107 ssr needing a little more power...

[Dudewith4x4]

Hey guys last night I picked up a 107 ssr pit bike from a buddy. He had put some inverted forks, mikuni carb and a aluminum mx style swing arm on it. In my buddy's shed I have a 125 and a 120cc motor torn apart. My question is can I put any of these parts on my bike? The head maybe? Would it be worth doing? Thanks!

 

[my67xr]

i'm pretty sure if you fit a 54mm bore, head and piston to it it comes out at around 118cc
you'll need to have the 107s' head and barrel off to check the gudgeon pins are the same size etc
maybe give it a bit of a port job etc while it's apart too
then add some heavy duty valve springs and a better camshaft

 

[Dudewith4x4]

Hey man thanks for the reply. I measured the piston and head last night and they seem to be the same length as the ones on it. Also I found I had 2 brand new pistons with 2 different sized pins. So I hope one of them will work. How does one go about porting the head? Will it notice a difference after I have done all of this? Also will the extra power tear up the transmission? Thanks

 

[my67xr]

yeah the heads and cylinders are the same length.

but there are a lot of variations to the big bore swaps.

what model is the 110cc 1P52FMI? or something close ?
if it is,
the bore is 52.4mm across and the stroke will be 49.5mm, it has a 13mm piston gudgeon pin, and is a 104cc (107cc cast into the cylinder of head)

one 125 has a bore of 54mm, and a stroke of 54mm, and has a 14mm gudgeon pin in the piston, and this is a 123cc engine (commonly known as a Lifan 125)

there is another couple of variation's,
one that has a 52.4 bore and a 57mm stroke, and the piston has a 13mm gudgeon pin in it, this is a 122cc engine (124 cast into the engine)
and then there's one with a 52.4 bore, 55.5mm stroke, it has a 14mm gudgeon pin in the piston, it is a 119cc

so you need to know that the new bore/piston and gudgeon pin will fit the 110

using the bore off a 125 engine with a 54mm bore on the 110 (55.5mm stoke) will up the 110cc engines' capacity to 127cc
and it will give the engine a bit more torque, a noticable difference in power, the 110 gearbox will be fine.

 

[Dudewith4x4]

Hey man thank you so much for the info. The barrel I have on the bike right now says "107cc" on it. The barrel I have to put on it says "120cc". I have a piston for it has a 13mm pin so I should be good. For heads I have the head for the "120" and a head for a "124". So witch should I use? I also have a brand new cam from a 140cc lifan.. Should I use that cam in one of those heads? Thanks again for all the info man.

 

[my67xr]

i would use the matching head for the piston/barrel incase it has clearance issues if one has a raised piston etc

once you have swapped the barrel,piston and head over make sure you set up the timing correctly,
and adjust the valve clearances before trying to start the engine too.

i'm not sure if the 140 cam will be much of a difference in performance
have a look at the TBolt US website, they have some upgrade cams and valve springs too.

 

[rotn50]

Using the head for the matching barrel is a good idea. I have found on a few occasions that different heads have a bigger combustion area and in turn lowers compression resulting in power loss. But having them machined a lil if your in that position could work out well. Just double check the combustion chambers and a few other points. Ive had a lifan 150 cam in a lifan 125, was a very lumpy idle with little bottom end but good mid to top.