Topic: 400T (free!!!)

[Red750K1]

Hey all, Just got a new bike for free!  It's a '78 Honda CM400T.  Very nice shape, only 9K on it. It won't start and the guy who had it said it just started running funny so he parked it.  The one plug was fine and the other side had the electrodes bridged. I'm pretty sure its actually melted which would be pre-iginition.  The deposites seem too hard to be carbon build up but the insulator doesnt have metal or anything funky on it.  Since this is a electronic iginiton bike I'm going to have to ask around for tips on fixing and buy the clymer book on it.  Anyone know some good sites/forums for 400 twins? I'll try rebuilding the carbs today and see if I can get her running. It DOES have spark on both sides though. I'm going to run a compression test also.    any tips anyone?

[bryanj]

Carbs are an absolute nightmare and frequently do not respond to cleaning even ultrasonicaly! When it runs check the advance timing with a strobe, if it advances too far it will be the generator complete MEGGABUCKS

[Red750K1]

How would the generator have anything to do with timing advance? I was mostly worried the electronic ignition stuff would be shot because its one of the earliest designs for CDI. but it does have spark , hmmm,  anyone know a good place for parts for these, haven't fond much yet.

[Slapguts]

If it's a 1978, it should be a CB400T, either I or II.

<--That's mine, post crash.

Not alot of websites/info out there on these bikes. They're great, cheap, and pretty peppy for what they are. If the compression test has bad news, an engine from a CM450T will slide right in.

[dustyc]

In the index for this board, there is a board for other bikes.  I see people asking questions about twins there.  I think alot of people here know about the bikes, but it keeps this board for fours which makes things easier when searching for answers not to have to sort through all of everything else.

I think that's how it works, but I'm a newb here, so correct me if I'm wrong.

[KB02]

I've got one of them, too!!   
It was given to me for free as well!!    
And has just under 9000 miles on it!!   

Great bikes. My wife and I just took it (It's her bike) on our vacation to the Americade rally in Lake George, NY. When my DEucati broke down on me (  ) we were riding the little 400 all around. With a combined weight of over 350, it was hauling the two of us at 65+ on the highway without too much trouble. 

[bryanj]

I have no idea why, or how, the generator fault causes the excessive advance just know, from when they were knew, that it does and the only cure is replacement. Origially it was a complete unit, stator and rotor, which was MEGGAMEGGA bucks then Honda changed the part number so you could get just the stator reducing it to MEGGA bucks and low and behold when we ordered one(for a customer) and opened the box it contained a rotor as well.

I know that if there is a problem all logic and sense says it ought to be the cdi but i NEVER replaced one of those and here in UK we had a 250 version for our "learner" laws in force at the time so there were 1,000's of those about, strangely never had a generator go on a 250 only the 400 and usually the symptom was a low compression piston-----Hole in top!!!

[crazypj]

I have no idea why, or how, the generator fault causes the excessive advance just know, from when they were knew, that it does and the only cure is replacement. Origially it was a complete unit, stator and rotor, which was MEGGAMEGGA bucks then Honda changed the part number so you could get just the stator reducing it to MEGGA bucks and low and behold when we ordered one(for a customer) and opened the box it contained a rotor as well.

I know that if there is a problem all logic and sense says it ought to be the cdi but i NEVER replaced one of those and here in UK we had a 250 version for our "learner" laws in force at the time so there were 1,000's of those about, strangely never had a generator go on a 250 only the 400 and usually the symptom was a low compression piston-----Hole in top!!!

I know, was at Honda UK for a course when they had the problem.
 The windings on trigger unit were wound too tight on low speed coil and they shorted internally so it would run over advanced at low speeds (until it stopped completely)
 Even though its 'non-adjustable'  you can drill out the rivet, slot mounting and fit 5mm screws to get timing right where you want it.
Never had a CDI box fail either, the generator was good,( would put out 20Amps ) just the trigger units sucked big time
PJ