GN125

koriemouse, Jun 22, 1:45pm
My sons friends GN125 is not running smoothly. A little hard to start, idles ok, coughs and splatters at about 4000rpm. Will replace fuel filter, have cleaned air filter and cleaned spark plug. Any other suggestions greatly accepted. He is a uni student and rode it here from Otago, was going well, refuelled and then stopped for the night and next morning running as described above. :)
plasticboys, Jun 22, 1:58pm
hope the cam has not run the head! cheak the oil
koriemouse, Jun 22, 2:00pm
"hope the cam has not run the head"!plenty of oil.
jsbike, Jun 22, 2:02pm
clean the carb and jets out.
koriemouse, Jun 22, 2:36pm
Sorry meant to say I had also drained the carb. Never cleaned jets out before , how do I do this!
bitsy_boffin, Jun 22, 3:37pm
Remove jet, blow compressed air through jet, or just squirt carb cleaner through it if you don't have a compressor.Don't stick wire through it, you don't want to mess up the inside surface.
ceebee2, Jun 23, 2:28pm
Sounds like water or crap in the carb from the last fill up maybe. Remove carby completely, easy enough (Remove tank first). If you need a manual I have an electronic copy some where.

Cheers CeeBee (Auto Tech 30 years)
koriemouse, Jun 23, 3:23pm
Cheers, have had carb off today, cleaned jets and carb. Waiting for the boys to get back from buying a new air cleaner and spark plug. Have also put fresh fuel in. Will get it back together tonight and see how we go.
koriemouse, Jun 24, 3:41pm
so,. new fuel filter, cleaned carb and jets, new spark plug, fresh petrol. Put all back together started straight away, idles well but still has the same problem. Took spark plug back out and it is sooted up after only a 3km ride. Where should I look next! Also bike spent the night outside in the rain the night before the problem started. CDI ! cheers
muzz67, Jun 24, 5:20pm
Does it come right after 4000rpm! Or run rough all the way to high revs! If it comes right, it may be pilot/needle combination running too rich. Continuous misspossibly electrical, ie water in ignition, sidestand switch etc
koriemouse, Jun 24, 5:39pm
continuous.
koriemouse, Jun 24, 6:02pm
Also, bike is fine when revved in neutral only affected when actually riding it.
sabbath-black, Jun 25, 7:19am
see if pulling the choke out while riding at the problem speed makes any difference.
dr.doolittle, Jun 25, 7:24am
Didnt fill with 91 instead of 96! Lower octane might not help in a small donk. Would it make that much diff!(Just a thought).
sifty, Jun 25, 8:46am
Don't rule out electrical, often spark will work fine at rest but is too weak under load.
koriemouse, Jun 25, 3:44pm
where should I be checking next!
franko171, Jun 25, 4:01pm
with the info u guys give one mite be able to complete rebuild keep the good work
koriemouse, Jun 25, 4:20pm
what about vacuum leak!
jsbike, Jun 25, 4:30pm
there you go, blocked main jet.
koriemouse, Jul 25, 6:00am
Where exactly is the main jet! I have had the carb off and cleaned the 2 jets in the bowl end and 1 in the top where the diaphragm is. BTW they looked reasonably clean, but blew them out with compressor and soaked in carb clean.