You will NEVER guess why this Vespa GTS250 wouldn't start...

This is a quite a tale, are you sitting comfortably? Then we will begin:


Relatives 2006 GTS250 was parked up working perfectly 2 weeks ago under a large carport protected from the elements.


Due to take it on a 3hr ride we attempt to start it.


It turns over but does not fire.


Check Engine Stop switch – but of course it wouldn’t turn over with it off anyway.


Check petrol (gas), can hear some sloshing around – indicated half a tank but fill it up any way.


Remove sparkplug – plenty of spark.


Remove air filter – curious hole 1 inch by ½ inch at intake with some black around the edges (mmm first clue – though we don’t realise it at the time.)


Spray Ether based starting spray can stuff in the air intake – nothing.


Remove spark plug and spray a bit in the combustion chamber – small rumble on starting.


Remove air filter pipe to ECU – is something stuck inside like the foam piece? No its not.

Undo Fuel line to injector – turn it over – plenty of fuel.


Remove fuel injector (accidentally break brittle electric plug) – steal fuel injector of another relatives GTS250 nearby (mmm have to explain that one to them later).


Could it be that the ECU is not sending signal to injector?


Fuel injector is spraying fuel out nicely – put new fuel injector in – turn it over – nothing.


Battery goes flat – could it be that ? Get 40Amp charger out and put it on. – turns over no start.


Pull out injector a bit turn it over – it sort of starts – switch it off quick.


Mmm it will run with injector half out but not in. Would seem it is starved of oxygen but the ECU is just a throttle body with a butterfly valve – and it’s not blocked???


Okay think a bit – maybe the exhaust valve is stuck shut and gasses can’t get OUT of the combustion chamber. This is going to be fun as getting to exhaust valve is not easy.


Back is hurting from leaning into engine bay / laying on the ground.


Okay lets do it – take off exhaust to get to header to at least see if valve is shut.


Kick over engine with header and LAMBDA sensor still attached – IT STARTS ………

Mmm is the sensor being tricked with no exhaust on as its now getting a mix of exhaust and open air?


Look at exhaust – looks fine – try blowing into it – no air will go in by mouth either end. Start air compressor – still can’t get air in.


Take exhaust off other GTS250 and fit it – bike runes FINE…


Go back to original exhaust consider cutting it open resigned to buying a new one.


Bash it very hard against pine cattle race post – mmm what's coming out of the end? Bits of mud and spiders? No wait they are European Wasp larvae that make nests in holes made up of spit and dirt.


They have completely blocked the exhaust in 2 weeks!


Pump water in the exhaust and clear it – take other exhaust off fit original – bike runs perfectly.


4.5 hours to diagnose and fix the problem (and new injector and air filter foam required to fit to other GTS). Oh and the black hole in the foam air filter? Must have been the engine blowing black through it on the first attempt to start it.


In 40 years of fixing engines / vehicles of all kinds never came across this!


Still just shows you a process of elimination will generally find the reason.


Thanks for reading.

Paul S

Views: 89

Reply to This

Replies to This Discussion

Who would have guessed that European wasps could have killed an Italian wasp? Great story Paul. You are to be congratulated on your knowledge and tenacity to find the cause of the problem.

And I thought my bee-stings were a problem . Well done Paul, and thanks for your help today.

I think Yvonnes' changed her tune, just like your engine.



Registered Users

© 2019   Vespa Club of Melbourne Incorporated in Victoria A005069N   Powered by

Badges  |  Report an Issue  |  Terms of Service