Yamaha XT 125 X Wont run!

[DarrenTaylor]

Hello chaps
My son has bought a 2008 Yamaha XT 125 X as a project . After a bit of cranking the engine starts but won't rev properly and then cuts out after a few seconds, sometimes the choke helps sometimes it doesn't. In my day I'd go straight for the carb but before we strip anything down do these bikes have electronic parts that are likely to cause this kind of problem? Many thanks.

[Teflon-Mike]

What does it say in the Haynes manual?

Dont know? Then go get one! They are like £15, if you cant afford that to discover what the thing should look like, where things go and what the tappet clearances etc aught to be, where will the money to put petrol in it come from?!?

At a guess, I would suspect that the biggest problems are likely former owners, and ideas it aught go as fast as a two-stroke DT 'cos it Yamaha... ragging the heck out of it and too scared and/or too tight to basic maintenance like an oil-change, and or, more determined to try make it as fast as a DT by doing daft things like drilling holes in the exhaust and chucking away the gasket, sorry, 'Magic Restrictor washer" or, inordinately contentious, actually doing the things they should, like change the oil... and stripping the sump plug, or tensioning the chain... and killing the out-put shaft bearing, or checking the spark plug and stripping cylinder head threads!!! In short... killing it with kindness!

A-N-D... cos its wot everee wuin sez... 'cleaning the carb'...

The very best, example of which I ever came accros was a lad who reported bad running bike, and insisted when suggested he clean the carb, he had... six times! Scary.. very scary.. ideas of the thing being pulled off and refitted with old gaskets or no gaskets of gloopychit, float-bowls full of RTV, etc abounded... until he said, "Well, I used a tooth brush, but there's still a bit of muck at the top where I cant reach' and showed a mobile phone photo of a VERY 'clean' ... on the outside! and other wise untouched carburetor! PHEW!!!

But go get a haynes... no.. not some free online pdf... ever tried following a wiring diagram on a 4" LCD screen?! Yeah... just buy the book.... it dont have batteries to go flat and the screen don't break when you drop a monkey wrench on it!

£15, and it answers ALL the silly questions before you have to ask them, A-N-D has all those awkward nuggets of info like valve clearances, and spark-plug grades, and model variation wiring diagrams in it!

Possibly add a new spark-plug to the e-bay order; and then do a full service, from the haynes guidelines, including an oil change, a tappet tickle, cleaning air-filter, oiling cables and flushing brake fluid, as a first step to 'base-line' the thing and answer or avoid even more silly questions later, and give yourself a known 'should be good' starting point for fault finding.
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[Hawkeye1250FA]

Tl-dr:
Spark plug
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1993 RF400R - 2002 Bandit 1200 - 2012 1250 FA