Not Starting When Hot

[Dham]

Now that my '03Tiger is running again, I wanted to see if anyone has any input on a longstanding starting issue.
When hot the Tiger will turn over 4 or 5 times then go pffft, then repeat this cycle endlessly without firing . When it originally started doing this it would happen only on very hot days. Then, it would just turn over continuously without starting and I would have to wait 15 minutes until it cooled to start it. Now, it happens on cool days after running for a while.
A mechanic suggested the sprag clutch, but wouldn't that just produce a whine like a failed Bendix?
Any help here will be greatly appreciated.

[iansoady]

Not a specific answer, but I would be looking at a sensor going bad when it's hot.

You need Tuneboy or Tuneecu to look at the codes and see what's going on.

Definitely doesn't sound like sprag to me.

[Bixxer Bob]

Correct, classic crankshaft sensor symptom.  But I'd also ask when the valve clearances were last done.

[Dham]

Bike has about 65000mi. Last check on valves was at 36000 miles, I believe. No adjustment was necessary.
Oh, I should say that it was at that time just starting to refuse to start after running on a 100F day.
Another point, it does seem to run a bit hotter on a hot day than when new.

[blacktiger]

Bike has about 65000mi. Last check on valves was at 36000 miles, I believe. No adjustment was necessary.
Oh, I should say that it was at that time just starting to refuse to start after running on a 100F day.
Another point, it does seem to run a bit hotter on a hot day than when new.

I would give it a full service first. After another 29000 miles those valves could need a few shims by now. Also, what about spark plugs? If they're also 29000 miles old and worn out it'll also contribute to those symptoms. Fuel filter partially blocked? Air filter dirty etc etc.
A full service will give you peace of mind that all those things can be eliminated from your hunt for the fault....if it's still doing it.
Don't forget to post what you do find.

[Dham]

Thanks for the replies!  I need to correct my last statement that I made without looking at the bike. It has only 58000 miles. Still quite a few since the 36000 service and time to have the valves adjusted. However, it was already having trouble starting when hot at that time, and I was hoping that the service would correct it, but it didn't. After that, I replaced the air temp sensor, and had replaced the fuel filter earlier.
I think my next move is to figure out how to measure the resistance of the crank position sensor to try to eliminate it as the problem.

I talked to an independent mechanic who has a Tuneboy unit and from what I understand he would need a $400 software package then some kind of a $200 fee for each individual bike.

[Bixxer Bob]

he's right about Tuneboy but TuneECUis free, use the sticky in the Girly section.

Symptom for crank sensor fail is engine cuts when hot but starts when it cools down.  Just remembered the simple check is when it cuts  but engine is still spinning down and ign is on, if sensor is good rev counter will spool down. if sensor is bad rev counter cuts to zero.

[Dham]

In my case, engine has never quit when running. It just refuses to start when hot. Maybe it gets  a heat "soak back" while sitting for a couple of minutes?

[Bixxer Bob]

then I'd be doin' valve clearances first...

[blacktiger]

Thanks for the replies!  I need to correct my last statement that I made without looking at the bike. It has only 58000 miles. Still quite a few since the 36000 service and time to have the valves adjusted. However, it was already having trouble starting when hot at that time,

I'm with Bixxer.
Just because they were supposed to have been checked doesn't mean they were checked and adjusted correctly. I've heard that some dealer mechanics assume that they're going to be alright and not bother to do them. Saves them an hour. Do it again yourself and make sure you get it right then that will eliminate that possibility from your investigation.