Hi, the bike will idle ok but splutter and miss when the throttle is increased.I have dismantled and cleaned the carby twice and adjusted the air screw heaps,cleaned the plug which was covered in black carbon and swaped the lead to plug cap. Whats left to do.??

the sequence to throttle adjustment is to adjust to high speed first ( screw closest to the air filter) turn in in or out until it fires evenly at rpm and picks up rpm easily
now hold the throttle at full throttle and slowly idle down while adjusting the idle screw ( closest to the butterfly) to maintain engine running
the screw should have been turned all the way in then back out 1 1/2 turns before starting the engine
keep slowing the engine while making very small adjustment until it idles at rpm slow enough that the chain is not driving
If you get it low but it stalls out , then adjust the throttle stop screw to maintain idle rpm
Correct adjustment is from this point the rpm increases rapidly with out falter ( fine tune high speed screw to achieve that)
and when left to idle will do so evenly without driving the chain
all of this working is depending on the carby having new diaphragms , needle height adjustment correct and the system cleaned out

Check the gap on the points and check to see if they're pitted or burnt. You might just need to clean them with some emery cloth or something similar. If they're pitted or burnt, they need to be replaced

Try changing the spark plug first and clean the air filter.

First and formost make sure air filter is clean.Then start bike and warm up engine.with engine warm adjust idle screw(the big screw with spring around it)Turn clockwise to increase and counterclock wise to decrease.with bike idling properly the low speed air adjustment screw (small screw located just above fuel bowl on side of carb)Adjust in small increments 1/16 turns at a time till bike has smooth throttle responce.This screw contols air flow during idle and up to 1/4 throttle.From 1/4 throttle and up the needle setting on plunger inside of carb takes care of 1/4 and up.You usally dont have to mess with needle unless you do upgrades to get more power out of bike.But over time the low speed settings can change due to wear on idle needle and air needle.So thats why you have to make adjustments.If bike still dosent respond or idle correctly I would purchase carb rebuild kit and your problem will be solved.

If it runs fine otherwise, check valve clearances and clean carby ,new spark plug, new oil, clean airfilter

Hi, had many different motos for many years..... ( Am a 42 year old Australian, biker living in China )
Firstly, why the hell are you servicing this machine SO regularly????!!!! Twice a year is ok.... I see many old bikes rolling around here that have never had a service or oil change in their entire life yet can still do a daily job, carry unimaginable loads and go at fantastic speeds. You have to let the engine and gearbox run how they like to... Don't "love" your bike to death.
Chinese bikes are not much different to Indian bikes, in fact the Indians take much technology from the Chinese, the Chinese get ALL of their technology from the Japanese...
Simple procedure....
Good fuel and a good clean, rust free fuel tank, no dirt in the fuel tank or reserve tap, then, check fuel supply and make sure fuel is reaching the carby well.... Check sparkplug and electricals, being an older Asian machine, this may be a problem.. Check carby jets as well, if they are clogged, you will have crappy performance and power...May idle well, but open the the throttle and the faster you want to go,...the slower the bike wants to go...( Different jets,,,,idle and acceleration) Oil changes should really be made around 3000 to 5000k"S, depending on your milage or use of the bike.....Even a 15 year old car can safely do 10000 k's between oil changes. I have a Chinese 2009 model 48cc scooter here, that can go for at least 280kms on a small tank of 93 octane unleaded fuel, and at times can reach 90km/h with good acceleration, sometimes with my wife on the back!.... no problem. After buying it, I just read the manual, adjusted the mixture and idle screws on the carby and off we went.

Hi!!
The spark plug has shortted....
Change the same and all will be well.

Regards
Berry

You sound like you have a blocked idle jet in the carb. Honda trail bikes love new oil, clean air cleaners and clean fuel. After a while a build up of tannins and crusty residue will invade the carby bowl and usually migrate through the carb via the jets and the emulsion tube where the jet needle runs. The easiest way to fix your problem is to remove the carb and go through it. Clean all jets and check float height and generally get it back to scratch. You will have to re- adjust your idle and mixture settings after you have fited it back to the bike. If you are not Mechanicaly savi then I would suggest you take the bike in to your local honda dealer and get them to go through the carb for you.. It's not a big problem and is easlily fixed.

Hope this helps...

Cheers...

1. The carb could need cleaning.
2. Sounds like the exhaust pipe needs to be de-carbed.