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H-Train

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Hey guys,
So my chain flew off on my lifan 125 and snapped the pulse sensor off. So I bought a new stator plate. It seemed to be exactly the same except the sensor was a tiny bit closer to the flywheel and I had to grind about half a mil off the 'nib' of flywheel so it wouldn't hit when it expands.
But now the bike is a massive mission to start. Takes really huge kick! Then it will run but won't hold idle.
I took it to pinkenbah and it goes alright when it's revving hard but hated how tall fourth gear was.
And it just would not start once it got properly hot. ( after 15 min)
So I think the ignition timing is out. I think it's too late
How do I fix this or even check the ignition.
It may not even be that. I'm lost
 

my67xr

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with the hot start problem, i would guess at it needing a valve adjustment
have a look at this video/how to-
ooracing.com how to set your Valve Clearance - YouTube
it is a general thing to show you how to do it.
set the intake valve to .003" clearance, and the exhaust valve clearance to .004"


with the pickup sensor hitting the flywheel,
you can normally loosen the 2 screws holding it to the stator backing plate and move it away from the flywheel.
if this doesn't give you enough movement, you could file out/slot the holes on the pickups' mounting plate
so you can move the pickup away from the flywheel.
it needs a pretty thin gap between the tab on the flywheel and the pickup, about .1 of a mm (a piece of A4 paper folded over so it's 3 layers thick.
i smoke rollies, the papers' cardboard packet is the correct thickness too.


by grinding the tab off the flywheel, you may have weakened the signal through to the pickup.
 
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H-Train

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i thought i may have weakened the signal too much..
im going to try moving it slightly and filing a little off. thats awesome help.
ive got feeler gauges so ill probs just use that and not my rollies pack. dont want to get any crap on my potential roaches!....
its just the bike was running so sweet before i hit the sensor i assumed the valves wouldnt be a problem. its only been 10 days. ill do clearances anyway.
may need a new fly wheel.. :(
might just drill it out and put in a steel screw to try and regain that signal......
pretty ruthless method tho.
 

my67xr

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so it's a new bike ?
if so, the cheap chains they come with, will stretch so much that it can let the chain jump off the front sprocket as you have found.

when the engines are assembled in china, the valves aren't set properly imo, just roughly set up and are too tight.
when the motor warms up, everything expands and the valves don't shut properly.
this causes it to be hard to start, backfires through the carby and exhaust etc etc
 

H-Train

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yeah pretty new.
just gonna go get a new flywheel, just called a bloke a second hand one is 20 bucks. and ill just move the stator plate a little to avoid hitting the sensor. pretty sure thats the problem.
ill do clearances too.
is there a way to move stator plate without draining oil?
i.e. lay it on its side? or is that too dodgy?
i just dont have any oil. its got fresh as oil in it.
CBF buying more. i shoulkd run mineral oil only?
cuz i have good oil for my road bike i could use but its fully synthetic
 

H-Train

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also whats the best way to get TDC?
just use the flywheel marks?
 

my67xr

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stick with the mineral oil, otherwise your clutch could slip

have you replaced the original oil ?

you wont need to remove the stator to swap flywheels over ?

finding TDC is easy enough ,
remove the stator cover off the side of the engine,
kick it over slowly till you feel some pressure on the kickstart lever.
then look at your Flywheel it should be very close to TDC

by just going off the flywheels' TDC marking, you could end up 180 degrees out.
 

H-Train

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i saw on you tube some other bloke turns it a little each way after he fidns T
and if the valves move heaps then its 180 out? is that true

yeah ive changed oil.
i wanted to take stator plate off to move it to the right a tiny bit with the slack in the screw holes so the new flywheel wont hit the sensor.
i thought that would be better than filling the holes.
ill do that aswell if i have to
 

Blender

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yes make sure to use mineral boil, 10-40w, you could even do 15-50, if you really had too. i put fully sinthetic in my bike, and now it sometimes click from 2nd down into neutral, which when your going down a big hill, its quite scary lol!
 

H-Train

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New flywheel with the 'nib' on it fixed it up, so the problem was the pulse sensor not getting a strong enough reading off the flywheel.
I didn't do the clearances as it's still a little intimidating.. Do I need to wedge or Jam something on the flywheel so it stays at T mark. As it won't sit there by itself.
But now the bike just feels like it won't get fuel when it gets hot. And will just stall when it's hot, but when left for 30 min runs sweet again.
Could this be anything other than valve clearances?
 

zwebx

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New flywheel with the 'nib' on it fixed it up, so the problem was the pulse sensor not getting a strong enough reading off the flywheel.
I didn't do the clearances as it's still a little intimidating.. Do I need to wedge or Jam something on the flywheel so it stays at T mark. As it won't sit there by itself.
But now the bike just feels like it won't get fuel when it gets hot. And will just stall when it's hot, but when left for 30 min runs sweet again.
Could this be anything other than valve clearances?
So when you kick it when its cold it has good compression (hard to kick over)
then when its hot its easyer to kick over (less compression)
thats the tale tell sign that the valves are too tight and when you loose too much compression it cant light the fire with a explosion so to speak.. makes it hard to start

the flywheel can be held with your hand as you do the clearances, or put the bike in gear and roll it to tdc
 

my67xr

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with the spark plug out, the flywheel shouldn't move
 

H-Train

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Ahhh yes the spark plug removal made the flywheel stop moving at TDC.
I did my valves. Much easier than I thought.
The exhaust was a little dufficult with the bash plate. But I but the bike up on two milk crates and bent the bash plate a bit and got it no worries.
Can't wait for next weekend to see if doing the valves has fixed my problem.
Might even head out to pinkenbah Tomoz to see how she runs hot.
 
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