Cam question.

[swifty_ano]

I've been reading some older post and they say that the Lifan 140cc engine comes stock with a 6mm lift cam. Can anyone confirm this? would a 6.5mm lift make much of a difference?

thanks guys.

 

[Cactus Jack]

Mack says that Lifan 140 cams have 6 mm inlet lift and 6.6 mm exhaust lift . He measured one and knows precisely what he's talking about ..... BUT a lot of other people say they only have lift that's in the 5 mm's range !!!! He also said they have higher lift springs than 120/125/127/138 Lifans ..... Since Mack was talking about the first run of 140's .... it's quite possible that the later runs have SMALLER cams ....

http://www.miniriders.com.au/forum/tech-talk/11100-modified-cam-not.html#post184874

Duration is more important than lift .... The lift gives the snap and punch due to allowing the engine to take in a bigger "gulp" of air and duration gives the engine the legs to rev harder than stock by delaying the building up of peak dynamic cylinder pressure .... When PDCP hits a peak .. it acts like a brake to limit further increase of rpm .... The best combo of punch and revs comes from using a fast opening / slow closing cam with high lift ..... The TB 300 A has FOSC lobes and is reported to be a great cam .... So is the Z-40 (both 70 mm long) .. but it's hard to find them in those grinds to suit the 140's which take a 73 ~ 74 mm long cam ....

Mack says he can regrind cams in any spec to suit your needs ... but he hasn't been on here for a while

z 40 cam - Planet Minis

http://www.miniriders.com.au/forum/tech-talk/11714-lifan-performance-cam-2.html

DRATV has a Lifan 140 "rev" cam ... and Akunar has A1/2/3 cams in 3 different lifts .... The A-2 / 6.7 mm lift sounds like a good all 'round choice ....

 

[themountain]

its not only the lift what makes a cam better or not, the duration is very importend too!!

 

[Cactus Jack]

Yup mountain .... it's actually ... duration at full lift that matters .... "Nose Duration" .... Cams with moderate duration that snap the inlet valve open quickly then close it slowly give the best snap and punch (throttle response) plus over rev for dirt riding ...

If you go too big in a cam the engine loses its sharpness under load and won't pull unless its revving in the right gear ratio like a two stroke ...

 

[swifty_ano]

wow man, how do you know so much about cams??

 

[I_THUMP]

Cactus you always come through with the answers in great detail when no one else can. When swifty asked me this question I told him that cactus will know and will post the answer for u and cactus u came through with a well detailed answer as always.

You are a real credit to this site and im always interested to read your posts.

Cheers mate

 

[Zirtech]

all in all...without getting to confusing....most people would be happy with the z40 or t300 or r20....or as im thinking of going the 150cc lifan cam

the cams above are repeatedly said to give great results

 

[themountain]

wow man, how do you know so much about cams??

..because he´s the man ...30 years of bike experience

 

[swifty_ano]

I_THUMPS right.........I feel like marrying this guy (L)

 

[Cactus Jack]

Ha Ha Ha ... I researched all this stuff over time in order to have a bit of an idea on what's what ... And when I got into pit bikes I did a ton of sifting and searching for info on cams and other mods for horizontal engines ... 'No point in wasting the info on myself when it could possibly help others ... or at least save them a lot of time and maybe avoid losing money buying parts that won't fit ...

I put up a few pics in this thread ...

http://www.miniriders.com.au/forum/tech-talk/19466-150cc-cam-140cc-lifan.html