Lifan 140 with chewing gears

[avenger_125]

Hey Guys,
This probably isnt the right place to put this but im not sure, if it isnt jsu tell me.
Anyway i bought a lifan140 around 6 months ago 2 put into my avenger and recently i have had some troubles with the kickback that it creates smashing gears on the kickstart. for those who know wat im talking about, its the little one that slides over the shaft under the clutch and the gear between that and the kickstart gear.
So i contacted dhz(who i bought it from) looking for parts or somewhere to get them and have had no response.
Tried Epping Motorcycles - They had a lifan 140 sitting there and i was able to get the gears from them but they were a different pitch and diameter, so had to bring them back.

Now im wondering if anyone has a lifan 140 sitting around that would be willing to part out the 2 gears for me.

Cheers Avenger_125

 

[slick 50]

yer dude got a spare set of gears for the 140 in the shed
pm me a message if you want to buy them ,
Cheers , Rick

 

[tubes380]

yeh dhz has something about replace/fixing engines, same thing happened to my mate with a engine he bought from dhz, gears stripped from proper use and they didnt want to know about it
he just bumpstarts it everywhere now

 

[avenger_125]

Yeh the worst thing is i cant find anywhere that i can get them 2nd hand(parts from blown engines etc) or brand new from a shop, which would be my prefered option as the only set i found ended up not being the right size although they were both out of "so called" lifan 140s

 

[Maylands Performance]

Hi avenger_125
We have Lifan 140cc kickstart gear sets in stock !
Give us a call or shoot us an Email and we can get you going again !
Cheers Brian

 

[numroe]

Tried Epping Motorcycles - They had a lifan 140 sitting there and i was able to get the gears from them but they were a different pitch and diameter, so had to bring them back.

Hey now, the above comment caught my attention! Can you or East-50s explain that one?? I mean, really, some 140s have diff starter gears or was that one a 138cc engine and not a 140?

My Lifan 140 is about 6 months old and it's starter gear(s) will need replacing in the not too distant future. Near impossible to jump start my engine in any gear, just due to the compression.

It's ironic that with the Lifan stock camshaft with auto decomp mechanism, I used to get kick back, because it was difficult to find TDC even when concentrating on the task. The old steel slinger mass seemed to make the kick back worse (go figure). Now with a normal meaty cam, finding TDC is a no brainer- my crank just stops turning at TDC almost every time now. But my kickstart gear teeth still have the scars, and they are getting worse.

 

[avenger_125]

Hey now, the above comment caught my attention! Can you or East-50s explain that one?? I mean, really, some 140s have diff starter gears or was that one a 138cc engine and not a 140?

My Lifan 140 is about 6 months old and it's starter gear(s) will need replacing in the not too distant future. Near impossible to jump start my engine in any gear, just due to the compression.

It's ironic that with the Lifan stock camshaft with auto decomp mechanism, I used to get kick back, because it was difficult to find TDC even when concentrating on the task. The old steel slinger mass seemed to make the kick back worse (go figure). Now with a normal meaty cam, finding TDC is a no brainer- my crank just stops turning at TDC almost every time now. But my kickstart gear teeth still have the scars, and they are getting worse.

IT was definately a 140! Same casings and markings as mine so it left me stumped!
The whole compression problem that you had was the exact same problem that i had and smashed the gears. I agree with you 120% about roll starting aswel, mine jus pressure locks in any gear no matter how hard i jump on the bike wen i dump the clutch.

 

[Cactus Jack]

That's because you're both doing it wrong ...... If you take a good look at what they say on bump starting speedway bikes .... you'll start to get the drift .......

[* Starting the engine is accomplished by pushing the motorcycle or rotating the rear wheel. Cold engines should be started with the choke on and without using the throttle. Starting the bike is made easier by "tightening" the engine before pushing the bike. This is accomplished by gently pushing the bike backwards until resistance is felt in the engine.]

Description of JAWA Engine Type 884 and 888

What they are doing is pushing the bike backwards in gear to get the piston back up on the downward stroke side of TDC (just after TDC rockover) ..... PRECISELY where I advised people to start kicking their engine over from ... if you do it that way ... the engine CAN'T kick back and there's less chance of the wheel locking up and skidding or gears breaking because the crank has to rotate TWO full turns before any compression force is encountered again ..... at which point the load is passed around the quickly rotating gears so no particular gear tooth gets stressed for any longer than a split second .... too short a period for damage to set in ........ It's the exact same principal that karate guys use to be able to put out big force to break concrete blocks and wood without damaging their hands or snapping their forearm bones ..... get it wrong and it's off to the hospital ......

Kick back causes the gear , case and whatever other damage by working in reverse a la karate style to bust things ...... so to overcome the sudden force that it puts out ..... half of the engine would consist of HUGE , heavy kick start gears , shafts and thick cases ........ the exact reason why most big cc race engines such as speedway Jawas don't even have kickstarter mechs designed into them right from the drawing board stage ...

The reason why they say to not touch the throttle and have the choke on is to maintain a partial vacuum and prevent the cylinder from taking in a full charge .... because more air in the cylinder RAISES the compression even higher and makes the mixture more explosive ...... dramatically increasing the possibility of severe kick back ...... plus adding excessive load on the mechanical parts ...

http://www.miniriders.com.au/forum/mini-chat/15164-im-having-trouble-my-kickstart-3.html

 

[Cactus Jack]

IT was definately a 140! Same casings and markings as mine so it left me stumped!

Maybe Lifan lowered the ratio of the kick starter gears in later model 140's to speed up the kick shaft rotation in relationship to mainshaft rotation ...... meaning the kick shaft gear would be smaller than previous models and the mainshaft gear would be bigger .... They'd do that to pass the resistance of compression over a greater degree of mechanical turning moments ........ basically an anti "knuckle head" measure to overcome the inability of people who learnt to ride on two stroke bikes to get their kick starting technique right .....

Snitchy talks about getting his CR500 to TDC before kicking ....... it's a well known fact that two strokes have lousy compression holding ability ...... the ring leak down rate is pathetic compared to that of a 4 stroke .... anyone who doubts what I'm saying .... need simply get the rockers of their 4 stroke engine onto the base circle of the cam ...... disconnect the timing chain .... then try to turn the motor over with both valves permanently closed .....

The superior ring seal and light years slower compression leak down rate also accounts for their superior bottom end torque ...... and ability to break kick starter shafts and gears .... LOL .....

Numroe has fitted a cam with higher overlap than stock ..... and that also increases compression leak down at low engine speeds purely because the valves open earlier and close later ...... whereas a stock cam keeps the valves shut for longer which also holds compression for longer at kick start cranking speeds .....

 

[numroe]

That's because you're both doing it wrong ...

Firstly I must say I do appreciate your advice and insight. some interesting things you just shared there.

I assume you are accusing us of doing both kick starting and bump starting wrong. Well, maybe, but I don't (yet) believe so...

With the stock cam's decomp mech in my engine (pre cam change) no mortal could reliably find TDC. For whatever reason that decomp mech was far too effective and the engine just turned over and any resistance pattern was very vague. Yep, my valves were at 003 and 004 thou. I would try try try, then kick, but once in a while find I got it wrong. So my engine was neither knucklehead proof nor was it kind to people who tried to do the right thing. If I only got it wrong 5% of the time, that's enough to strip gears big time. It simply should not be so hard. With the stock cam I could bump start it at times. Yes, I always hand setup at just past TDC then bump start it.

BTW: With my new cam I don't believe I have noticeable extra valve overlap - according my rough comparison "measurements" of the cam. My cam does have much more lift and some more duration. Plus I have new valves which I assume seat better. The springs are quite stiff too.

With the A1 akunar cam and valves and springs the results are: 1) that it's now much tougher to turn the engine by hand over due to lots more low rpm compression. Real tough when the oil is thick. Of course since no decomp mech now and maybe for other reasons. 2) It's easy to find TDC before kick starting. Very easy. Thus MUCH easier to avoid kick back. 3) Bump starting is near impossible now if my engine is cold and needs a few revolutions to get going, even with a TDC setup and in 4TH gear it will turn over once then lock the rear and shred some poor unfortunate tyre nobs.

I'll do anything to avoid reckless mechanical damage of any machine I own or am responsible for. Have done for as long as I can remember working on things. No one should need a special user guide or anything beyond some basic care and common sense to start a Lifan 140. But that's not the case. The engine (or at least some of them) does have a fault.

Interesting what you wrote about "not touch the throttle". I've been used to that for a couple of years in my 450, so it's become a habit. No chance to start my 450 with just a tiny throttle turn (pump). But with my far more basic OKO26 I get far better results with a tiny throttle roll on during my kick.

I am happy with my engine's starting now. I just have some gear teeth missing/damaged in there from the past, so sometimes I feel problems - with no kick back. So I will need parts in the near future.

 

[Cactus Jack]

I assume you are accusing us of doing both kick starting and bump starting wrong. Well, maybe, but I don't (yet) believe so...

I'll do anything to avoid reckless mechanical damage of any machine I own or am responsible for. Have done for as long as I can remember working on things. No one should need a special user guide or anything beyond some basic care and common sense to start a Lifan 140. But that's not the case. The engine (or at least some of them) does have a fault.

The kick in gear engines are based on a 110 cc Honda Nice engine that has a 49 mm stroke .... and probably runs about 9 to 1 compression ........

So here we have a chinese made version of the engine that has a 10 mm longer stroke and compresses 30 cc more .... EVEN a stock Nice engine would bust the kick start mech and gears or at the very least ... wear them out a lot quicker if modded to the same level .......

Honda XR100 engines also bust kick start gears when modded over 120 cc ..... just search Thumpertalk .......

You should have replaced the worn kicker gears when you fitted the other mods ..... and work out a replacement program based on your past knowledge of kicker gear life expectancy ...... just like how MX 4 strokes and 2 strokes need valve , piston and ring maintenance ...... it's got nothing to do with quality and everything to do with the fact that lightweight parts are being forced to do a heavy duty job ...... you have to be realistic .....

The "anti kick back" mech (NOT a decompressor) doesn't prevent kick back ...... it simply minimises the effect of kick back when it occurs by opening the exhaust valve to let some of the force of combustion pressure escape when the crank tries to go backwards ......

For people who expect too much and complain about a $300 engine ... I say get real , take your stock Lifan gears out and get an engineering firm to machine you up a super tough set ....... and be prepared to dig deep just so you can kick start your engine any old way and have it survive ......

The flywheel /slinger weight WILL most definitely increase the force of kick back in the same way that it increases force to the rear wheel when the clutch is released ...... that's how it minimises stalling ..... What would you rather be shot with at close range if you had the choice ... a gun loaded with a styro foam headed bullet OR a copper or lead slug ?????? Weight creates inertia ........ and even a slight increase in weight can have a profound effect in certain situations .....

Also .... cam duration ALSO affects cranking compression .... I just neglected to add that fact since it has the exact same effect on compression that overlap has ...... overlap lets compression escape from the inlet and exhaust at the same time ..... and duration allows it to escape from the inlet valve at cranking speeds ..... IF your A1 cam allows your engine rev higher than stock ..... then it's definitely lowering the static compression ...... cams work by delaying the rpm that peak dynamic cylinder pressure peaks at ......

Kick back is caused by exploding fuel/air charge trapped in the cylinder ..... 2 other factors greatly influence its force and when it happens ..... compression and ignition spark ...... Eliminating one of the latter two from the equation can make a BIG difference ...... and since there is NO decompressor ..... the ONLY other alternative is to eliminate the SPARK .......

A sensible person (aka NON knuckle head) would hold their thumb on the kill button as they give their engine a good , fast and hard kick ...... THEN let their thumb off the kill button when the kick lever has passed the halfway point in its swing .......

Now there may be a few fools who have a problem with things I say (not you numroe) .... but they should simply smarten themselves up and get a life .......

 

[numroe]

Hmm, a good write up. Thanks. Good point re Honda origin of the starter gear parts versus the Chinese stroke increase.

I shall try that kill switch holding trick! I also intend to get new starter gears very soon. Actually, it's a must-do before my next ride.

An anti-kick-back mechanism. As opposed to a decomp-mech. Now thinking of that little one-way rotation device on the stock cam, I can relate to what you've just explained. I'd say mine did not work too well at the designed function. But far worse was the other problem (early days) I had with that cam (and old valves) where I could sometimes not feel TDC for the life of me. No kidding. It was like WTF is going on here. Near zero compression. Although the engine ran fine once running.

The A1 cam is a bottom end boosting cam. Not a rever. I put the A1, A2 and stocker side by side and had a good look from different angles. I did not take any pics, and could only offer subjective comments which would not be worth much. Certainly maximum lift (dremel on piston and new springs to make the A1 fit). Certainly it has boosted the bottom end torque. Certainly sharper inlet opening and exhaust closing - compared with stock.

For some reason now with the A1 and new valves+springs I feel much *more* static compression. But it's cool. With new starter gears and finding TDC (easy) and good footwear, it'll be fine from now on. I much prefer it as it is now. I just need some new healthy teeth so I don't literally have to pussy foot around finding a good spot on the cogs. Plus I can try the kill switch trick.

 

[Cactus Jack]

Be very careful if you've already got stripped teeth ...... if one tooth catches on another , it acts like a wedge to force the shafts away from each other . The force can easily split your cases ...... I've seen it a few times in pics from Planet Minis threads but they were Jialing GPX's .........

Ha Ha Ha ...... well look what I found while searching for pics of cracked cases .... it seems that my info is preeeettty accurate and others have found the same thing ..... except for the kill switch idea .......

Kickback? - Planet Minis

Kawasaki KLX 110's crack too ....... bone stock :

Why do the left cases crack around the kickstart shaft? - Planet Minis

Crank case problems! - Planet Minis

Maybe you should check your cases (numroe) to make sure it is the gears and not the cases already cracked ........

 

[numroe]

Maybe you should check your cases (numroe) to make sure it is the gears and not the cases already cracked ........

Yeah I see, possibly more to it than missing teeth. Ques: Right side engine cover off and I'd see the region where the inner metal casting could be cracked? Good web links thanks.

 

[Cactus Jack]

It looks like you'd have to remove the clutch ....... but you might be able to look behind it with a torch ......

http://us.st11.yimg.com/us.st.yimg.com/I/dratv_1997_46767082

 

[numroe]

See pics below. My starter gears are a little burred over. My case is indeed split. Just under the bearing which supports the clutch shaft.

Questions Cactus:
1. How does a kick back crack the case on the clutch shaft? I am guessing the load could mean anything could brake around any bearing.
2. Upon kick back, I'd expect the start gears to disengage once the kicker has returned high enough. They have to. So by looking at it, I'm still confused as to why a gear rotation "lock-up" of sorts occurs upon kick back, which in turns creates the loads from hell which breaks case castings etc. Can you enlighten me?
3. What is the type of nut called which holds on the clutch basket? I used some big multi-grips to get it off without much effort, but wondering what it is called.
4. Can you or anyone confirm that my Lifan 140 head (where all my work is) will drop onto a Lifan 150cc no probs?

Thanks in advance. You advice to check was spot on. I was awaiting my new clutch springs, but got an urge to look now.

 

[Cactus Jack]

Hi mate , sorry to hear it was your cases cracked .

1) The main shaft is the driven shaft so it cops all the load from the crank and kick start gears .... as I explained before .... kick back is like a sharp karate kick that shocks the parts and since cast parts are brittle ....... they shatter or crack easily ..... When shafts are turning slowly the stress gets concentrated at a fixed point ..... ie if you rev an engine and drop the clutch in a car from a standing start you are likely to blow the diff because the parts are sitting at a stand still ...... whereas you can get away with it if the car is moving because the stress can't get a chance to act on any particular point .. it gets passed around the gear teeth and bearings ...

2) The kick gear ratchets are designed to hook in together under load ..... a kick back is a reverse load that acts so fast that the load is maintained for too long so the ratchet sometimes doesn't have time to disengage quickly enough ...... even after you let your foot off the lever ... The ratchet gets relief when the motor starts and the clutch rotates faster than the kick speed .... the teeth act as a ski jump to avoid damage when the engine is rotating in the proper direction ..... but lock in when it's going back wards ..... You'd have to have some type of shear pin or soft key designed to sacrifice itself at a lower load than what other parts (such as cases) fail at ......

3) The clutch and slinger retaining nuts are called ring nuts and require a ring nut removal tool to get them off and replace them .......

Ring nut tool :
http://tbn0.google.com/images?q=tbn:QhBKCPZe7rMR9M:http://www.mgcycle.com/14912600K.JPG

Ring nut :
http://tbn0.google.com/images?q=tbn....com/parts/355_360/355_360fr106095RingNut.jpg

4) Yes your 140 head will go straight onto a Lifan 150 ...... but you can fix your 140 pretty easily with a half case and kick gear set from Maylands ......

In a nutshell ..... NO kick back at all is acceptable ..... you should avoid it at all costs whether you've got a cheap chinese engine or a Ferrari ...... it WILL eventually bust something in your engine no matter how many millions it cost to build .......

Incidentally your kick gears look to be in good shape ...... you only really need a right crank case ......

 

[numroe]

Thanks Cactus.

I'm not fussed about the failure. No better way to learn really. Interesting the crack is at the thinnest part of the casting around any of the high loaded bearings.

The crack probably happened a while ago. Before my head mods. Probably on a day (way back) when I let someone else ride it for many hrs and didn't know about this potential problem, and he often stalled it and I watched him kicking away while I rode my other bike. My guess is the crack flexed open more with time, and gave me more problems recently with kicking it over. Problem just became more obvious with the static compression increase with the new cam, valves and springs. The head, carb and rest of the bike is unreal. She'll be back...

I thought about a new half case and gears. Might do it. But new 140 engine are just too cheap. I (assume) could drop a new engine in the frame and put my old head and clutch and slinger in it far quicker than I could split a case. Then have my old donk for spares. Unless of course I can remove the right half-case while keeping all the internals sitting in position. Is that possible??

Ring nut spanner eh. That's the one. My big multi-grips can turn them on/off with no nasty force required. Okay to keep doing it that way?

I hear ya re your bottom line. I'll be doing the in-gear roll backwards, then kick method from now on.

Thanks again. I enjoyed the detective work this afternoon. I get nervous with side covers off my precious 450F. Or even the rocker cover! But on these china engines we can just rip in. It's great fun!

 

[Cactus Jack]

Splitting small 4 strokes and replacing the cases is pretty easy . You should be able to just remove the right half and leave everything intact . Just be spotlessly clean when you do it and treat it as a learning experience . Don't wedge screw drivers in between the case halves as you'll risk damaging the gasket sealing surfaces ....... gently and methodically coax them apart from both ends while trying to keep the gaps even .

I notice that it looks like the crack extends into the pegbar bolt boss ????

When the crank is driving the clutch , it pushes the main shaft upwards so you'll find the case is designed stronger at the top with that in mind .... a kick back would shove it downwards . Another factor that's bad with these motors is the fact that the riders weight is pulling downwards on the bottom of the cases . IF the top to bottom hole spacings aren't spot on , or the pegbar doesn't sit flat on the bottom of the motor or the motor sit dead flat in the cradle BEFORE the bolts are tightened , then that'll add to the load . The motor should be bolted to the cradle first ..... then the top plate bolted up without anything needing to be forced or pulled up by the bolt tension . Most people think of steel as being solid and rigid but it isn't ... it has flex and elasticity .... so a cradle frame can actually add stress to pre load the cases of the motor if all the 6 bolt points aren't aligned properly . The motor should really only hang from the mounts and have to support its own weight ... the riders weight should be supported totally by the frame with no bolts going into the bottom of the motor .

Now a lot of people won't understand that and I don't care if they do or don't but I can assure you that I know fully what I'm talking about .... I explained it all to my brother in law and he argued ...... until I showed him a pic of a brand new Pitster X4R with a cradle frame that split the top engine mount after landing from a jump ...... What the average Jo Blo thinks can't happen ...... most certainly can happen ......

Guy landing Pitster X4R :

Split top engine mount that "can't possibly" happen in a cradle frame :

 

[numroe]

I read ya re the static stress in the case due to incorrect mounting. I'll be careful when I install the next or repaired engine.

The crack firstly goes in toward the bottom of that cavity under that shifter gizmo (about 12mm), then turns down/rearward and runs toward the peg mounts, but only for about another 5mm in that direction.

Hey you heard anything positive about the Lifan 150 in terms the kick starter mechanism improvements? NOT that any engine will be kicking back when I'm starting it.

My 140 was running nicely. The responsive bottom+mid rpm output made jumping and cornering very easy. Ample power after the head mods. Just needed a stronger clutch which is trivial to solve. If the 150 has the same kick start probs (of course for when I let my mates ride my bike), then another (or repaired) 140 would seem wise/safe/conservative. BUT my guess is that the 140 and 150 have a LOT in common, and a little more bore and an oil filter looks tempting.