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Discussion Starter #1
Hello,

New to the forum, Names Brian. Northeast Ohio Lorain County Area, 28 Years Old DIY motorcycle enthusiast, Backyard mechanic no professional here but I do my best, Ive got a few motorcycles (74 cb500,71 Triumph Daytona 500,04 Suzuki DRZ400). I Rebuilt the top end of my cb500 and multiple carbs on bikes and other things just so you know my skill level, self taught, I can tackle most things with a little help.

Anyways,
My brother and I have a pair of 78 CB400a bikes, one runs perfect and is in mint shape the red one, the other was sold to us as a parts bike, being the blue one. We're trying to get the blue one running, we can get the bike to run and idle fine but any time that it is put into gear the bike stalls out and dies, We have bypassed the kick stand switch to confirm that was not an issue and actually pulled the whole side panel electronics from the perfect running bike to see if that changed anything and still have the same verdict, I do have the Honda Hawk Shop manual for this bike but I don't see a whole lot in it with maintenance on the transmission. I'm assuming it has a torque converter similar to an automatic transmission on a car? Could this be locked up? It has a kick starter and its notorious for kicking back on you abruptly also (messed up my leg actually). Been tinkering with the bike for a year or so now and am kind of at wits end with it, we have pulled and cleaned the carbs and replaced the boots on the carbs also, just wasn't sure where to go next on this one, i've tried searching online and anything I've searched we looked over, which its been a little while so I may be missing something we tried. But I do have a good running bike I can swap over parts to, to test them at least. Thanks in Advance!








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The 400as timing is at 7,5 degrees at idle . the change switch tells the CDI box to change the timing to 12 degrees when the bike is put into gear. This is done because the extra load put on the engine by the torque converter. This is controlled by the CDI box so changing the electronics wouldnt change any thing. Swap out the CDI box and see if that helps . The side stand switch only keeps the bike from starting when its down so wouldnt effect the running.

Bill
 

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Discussion Starter #4
Thank You guys, going to try this and will let you know!
 

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Been thinking about your problem and am not sure its CDI box.

From the FSM.

Motor runs but bike wont move.

!,No oil or lack of oil.

2, torque converter check valve not installed.

3, Torque converter check valve stuck open or weak or damaged check valve spring.

4, clogged oil passage.

5, Oil pump drive chain broken.

6, Defective oil pump.

7, Damaged primary drive and/or driven gear.

8, Torque converter pump flange or 6 mm rivets broken.

You will need a FSM. Trust me its not like any thing you have worked on before. You might be able to remove the converter without the manual but you wont get it back together without the manual. There are three shafts and gear sets to line up to install the torque converter and the manual tells you how to do it.


Good luck.

Bill
 

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any time that it is put into gear the bike stalls out and dies, We have bypassed the kick stand switch to confirm that was not an issue
Don't bypass the side stand switch, try to disconnect it instead if you suspect malfunction.
If that switch is shorted, the CB400A switch-relay will send a signal into the CDI to stop ignition, whenver you engage any gear other than idle.

Robert
 

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Discussion Starter #7
Well. You were right off the bat. Swapped the cdi off the other bike and it started second kick and went into gear without stalling, rode it down the street for the first time in who knows how many years. So now its trying to find the parts used. But the better option seems to be taking our nicer bike and upgrading it to 400t flywheel and parts with a brand new cdi they sell online i think was cdimagician.
Glad we can finally get this bike rolling again. Thanks guys!
 
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