Lifan 140 with chewing gears

[Cactus Jack]

You'll have to search Planet Minis and Thumpertalk where there are guys using the Lifan 150's to see if kick starter or case problems occur ... time will tell ... but they all give the 140's a good rap and the 150 an even better rap ... they say they're faster than the 140 and the YX150 on most tracks ........

Yeah , the cradle is a bit of a gimmick ...... they'd be a lot stronger and stiffer IF they didn't have all those big holes punched in them .... which weakens the crap out of 'em .... If you bolted just a peg bar on a frame with no motor in it and stood up on the pegs .... you'd see the cradle flexing if you simply bopped up and down on them . That's why the top of the cases split on that GPX ... they were most likely already pre loaded as explained in my previous post ..... then the cradle flexed over the jump and it was just too much strain ..... you can see it's a clean fresh split . Lifan engines have much thicker top mount lugs than GPX's ... but the pics show that if something didn't let go .. the cases would have got pulled downwards which could also cause an internal fracture like your engine has .....

 

[numroe]

... but the pics show that if something didn't let go .. the cases would have got pulled downwards which could also cause an internal fracture like your engine has .....

All a bit too much at times for the "scooter" engines.

 

[Cactus Jack]

None of the bigger MX bikes have pegbars bolted to the engine cases or the motor hanging on rear ward mounts with no front down tubes for very sound engineering reasons .... Pit bike engines were originally designed as road going step thru or scooter motors and were never engineered to take the full weight of the rider standing on the pegs over a jump ........

When Honda used them in SL70's they fitted twin cradle rails to strengthen things up ...... and needless to say ..... CRF50's and Z-50's were designed with lightweight kids riding them in mind .....

In fact you're better off using a pegbar that will bend and absorb excess stress from jumps rather than overload the engine cases ........

 

[numroe]

In fact you're better off using a pegbar that will bend and absorb excess stress from jumps rather than overload the engine cases ........

As in "peg springs". I like it! Some kind of metal tube for the peg bar, which can flex but has a high yield stress and doesn't stay bent. The right grade stainless tube might be good (I know some SS grades are much more springy than others, and easy to find a welder too), or maybe thin CroMo tube. What are your thoughts on a practical/economical material? I would not care if it bent occasionally on heavy impacts. I'd bend it back a few times then replace as required. Given that frame design (and increased bike weight) aint going to happen in the near future, this could be a standard high performance pit bike option in the years ahead. Neglecting idiots who dont wear real riding boots. Great idea Cactus!

 

[Cactus Jack]

Well I actually meant that you're better off using a weak peg bar such as a stock CRF type bar rather than fitting a super strong solid chromo bar .... but a spring steel bar sounds like it might work ...... I can't take credit for your idea mate ! You can buy solid alloy handle bars that flex to reduce stress to the rider so a flex peg bar doesn't sound too far fetched ... it might feel a bit strange tho' .....

The top engine mount should really be like a rubber shock bush ..... as in control arms , diff trailing arms etc of cars .... Hell ... even car engines are rubber mounted ... In full chassised drag cars with slicks that give solid traction ...... they use mount plates between the bell housing and water pump .... they tried solid replacement mounts for the stock mount points ..... only to have those parts of the block break out ......

 

[numroe]

Hey, In line with these concepts, another option on a mini subjected to hard peg loadings could be to put some tough rubber bushes under the heads of the bolts which hold the peg bar up thru the frame to the engine. That is of course after making sure the engine is first sitting down on the lower frame mounts. So the rider weight causes the rubber to compress a little and reducing the peak force on the engine casing. That'd be easy enough to do.

 

[avenger_125]

Hate to change topic, but back to the gears i neede, anyone got some or know where i can get them? asked maylands but havnt had a reply

 

[numroe]

Guy landing Pitster X4R :

Nice photo of a bottom out on landing. Reminds me that good suspension tuning will go a long way toward avoiding harsh peg and case loadings.

Hey avenger_125, it's your thread. Sorry I cannot help re suppliers of cogs. Just keep phoning around. btw: a couple of days agao, I saw a new 140 sell on ebay for about $205 + freight. Food for thought ...

Cactus, about the kickback thing (again) and preventing gear box damage. You listed a lot of things. In summary:
1) posn past TDC, before a firm kick or bump start. The in gear roll back method being the safest if in doubt.
2) kill switch held on then release at the right moment.
3) Engine mounting and peg loadings.

You also mentioned the Lifan anti-kick-back exhaust lifting lobe on the Lifan cam.

I have to two other ideas to put on the table which might help.
A) An ignition system which is smart enough to not fire on initial kick depending on crank posn (might be possible).
B) Postioning the kick starter lever lower (more aft) on its spline, so that upon kick back, the riders foot+leg+body need not be lifted so far before the starter cog teeth disengage mechanism is used sooner.

Thoughts?


btw: I have my new 150 installed and running. Seems nice. Will test on Saturday. This engine comes with a big monster CDI and coil, but it can still kick back (had just a wee one but never again!).

 

[Maylands Performance]

Hi Avenger.
I have tried to return your Email but it gets bounced back everytime !!

We have the Gear sets you require,just give us a phone call at the shop and we will get them out to you ASAP

Cheers Brian c/o East 50's

 

[avenger_125]

Hi Avenger.
I have tried to return your Email but it gets bounced back everytime !!

We have the Gear sets you require,just give us a phone call at the shop and we will get them out to you ASAP

Cheers Brian c/o East 50's

Interstate phone call = parents not to happy, can u try PMing me?
Thanks Avenger

 

[numroe]

Off topic but: If you have ADSL or cable internet, then for interstate or international calls just use VoIP! Eg. skype or one of Australia's many VoIP service providers (such as Oztell or Pennytel). 10c per call. Not timed. Been using it in our house for a few years now with an ATA to keep using our old style phones. The misses just goes ballistic on the phone (Aus and calls to France) and I dont care less because pay like $25 per month. Stuff Telstra and Optus if you are calling to a non-mobile phone!

 

[Cactus Jack]

You also mentioned the Lifan anti-kick-back exhaust lifting lobe on the Lifan cam.

I have to two other ideas to put on the table which might help.
A) An ignition system which is smart enough to not fire on initial kick depending on crank posn (might be possible).

btw: I have my new 150 installed and running. Seems nice. Will test on Saturday. This engine comes with a big monster CDI and coil, but it can still kick back (had just a wee one but never again!).

Yeah mate , watch that kick back ........ As you know I've also just bought a Lifan 150 too ....... (curiousity killed the cat .. ) I've had trouble getting onto this site again for a few days ....

As for ignitions ... maybe one of those semi digital set ups might be able to be adjusted to cut kick back ????? The only other thing would be to have a manual retard switch that you flick to start mode for starting ... then flick to run / advance mode once the engine has started .....

Some older british singles had a cable operated advance retard plate .... they needed them just so that weak legged riders could start them ......

Some links with info :

331

Sportbike Performance Handbook - Google Book Search

331 Series - Boyer Electronic Ignitions

JP7 Simple CDI Motorcycle ignition system.

 

[avenger_125]

Nudge Nudge. Maylands hows about them gears?? i want 2 get my bike running

 

[Hans]

Hi guys....ive seen lots of stipped starter gears , blown gear boxes(...and so on) I have a Lifin jaihling 141cc outlaw engine . After lots of engine work we used to have all sorts of problems with the kick starter gears breaking and bending the kickstarters......so we used and moded the standard camshaft, which most Lifin engines have a decompression mechanism at the end of the cam..then we reground the camshaft inlet and exhaust lobes for more lift and duration, and since this cam has a decompression mechanism, stating this animal of an engine is like starting a PW 50 2-stroke ...with all the engine work and a hi compression flat top piston.I NOW DONT HAVE ANY BROKEN STARTERS or GEARS...sometimes the bike sits for 2-3weeks not being used...and she starts 3rd -4th kick everytime.......after all that i have got a couple spare dead engines that have good parts in them(starter gears, etc) if anyone needs parts your most welcome to use them.....they cost me nothing.....(however i wont pay for freight)

 

[dirttau]

hi
i need a set of gears for my 140 to a price would be nice to know from maylands

 

[avenger_125]

dirttau im in same boat, hence why i started this thread. and im still waiting lol

 

[Maylands Performance]

Hi guys.
Sorry I am so busy these days I hardly manage to check Forum posts etc.
Yes we have the gears in stock @ $50.00 [Set of 3]!
Just give us a call at the shop Ph 08 83635050 or Email to order the gears.

cheers Brian