Hard start when hot

Ambergrismooon,
No longer off the grid, though I was for 11 years. I'm in the Sangre de Cristo Mountains of Colorado. Air drop is possible, but probably more pricey than UPS, which does deliver up here.
Locomotion: 1982 KZ1100 bagger
2004 Suzuki DL650
2002 Suzuki DR650
1975 Norton Commando 880
1973 Norton Commando 850
1996 Buick Roadmaster Estate Wagon LT-1

RoMoMoTo...

Z1Enterprises.com sells shims individually and in kit form for a good deal less than most Kaw dealers. They ship to Colorado. Once you have meansure clearances, measure all shims and record the data. You MAY be able to reshim by shuffling existing shims or just buying a couple. Your problem sounds valve clearance related. Good luck!

WG,
Thanks for the tip on Z1 Enterprises. I'll check them out for the shims, as soon as I do the valve adjustment check. I don't mind mail ordering these things.
RoMoMoTo

hard to start when hot usually is a condition that is caused by a couple simple things --but not always--

tight valve or valves leaking compression

cam chain tensioner needs adjusted

these are the two top things to check
after that it is the balance of

fuel
compression
timed ignition

Trippivot,
Thanks for your insights. I'm thinking that WG is probably on the mark with tight valve clearances, and will look at that first - esp. since I haven't checked it yet on this bike since I bought it.
RoMoMoTo
'82 KZ1100 bagger

wiredgeorge wrote:

Later, they started putting another type of relay in place that kept the light from coming on immediately when you cranked the bike...

FWIW, My buddy's 84 Virago has it built into the starter solenoid. when the solenoid actuates and connects the starter motor contacts, it disengages the headlight power -- like a double-throw switch.

good luck RoMo, let us know if it helped.

Sounds like the setup cars use - and it makes perfect sense. Guess I'll double-check and see if my headlight is lit when I crank the starter, before getting out the soldering gun again. Thanks for the tip.
RoMoMoTo
'82 KZ1100 bagger

By the way, WiredGeorge was spot on with his diagnosis. I found three out of eight valves under .03"...
RoMoMoTo
'82 KZ1100 bagger

Any resolution to this one? My scoot has begun refusing to start when warm (I had to push it home 3 miles the other day :blush:). To make a bad deal worse, it won't reliably start cold now either. After making adjustments I kicked it over this morning when the battery started complaining and after I shut it off it started 15 seconds later with the starter, but then it wouldn't start at all later in the day.

Points are adjusted, brand spankin' new plugs which are getting a healthy spark, once it's running it runs normally, even during warm up (nixing, in my mind, carb issues), it is running a bit on the lean side though(which I'm also concerned about).

I will say that the hot starts have been getting progressively more difficult, although cold starts have never been an issue before this hissy fit.

I'm beginning to think valves myself, I was getting backfires when engine braking with a higher frequency as time marched on. I think I was in denial. what do you guys think?

Post edited by: 78_KZ750_Cafe, at: 2006/08/12 18:44

Don't know if your problem relates to mine, but pushing a big bike three miles is beyond my patience level at this point!
I found that a couple of my valve clearances were tighter than spec, but I had to wait while I ordered/received a tool to pull the shims. Now I have them out, will do some arithmetic, figure out what I need to buy in shims to bring all the valves into spec, buy said shims and install them.

Since I have a lot on the table right now, this isn't going to happen right quick, but I'll report my results when I get the job done. Good luck with your own problem. I bet some of the experts on the forum here can steer you in the right direction...
RoMoMoTo
1982 KZ1100 bagger
other bikes

WG is right, a shim clearance check is always a good thing to do when you get a bike, but the symptom of hard to start when warm is not exactly the classic symptom. If it's hard to start from being warm due to no-valve clearance, it will usually not run too well at idle either when hot. It will die unless you raise the idle or keep on the throttle a little.

The classic symptom for no-valve-clearance is that it will run fine when cold, but after a hot highway run, it will die if you come to a quick stop and try to idle. Usually sitting (engine off), or even just riding slowly for even a couple minutes will return the clearances enough to start and idle normally. This when the clearances are just starting to get below the recommended values (cold clearances are what you measure).

If the clearances are way off, I suppose it could affect hard starts, but then idling will be a problem.

I hope the shims fix it.

Interesting that you have a Dyna. They do require more power than stock ignitions (about twice as much). But not so much that it shouldn't start if the battery is good.

Post edited by: loudhvx, at: 2006/08/13 19:06

Loudhvx:
Thanks for another perspective. Worse case scenario, I get the valve clearances in line and still have a hot start problem due to another cause. In any event, I won't burn valves out of neglect.

When I have trouble starting the bike hot, it will crank over for maybe 7-10 seconds, then start to catch, suddenly clear out and run great. I first thought it was carbs percolating dry in the heat and not refilling until the suction from the cranking engine drew enough gas into the float bowls (which is why I posted the problem in the carb forum.) But I started leaving the petcock in the prime position, and it made no difference.

RoMoMoTo