Fuel vapour lock?

[Bruce Jones]

I am pretty sure I copped some dirty fuel on the way to the Adelaide Hills last Cup w/d.  Anyway, the boys at Murray Bridge Honda cleared the tank.  When I returned and went for my next service, the fuel lines were cleared as well.  But then I had further trouble with the bike pig-rooting; all of these problems were in hot weather (35o-45oC).  It was too close to Christmas and I was in for a Club Ride over 6 days.  A code showed up and I took it in where they found a mapping sensor was at fault.  It played up again in stop-start traffic and 35oC day at Lorne but then behaved itself for the rest of the ride.  On returning, they replaced the fuel filter and found the mapping sensor itself was okay but the hoses giving its readings needed cleaning.  They also replaced the spark plugs.
The other day returning from work on a 40+oC day in traffic, she pig-rooted again.  I am confident it isn't the mapping sensor or dirty fuel now but I'm wondering if I'm getting vapour lock.  The bike is an '05 ST1300A that has done 123,000+kms.

 

[StinkyPete]

Hi Bruce,
Fueling problems can be caused by a blocked tank breather pipe, which of course will cause fueling issues after a while.    To make sure this is not the problem, squirt some WD40 down the top of the breather under the tank cap, and GENTLY blow some compressed air down the breather tube.   Look for WD40 coming out the breather under the bike.   At very least this will eliminate one possible cause.    Good luck with tracking down the problem.

[Turtle]

Maybe the 5 way valve under the air box gummed up ?

Turtle

[Biggles]

Maybe the 5 way valve under the air box gummed up ?
Turtle

It's not a valve, just a plastic hose joiner. 
Since you've already gone to the trouble to get in there, remember to check the connector on the hoses beneath it as well.

[Cerebral Knievel]

I had an identical problem that would come & go with no rhyme or reason in hot conditions over the space of
6 months. Since replacing the fuel filter it has not happened again, even with the bike hitting the low 40's this summer. 

[Bruce Jones]

Thanks for the rapid responses.    The fuel filter has been replaced but it happened again on a 40's day.  The plastic hose joiners are okay.  I haven't checked out the tank breather pipe but will do so. 
Thanks again everyone. 

[alans1100]

Vapour lock is rare in EFI motors and Carb systems with fuel pumps that are located with in the fuel tank. Not saying it doesn't happen, just rare.

http://en.wikipedia.org/wiki/Vapor_lock

A vapor lock is more likely to develop when the vehicle is in traffic because the under-hood temperature tends to rise. A vapor lock can also develop when the engine is stopped while hot and the vehicle is parked for a short period. The fuel in the line near the engine does not move and can thus heat up sufficiently to form a vapor lock. The problem is more likely in hot weather or high altitude in either case.

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I guess they also mean if you stop the motor while in traffic as some people tend do.