Hard start when hot

I put 850 miles on my '82 KZ1100 bagger this weekend, down in New Mexico. Weather was hot, and after running the bike for a while and shutting it down, it was very hard to start when hot. I found that I had to crank the starter for quite sometime with throttle applied, and then finally it would catch, clear out for a second and rev up fine. At first I thought it was due to hot gas percolating out of the bowls, so I tried setting the petcock in the prime position to make sure they were full. No change.
Anyone else have this problem, and if so, what was the diagnosis?
RoMoMoTo

del

JMK-
Unfortunately, it's not often practical to just wait for the motor to cool down when on a road trip. I wonder what the issue is, though? Carbs getting too hot, and gas boiling out?
RoMoMoTo

Without other details - such as coil mods, last carb rebuild, age/condition of the manifold adaptors, age of the spark plugs, it's a shot in the dark to guess...

But here's an odd question for you - while cranking when hot, are you keeping the lights on?

Keeping the lighting circuit energized while turning over the motor can sap a fairly significant chunk of the current that otherwise your coils would convert to spark.

Just a suggestion you might care to try...

Pterosaur,
The bike has all-new ignition components - Dyna S ignition, Ninja coils run through a relay, new plugs, wires and caps. When cold, this sucker fires up in 1/2 second. Carbs - dunno. I bought the bike a few months ago and haven't gone into them at all. Lighting circuit - on this bike, the lights are on as soon as the ignition is turned on. Thinking of introducing a switch to the lighting circuit, but haven't done so yet.
RoMoMoTo

Two things come to mind... FIRST is what altitude were you at when the hard starting occured. If you were above 5K feet, the bike might actually have been a shade rich. I doubt this is the reason though... it is far more likely that the valve clearances have never been checked. When the bike gets nice and toasty and metals expand, the valves may lack the proper clearance and be ever so slightly ajar... I think this might be the #1 reason for hot bike hard starting...

WG-
The bike "lives" at 8000 feet, and my travels over the weekend varied from about 7500 to 10,000+.
The valve clearance issue is a good thought. I haven't checked it since I bought the bike a few months back, and though the P.O. claimed a "major tuneup" in its recent history, we all know that's a meaningless claim in most cases.
Now that my mail order valve cover gasket has arrived I can do that check. Though it may be a while since it's riding season, and I ride. Other bikes in the stable, so I can let the bagger lay fallow until I'm ready to mess with that check.
Interestingly (thought this belongs in one of the other forums, I guess) by the end of the weekend the starter was getting weak, cranking slower (and a couple of times, just clicking until I rocked the bike in gear.) Bad charging system? New battery this spring...
RoMoMoTo
'82 KZ1100 bagger

RoMoMoTo wrote:

Pterosaur,
... Lighting circuit - on this bike, the lights are on as soon as the ignition is turned on. Thinking of introducing a switch to the lighting circuit, but haven't done so yet. RoMoMoTo

Okidoke.

As always, WG's giving good advice, so I'd include his list in primo things to check.

Those full-time light setups always puzzled me, as though they got around to thinking that owners couldn't be trusted to know when and how to turn on the lights. At times (like yours), all those elctrons going nuts in the filaments would be of much more use in the coils.

See somewhat the same issue on mine after long runs on hot days, and a flick of the light switch turns a several-second crank start into an immediate fire-up.

Best of luck...

Pterosaur,
The Japanese bike makers have always assumed we can't be trusted to wipe ourselves when necessary, let alone operate a machine. Back in the days when their motorcycles had a kickstarter and a button, often they would cast in the word "kickstarter" on, well, the kickstarter...
Certainly power to the filament during cranking is electrons misdirected. Maybe I'll buy another relay and a toggle switch and put an end to that while at the same time sending more juice to the light when needed...
RoMoMoTo

The headlight issue was due to federal mandate. The headlight HAD to be on at some point in the late 70s because of the Fed... the bike makers figured that meant that no switch was needed as a result. Later, they started putting another type of relay in place that kept the light from coming on immediately when you cranked the bike... a MUCH better idea than hardwiring the light so that it was drawing at the same time as the starter was drawing. Start another thread in the electrical section... BTW: It only takes a short time to check valve clearances and I personally don't consider this small bit of maintenance an activity that would get in the way of my riding season; especially if I were posting problems like you are having which would do more to ruin my riding than taking an hour or two to do routine maintenance. And the previous owner telling you he had the bike tuned? Bwhahahaha Why would he tune a bike he was selling? Because he was a good citizen? I suggest you tune the bike just to baseline things... good luck!

WG-
In theory I totally agree with you on the routine maintenance issue, but in my case it's more complicated. I live about 150 miles from the nearest source of valve shims, for one thing. Which makes a 1-2 hour job a bit more time-consuming. And myriad obligations intervene... Since I do have other running bikes (with up-to-date maintenance done) I can ride, the KZ may have to sit in the shade until I have a trip planned to the big city. Such is life in the mountains...
As for the P.O.'s tune-up claims, this guy bought the bike from a neighbor, and knew its history. He said the neighbor kept up with routine maintenance over the years. This doesn't mean I take it on faith, of course, but the guy I bought from wasn't making his own bogus claims.
RoMoMoTo

Would be help if you put your location and locomotion in your signature. I take it you are well off the grid and an air drop is out of the question?:ohmy: :woohoo: