My Honda xr 125L won't start need help

[monky]

I bought a Honda xr125L about last week I rode it about 75 miles and it's started dying lost all power and then died, now won't start, battery has plenty of power, brand new spark plug, it has compression, checked the valves, cleaned the carb and the fuel jet and tried everything I can but still won't start, really need help as I don't have the money to put it in a garage and need it for transport for work!

[Reid]

Wrong section and sensing a potential troll but...

Does it have petrol in?
Is the fuel-tap turned to "on" or "reserve"?
Does it bumpstart?

[monky]

It does have petrol and the tap is turned on and works fine but no it will not bump start

[dungbug]

You've fitted a new spark plug, have you checked that you're getting a spark? If you've got compression, fuel & spark then the engine will run.
Does the fuel flow from the tap? I had an issue with my GN, the fuel tap bowl was clogged with cack which meant the fuel was barely seeping from the tank.

[monky]

Yes the petrol is flowing from the tap and I've already cleaned out all the cack but still nothing

[mammoth200]

Unfortunately he's not a troll, well he is to me, the poor older brother who has had to work on this stupid vehicle!

To cover a few bases:

The bike has fuel which is getting through to the combustion chamber, there is a good spark coming through as well. When I have bumped it, the bike barely fired up, but conked as soon as I run out of hill.

One thing that had been suggested is the valve clearances might be off. So these have now been set to 0.003in/ 0.08mm as per the workshop manual, however we are still not getting any life from the engine. you don't even get any nasty backfire from the build up of fuel.

I did have the intention of checking the compression, I don't know what is should be on a little 4 poke 125, but I assume it would be fairly obvious if it was dangerously low. However the Gunsen hi-gauge compression tester doesn't come with the necessary sizes for motorcycle spark plugs. So I never got the chance to check.

The other thing I did think was the cdi might be borked. but other than that or compression I'm completely out of decent ideas.

4-strokes aren't really my area of expertise, give me a 2-stroke bike any day!

[Reid]

So compression hasn't been checked after all? Could it be head gasket gone? It's something that's pretty easy to overlook, I had a similar problem ona CG125 and after doing pretty much everything you've done (valves, carb strip, etc..) found a load of grit had worn into the rubber gasket and chewed it up a bit. If the bike ran fine for a while maybe it'd been bodged and finally given out.

[dungbug]

If you're getting a good spark I'd say the CDI is doing it's job, also with fuel there it could only be loss of compression I would have said. As Reid mentions, it might have been bodged to sell unfortunately.
You could drop the downpipe and look at the condition of the piston, see if there's any obvious burns or other damage.

[mammoth200]

Well thanks for the assistance folks, at least I can tell the poor mechanic who cops the job roughly where to look!

[rockers]

dung bug - surly being a 4 stroke he isnt going to see the piston by dropping the downpipe ?


Hair dryer on the engine keeping away from carb and fuel lines etc, and get a can of Easystart spray,

[dungbug]

[weasley]

Maybe the valve timing has slipped? I assume these are chain-driven cams? Maybe there's a hole in the piston?!

You have fuel.
You have a spark.
Not sure about compression.

All you need is those three things at the right time, in the right order, to run. Once you have determined which one isn't where it should be, then you can trace the cause.
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