750 Saber

I have a 1983 honda 750 saber vf. A couple of issues I need help with.

1) when I first start riding, not quite up to normal engine temp yet.
The tach stops working, drops to zero. Then it looses power, feels
like it drops a cylinder or two. Runs really slugest for about 30-60
seconds. and without warning comes alive again, and tach starts
working again. Once it reaches normal engine temp It runs perfect. It
doesn’t do it again till the next warm up period.

2) This bike has a instrument cluster that has a red trouble warning
light, and a digital readout of the systems it montoirs. The same
little digtal window is also the gear indicator, when not showing the
systems it montiors.
The problum is the little digital window just continuely toggles
between headlight, taillight and battery. It never shows the gear
indicator. All 3 systems appear to function properly.

Thanks,

Patrick

 

The '84 honda V-4s essentially have two entirely separate ignition
systems, and the tach is hooked to one of 'em. It sounds like one of
the two has some sort of thermal problem - could be a hall sensor in
the engine case (picks up the crank position and sends the impulse to
fire that plug - or actually, both plugs at once). It could be the
computer, wiring harness or a host of other things. On my '83 Magna,
one of the hall sensors failed and did the same thing. The difficult
thing is that it's an intermittent problem - you'll never really know
if you've fixed it or not.

This is the kind of electronic bug that I used to troubleshoot using a
spritz or two of freon (when you have it running rough, and hit the
bad part with freon, it'll immediately start working right). Of
course, a spritz of freon will now cause all life as we know it to
vaporize instantly so I would never recommend doing that. ;-)

Mark Hickey

 

Thanks Mark,

Before I vaporize the planet with freon, what componet is it I would
be spraying?

Patrick

 

Krusty had a great idea as well - I had forgotten that trick
(obviously because it didn't work for me... harumph).

It's been a while, but there are two hall sensors under the side cover
on the Honda V-4 - little brown/black thingies that are hooked to
wires that come through the top of the case somewhere near the base of
the cylinders IIRC. You might try wiggling them a bit to see if you
can get a solid correlation between moving them and getting the
roughness to appear/disappear.

You symptom is exactly like mine, BTW. It would start fine, warm up
and run rough for a while, then run fine again.

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $695 ti frame

 

My bad - I don't know why I thought it was Krusty who wrote about
swapping the two ignition boxes - it was Jack Hunt... D'Oh..

Mark Hickey

 

Thanks for the help on the tac/sensor. But can anyone address the #2
instrument read- out problum?

Patrick