 1975;
i mentioned on these unorganized post that process of elimination continues with no certainty yet of a running bike. thanks for the help so far, the lack of spark at the plugs were my inexperience of the clutch saftey switch working on another 400f, that i've riden for over 40 years. and only by luck one night it came out of nowhere, to try and pull the clutch lever while trying to start it, and i grumbled.

the cam spray bars i haven't been convinced they're producing what they're intended to do. after like 4 or 5 second spurts of running motor, only 2 attempts, the appearance of the valves hasn't changed and i thought i seen dripping on both sides of motor so i had hope. and that seemed to have vanished. so i took the oil pan off to check if the screen pick up was functioning. after 2 days of no oil in an exposed lower gearbox, pan off, i pulled the oil pick up screen and it had a cup of oil or 1/2 in it that dumped while pulling it off? so i checked the screen and put it back on, and the oil pan also. now full on oil, i'll try to get a good prime on the pump from a large drill in reverse turning the motor over in the run direction  at the alternator nut, with the plugs out. i'm hoping that's a reverse threaded nut. . appreciate the tips so far.

i'll give an update on the last check: so with a standard old Milwaukee 3/8" f&r drill with a half inch chuck on it, i removed the alt cover (cb400f 1975 just a reminder,) (but before that i added the oil and then just kicked over the motor without hard kick or trying to speed kick any other than turning it over. and the oil level was dropping so i knew the pump is pumping.) but i wanted to see the oil dripping from the cam. so i connected the drill to a 14mm socket, this should get some chuckles of satisfaction by a few here-now i'm in the living room, carpet, coffee tables and white plaster walls. and i get to turning it  pretty fast. and all of sudden "boom, the plug shot out, with a burst of oil that went every where, i had to plug the hole with a finger to look where the plug went. i'd never done that so i didn't expect it even though last night was telling someone about checking those middle of line right angle turns and how the alt covers holds one in place,   put it back together now  and in no particular order, point gap, and get a ball park idea on timing, and sync the carbs, the last 2 i hope a running motor is part of the plans. and put more gas in to run the motor instead of low levels. possibly get through that in less than a month. that's the plans. of any more clutz operations i'll mention it in case another "builder" happens to get lucky and see what not to do. i'll check the valve gaps for the 3rd time and make sure i tighten any that i adjust . last project of new head and base gasket job took a year, and upon the first ride around the block thankfully one side was getting warmer and it was because i forgot to take out a plug of terry cloth out of the lower base gasket, and that's when i found an adjuster nut fell off and was laying right next to the valve/spring. so i put that one back together, then the next trial I was getting oil on top. and went to check the valves, and another nut was missing. so back to taking the cover off again. i found the nut wedged down the outside channel
that drains into the crank case. i'm not sure if it could have gone all the way but with bailing wire pulled it back up. 2 close calls on the low tightening of the adjuster screws. now i use a torque wrench and go for at least 14ft lbs. it's only 15/40 clean honda oil. wingin it.

[Redline it]

without the little motor running cb400f 1975 the oil gallery plug at the alternator wouldn't necessarily drain any large portion of oil other that what's on top of it going through the restrictors, correct? on the pump side if any would drain out of the alternator plug, it wouldn't be that much would it? from a complete drained pan and cleaned oil pick up screen, filled the tank and kicked it maybe 10 or 15 times then did the drill powered crank shaft spin, in the direction that it runs for maybe 6 seconds before the alternator plug blew out and it was already producing oil dripping on the cam. what i'm trying to figure out after putting the alt cover back on is the possibility of a slightly plugged restrictors or the pumps ability or lack of in terms of volume for those short seconds and developing that much pressure while artificially getting rpm with a drill. oh heck nevermind i'm gonna let it go. if a half of the cam bearings seize. i'll just find another spot for that motor to be a permanent resident and have some more extra parts on hand. the parts are adding up to too much. it'll be parts cemetery, for sure.