valve clearance?

[roost]

hi, does anyone know the valve clearances for Lifan 125 big valve and any links to detailed instuctions on pit bike valve clearance setting as i am a motor mechanic(car, truck) and have never realy played with moto cycle internals. Not quite sure about how get valves at TDC is there marks on flywheel if so what mark on caseing do you line it up with?

 

[Mack]

.003" inlet .004" exhaust. The flywheel has tdc mark and so does the case. You can tell which stroke you have by valve action, or take the centre bolt out of the cover on the opposite side to the round cam sprocket cover This will release the cam cover. Just line up the dot on sprocket, with mark on the front of the head, which is situated at about 9.00 o'clock. This is TDC.

This is about how far you have to go roost to install a big cam. You'll see how easy once you get in there. Easy power gains, especially if you port this head. The inlet port is a real mess, with a huge obstruction from the valve guide. This can either be ground all the way flat to the port roof (I've done this) but you will break through to the spring seat area and this will need welding up if you want maximum port shape and area. But this is not nessesary for the average motor and the valve guide can be ground a long way down without this trouble. Big gains can be made with this motor from these mods. For a mechanic these are well within the realm of an easy job. If you want more detailed info I can help.

 

[noidea]

".003" inlet .004" exhaust" that the same for all china 125's? If not you know what the loncin 125 clearances are?

 

[Mack]

this is a safe setting for all of these engines in stock form. guys sometimes run greater clearances in very hot motors...(thats temperature and performance)

 

[roost]

thanks mack, if i fit say 1mm bigger lift cam does the valve guide need to be shortened and will 1mm lift cause valve spring bind?

 

[Mack]

Leave in standard guides and valves. It depends on the cam you select for the springs. If you want to run the biggest and best just replace springs with those from trx 90 or order a set for pretty cheap with wider coil spacing and heavier action. http://dratv.stores.yahoo.net/vaspspra.html

 

[Mack]

I just went and got my little engine book...I recorded the cam specs for the stock Lifan 125. At zero lash the lift was intake/5.88mm and exhaust/

5.64mm. Now the two most popular cams for these that I know guys in the US run is the crower g2 and the Z40. The z40 would be my pick and is

the choice of quite a few guys who favour these engines. The lift on the z40 cam is 6.92mm on both in & ex. Now because of the crank mounted

clutch in these engines you won't be installing any unlimited rev kits so the standard springs may be fine you would just have to check for coil

bind. If unsure just get trx 90 springs from any Honda dealer and while your at it pick up some trx 90 clutch springs as they are heavier than Lifan

stock ones and will stop slippage and extend clutch life.

 

[Mack]

I forgot to add there is an intermediate crower g1 cam that will retain good bottom end and fatten up the middle heaps and can be used with standard springs quite safely. The stock cam for these has a negative 10 degree overlap and less than 200 degree duration @ .050 lift so any race cam with these big valves and a port job really wakes the motor up.

 

[roost]

thanks, have you come across the two differant size cams in LIFAN 125 as people have told me ,one is meant to be 66mm and the other smaller. Do you know which one is in the big valve head, also are the big valve heads different between 120 and 125 cam wise? Do these cams fit crf and xr 50. Sorry about all the questions but i am not up to speed with small engined bikes yet.Slowly getting there.

 

[noidea]

hey mack, where might i get these cams, and what sorta price range am i looking at? Some1 shud get into importing performance cams etc coz the performance parts market is going to start booming!

 

[Mack]

Yeah, we're all slowly learning about these motors! I think both the short and long cams have been used in the Lifan motors. This link shows the definate determination of which cam you have. The 125's imported into Aus. I think you'll find have the long cam. Easy to tell once you dive into the head.

http://us.st11.yimg.com/us.st.yimg.com/I/dratv_1906_22349265

These cams and all parts for that matter should be able to be sourced from Aus. Just have to email them and ask. The reason I don't seem to know who sells what in Aus. is cause I have found it cheaper to import from OS and they can advise better what will work.

http://www.rovaza.com//index.php?SCREEN=welcome&cat=17
http://www.faddybike.com/scripts/default.asp
http://dratv.stores.yahoo.net/index.html
http://tboltusa.com/store/

There's a few to get the juices going. Good for research purposes anyway.