82 750 loss of power...

[SpudMagna]

This bike was running great for about a year then all of a sudden there was a dramatic loss of power, like its running on two cylinders.  It came and went for a while now pretty much stayed at half power from then on.

After advice found here I bought a new set of spark plug wires and installed new plugs (the bike had the original 82 vintage wires still on it) - No change, stumbles along at half power, then will jump to life for a few minutes then back to half power.

It starts out from an idle in first gear with major loss of power and it rarely if ever gives normal output regardless of the gear or RPM.

I also installed a good heavy wired ground to the battery negative terminal from where the coils were mounted. The tank was flushed, the fuel pump tested and the fuel filter was replaced, no change.

The tach also dives to zero then jumps around if you rev it up in neutral.

I can't remember how to trouble shoot the coils though I did that last year, swapping left to right coils, checking with grounded out wires through a spark plug and gave up after finding nothing definitive there.  I should probably do that again if someone could point me to a step by step procedure to check the coils again.

What is the best guess on what is causing this? I am guessing the next step is a set of new coils?  Could it be something else?

Thanks in advance for any advice.

SpudMagna

[SkyRide]

There are two spark units, CDIs, under the seat.  Each controls the spark to two cylinders PLUS one drives the tachometer and the other the fuel pump.  My 83 did the same thing.  Best way to troubleshoot is to have a good unit that you can swap.

Rick Frankenberger
83 V750

[SpudMagna]

Thanks. I will order up a new coil and proceed from there.

[SkyRide]

I'm not referring  to the coil.  That could be your problem, but it doesn't explain the tachometer problem.

The spark unit (AKA CDI or Ignitor) is a 2" x 3" x 1" black plastic box with a 6" long cable coming out one end.   For 82 the Honda PN is 30400-MB0-004 or -005.  The same ones fit 83 and probably others.

As it turns out neither of the spare units I have are those numbers.  They are marked:
HITACHI
IC IGNITOR
TID12-04A
MBO K7925

and
NIPPONDENSO
AKBZ02
1311008491.  The 8 is smudged; it could be 3 or 9.
1.2V
another number that I can't read

The Nippon fits the original holder under the passenger seat.  The Hitachi is a little larger and won't fit in the original spot.  Both work fine in my 83.

I don't see any on ebay just now, but it is worth a look later.

Rick Frankenberger

[Greg Cothern]

Coils are easy to check, identify which bank is not running normal, swap the coils and problem should move with them.....  Coils are notorious when they start to die for going weak under a load.