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Discussion Starter · #1 ·
Recently bought a 1978 cb400t II. Bike is really low on power and upon checking for spark I saw it was very weak. I've gone through and tested the coil and stator and the only thing not in spec is the advancer pickup sensor. Ant help or advice is much appreciated. Pretty new to a bikes electrical but have a decent understanding of electronics. Thanks
 

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Discussion Starter · #3 ·
Original air box and exhaust. Compression tested low at about 130 for both sides. Previous owner said he installed a new cdi.
 

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Is it mis-firing under load or is it just weak overall? What color are the spark plugs? Have you used a strobe light to see if it is advancing?
 

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Discussion Starter · #5 ·
Haven't strobed it yet. Need to buy a light. When I pulled the plugs they were damp. But the spark is just weak overall. Haven't noticed any misfiring.
 

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If the stator produces a spark your winning!.? New plugs are good but if the coils are pathetic you’ll have a problem. Clean all the contacts properly with wet and dry; dry.
 

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You have resisters in your spark plug caps
 

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That's good,inspect for corrosion in the holder.
 

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When you check the timing advance you'll see that it either isn't working or it's extremely slow/late in working.
 

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Look into plug side of the cap and see if there is a screwdriver slot. If there is you can unscrew it and a small resistor will fall out. Cut a piece of brass brazing rod or solid core copper wire the same length as the resistor and install it in the cap. You can do this with the older caps, the new ones have been "improved" so the resistor can't be removed.
 
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Recently bought a 1978 cb400t II. Bike is really low on power and upon checking for spark I saw it was very weak. I've gone through and tested the coil and stator and the only thing not in spec is the advancer pickup sensor. Ant help or advice is much appreciated. Pretty new to a bikes electrical but have a decent understanding of electronics. Thanks
Back in the day, within the first several years after the 400Ts were out of warranty, I recall dozens that came in as non-running machines, that left as non-running machines, no sparkee, needing a $500 stator assy. that nobody wanted to purchase....too bad, there's GOT to be hundreds that turned into rust buckets because of Honda's defective ignition. Could have made a fortune by either finding a workable pickup coil replacement or converting them to points... The stator & pulsar pickup were only available as a unit for over $500... Other than that, it was a good design.

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Discussion Starter · #17 ·
Are the pulsar pickups available to purchase separately anywhere? From my testing the only thing I've found out of spec it the advance pickup.
 

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Are the pulsar pickups available to purchase separately anywhere? From my testing the only thing I've found out of spec it the advance pickup.
The pickup coil isn't any kind of complicated or 'valuable' item. If it was mine, I would check the wiring diagram to see which wires go to & from it, penetrate the pickup wires with T-pins, clip my multimeter leads, & spin it over, checking for flux. If you get a pulling power spike, it's doing it's job. Nobody ever attempted to fix those defective ignitions back in the day. We were always so covered up it was check spark, none, check components, find that the stator wasn't supplying spark, write an estimate, & move on to the next bike. I was service manager for decades & don't recall ANYBODY ever dumping the $500 + labor on those. Usually, with electronic ignition, it either works or not. I wouldn't put too much stock in whatever you've found unless the readings are WAY out of spec. Back in the day, ALL the electronic specs were ONLY valid IF using the Honda specified meter, Fox Valley, out of Wisconsin, if I recall correctly. Different meters read to different degrees of accuracy & when such small variations mean go or no-go, you're gambling. Working in the dealership made it easy to do exactly what Honda Suzuki & Yamaha suggested - substitute a known-good unit, if it fixes it, order the part.... I'd look elsewhere for the problem. I'm gonna go back up to the top & read your bike's symptoms. I was replying as to the stators, don't recall what else you said... I'll comment if I have suggestions...

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Recently bought a 1978 cb400t II. Bike is really low on power and upon checking for spark I saw it was very weak. I've gone through and tested the coil and stator and the only thing not in spec is the advancer pickup sensor. Ant help or advice is much appreciated. Pretty new to a bikes electrical but have a decent understanding of electronics. Thanks
What is it using for air filters? OE? Make sure this area is top notch, your engine depends on clean air in the proper amount. OE airbox needs to be fully intact, including any & all covers. I've seen bikes that ran like crap because the seat was weak & closed off the intake, not necessarily your model but something to check. I've seen bikes that wouldn't start, some that would but run like crap, with nests in the exhaust pipes...if your bike sat for decades with a bad stator, could be. If the advance is DEFINITELY the culprit, I'd see about modifying the pulsar mount to dial in advance. There's no reason not to have your advance locked in. I do that on my 600HP AMXs & they scream, & start easily.... I wouldn't necessarily say 130 psi is too low, at least they're both the same... May as well set valve clearance, if you haven't. This bike is now pretty darned old, every facet needs to be checked. Gas tank vent... Petcock....CARBS....

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Discussion Starter · #20 ·
I have been reading through other posts with people having the exact same problem so I just pulled the trigger on a used stator and pickups. The resistance readings I have gotten were all in spec except my advance pickup witch was reading 35 ohms too high. Am going to change out this assembly and see the results. If all things go well I might still go ahead with the gm hei mod. Will post results afterwards.
 
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