YBR 125 will not start for some unknown reason.

quality4455 · L Plate Warrior Joined: 12 Sep 2018 Karma :

Hello.

I have replaced the cylinder and piston on 2014 YBR 125 and now will not even attempt to start for unknown reasons.

- Spark good
- Compression good
- Fuel good
- Valves good
- Timing good
- Flywheel woodruff key good

How can it possibly not work? It will just turn over but will never start up.

Any help would be greatly appreciated as this has got me completely bewildered.

Thanks.

Jewlio Rides Again LLB · World Chat Champion Joined: 06 Oct 2015 Karma :

Tried spraying easystart into the airbox?
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quality4455 · L Plate Warrior Joined: 12 Sep 2018 Karma :

jaffa90 · World Chat Champion Joined: 06 Apr 2016 Karma :

"""Compression good """
What reading did you find?

quality4455 · L Plate Warrior Joined: 12 Sep 2018 Karma :

Teflon-Mike · tl;dr Joined: 01 Jun 2010 Karma :

Isn't 2014 on the change-over between carb & EFi?

You say 'Fuel-Good'... do you mean that it's fresh fuel? Or a good brand? Or that the spark-plug smells of the stuff?

Is it getting to the cylinder? Is too much getting to the cylinder? Choke/Cold-Start circuit?

When you rebuilt, did you time the cam in correctly?
Did you set tappet adjustment right?

Did you use assembly lube?

I tend to use a lot of two-stroke oil on rebuilds on things like piston rings and the bore, as it burns off more easily when running, but is there on first fire when needed.....

Thicker oil, tends to foul the plug and make first fire rather short, if at all...

No oil, can leave compression low, esp if rings haven't been soaked, and leave new bits to cut themselves to bits on first fire.

BUT... right lines: Fuel, air, spark, compression.... should have all ingredients for life... so...... if it aint living... either one of them AINT present, or one of them aint present in the right amount, or at the right time..... and back to the head-scratching.
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