Hard starting when warm.

Alright, I know my bike isn't a VFR, but my FZ1 forum has been down for almost 2 weeks now and I figure the diagnostic procedure should be the same.

It cold starts perfect every time, though, when I ride to lunch from work and let the bike sit for about 20-40 minutes, the restart is very difficult. The motor cranks and cranks, but it doesn't seem to 'catch' unless I blip the throttle.

I did some googling and people say that the fuel pressure regulator is usually the culprit for a hard starting when warm FI motor; though I'm not sure if that applies to my bike... as I find no mention of it in the official yamaha service manual.

Any ideas?

 

This happened twice before the TBS too.

I should clarify, this doesn't happen EVERY time the bike sits for a bit, but it does occur often enough that it concerns me.

I can only hear the pump come on from a dead cold start. It's a little whoosh noise that comes on when the kill switch is in the On position (or if the switch is already in the on position, whenever the key is turned to On). It's on for a second and that's it.

Doing more research, this sounds a lot like vapor lock on carbureted bikes, but my bike is FIed, this shouldn't be an issue.

If the motor is running and I kill it, it'll start right back up, even for a up to a few minutes after.

It seems that 20-40 minutes is the sweet spot for the problem. Anything before or after that the bike starts just fine.

No trouble codes, bike has power (and loads of it). it's just a starting issue.

Yamaha specs 8k miles for the spark plugs, which according to every other FZ1 owner is complete BS, as many users go 24k with no problems. But I may end up taking them out (complete PITA BTW) to see if anything's up.

EDIT: Oh and bike isn't overheating either. The highest I've ever seen it is 220 on VERY hot day a couple months ago; 185 is the norm above 45. the owner's manual states that the display won't show a warning until 260.

 

Fizz, I just read this thread today. I hope you have this fixed by now, but see if you have a fuel line running close to any heat source. There could be vapor lock just in that section of the fuel line. 20 to 40 minutes is perfect for the heat source to add heat to that portion of the line. When bike is running fuel is flowing keeping the line cool. When bike sits for a short time heat will transfer to anything near the heat source. When bike sits for a long time everything cools off. I notice you live in San Diego, do they use Ethanol in the gas there? In Chicago we use up to 10%, this boils at a lower point than water and is prone to vapor lock. Try pulling your lines just a little bit further away from any heat source and see what happens.

Good luck!

 

I've only seen 76 stations that post an up to 10% ethanol warning around here.

Maybe I should invest in some heat shrouding for the fuel lines?

I haven't actually had this problem much since I fixed my low idle (900, when it's supposed to be 1.1.-1.3k). When it happens now, the motor doesn't crank forever, it just seems to stutter a bit before it starts.