Firstly if they are have trouble starting the bike try...
1 Check your fuel mix
In most case your bike fails to start due to much oil the oil you add to the fuel is for lubrication and is not as flammable as the fuel itself the more oil you use and less flammable the fuel becomes 25:1 is the best mix whilst running the bikes in and should be used for the first 2-3 tank fills of fuel after this the mix can be reduced to 32:1 use a good quality semi-synthetic 2-stroke oil if you check the rating on the back of the bottle you fill find the oil’s JASO rating you are looking for a minimum spec of JASO FC if you are using an oil with the lower rating of JASO FB this is not good enough please change the fuel oil mix and try again
Most fully synthetic oils carry a JASO FD rating this can be used but it very expensive and not necessary JASO FC is perfect
2 Drain the carb to refresh fuel
tip the quad on it side you will see and the back of the engine the carb is fitted there is a small Phillips head screw in the centre of the carbs float boat remove this screw and allow fuel to flow out of it. If you do not get any fuel flow please check the fuel tap is on (fuel tap points to the ground in the on position) if the fuel is turned on check for kinks in the fuel line
Once you have a fuel flow into the carb refit the drain screw and try again.
###Note that there will be two screws, one for idle speed setting, the other for mixture.
2:2 Adjust the idle speed
If the idle speed setting is not correct the quad will run then cut out when the accelerator is depressed.
Idle speed is the "tick-over speed" so make small adjustments until the engine runs smoothly.
2:3 Adjust the mixture screw
The mixture screw should have been set at the factory. however, from time to time you might need to adjust this setting youself. Always adjust the idle speed in the first instance.You can also adjust the mixture screw on the side of the carb in the same way as the idle screw,this will ensure a good fuel to air ratio and help the quad to run.
Please see the image or video below:
3 Choke is not always necessary
On most small engined 2 stroke bikes using choke is not always necessary please try starting the bike with no choke then half choke then full choke
Choke lever down is the choke off position
Choke lever up is the on position
4 Check for a spark at the spark plug this will tell you if there either a fault with a kill switch or ignition coil
remove spark plug cap and spark plug place the spark plug into the cap and place on its side on the engine and pull the pull start to turn the engine over you may need help as one will need to pull the starter and other need to check the end of the plug for spark
poor starting is either due to weak or no spark, or a lack of fuel.
When you crank the bike over, if there is a smell of petrol from the exhaust then
your engine is probably getting fuel OK.
Once it starts, does it rev cleanly or roughly?
Rough or stuttering response to the throttle could indicate a carb problem.
Next take out the spark plug. Have a look at the end of it. It should be a darkish grey in
colour, but not covered in sooty deposits. If it's dirty, replace it or you can try to gently clean it up with a wire brush. Have a look in the bike's manual and find the plug gap that is specified. Use a feeler gauge and either open up or close the gap accordingly.
With it out, plug it back into the plug lead and touch the outer body of the plug against the engine. Now, crank the engine over as normal. It won't start with the plug out, but you can look at the spark plug gap to see if you are getting any spark there as the engine turns over.
Be very careful when you do this and make sure that you are not holding onto the metal part of the plug or you will get a spark yourself!
If you don't see a spark then try the following, each time looking for a regular spark as the engine turns over. When you get a spark, refit the plug and try starting the bike:
- Try another spark plug.
- If your quad has one of those kids safety cut-out switches that kill the ignition circuit then remove it. just unplug the connector check the wiring to see if you need to short out the pins inside to keep the ignition circuit going.
- Follow the wiring back to the coil, then the little black box (called a CDI unit) and make sure that all the connections are OK.
6 If after trying the above please check out this video.
This applies to 125cc and 110cc quad bikes.
please note that the quad bike here in this video may differ from the ones on sale at welbo.co.uk; however the principle is the same for the majority of quad bikes, regardless of make and model.