When put fisrt gear and start to go it jumps in to second gear .

Some popping on deceleration usually means a lean idle mixture.

However, a backfire like you describe, I'd start looking at an exhaust leak, like a bad gasket where the pipes bolt to the head.

Beings it only recently started, and getting more common, yep, sounds like a bad gasket that's not getting any better on it's own.

maybe wrong viscosity in the clutch cavity, make sure its the proper oil. then think about making a complete clutch adjustment.
check the service manual for making adjustments.

incorrect oil levels are the main cause for this, it usually starts with low gear to high gear as the level don't reach the gears properly or the other thing to look at is mounting engine and gearbox as when tuque is high then mounts are under a lot of stress, then there's the exhaust system could be near something Re: Jeff

check your cable and connection points where it hooks up check your shifter and linkage for bends breaks and bends or any bangs or dings in clutch cover i hope this helps you

you probably have a bad neutral switch, if it doesn't read neutral the light won't come on and the vehicle won't start unless it's in the neutral position. try push starting it in gear and see what happens.

You will have to run the atv and drain the oil when warm a couple of times use cheap mineral oil to do this. do not ride it as the petrol will have broken down the oil protection.When drained twice with fresh oil ,use good oil the third time.How is the atv not working properly,is the air cleaner clean and fresh spark plug fitted.

Yes, that should be corrected before you pop a gear tooth. Make sure your linkage is allowing the shift to fully engage.

Bent shifter levers or a cause most mechanics miss, chain is jumping over rear sprocket.

dont think its the clutch sounds like a bent shift fork, in first gear starting off the transmission has torque or pressure applied to the first gear set when you let the throttle off (no torque or pressure on tranny) it shifts by its self this is a sign of a bent shift fork hope this helps leave us a rate please

Hi!
I havn't come across your Machine before but hopefully a little Q 'n' A will solve/FiXya problem.
O.K. 1st is the clutch cable operated? if so can the cable should be adjustable from the handle bars?(Then take up the slack to leave a slight gap when lever is pulled) Do this by loosening the locking screw on the end of the cable and turning the adjuster anti clockwise so tension is put on the cable Not the lever.
If the cable isn't adjustable from lever go down to the engine and do the same as above on the cable there.
2nd Is the clutch fluid operated (Master Cylinder on clutch lever) If so look for clutch pushrod and adjust it by loosening again the locking nut and winding it out to create less gap between pushrod and clutch arm. You may need to bleed the system if after adjusting still the same.(Come back to me on that if needed)
3rd If when carried out the clutch starts slipping i.e. in top gear Engine Rev's and doesn't move forward well? then release the tension on either cable/pushrod until happy medium.
Good Luck!
Paul 'W'