help needed kymco agility rs 50 2012 wont start

[crv1035]

help needed i am pulling my hair out.my sons rs 50 will not start
i have fitted a new battery,new carb with electronic choke and a new plug.
it was fine and then he came back to it and it struggled to start.
it turns over but sounds different to before,it seems like it needs to turn over really fast for it to at least fire,its that difficult trying to get it to start the battery goes flat before it kicks up,if you try and put revs on  while trying to start it hardly turns over.
i managed to get it to finally start by jumping it from my car but didnt seem right.
i have cleaned fuel filter,plug is getting wet and ive got a spark, fumes come out from exhaust when turning over.
has anybody got the slightest idea what i can try next.
i was contemplating checking valve clearance ?

[CROSSBOLT]

First, there is no need to run the battery flat trying to start it. Agility 4-strokes can be a pain in cold weather to keep running but they usually fire very quickly. This means something is different inside the engine which sounds like loss of compression. Valves could be the problem but you should start with a compression test. Tell us the result of the compression test and we will go from there.

Karl

[zombie]

Perhaps the air filter is clogged up... Try removing it/close the box lid, and try to start it.

Karl is on the right track Compression test is always first.

[The moped learner]

Can anyone find a kit for a comp test i couldn't find one a link on eBay or something could help

[zombie]

http://www.amazon.com/INNOVA-3618-Adapters-Compression-Tester/dp/B001QUHFQA

http://www.ebay.com/itm/FLEX-HOSE-DRIVE-COMPRESSION-TESTER-TOOL-PRESSURE-PSI-TESTER-GAUGE-14-18-MM-/321113343598

[blue]

You said feums comeing from muffler.check and see if gas got in your oil.if so change the oil.the petcock may poo f leting to much gas in.

[The moped learner]

So do i need both of those or just one?

[zombie]

Both... One is the adapter set to fit your engine plus others, and the other is the tester itself.
Place the adapter on the end of the gauge, screw that assembly into the spark plug hole, and kick it over 4-5 times with the throttle wide open. You should see 120psi or better for the bike to start/run. 135ish is normal.

[crv1035]

so sorry all for my late reply,i have now managed to get the bike to run,i had a problem on the variator side,i have replaced variator,rollers,pulley and fan etc.
I still have a couple of issues,
first problem,i did the valve clearance at tdc  set in & ex to 0.04mm but it seems very rattly any ideas on that one,do I need an even smaller gap ?.
second problem,i seem to have an electrical problem,im guessing maybe rectifier.bike was starting fine but now I get a clicking from starter relay ive been told should be a voltage problem,high beam light flickers on and off on clocks too.
I will get this bike sorted for my son one day hopefully or I may 

[zombie]

If the light, and gauges are "flickering" then I suspect a bad ground to the frame/engine from the battery or perhaps the rectifier is loose or has a corroded ground at the mounting point. That will also make the starter relay "click".

Maybe you forgot the main ground that attaches to the valve cover/cylinder...

The valves should be set to .04mm but I have set them much lower on hat engines. It is easy to have the adjustment change when locking it down too. Simply re adjust them. You can get away w/ .02 on a cold engine, and I set mine to 0.00 on a hot engine. When it cools the gap is usually at or near .02mm.