Lifan 150cc big-bore kit: Installation

stroker crazy

crazy as a fox
Remove seat and petrol tank to allow clear access:



Remove carburettor and intake, spark plug, exhaust, horn and bracket:



Remove head steady bracket, the two bolts holding the front engine mounting bracket to downtube, top rear mounting bolt, and loosen bottom rear mounting bolt:



Remove tappet cover:



Remove rocker assembly; when lifting pushrods, make a note of which is intake and which exhaust:

 

stroker crazy

crazy as a fox
Remove the four head bolts, not forgetting the cam locating bolt on LHS of motor:



Lift head clear, keeping a look out for the dowels between head and cylinder:



Undo cylinder location screws on LHS of motor:



Lift cylinder, taking care to stuff crankcase openings as soon as possible



Pry out circlip from one end of gudgeon pin and push pin through the piston from the opposite side. (do not re-use circlips!)

 

stroker crazy

crazy as a fox
Install new piston noting marked inlet side (lightly oil gudgeon pin to install),
make sure circlip gaps are to top or bottom rotate rings so that the gaps are 60 degrees apart:



Swap cam followers from original cylinder (be careful not to lose the wave washer) to the new cylinder:



Dowels in place in head:



Install 8mm/6mm exhaust studs:



Smear a very light coat of silcon sealant on cylinder mating surface, if you are not using a base gasket:

 

stroker crazy

crazy as a fox
After cleaning any gasket remains from crankcase and replacing dowels, lightly oil the cylinder and carefully slide into place over the piston (remove the stuffing when the rings are inside the cylinder):



Position head gasket and top dowels:



Bolt head in place (20–22lbf. or 28–30n/m) and replace cam locating bolt (13–16.5 lbf.). Be very careful when replacing the pushrods – angle them toward the outside corner and rock the cam using the kick-start lever to ensure contact. If not positioned correctly they will drop into the motor, necessitating the removal of the head and cylinder in order to retrieve them:



Replace rocker assembly:



Replace engine mounting bolts (8mm 22.5–27.5 n/m)

Adjust valve clearances – intake 0.1mm (0.004˝), exhaust 0.15mm (0.006˝). For correct TDC inlet valve should be closing as piston rises.

Replace tappet cover, refit head steady, carby, spark plug, horn, tank, etc.

Before starting, remove oil bleed screw from rocker cover. Start motor; when oil bleeds from from vent, replace screw.
 

2b

Been Around the Block
And if like my kit, your rings are not fitted on arrival.....

Steps 1-3
1. Fit the corrugated type ring first, its actually an inverted T shape, so has to go in first to allow the two thin oil rings to fit in either side afterwards.

2. Fit the dark ring (D) facing up in the second groove.

3. Fit the silver ring (DY) facing up in the top groove.

READ MORE DETAIL IN THIS LINK>>>
http://www.duncanracing.com/TechCenter/4strk_ringinstall2-24-05.pdf

Clocking the rings vid
https://www.youtube.com/watch?v=GJsJNjYEbKg
 

Niek35

New Member
Hi Guys,

Had a question about the big bore kit. Is it possible to drill out the 150cc cylinder to a bigger cc? Have a friend with a 50cc Honda cylinder drilled out to 70cc. And a 70cc drilled out to 125cc.

Thx,

Niek
 

stroker crazy

crazy as a fox
a 70cc drilled out to 125cc.

I would like to see that!

You won't get much more out of the 150, even if you could find a suitable piston.
The easiest way to get more power is to fit a 250cc clone.
But you would have to do something about the inadequate brakes.

Just buy a bigger bike ...
 

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