Stroked, Bored, 171cc Monster Mini.

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Scott

Scott

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Hey Guys, Some of you Know me Some of you Don't. I was one of the Founding Members of MiniRiders. I Helped the Old Admin (David, Also owner of PBR Forum) Build and Design this Forum. I've Been away for a Long time and Have Decided to come Back and Stay Back, There will be alot of Tidying up Happening and hopefully some Changes and new stuff Coming Along.

So Hope you will all welcome me back ;).

Ok Now down To Business.

This Build will be complete in about 1-2 Months Time. First Set of Parts Is getting ordered this Thursday and should arrive 7-10 Days Later. Second Shipment will be ordered the following Thursday and should arrive another 7-10 Days Later. Then Let the Building Begin.

Currently I Have a No Name, Chinese Import, that I Imported my self from china, The bike along with 18 others were made in the Bosuer (BSE) Factory so the quality was pretty good for a chinese bike in the first place. The bike is now about two years old an has been Sitting around collecting dust. I've done about 3 Oil changes and thats about it. I've been into Mini bikes for a few years now, starting out being one of the first importers and sellers of pocketbike and mini bike performance parts from china, that didn't last long before bigger companies realised the money to be made. I've decided its time to bite the Bullet and Totally rebuild my Mini and Hopefully respark my interest in the Mini Bike Scene.

The First order is all the Misc part's im getting strait from the chinese manufacturer, These Parts are coming from the Bloke that supplies PBE and many other Big Brands. He is a great middle man and really knows his stuff, His name is Walker.

Order 1(Misc Parts):

Alloy Swingarm
DNM Rear Shock
Stem Nut
Joker Style Throttle
Alloy Oil Cooler Kit
Inner Rotor Kit
Chain roller
Chromo Footpeg Bracket
CNC Gear Shifter
CNC Kick Starter
CNC Break Lever
Alloy Footpegs
Hydraulic Clutch Kit
Fuel Tank + petcock
Hi Spark Coil
Hi RPM CDI
5 Plate Clutch Kit
Throttle Cable
Alloy Front Break Kit
Alloy Rear Break Kit
Alloy Axles
Alloy Chain Guide.


Order 2 Is My engine Order, these Parts are getting custom made in an overseas Machine shop (Not Chinese, Wouldnt Trust them with this work haha).

Order 2(Engine Parts):

28/24 Custom Valve Size Lifan Head
Custom Hi Lift Camshaft
61.5mm Stroker Crankshaft
60mm Hi Comp big bore Pistons
28mm keihin Carb

I Am Going to Custom make the Exhaust Pipe and it will Be 32-34mm.

Happy with anything over 18HP. But could see anywhere from 18-22HP.

Keep Checking Back for updates, I will add pictures Soon.
 
22hp maybe is insane, goodluck with it, sounds sweet!!

as for the forum changes your planning, good on ya, it needs a revamp IMO, its getting pretty stale lately i beleive, it always just seems to be reading the same old same old every week, we need more things to keep people coming back IMO,

anyway welcomeback dude:)
 
damn man, more impressive them my build. i've got the same size valves, helps it breathe alot better!!

any idea on the cam specs for the "hi lift camshaft"?

for the stroker crankshaft, are you going offset pin or done the proper way?

with the 60mm piston, will there be any meat left on the cases? guys in america have done this and they say they can't tighten one of the bolts, only hand tight and loctite because they'll crack..

interesting, if i can help you with anything let me know cheers
 
hey man =)
yeh looks like your putting the hard yards in and going to get it out =D
id like to know how the hydraulic clutch goes.. on a 50 that is ;) my clutch is nice and soft and easy to shift so the hydraulic one would have to be a big improvement for me to get one =)

just an idea for your pipe is =D make it and cut your baffle in half XD or only make half and pack the shit out of it with insulation =) it sounds sweeeeeet and looks sik ahah just and idea

good luck man =)
 
Should that build be for street??...because on dirt you won´t be happy!!
 
Le|Garage: No Specs yet and probably no chance of getting them, this kits getting built for me and I don't think there too keen on sharing info..

As for the Crank, Using a 3mm shorter custom made rod.

Lifan 120 cylinders have been bored to 62mm previously. Ive seen a few guys in the US with 61-62mm Bores with no worries. But An aftermarket Cylinder will be supplied pre-bored. I think it may be an Aluminium Cylinder also, yet to confirm.

Themountain: The Bike will see Both street and Dirt, I wanna strap her on the Dyno and get some sheets with Streeties on, and Wouldnt mind taking her to the local go-kart track :). Dirt will be Fun too... Just stay in 2 or 3rd.

I'm also getting a 5 Plate Clutch for the Lifan Monster and The Lifan Shift Fix Star from SDG In the USA which will stop the False Neutral Problem.

My only problem is.. Will the Gearbox hold up?
 
good luck keeping the gearbox together, IF you get over 18hp.....
 
Scott said:
Le|Garage: No Specs yet and probably no chance of getting them, this kits getting built for me and I don't think there too keen on sharing info..

As for the Crank, Using a 3mm shorter custom made rod.

Lifan 120 cylinders have been bored to 62mm previously. Ive seen a few guys in the US with 61-62mm Bores with no worries. But An aftermarket Cylinder will be supplied pre-bored. I think it may be an Aluminium Cylinder also, yet to confirm.

Themountain: The Bike will see Both street and Dirt, I wanna strap her on the Dyno and get some sheets with Streeties on, and Wouldnt mind taking her to the local go-kart track :). Dirt will be Fun too... Just stay in 2 or 3rd.

I'm also getting a 5 Plate Clutch for the Lifan Monster and The Lifan Shift Fix Star from SDG In the USA which will stop the False Neutral Problem.

My only problem is.. Will the Gearbox hold up?
Click to expand...

Believe me ...thats the smallest issue you will have....your bike will be uncontrolable on dirt:p

and BTW the gearbox will go before the crankcases.....or contrary...hahahahaha
 
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hey scott, having a 3mm shorter rod won't change the stroke at all, i think you mean 3mm offset pin? that's what i have in my jialing crank, need to bore out the cases to clear the crank. If youre doing it the proper way (without offset pin) could you let me know where you got it done?

with the cylinder for the 60mm piston, i've seen that done before also in the U.S, guys just bore out the old sleeve and press in a new one, it's easy, but the problem is boring the cases to fit the sleeve, i was just unsure how much you have to bore it and if it'll be stable
 
Sorry Yeah dude, Miss-read you, Using the 3mm Offset Pin I think, Its all the Supplied in the kit I Dont really know specs until I Get the Kit. The Crankcase will need to be grinded a small bit (So I've been told).
 
I was thinking of this problem recently about the Hi comp and Trying to Kick Start, I will be running a thicker gasket so it will reduce comp a bit so not running to hi. Also was thinking about installing a revamped electric start, or just Starting her at TDC.
 
As stock 120 and up motors have auto decompressors to minimise the problems but flip heads raise the compression and fit cams with them removed ....... then wonder what went wrong ..... Duuuuurrrhhhhh !!!!!!!
 
Incidentally I've also looked at what they do with the cases with great amusement . Why the hell would any sane machinist with a decent IQ bore them out to the point where the stud thread is nearly exposed ??????? It's beyond me and defies logic ....... LOL ..... they are lazy and just want to take the easy way out by using a borer instead of a mill .....

What a REAL engineer would do is mill the sleeve bore in the cases leaving 4 bumps to keep a sane amount of thread around the base of the studs ... then carefully die grind the bottoms of the cylinder sleeve to clear the protruding stud bosses . It doesn't matter if the sleeve is thin in a few points at the base .

Also I've seen how people fit grooved cylinder sleeves to clear the studs with the bore paper thin all the way down the cylinder ........ that's a guaranteed recipe for cylinder sleeve distortion and blowby . Alloy cylinders bored out big are weak and prone to cylinder wall flex and "ballooning" . The cylinder goes egg shaped from piston thrust and tries to squeeze onto the sides of the piston ... at worst ripping the studs out or at least creating power loss at high rpm ....... and remember ........ pistons only have a few thousandths of an inch clearance so there doesn't need to be too much distortion for things to go bad ......

I've seen all the pics of shattered cases and as for leaving one stud loose ........ Bwaaaaahahahahahahahaha ......how friggin' bodgy and backyard is that ........ sheer lunacy ........ LOL ........

It would be far , far better to keep the sleeve an equal thickness all the way around and grind a flat on the insides of the studs to clear it . Equi thickness objects expand evenly when heated ....... You could even get special hi strength moly studs made up ............. :)
 
themountain said:
Believe me ...thats the smallest issue you will have....your bike will be uncontrolable on dirt:p

and BTW the gearbox will go before the crankcases.....or contrary...hahahahaha
Click to expand...

According to BBR ..... going bigger than 160 cc turns them into trail bike motors meaning ........ they'd actually go slower ........ and from my experience with modded XR 75 K1/3 engines that rings true ....... an 80 cc engine is a super reliable high revving screamer and a Powroll 96 cc kit is a lower revving torquer ...... I prefer the nippy revver ........ the 96 cc kit was lazier ........ didn't last too long and didn't accelerate any quicker .......

From the Daytona DOHC test link :

When asked about limiting the displacement to 119cc against such beefed-up competition, the brothers cited the high-revving capabilities as the primary reason. According to Duane, going larger requires increasing the stroke which in turn generates increased torque and a lower rev limit. Even the 160 we tested for comparison had a significant difference in power deliver and rev range, and that's about as big as the BBR guys want to go. "It seems like anything bigger than 160cc just turns into a trail bike motor," Duane says.

2006 Title-Winning BBR 119 Test - MotorcycleUSA.com
 
Scott said:
They are the small pins i mentioned, which you can see in the head through the intake and exhaust ports.
Click to expand...

All we can see are the valve guides and stems inside the ports !!!!!!

All that you could be talking about is fitting re located dowel pins to replace the dowel sleeves over the studs which would HAVE to be removed . They align the head with the top of the cylinder and stop it from moving around and causing blown gaskets and oil leaks . They have nothing to do with bore or cylinder distortion ........... meaning pressure leaks past the rings and increased piston to bore friction ........

I've just checked a cylinder with verniers and and the inside wall of a 60 mm bore would be right near the edge of one of the stud holes .... the diagonal measurement between the stud holes is 64 mm and a 54 mm bore has only 4 mm between the inside bore wall and the top right hand stud hole . 4 mm - 3 mm (half of the 6 mm over bore to 60 ) = 1 mm . So you'd probably get away with that even though it's extremely marginal . But you wouldn't want to go any thinner than that . What I'm saying is that it's stupidity to thin the sleeve up top along its length with part round furrows on the outside so that it clears the studs . IF the sleeves aren't an equal and uniform thickness all the way around in the piston thrust and combustion pressure area - then I say your ring sealing won't last too long ........... mark my words ..... :p

Check this pic of a 57 mm bored cylinder that has NO sleeve ...... 60 mm would be a further 1.5 mm closer out towards the stud holes all the way around ......... now think about where the thickness of a sleeve is going to fit ..... then have a good hard think about if you could go to 61-62 mm ..... that means the edge of a 1 mm thick sleeve would be just about be touching the side of the stud !!!!!!! Then think about the stud threads in the cases ......

http://home.exetel.com.au/miumiuxuxu1/DB/145jialing.jpg
 
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The engine is a Lifan 120. Cases need to be bored 62mm to fit the sleeve. There is enough room. people have run 62mm bore which needs about a 64mm grind to fit the sleeve no problems..
 
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