LIFAN 150CC POPS OUT OF 1ST AND 2ND? heeeeeelp!!!!

[bronx188]

hey everyone
just a question... I just bought a 150cc dirt bike with the 150cc lifan in it from a bloke.
has a dual stage carby, special air shock on the rear, usd forks, exhaust, bifolding clutch and accelerator and a few extra bits..
.im happy with what I got...
however it pops out of 1st and 2nd gear..
it can run for a minute and be ridden for 2 mins and dies
or itll run for a minute then pops out of 1st and 2nd.
sometimes from a stop just trying to get it into 1st pops it up or does its own thing...
its really temperamental.
I do have mechanical knowledge but im just new to the dirt bike side of things...
im guessing the obvious.. gearbox.. clutch..???

I also got a 2nd engine aswell for parts...
just asking for some help from some more experience riders/bike mechanics lol
thanks

 

[my67xr]

The first thing i'd check on it it is the outer shift drum bolt,
it's behind the stator cover, above the sprocket.
So take the stator cover off, and above the sprocket you'll see a philips head screw holding a metal tab to the engine.
take the screw out and tab off, then there is a rubber bung that will come out now revealing a bolt head.
Check that the allen head bolt is tight.

If that is tight then it gets a bit more involved.
the kick start lever needs to come off, unhook the clutch cable, then the clutch cover can come off.
next you need to undo the 4x clutch cover bolts, once they are out the cover will come off and you'll see the clutch hub nut.
you can usually undo them with a large flat headed screwdriver and hammer. (there is a correct tool for it on ebay etc too)
undo the nut and remove the clutches, you will see a lock ring and a washer, take the lock ring off, and turn the washer until the splines line up with the slots in the shaft, and the washer comes out.
now the clutch basket can come off.

being a Lifan 150 they are prone to cracking the engine cases. look at the shaft the clutch came off, where the bearing sits in the centre case, they crack at about 4 o'clock.
If the case is cracked then that will cost you about $75 for a new one, and the engine needs to be split to replace it.
If there isn't a crack, just above the shaft to the left you'll see the shift star, in the middle is a locking bolt.
check that this bolt is tight.
if that is, then the problem is internal, possibly a worn shift fork, or could also be chipped dogs on the gears