Intermittent Starting problem

Bike details:
'08 WR250X Mods: FMF muffler w/programmer, airbox & related mods, speedo healer, heated hand grips, Safari tank, R wheels

I replaced the fuel pump last summer after it failed. About 2 months ago, Yami dealer replaced piston, rings, valves and valve seats after another no-start incident. They diag'd no compression & found leaking valves and collapsed rings.

It's been doing fine since the repair...until yesterday. I road to work (startup temp ~99F), parked under work carport shade. Went out around 5:30pm (peak temp yesterday was ~108F) and bike would not start. Fuel pump was priming, I opened the gas cap and could see fuel flowing when I cranked over the bike. Tank is more than half full so the pump is almost fully submerged.

Took it home. Went out this morning around 10am (~99F), after 4-5 attempts, bike started.

My WAG: vapor lock between pump outflow and FI system...but how to get past this in the field? Any suggestions or thoughts as to other things to check?

I'd like to be commuting on it, but if it's not going to reliably start in the heat there's no way I can do that.

How did the fuel pump sound when it was priming? Lower pitch than normal? I'm thinking that the gas moving in a Safari tank could be on account of the secondary pump - the one used to get gas out of the wings. I'm not saying it is the pump, just that I wouldn't rule it out just yet. Nonlinear recently posted what sounds like the starting stage of a second pump failure on his bike. He got the bike to start by cooling it off with water (tank, radiator & engine). Perhaps you have access to a water hose at work?

If it wasn't for the fuel pump issues with these bikes, my first thought would be to check spark. Kind of a pain considering where the spark plug hides. Of course if you dig that far into it, you could check the pump output. If you have not dug that far into your bike, I'd suggest you get familiar with digging in that far in the comfort of your garage before you need to do so in the field.

It seems vapor lock would not be very likely with the fuel setup on our bikes. Electrical pump in tank and the pump supplies a relatively high pressure vs. older mechanical pumps. Old gas in the tank? Winter gasoline used in hot weather is a possible cause of vapor lock.

Suggestions: dump the gas that's in the bike into your cage and put fresh gas in it. You may also want to set it in the sun on a day off and see how it does later in the day. And perhaps get familiar with the diagnostic mode on the bike. It will let you check some readings, and activate some items on the bike so you can listen to see if they are functioning.

The fuel pump didn't sound any different than it usually does. The gas is not old, I've put almost 500 miles on it since the rebuild, riding 2-3 times a week.

After discussing the failure with a buddy who has worked on EFI bikes and cars, he said he doubted it was a vapor lock issue as well. I reviewed the service manual again, especially the troubleshooting section. There are some basic things I can check which could be fall-out from the work the dealer did. I should probably get the battery tested as well, since they tend to die quickly here in the desert, and I don't recall when it was installed by the PO (or even if he told me).

I have a question about the throttle body. The trouble-shooting guide refers to "clogged pilot air passage," but I don't see any reference to that on the diagrams in the fuel system section. Any ideas?

Thanks.

Since your bike started and presumably idles now, I'm inclined to run with the idea that the pilot air passage is not clogged. I wouldn't expect it to get clogged randomly.

I have not taken a good look at the throttle body and all I could find is an example here. They're calling it a bypass passage in the text. Keep in mind that it is a generic example.

I went out and tried restarting it around 4pm yesterday, too. It was sitting in the sun on the back of the truck, still. Fired up on the third try, so I took it off the truck.

I'm going to go over it today with checklist in hand. The throttle is sticking closed after it sits overnight, which I'd forgotten. Once I crank hard it to get it open, it moves freely and doesn't stick, but I have to crank it to get it to move at first.

Thanks for finding that picture for me. I should go find a primer on EFI systems so I can wrap my brain around the system.

=RT=

Look for the Killswitch/Starter?! I have had the same Problem with mine two times: first the engine won't start- no idle= Killswitch (the contacts of the wires have been green). At the second time i could hear the starter but it won't start (as if there was no spark)- spray wd40 in the Killswitch and it works fine...

So, the techs at the Yami dealer diagnosed this as a failed fuel pump. I got it to the shop at 13 months after the last fuel pump replacement (getting it into shop was delayed due to travel related to job interviews).

The local Yami shop I took it to is refusing to help on the fuel pump warranty because I purchased it over the internet and installed it myself. I have a call in to Westfield Yamaha in IN to see if they can get it warrantied.

I didn't check the build code on the pump before I put it in, so there's some possibility that it was from the "bad" build period.

I'm debating keeping the bike, now, since I intend this to be my primary commuter after I move for a new job, and I need reliable transportation, not something I'm fighting with all the time.