Weak hot starting - '82 KZ 750

  I have a 1982 KZ-750 E (4 cylinder) that runs great. I am having a
problem with hot starting. When the bike is cold, the starter cranks
the engine over Ok, and the bike starts well. After riding the bike
for a while (10-20 minutes) if I shut the engine off, the starter will
not crank the engine over. It tries to crank, but it just doesn't have
enough power to spin the engine over. The battery is new, and it holds
a charge well, and the charging system checks out Ok. I have 14.5
volts at the battery at 4000 rpm. If I let the engine cool off for a
while, the starter will crank the engine over and the bike will start.
I suspect that my starter is just weak after 26 years of use.
 I was just wondering if anybody else has encountered a similar
problem. I am going to try to pick up a used starter at a junkyard, or
possibly pull my starter apart and take a look at the brushes.
 Thank You for your help!
 Greg

 
The starter (specifically, the starter clutch) on that engine is well-
known for wearing out and/or seizing up over time. It probably needs
to be stripped out and the clutch replaced.

According to the manual, this means splitting the engine cases. In
fact, it can be done with the engine in situ, but you still have to
remove the sump and engine clutch assembly. It's fiddly, but it can be
done.

 
Doesn't sound like my experience with my KZ650 shagged starter clutch.
It would slip, and consequently the engine wouldn't turn over, but this
sounds like nothing is spinning.  Even though it's rare for a starter
motor to go bad, I would suspect that is indeed the problem in this case.
A clarification from the OP WRT to the symptoms would be welcome.

As far as replacing the starter clutch, I am quite sure the manual doesn't
recommend splitting the cases, as you say it can be done by removing
the sump, BTDT.  I have the KZ750 manual (as well as the KZ650 manual)
at home so I can check if need be.

--
'07 FJR13AW  '99 EX250-F13
OMF #7

 
It's the temperature thing that's puzzling me. Yes, I'd agree that a
knackered starter clutch doesn't usually behave this way, which is why
I was wondering whether, as it gets hot, something's expanding and
sticking in the clutch. I have seen a GT750 (same engine) with a very
sluggish starter before, but then as you say, that could just as
easily have been a defective motor.


The factory manual probably doesn't. I think it was a Haynes BOL, but
as you say, wtf, as long as it can be done through the sump.

 

Is it possible that the starter relay is weak or has a high resistance
in it so the full current is not getting to the starter which is harder
to turn over anyways as the metal has expanded. On some relays you can
take them apart and clean the internal contacts.

Ian Singer

--


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