What are the best bang for buck lifan 125 upgrades?

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gottagetacheaperhobby said:
standard 54mm piston would till give you a little more torque.... i reckon the stator of your 150, the 54mm bore with a standard piston, head work h/d valve springs and the 24mm oko would be a noticeable improvement for a quite cheap outlay, the valve springs on ebay were only 10 bucks plus 10 postage i think, a piston and rings wouldnt be to much either......
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Yeah the oko is going to be an interesting fit, there is only a few mms between both the tank and the bore where the carby sits with a mikuni....so I'd have to get a new manifold etc...might just leave the 22 on it unless it really needs to be changed! 22mm Ive been led to believe is on the high side for a 125 anyway.

Then again it is a big valve head too so any new piston I would have to get would have to have the corresponding grooves for the valves wouldnt it?
 
yeah, you'll still need to check the valve to piston crown clearances
 
Yeah will contact T-bolt and ask about the 52.4mm piston. The motor I have the 1P52FM1 in a few specs I found is a bit better than the 54x54mm 1P52FMI.

Ill pull the head off the other motor tomorrow and measure the piston size, although it might be hard without calipers...and have a look at the valve to piston crown clearances on the stock piston too.
 
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i have that other 125 in bits here, i'll just measure the Gudgeon pin in the morning
 
my67xr said:
i have that other 125 in bits here, i'll just measure the Gudgeon pin in the morning
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Cool cheers. Did a bit more research before sleeping. This should fit...73mm piston height the cheaper one is like a 53mm piston height...this is also for the big value heads! If my piston is 52.4mm and gudgeon pin is the same size then it should by all means work...not sure if its a typo at the bottom...I think it should say no boring required!!??

.TB 613 52.4MM High Comp Piston w/14mm Pin Kit GPX Lifan YX Piranha - Pit Bikes - Parts by Brand - SDG Parts - TBW0613 - TBolt USA, LLC

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stoozo said:
22mm Ive been led to believe is on the high side for a 125 anyway.
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maybe a little on a stock 125, but if you do the work to it your planning i would definately recommend the oko24.
between ease of tuning, and the extra kick up top, its probably the first upgrade i would do, and then just re jet it as you start the upgrades.....i just want to clarify something to. your clutch is nounted on the front of the engine yeah? because if it is your also limited to just how much power it can put out before you start having problems. i did find something on the net a while back about it but cant find the article now..... from memory its around ten/twelve horse and they start snapping cranks....
 
gottagetacheaperhobby said:
maybe a little on a stock 125, but if you do the work to it your planning i would definately recommend the oko24.
between ease of tuning, and the extra kick up top, its probably the first upgrade i would do, and then just re jet it as you start the upgrades.....i just want to clarify something to. your clutch is nounted on the front of the engine yeah? because if it is your also limited to just how much power it can put out before you start having problems. i did find something on the net a while back about it but cant find the article now..... from memory its around ten/twelve horse and they start snapping cranks....
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yeah right, well that motor stock is rated at 9.5hp by chinese standards that means, 8hp so probably have around 2hp to play with before stuff starts blowing up...thats why Im thinking high comp piston. Carb and rotor kit...that should be enough to liven it up a lot without blowing the bank account and without blowing up the motor :thumbup:
 
yeah you will get a noticable difference with those mods....... i was just reading some info in planetmini's about the gpx hi comp 125 and they are a 54mm by 54mm bore and stroke, supposedly that configuration is rather unique and special....allows more revs or something...here is a link if your interested, also shows the similarities in heads etc to the other 125 engines. might give you some ideas on how to get your engine to where you want
125 HP (High Performance)
also something interesting, the supposed gpx i have may not be according to post 27...
 
gottagetacheaperhobby said:
yeah you will get a noticable difference with those mods....... i was just reading some info in planetmini's about the gpx hi comp 125 and they are a 54mm by 54mm bore and stroke, supposedly that configuration is rather unique and special....allows more revs or something...here is a link if your interested, also shows the similarities in heads etc to the other 125 engines. might give you some ideas on how to get your engine to where you want
125 HP (High Performance)
also something interesting, the supposed gpx i have may not be according to post 27...
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Well I have some experience in this. The TRD was a 1P54FMJ with the single bolt valve covers...that is the 54x54 I recons. My big valve headed motors are 1P52FM1's with 52.4mm bore and 57mm stroke if I got that all correct. So your GPX should technically be pretty similar to the big valve head motors I have. Does the GPX have the big valve head? As far as I know(im often wrong) the 52.4x57 big valve has a fair bit more kick to it...comparing the ducar in the TDR to the pitpro 125 big valve....just my experience!!! Pretty sure your GPX is a GPX :thumbup: should have a big valve head v2 head or similar(whatever the 125 version is) and high comp piston from the factory....what are the GPX motors rated at like 11hp or is it 11kw?
 
Reading through that planet minis thread it looks like that was the first gen GPX 125....I recons yours is the second or 3rd gen gottagetacheaperhobby, that head is certainly a 54x54 big valve. I think the ducar may have had a big valve head in it too, damn I really want to get a high comp piston now as it seems thats pretty much all I have to do plus lift the cam a bit....and basically it should have gpx power with lifan internals.....thats probably not so good!!
 
thats gonna hurt your bottom end for sure lol but hey it will be fun...... until it snaps the crank or disintegrates the gearbox lol

mine has 28mm inlet and 23mm exhaust valve, 54 by 54.5mm bore and stroke, but most importantly a start in any gear bottom end ;) with a zonger/daytona style oil filter
 
gottagetacheaperhobby said:
thats gonna hurt your bottom end for sure lol but hey it will be fun...... until it snaps the crank or disintegrates the gearbox lol

mine has 28mm inlet and 23mm exhaust valve, 54 by 54.5mm bore and stroke, but most importantly a start in any gear bottom end ;) with a zonger/daytona style oil filter
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yeah all good then you have a real GPX :D kinda surprised they work off the 54x54, will have to look into that one a bit I think Craig probably knows why....

Well maybe I'll forgo the piston and just do the new rotor kit, and port that head to the limit, new ignition coil, new CDI, etc....see how all that goes and if nothing gives up like for a while I might go the piston if I'm still looking for more grunt!
 
i think a square engine revs better, dont quote me on it tho just something i seem to remember hearing......
rotor kit is free so thats a massive bonus, and with the splitfire lead and coil being both cheap and usable on your next engine you would be silly not to i guess. you wont need a new cdi, there arent any upgrades for those cdi's, and it will allow high rpm anyway its the same cdi on my gpx :)

if it gets to the point that you still want more, but with the light weight of the 125, then it will be time to save your pennies and just buy a gpx.....
 
shorter rods are better for higher rpms

the 'square' engines have a good balance between power and torque, eg 54x54 lifan 125's, 62x62 Daytona 190's
 
my67xr said:
shorter rods are better for higher rpms

the 'square' engines have a good balance between power and torque, eg 54x54 lifan 125's, 62x62 Daytona 190's
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Yep this is a good learning thread for me!! I knew you'd know :thumbup:

Makes sense. So its about balance? I guess physics wise there is more inertia on a longer rod making it more prone to all sorts of things is that about right?

Yeah might not go to silly with it then. Just new coil, lead and swap the lifan 150 stuff that can go over and put the remaining good parts of the 150 on ebay...someone will be looking for lifan 150 parts!

or can we convert the 125 I have to 54x54 cheaply....is that what you were saying with the 54mm bore you have!?
 
your crank has a 57mm stroke, so not really.

putting a 54mm bore onto yours will make it a 127cc, up from a 119cc/120cc
the 138cc engines that came out for a while were actually 127cc
 
Yep thats what I kinda figured. Hmmm ill have a chat next time I come down and sort out what is and isn't feasible!!

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so longer crank, more torque less revs, shorter crank more revs less torque?

even with the 54mm bore you would still get a torque increase out of it, and make it worth more money when you sell it. might be worth looking at one of the oil cooler's that runs of the head for some extra security to :)
 
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