Gearbox slipping into neutral

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warners.90

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g'day i got a tdr pro, running a 150cc lifan cdi engine and i'm having a few problems with the gear box.
when its just started up it fine, but once its been running for a bit longer and the engine is hot it has, on a number of time slipped into netural (or not engage the gear, i'm not sure what) during changes. this has happened between all of the gears on one more occasion (not just between 1st and 2nd). i was wondering if there was a problem with my clutch not properly engaging, a cooling problem, gearbox problem... i'm not to pitbiking so i hav no idea.
 
i gota ask 1 question first,, where did you get yr bike and how long ago? is it possible to post a pic of your bike from the right hand side... maybe post a link of your bike from ebay or the store you got it from.

ok there is a problem with some engines where the shift drum for some reason needs to be modified so it will select the gears properly. ill try and find a link to show you..
 
Fixing Gearbox Issues

im not 100% sure if its the problem in your case but it makes sense as it only happens when it heats up..
that arm in image 1 has a spring behind it and when the engine heats up the spring maybe loosing tension and allowing the shift drum to turn a bit..

how hot does your bike get?
also is it getting regular oil changes?

because believe it or not the oil acts as a sort of coolant, if it is old then the oil will be getting hotter than usual allowing components to overheat...
 
i got the bike a couple of weeks ago, it was second hand, but its still only used 2.5 tanks of petrol in its life (the guy i bought it from had hardly ridden it). so its still on its first lot of oil, but i checked that and its still pretty clean.
Also some times the gear lever gets stuck up or down (rather than centering) after a change, i thought that might be because its not greased. but i was wondering if that might be caused by the spring loosing tension
here is a picture of the bike: http://lh5.ggpht.com/_9B5bhxAaYoc/Soz_lK-EZ0I/AAAAAAAABBA/cC1uGJGvd4A/s640/150ccTDRPitBikeWhite.JPG
 
I the lever gets stuck like that sounds like your shift star and shift arm aren't working right
 
warners.90 said:
(btw. i'm not sure what image your talking about, i can't see any link)
Click to expand...

the image i was referring to is in the link Fixing Gearbox Issues

i seen these bikes on ebay everywhere.....can you confirm that it says 150cc on the barrel and also what is the engine number, because they only have a lifan 140 clutch cover...and all the 150's i have seen have the daytona style clutch cover also is the barrel alloy or cast steal?

im almost gona bet that the little washer behind the detent spring is missing and that arm is stuck open.. look at the picture below...there should be a washer between the arm and where it mates against the case. without this washer the arm jams up.
 

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Ive had this issue myself and i agree that it'll be the star cam and roller, either the roller has slipped of the cam or the cam has fallen off which may lead to the pins falling out of the shift drum ( had this happen on my CT last weekend)
 
warners.90 said:
g'day i got a tdr pro, running a 150cc lifan cdi engine and i'm having a few problems with the gear box.
when its just started up it fine, but once its been running for a bit longer and the engine is hot it has, on a number of time slipped into netural (or not engage the gear, i'm not sure what) during changes. this has happened between all of the gears on one more occasion (not just between 1st and 2nd). i was wondering if there was a problem with my clutch not properly engaging, a cooling problem, gearbox problem... i'm not to pitbiking so i hav no idea.
Click to expand...

Hi there, I am new ti this site but I had a similar problem last week.
When shifting into 3rd gear the bike seemed to be in neutrl and there was a loud clicking coming from the gearbox.
I renewed the clutch and cable etc but it still happened.
I split the engine which is extremely easy to do and found that the fork gear shift had a slight bend in it so that 3rd gear on the main shft was no engaging properly with 3rd on the countershaft.Also the kickstart mechanism was slightly loose.
After replacing the gear shift drum and the 3rd gear cogs on both shafts it now works like a dream.
There is a website out there with an exploded view on a complete sprip down of an engine.
I will find it out and post.
 
some more information about the strip down would be very helpful, i've removed the casing from the left side of the engine (gear lever side) and have not got a the tool to remove that hub (well i think thats what it is) near the chain sprocet. but i haven't yet seen anything that looks similar to that link to " Fixing Gearbox Issues " posted above.
 
you sure? I haven't seen the insides of a lifan 150 but it can't be that much different to what's in that link. the thing you're calling the big sprocket is probably the clutch, the shift star should be right above it to the left a little bit
is your engin e much different to what's in this video? YouTube - How to fix broken Kick start gears, Lifan 140, Pit Bike engine I don't go anywhere near the gearbox in this video but it shows how to get the clutch and sling off which would give you access to the shift star in the Fixing Gearbox Issues link
 
its called a magneto removal tool
have you looked in the tutorial section?
there should be enough information regarding the drama your having
if not let me know and ill hook you up with the info you need
 
warners.90 said:
some more information about the strip down would be very helpful, i've removed the casing from the left side of the engine (gear lever side) and have not got a the tool to remove that hub (well i think thats what it is) near the chain sprocet. but i haven't yet seen anything that looks similar to that link to " Fixing Gearbox Issues " posted above.
Click to expand...

oh I just reread that ^^^^
you're looking in the wrong side of the engine, see my video that's where ya wanna be looking
 
lol, im not sure who's on the wrong side now...probly me doh... pretty sure he said "gear lever side"...

as for inside a lifan 150....they are exactly the same apart from the obvious no slinger.

but yeah.....not sure why i didnt pick up on it too....
dude your on the wrong side of the engine if your on the carby side...
 
really no slinger at all? not even a lightened one? btw other than balancing the crank does the slinger serve a purpose? by the name I'm guessing it picks up oil and slings it ?
 
roger...no slinger at all..id say its purpose is to balance the engine. tho i cant see the need for it. theres hundreds of other engines around that dont use 1.. but theres also hundreds that do
and the slinger side of the crank already has to deal with enough drag....
and iv never seen a broken crank that is 100% slinger related...

and im pretty sure that a daytona clutch cover kit deletes the slinger.

im not sure if harmonics of the engine is reduced with a slinger...maybe but not too sure...

id say cactus jack would know exactly what its purpose is or have a good theory..

tell ya the truth i never googled it either....

oh and by the way i dont think oil slinger is its proper name....and for some odd reason the exploded view of a china engine calls it an oil filter, it has no permanent way of filtering the oil

http://www.miniriders.com.au/tech-talk/18528-150cc-t-rex-daytona-motor-photos-2.html#post175825
 
hey it does catch ALLOT of those fine shavings like you get off a magnetic drain plug tho, it all sits in there like a putty. I think it has an effect like those theme park rides that spin on the spot really fast and push you up against the walls. Cactus did say once that not installing a lightened slinger while installing an IRK can kill and engine pretty quick.
 
yeah iv seen that metallic putty(sludge) in there too, but oil also sits in there when the engine isnt running so its always soft and im guessing when you next start your engine that that metallic sludge is the first thing that goes thru your crank and into your conrod bearing.

the only engines iv seen with broken cranks are lifan 140's and they all had standard magneto setups, but then the yx140 comes standard with irk and lightened slinger so it makes me hard to see the relationship between the issues...
because like i said.. you think of the strain that is on the clutch side of the crank opposed to the magneto side....makes you wonder how a slinger makes a difference...
hopefull cactus jack fills in the blanks for me...because im an engine re conditioner by trade which did not include motorbikes...altho in college we did dabble with bike engines a little. everything i know about motorbikes now is pretty much self tought
 
that youtube video helped alot,
today i had a look at super cheap, for the tool to remove the oil slinger, and the clutch puller tool, but couldn't find one. does anyone know where to find one?
 
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