How far can a 120 lifan go safley?

[Dirtrider]

What size can a 120 lifan go to safley?

I've got a spare barrel the origanil one off my lifan with a 52.4mm piston. I want to know what size i can take this out to so it will still be reliable, and with out having to sleve the barrel. How much meat will have to be left on the skirts? Would it be better to buy a 140 big bore kit to suit the 120, or bore out the old barrel and get a hc piston to suit. Looking at some pistons from akunar and a 57 hc piston caught my eye and that would take the motor to 141cc. Or another piston that was 58mm witch would take the motor to 146, but i'm not to sure if i can go that big.
Any input will be a big help thanks.

 

[themountain]

2-3mm...otherwise you don´t have enough heattransfer through the barrel!!

 

[Dirtrider]

So it would be better to get the 140 big bore kit to suit the 120 and go from there.

 

[themountain]

yop!...thats the one---->TboltUSA

 

[Dirtrider]

Cheers for that, i was looking at one from akurna probley be the same thing i just wanted to get some larger valves in the order aswell.

 

[Cactus Jack]

yop!...thats the one---->TboltUSA

Yeah the piston looks to be already sorted out in that kit (valve reliefs deeper to clear with race cams and the dome is shaped to suit the Lifan BVH and give proper burn / flame travel)

The Akunar pistons give me the impression that they'd direct a lot the combustion force and heat down the sides and onto the top ring ...... in pro stock drag engines they drill piston port holes to direct pressure to behind the top ring for better ring seal ....... but they ALSO run low tension rings to cut friction and drag on the non power strokes .......

That cylinder looks like it might be a sleeveless ceramic or nikasil job ????? Does anyone know if they hold up well in an air cooled engine ???????? Since they are mainly used in water cooled engines .........

Incidentally you can buy the sleeveless 143 ceramic big bore kits for Lifan 120/125/127 "138's" for around $179 plus postage in OZ .........

 

[edzy]

i can get you this...
153cc bigbore kit with hc piston designed for lifan 125.

for around 200-250
pm me for details

 

[Cactus Jack]

i can get you this...153cc bigbore kit with hc piston designed for lifan 125 for around 200-250 pm me for details

Do you know what the combined piston and pin weight is in those kits ? It's important that they weigh the same as stock (or a bit less) to maintain the balance factor ...... also what is the bore size and do they require case boring to fit ?

Looks like a really good deal tho' .........

 

[themountain]

UUUPS...beside the kit...if you got the old ironbarrel, I found this on dratv...experimental but worth a try
LF120 (146CC's_????) CAST_IRON_CYLINDER FOR_120CC_ENGINES WITH_78MM TALL_CYLINDERS

 

[Scott]

http://www.miniriders.com.au/forum/tech-talk/13442-stroked-bored-171cc-monster-mini.html

Was my plan. Still is when i get some Cash flow.

 

[Cactus Jack]

Yes , I saw that yonks ago ....... dratv won't ship to OZ ........ Some people claim iron cylinders will overheat but that's total BS ........ Diesel engines run 25 to 1 compression using iron cylinders revving for hours on end slugging heavy loads in trucks , in supercharged earth moving equipment , buses , and trains etc reliably without over heating and also ... air cooled aircraft engines described as being "hell bent on destroying themselves and attempting incinerate their exhaust valves" mainly run iron or steel (moly) cylinders for safety and reliability reasons .....

Iron cylinders being thicker are stronger and resist ballooning and cylinder wall distortion due to high compression and piston thrust at high loads ...... iron also holds its' shape when hot .........

EVERYONE knows that alloy cylinder heads in cars just purely and simply can't hack being over heated ....... they warp , buckle and go soft after losing their factory heat treatment (stress relieving) ....... Once overheated ...... they just keep on bending , stretching head bolts and blowing gaskets etc ......... as a matter of fact , they're more likely to be the cause of cylinder stud threads getting pulled out of alloy engine cases since a heated alloy cylinder would also elongate stacks more than an iron one ....... Honda also chooses to use iron cylinders on their Horizontal engines for very good sound engineering reasons .........

So the over heating argument is LAME ......... if you tune ANY engine to run at the right combustion temperature and clearance the piston to bore right ....... you'll have no problems .........

 

[Mack]

Go for a 57mm kit. Most dealers are sourcing there kits from akunar.
The original bore you have will need to have the borer run through many times and they will charge for every pass.

hey i'm gonna bump that thread to get you going scott!

 

[Dirtrider]

Cheers for the info guys.Would that be a 59mm piston in that kit edzy, would like to get abit more info on it so i can compare it to the 140 kits.

 

[themountain]

Cheers for the info guys.Would that be a 59mm piston in that kit edzy, would like to get abit more info on it so i can compare it to the 140 kits.

Don´t forget for that Kit you have to bore the cases too!!

 

[Dirtrider]

How much stuffing around would there be and you would just use a milling machine to bore the case out?

 

[themountain]

you have to get it out at least up to 62mm...speak with the seller if you are really interested, but its easier(and cheaper)to go the 57mmkit route

 

[Dirtrider]

Would the 140 have a heap more go over the 127 seeming it is only 13/14cc bigger?
Would 28/24 valves help the 140 kit out?

 

[Mack]

If you want to go over 57mm you can have the cases milled or bored. I have them bored to 61mm and only bore to the depth of the piston skirt at BDC. The sleeve before it is inserted into the cylinder is turned down on the lathe around the skirt to 61mm and shortened also to the piston skirt length. This means I can get to 59mm bore with minimal amount taken from around the top half of the stud drillings. The studs tighten into the bottoms of the holes and are fixed in stock thickness of aluminium. Perfectly acceptable. The cylinder skirt has a 1mm thickness, acceptable also and the cylinder liner in the working portion of the bore is maximised also by staying at 59mm. The top of the liner Akunar sells has a greater diametre flange to stop the sleeve pulling in the jacket and it is this that guys are drilling out to allow the studs through. So is not the length of the sleeve. I centre my sleeves a bit so that only one stud needs a small dish ground in to let the stud past. This wider flange should be left in place as much as possible for good head sealing as there is not that much room if you want to run high compression and keep it sealed good. I would not recommend going big with these unless you are fairly confident with all this kind of problem solving, or have a good engineer doing it for you. I intend doing a 185 soon for my next project bike but will be looking to use a method the jetski guys use to go big, by fixing a plate to the cases in the original stud holes and also drilling two extra fixings. Then you fix new studs at a wider stance in your plate and run a much bigger bore safely. You can use this method to run an entirely different and bigger barrel and head off something else.

 

[themountain]

Would the 140 have a heap more go over the 127 seeming it is only 13/14cc bigger?
Would 28/24 valves help the 140 kit out?

yes ...bigtime, but porting makes the difference

I would say even only the head worked will help you aaaaalot

 

[Cactus Jack]

Mack has got it all sorted out spot on (I'm impressed ) People considering a monster engine build should thoroughly read what he's saying and have a really good think about the messages he's trying to get across ~ we're lucky to have him putting his valuable info on here .......... I wouldn't do it any other way ....... his methods are sound and what any decent and genuine engineer would use ...... and believe me .... I've seen and read of a lot of bodgy engine building methods used to build big bore pit bike engines (as well as car engines) , some of which are downright sheer stupidity ........

Increasing power at the sacrifice of safety and reliability (or at least not doing all you can to attempt to maintain reasonable strength and reliability) is NUTS .......