My bike seems to be ok but when im riding it you feel the engine failing.sometimes when you are riding it you can hear pss pss .My question is ,dos my bike a tune up, or just a carburators clean?Thank you

Get it fixed ... you need back pressure on the engine to allow it to operate properly and not be damaged ... PLUS - big benefit - you will not annoy the neighbors and as a bonus, you will preserve your hearing for your old age.

axel bearing either is bad or needs grease or not adjusted correctly

i have that bike i am 6ft and 165 lbs the bike is awesome i love it, i have it the softest it can be and its still not a soft ride to just sit and cruise around on the bush tracks. the 4 speed gear box is alright makes going up tuff rutty hills hard but hold on and keep the throttle on and it will go. bike pulls in any rev range even when iv doubled someone so it has the torque
best of luck

That sounds ok, it would be more of a problem if it went over half sometimes. The only other things that may make it flucuate could be a sticky thermostat or an air lock somewhere in the hoses, but these generally cause overheating. At half way it is not overheating.

check your cluch cable it may be sticking up also check you have free play on this cable,, put the bike on its center stand and spin the rear wheel with the bike in gear holding the cluch in as you spin the wheel if it spins ok the cluch is letting go

If the bike has knobby type (bumpy tread) they do make noise.Just be sure they have the correct air pressure in them.
Try to support the bike so you can manually spin the wheels like if the bike had a center stand.Feel while turning, to see if the wheels feel to tight or loose.And try to feel any play in the wheels. Or hear any stange noise.
While your are at it go ahead a drain the oil and change it with a good quality oil. The bike should have come with a book to tell you what type oil it wants.Dont be afraid to change the oil more than it is suppost to be.They dont hold that much oil and the shifting of the gears will generate alot of break in metal dust that needs to come out of the engine.
To say if you made a mistake in buying the bike remains to be seen because their is no history of the Chinese bikes in this country.
If I could ride the bike I could give you a better opinion.
Another thing you could do is, while riding the bike with it makeing the sound,pull in the clutch and put it in neutral.Is the feeling gone?
This can help to be sure the noise is not engine generated.

possible crank bearing failed and incorrect adjustment on the clutch cable or the clutch it self

I think you should check the plugs and spark of plugs.

yz 250 two strok. measur your compresion. gas leak valve gasket cilinder. of your exhaust pipe full whit carbon. a good running 2stroke have a lot of power in al the gears. when is your last inspection of the engine? j kerkhof

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