If you like a challenge try and solve this

kneedown · Nova Slayer Joined: 14 Jul 2008 Karma :

Hello peeps
Here's the story, recently acquired a little yamaha teos scooter to use for work.
Four stroke two valve liquid cooled 125. As of yet I have been unable to get it to start, have got it to backfire a few times using easy start but that's it.
When I got it would not spin off the button, sorted the wiring to the brake light switches and it now spins, there is a spark and a conpression test shows that the compression is well within tolerance, but still wont fire. Removed and cleaned carb and tank and put fresh fuel, no joy.
I removed the head and barrel put new rings as a precaution, new gaskets, twosomes valves then vacume tested head and they are perfect.
Reassembled top end retimed and did valve clearances, all spot on. Decoked exhaust, new plug and still won't fire. Changed loom and cdi and replaced starter motor as it was knackered.
Tried easy start with carb on, carb off, airbox on, airbox off still no start, tested stator and other ignition electrics and still won't fire, strange thing is when spraying easy start in carb plug seems to get wet but with no easy start seems dry. Sorry for long essay anyone got any ideas. Also there are no side stand switches alarm immobaliser or any other lockout systems on the bike,
Cheers for reading I look forward to suggestions

MickC · Spanner Monkey Joined: 27 May 2011 Karma :

Ok. you say you have checked electrics and valve timing/clearances and it passes compression tests, but the plug is dry. So is the fuel flowing as it should, remove the float bowl screw with the the petrol tap turned to the on position, does fuel piss out?
As another thought, does it have any kind of automatic fuel valve ( a common fault on old CB750/900's is when the AFV dies and no fuel gets through)
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RIDINGforKICK... · Scooby Slapper Joined: 06 Oct 2011 Karma :

Sounds like you have got the timing 180 out.

Download the manual and check the timing again.

MickC · Spanner Monkey Joined: 27 May 2011 Karma :

jimmyRS · Scooby Slapper Joined: 01 Nov 2011 Karma :

as above, it sounds like its not getting any fuel.

If the plug is dry, try putting some petrol down the plug hole and see if it fires up or backfires.

Start checking all posible fueling issues, clean the carb out and blast it with some compressed air to ensure all jets are fully clean and the carb itself is clean internally. Check the feed from the tank to the carb - does it flow nicely when unplugged from the carb?

A quad ive worked on previously wouldn't fire at all because air was trapped in the fuel line. So if required, put the tap on, unplug from the carb and then put it back on when fuel starts flowing.

Good luck Smile

kneedown · Nova Slayer Joined: 14 Jul 2008 Karma :

Well i seem to have solved the problem, was turning it over againtoday and then suddenly it just locked up, took off variator and looked at starter clutch and idle gear, six or seven of the teeth on the starter clutch were ground off, this was allowing the motor to spin and then jumping a load of teeth so sometimes it was catching and sometimes just freewheeling, also took carb apart and diaphragm was sticking Down, replaced both with some spares I had and it fired straight up, thanks for replies guys most appreciated