Lifan 140cc piston diameter??

[damann33]

I need to buy a new piston and was wondeing if you guys could help me out. I need to know the dimensions of the stock 140cc piston, thanks

 

[Cactus Jack]

I need to buy a new piston and was wondeing if you guys could help me out. I need to know the dimensions of the stock 140cc piston, thanks

The TRUE Lifan 140's are 1P55FMJ and have a Bore of 55mm x Stroke of 59mm and use a 15 mm gudgeon pin PLUS they have super thick engine mount lugs . IF you have one of those 156FMJ OR 1P56FMJ things they are NOT made by Lifan and have a 56 mm bore x 57 mm stroke plus probably a pissy little 13 mm (50 to 80 cc engine sized ) gudgeon pin ....... In fact even Honda has now gone to 14 mm piston pins in their CRF80's because their engineers wanted to increase reliability ...... a 140 engine needs a 15 mm pin to handle the added load and live a long life ......

Man it's REALLY coming to something when sellers take to BS'ing that their engines are Lifan when they're merely glorified Jingalings with a Lifan copy BVH on top .......

 

[motoluver]

The TRUE Lifan 140's are 1P55FMJ and have a Bore of 55mm x Stroke of 59mm and use a 15 mm gudgeon pin PLUS they have super thick engine mount lugs . IF you have one of those 156FMJ OR 1P56FMJ things they are NOT made by Lifan and have a 56 mm bore x 57 mm stroke plus probably a pissy little 13 mm (50 to 80 cc engine sized ) gudgeon pin ....... In fact even Honda has now gone to 14 mm piston pins in their CRF80's because their engineers wanted to increase reliability ...... a 140 engine needs a 15 mm pin to handle the added load and live a long life ......

Man it's REALLY coming to something when sellers take to BS'ing that their engines are Lifan when they're merely glorified Jingalings with a Lifan copy BVH on top .......

So the newer bikes like the xr140 and some MSO??? Maybe DHZ etc what have the new 1p56fmj engines are not a "new improved" Lifan 140cc engine??

 

[Cactus Jack]

So the newer bikes like the xr140 and some MSO??? Maybe DHZ etc what have the new 1p56fmj engines are not a "new improved" Lifan 140cc engine??

NO they're not !!!! I have it straight from the Pit Pro sellers mouth that the 1P56FMJ's aren't Lifan engines ........ but YX 140's made up from Jialing GPX bottom ends with a BVH on top and close up inspection of pics of 1P56FMJ engines compared to a December 2007 bought DHZ 1P55FMJ Lifan 140 show that the heads and cylinders are a totally different casting PLUS the cases have the puny 120 to 138 Lifan and GPX mount lugs .....

Incidentally , I have both the original and improved Lifan 140's still brand new in the box from DHZ ...... and they are BOTH 1P55FMJ's ..... the 1st 140 has the weaker mount lugs like Lifan 120/125/138's and GPX Jialings that can crack from jumping ....... the newer 140 has the new improved thicker lugs to correct the weakness ...... and they could possibly have a 5 plate clutch hiding away inside ........

There apparently IS a 1P56FMJ-2E10 Horizontal Lifan BVH engine available that is NOT based on the YX150 KLX type engines ... BUT it's 150 cc with a (56.5 mm bore x 59 mm stroke) . How authentic they are is anyones guess , but you can bet ya' nuts that if Aussie sellers had them ....... they'd be plastering the 150 cc capacity all over their ads and listings ......

Lifan 150cc Engine (1P56FMJ-2E10), China Lifan 150cc Engine (1P56FMJ-2E10) products- China Lifan 150cc Engine (1P56FMJ-2E10) Manufacturer, supplier

Lifan 150cc Engine - JANGMEN QIPAI Motorcycle Co.,Ltd

 

[motoluver]

NO they're not !!!! I have it straight from the Pit Pro sellers mouth that the 1P56FMJ's aren't Lifan engines ........ but YX 140's made up from Jialing GPX bottom ends with a BVH on top and close up inspection of pics of 1P56FMJ engines compared to a December 2007 bought DHZ 1P55FMJ Lifan 140 show that the heads and cylinders are a totally different casting PLUS the cases have the puny 120 to 138 Lifan and GPX mount lugs .....

Incidentally , I have both the original and improved Lifan 140's still brand new in the box from DHZ ...... and they are BOTH 1P55FMJ's ..... the 1st 140 has the weaker mount lugs like Lifan 120/125/138's and GPX Jialings that can crack from jumping ....... the newer 140 has the new improved thicker lugs to correct the weakness ......

Thats very interesting to know. I wonder why they ditched the Lifan 1p55fmj 140cc for the yx140???

 

[Cactus Jack]

Thats very interesting to know. I wonder why they ditched the Lifan 1p55fmj 140cc for the yx140???

Well that's quite obvious ..... they must be getting the YX140 engines supplied to them cheaper than they can get genuine Lifan 140's ....... if they were genuinely a better motor they'd be honest and state precisely what they are to build up a good name for them in their own right instead of claiming they're Lifans ........

 

[damann33]

well iv got the 140cc OGM, it is a true 140cc, but after doing some research I found out its got the 81mm stroke cylinder, it does have the 15mm pin, and is 55mm wide. I am buying new valves, springs, rockers that are meant to be ran with a tb performance cam. I may just throw back together my engine and run it with the head. The engine cylinder still has the factory cross hatch pattern, so I think the rings will still seat even tho they have ben moved from their original position. You think I should get a hold of a new piston and hone the cylinder?

 

[Cactus Jack]

You can buy hi compression pistons to suit 15 mm pin Lifan 140's in the stock bore size (55 mm) from Akunar . They also have cams , springs etc and now take paypal for ease of payment ........

PRO PISTON KITS

 

[Cactus Jack]

well iv got the 140cc OGM, it is a true 140cc, but after doing some research I found out its got the 81mm stroke cylinder . The engine cylinder still has the factory cross hatch pattern, so I think the rings will still seat even tho they have ben moved from their original position. You think I should get a hold of a new piston and hone the cylinder?

You should stop listening to your info "sources" ..... they're bump steering you with fragmented misinformation .. you measure a cylinder from the base gasket flange to the deck surface and you can do that yourself with a school ruler ...

Check on the bore x stroke calculator and you'll see that a 55 x 81 stroke = 192.44 cc .......

Tuning - Cubic Capacity

It's always best to give any used cylinder a light re-hone before re installing either slightly used OR preferably new rings ..... when you remove the piston from the bore you break the ring seal and the rings go fractionally out of round ........ especially if you remove them from the piston ........ failing to re-hone and re bed in is a guarantee that you'll have poor ring sealing which means blow by and oil consumption etc = loss of power and inconsistent tunability ........

 

[ducar.r.spec]

well after reading all this
just curious of bore,stroke and pin size of a 138?? i know they arent true 138's but im curious of the dimensions

 

[Cactus Jack]

54 mm bore x 55.5 mm stroke = 127.11 cc ..... with a 14 mm gudgeon pin ....

Cylinder deck height 79 mm .... gudgeon pin to crown height 12 mm ....

You sound bored like me Ducar ..... do you want to know the piston weight as well ??? ... LOL ......

 

[ducar.r.spec]

lol yes im quite bored
just wondering what stuff will fit my bike from akunar lol
u seem to know ur stuff pretty well
whats a good cam to run???

 

[Cactus Jack]

What engine have you got ? Lifan "138" aka 127 with BVH ? If so any of the long 73 mm chinese cams and Honda cams will fit ..... As Mack has stated ... the main problem with every aftermarket cam is that they have no decompressor mechs on 'em like the stock cams have ......... so people fit them along with hi comp pistons then wonder why their kick starter mech claps out on 'em ......

For the 127 the TB cam would seem a good choice ... but for longer stroke 140's you want to run a longer duration cam to get them to rev up top ......

The yanks reckon Akunar cams aren't too fantastic .... but they say the dratv BCI cam which is a Z-40 grind is OK ......... the trouble is he won't ship to OZ ...... the only alternative is big50.com who want over $250 for the same cam ...........then there's Ivan Tighe cams in Queensland ....

I haven't actually gotten into trying different cams yet but I'd try an Akunar purely because (like a sleazy HO) they're cheap and available ... LOL .... although my instincts tell me to consult with Mack and get stock cams reground to his recommendations ......... regardless of the higher cost ......

 

[corey58]

an daytona 125 cam fits in and it the best cam u can buy that fits it(there are better cams but dont fit)

 

[corey58]

Yes but a Daytona is a high revving short stroke motor and what works superbly in a 4 valve Honda engine won't necessarily work the best in a long stroke 2 valve chinese motor ........ I'm sure Mack will agree ...... the good thing is that he says he can get stock cams ground to any spec ie duration , lift , lobe separation , overlap etc ....... and I don't under estimate his knowledge in that area for one split second ... Quote:

u sound like u no an lot but an 125 daytona is an 2v half chinese/jap motor

 

[Cactus Jack]

Yes well I obviously don't know much about the newer 125 Daytonas....... I was thinking more of the 119 DOHC four valve engine .... but I'd just had a few Tooheys Old beers which stuffed up my brain waves being a non drinker .. LOL ....in that case being a SOHC 2 valver the cam profile would be closer to suit a chinese motor but even then Mack still says that Honda grind cams aren't the best for a long stroke chinese motor .....

The Z-40 and Takegawa R-20 grinds are reported to be quite good for Lifan engines .

Here's some older info I got from Dan Crower :

We have our g2 spec that is a nice cam @ .257” lift and 236 duration

Then we have the # 18 spl- .264” lift and 248 duration

And a super grande’ that’s a .289” lift and 248 duration

Dan Crower

Owner/President Engineer Czar of Crower Power Parts


Plus this link full of info (compiled by Kurlon of Planet Minis):

http://www.x386.net/TTR/tech/cam2.html

 

[Mack]

I heard from guys that should know, but a while back, that the g2 specs are falsely stated and that all they are, is a stock cam, which has had a base circle grind leaving them thin as a pencil. I don't know this to be fact but is worth checking.
By grinding the base circle, they need no welding and therefore suffer no bluing on the cam, the profile remains factory finished and the sides of the lobe need no clean up. BUT...
the cam will never be a world beater because although some extra lift and duration is gained, the basic design and profile is unchanged from stock. Whereas with a properly designed race cam the ramp rates and profile over the nose are much more aggressive. The lobe centres will be different and the amount of retard increased. The z40 and r20 you mentioned cactus are widely used and proven good performers. The r20 is quite aggressive though and will need an eye kept on the top end over time. Springs sorted also if you like to rev.

 

[damann33]

well I had just bought a performance cam with the 32 tooth cam sprocket off of tbolt, along with his valves, springs, rockers kit that are suited for the cam. Now I have been checking out the pro piston kits from akunar and a lot of them have the cone head shape to it, so wouldnt the piston hit the head? maybe the second one down from the top will fit right into the stock bore?? HOME Akunar Motorcycle Parts & Accessories

 

[Mack]

Sorry to get a bit off topic damann33, AKPRP010-A is the one you want. The 140 stock piston has a greater pin to deck height than these pistons so you need the dome to bump compression. If you were thinking of going with the piston you were looking at above in stock bore size, you'd be better off sticking with the stock piston.

 

[damann33]

no problem man, that piston ur directin me to, it is a 57mm piston, the stock piston is 55. Does this mean I would need to find a new cylinder or bore out the one I have now? tbolt told me he can sell me a cylinder that uses the 57mm, but then id need to find a piston, maybe this one will fit into the cylinder hes talkin about?would the bigger domes hit the head as well?