Performance upgrades guidelines: Stage I-III

Mini Dirt Bikes & Pit Bikes Forum

Help Support Mini Dirt Bikes & Pit Bikes Forum:

thump*140

Mini Riders Legend
Joined
Aug 20, 2008
Messages
2,840
Reaction score
63
Location
adelaide
I’ve put this one together, hopefully to help those riders new to minis, or new to bikes on the whole, with the idea that all the questions can be answered in one section, in one thread.

Basic necessary upgrades:
Generally price will normally denote quality… and generally chinas aren’t renowned for it. Having said that, every jap mxer I’ve had from new, has had some pretty crap standard items on them as well. Chains, suspension seals, levers, bars, sprockets and grips have all been immediate replacement items. There are several items on your standard china which can also be binned from new…

Handlebars- usually crappy steel ones. Bite the bullet, get some pro-tapers. Genuine ones, or copies.. I’ve used both, still yet to bend either…
http://www.miniriders.com.au/mini-tutorials/12201-how-change-your-handlebars.html
Levers – Stock ones snap if you lean on them. Buy some ASV-copy bending levers. Look around on ebay, there are plenty of cheap ones available. If you cant stretch to ASV levers, drill a 5mm hole through the lever, roughly where you little finger goes around the lever, and using a file, grind/file a bit of a “V” above and below the hole you have just drilled. What this does is create a weak point in the lever, so if you fall off, it will snap off there, instead of snapping at the perch like they normally do.
Chain – Turf the standard one. The chain will be crap, and stretch in no time. Be a man, (or an empowered woman…) buy a D.I.D. chain and be done with it. Minis don’t shake the earth powerwise, and a quality chain will probably outlast the bike.
Tyres: Standard ones are often crap. Replace them with Kenda Millville’s or Carlsbad’s. They seem to be the ones to go for, and offer good grip and wear qualities. While your changing tyres, add a RIM LOCK and Heavy Duty tubes. The rim lock will stop the tyre spinning on the rim, and tearing the valve out. If i had a dollar for every mini i've seen going home early with a flat tyre and no rim lock... ha ha!
Spark plug- Stock is crap. Go buy an NGK plug and be done with it.
Fuel Filter – the plastic tanks on the minis aren’t renowned for being spotless.. buy a cheap in-line fuel filter, cut your fuel line half way between the fuel tap and the carby, and put the filter there. Pay attention to any arrows marked on the filter, as this will denote the direction of fuel flow.

That pretty much covers basic items that will require upgrading within the first couple of rides, or even BEFORE you go for your first squirt. Tie these upgrades in with the initial set-up, and you should have a happier day out on the track..

Performance upgrades Stage 1
These are more or less the first parts to upgrade if you want to go faster. They can all be found on either Ebay, or your local mini bike shop. You may actually have to get of you’re a$$es to find that shop though..
The below items are the cheapest way of making SMALL power gains, and can be done for under $70 if you do your searching on ebay..

Air Filter – Measure the external throat diameter of you carby, and find yourself a “UNIFILTER”. Even nanna could figure out how to attach one. Buy, attach… simple.
Quick turn throttle – These can be purchased in either ¼ turn or 1/8 turn versions. THESE WILL NOT MAKE YOUR MOTOR MORE POWERFUL… They will however allow your carby to go from closed to wide open much quicker…
“Racing” CDI – These effect the timing curve of your ignition, and will generally allow a stronger spark, and a higher rev-ceiling. In 99% of cases, they are a straight plug and play item. The gains to be had aren’t massive, but they do help once you start doing further mods. They’ll also prevent the “it was fine last time I rode it, now it wont start” questions that are CDI caused or related.
Gearing- Changing the gearing on your bike by going to a smaller countershaft sprocket is a cheap way to make your bike accelerate faster. It will be at the cost of top speed, and wont give you any more power, but it will be quicker from whoa to go. Going from a 17tooth front sprocket to a 15 is the equivalent of dropping between 6 and 9 teeth on the back sprocket. And lets be honest… when did you last wind your mini up to redline in top gear on the local track..?
I've found the easiest and quickest way to alter your gearing, is to buy a 37 tooth rear and leave it there. Then buy a 12, 14 and 17 tooth countershaft (front) sprocket. They take a couple of minutes to change, and give you a hell of a lot flexibility with your gearing.
Basically, the smaller the front sprocket, the better your acceleration will be, but at the expense of top speed.
The bigger the front sprocket, the better your top speed will be, but at the expense of acceleration.

Performance upgrades Stage 2
The following upgrades will net you some noticeable performance gains, and once again, search carefully on ebay, you’ll get out of it for under $250. Incorporate the below items with Stage 1 upgrades, and the gains will be rewarding.

“Performance” carbies – Most pittys come standard with “Genuine” Mikuni “30mm” carbies. These carbies are about as genuine as the acting skill portrayed by the hot girly in the transformers movies… You can start by replacing them with something like a Molkt or an OKO carby. There are also Mikuni copy carbies that are just as good as the Molkt or OKO offerings, but are generally 26mm in throat diameter, with round-bore throats, as opposed to the standard oval-bores in your “Genuine Mikuni”. Occasionally you will be lucky, particularly with the Molkts, and the jetting they come with is pretty close. The OKO’s on the other hand, usually require a bit more tinkering, but offer great performance when tuned properly.
http://www.miniriders.com.au/tech-talk/10183-mikuni-25mm-carbie-manual.html

As a guide, if you have a 110 or 125 motor, a carby with a 22mm throat diameter will work best. 140’s and above work best with a 24 or 26mm throat diameter. (only on extreme engines, and if you have the tuning skills and patience, would I suggest a genuine 28mm carby)
Exhausts- Mini bikes run four-strokes. Old-school design four strokes at that. Four strokes like to BREATHE.. A big bore exhaust, with a 33mm pipe diameter is a great place to start. The ones that step up from 33mm to 40mm are even better. Some of these, eg H-Bomb Carbon muffler pipes, have massive internal pipes in the muffler itself, breathe great, and offer a great, deep exhaust note, over the loud and crackly stock pipe. The big bore pipes are still loud, but the note isn’t as harsh. Shut your eyes, you’d swear someone was on a big-cc thumper somewhere. Where you source your pipe is up to you, and your conscience. Ha ha ha! Do Local business a favour, and buy locally.
IRK or ORK- Inner or Outer rotor kits – These basically are replacement flywheels and rotors/stators, and allow your motor to build revs a lot quicker. Initially it was the IRK’s that gained the popularity, and can be had from ebay for as little as $30 nowadays. The Outer rotor kits are rapidly gaining favour as they fit a larger range of engines, and offer much more than the IRK’s in regards to having switchable ignition curves, while still offering a marked improvement in performance. The ORK still offers a reasonable amount of flywheel weight, which means better traction, and more torque. These are better suited to a broader range of riding styles than the IRK’s, as they are less prone to stalling, idle better and offer better grip on slippery ground. The IRK’s are still a great, cheap upgrade, especially when used in conjunction with a lightened oil slinger, which also helps “revvability”… They are however, better suited to more skilled riders who can swing off the throttle and keep the motor screaming.. And are also great for supermotard, where bottom end power and response isn’t quite so vital. I wouldn’t use an IRK if you’re planning on ramp jumping your mini…
http://www.miniriders.com.au/mini-tutorials/13850-inner-rotor-oil-slinger-installation.html

Performance Upgrades Stage 3:
By now your motor should be a different animal to what it was in the beginning. “Stage 3” upgrades should turn it into quite the little monster, but are best carried out by a mechanic, or if you have the skills, go nuts. But then I guess if you had the skills and knowledge, you may not actually be reading this thread.. ha ha! A lot of the installations in this thread can be found in the “how-to tutorials” page… go have a looksee if it’s something you want to attempt yourself. Most can be done at home with the right tools

Camshaft – Again these can be sourced either on ebay or mini bike shops. A couple of brands supply different cams that offer different amounts of lift and duration. They are a great way to increase power right the way through the rev range. Most however, do not come with an anti-kickback mechanism, and can be harder to start once installed. In some cases, depending on the lift of the cam, aftermarket cam-springs should also be installed to ensure your valves aren’t hitting the piston.
http://www.miniriders.com.au/mini-t...10mm-14mm-sockets-n-ratchet-10mm-spanner.html
Porting – By cleaning up the passageways in the inlet manifold, carby throats, exhaust manifolds and the head itself, again more power can be gained. There are tutorials on the best way to do this in the “how-to” section that are very useful. There is no hard and fast rule, so grab the dremel, read the how-to’s and have fun
http://www.miniriders.com.au/tech-talk/6959-porting.html
 
Last edited:

thump*140

Mini Riders Legend
Joined
Aug 20, 2008
Messages
2,840
Reaction score
63
Location
adelaide
Big-Bore kit – These work by increasing the capacity of your engine. Some bike shops, and few places on ebay have been supplying these kits recently, and is a good way to get that Lifan 140 you have up to a 150 like your mates have, without the overall cost of a new engine. Do your research first, make sure you have the right kit for you motor, as some have different wrist-pin diameters etc. Installing a big-bore kit varies little from a normal tear-down. The only difference is, you are putting a bigger cylinder and piston in place of your old one.
http://www.miniriders.com.au/tech-talk/21075-how-tear-down-head-cylinder.html
  • Hi-Comp Pistons- These have a higher crown/dome, and sometimes recessed crowns for valve clearance. Essentially they increase the compression ratio, and squeeze the fuel tighter before it ignites. A very very basic description, but that's the simplest way to explain it. They're a good addition to make if going to a big bore kit.
  • Heavy Duty clutch springs - With all the above mods, your engine is going to exert more torque on the clutch. By replacing the springs, this will elminate any clutch slippage.


Additional mods and upgrades:
There are still things you can do to upgrade your bike, particularly with the rolling chassis. A lot of it comes down to personal taste, bling and shiny stuff that can actually make your bike better or more comfortable to ride.
Gripper seat
Suspension upgrades- Forks, shocks, swingarms etc can all be upgraded. Fastace, Marzocchi’s, GPX’s are all good brands of forks, offered in differing overall lengths between 635 and 735mm. Fastace and DNM seem to the pick of the bunch when it comes to affordable rear shock replacements. They all offer a fair degree of adjustment in both preload, compression and rebound damping.
Brakes – bigger rotors, better master cylinders, can all be fitted to give better braking power.
Hydraulic clutches – Again pretty easy to sourse. Offers a quicker clutch action/actuation and is lighter than the traditional cable set-up.
Alloy kick-starter – I’ve found this to make starting your bike a bit easier, as they move the pedal section away from the frame, and the leverage ratio is better than the stock unit, which means the motor turns over quicker for the same kick.
 
Last edited:

crim 87

Well-Known Member
Joined
Jun 22, 2009
Messages
141
Reaction score
0
some great stuff in here thanks will def being doing as few of these mods in the future
 

motorman

Admin "The Cougar"
Joined
Nov 13, 2008
Messages
6,213
Reaction score
49
Location
Victoria
This thread needs to be stickied on the front of the site!!

Would save 100's of threads of the same questions over and over again.

Top work mate.
 

roost666

Mini Riders Legend
Joined
May 13, 2008
Messages
3,005
Reaction score
20
Location
Tassie
yet another brilliant post good work mate....thread is stickied
 

thump*140

Mini Riders Legend
Joined
Aug 20, 2008
Messages
2,840
Reaction score
63
Location
adelaide
Thanks guys, makes it worthwhile. Must be a record for a sticky. ha ha! pretty much what i'd hoped would happen to it, as the questions seem to pop up every few days, the same questions get the same answers, and all the good answers get lost in the middle of it, and can be hard to find on the search button...
Got another one coming in the next couple of days, just waiting on shed time to actually take the pictures to coincide with the thread...
The idea i had, was a basic initial set-up from the day you get your bike... Seems we hear very often of a kid gets bike, rides it straight out of box, no maintenance leads to short life of bike, kid gets upset, blames ebay seller, then spams forum threads asking for help.. it's a pretty massive thread so far, and has plenty of pics, but like the one above, i thought i'd cover EVERYTHING in one hit, on one entry/thread... saves them going through pages and pages to find the bit they are after...
any thoughts or suggestions??
Oh and Roost666, cheers and buenos for making this a sticky... once i get a few responses to this post, i'll edit it off and leave it as is. :D
 

DvDRip

Mini Riders Legend
Joined
Jan 10, 2009
Messages
3,382
Reaction score
46
Location
Melbourne
great thread right here, now we can just link to when kids come on asking for more power (or ideally we won't see those threads anymore as they'll go straight here).
I think you might wanna add HD clutch springs to help deal with the extra power, and Hi-Comp Pistons (I don't know what they do? raise compression?)
 

thump*140

Mini Riders Legend
Joined
Aug 20, 2008
Messages
2,840
Reaction score
63
Location
adelaide
Good point DVDrip... i'm hoping a few of the more experienced guys will add their suggestions to this one, i can edit the original post, and like you said, it will all be in one place, in one thread... as opposed to thirtyeighteen different "how do i make my bike faster" threads...
so please, anyone reading this thread that has extra suggestions i've missed, add them or pm me, i'll add it to the original post. :D
 

wogtaz ryder

Well-Known Member
Joined
Aug 27, 2007
Messages
4,869
Reaction score
65
Location
brisvegas
Looks like you covered most of it! nice work!

Maybe add to the Tyres: Rim locks and HD tubes
 

dhz140cc

Well-Known Member
Joined
Dec 22, 2008
Messages
199
Reaction score
1
Location
sydney
yeah great thread, thanks for taking your time to write it. alot will benifit from this thread. good job:D
 

I_THUMP

Well-Known Member
Joined
Jul 22, 2007
Messages
3,227
Reaction score
27
Location
location, location
Excellent work mate, it is much appreciated that you took the time to put this all together. Its a good read for everyone and will help out a lot of people. Id rep you again but it wont let me so you will be made a miniriders VIP because you definitely are one.
 

DvDRip

Mini Riders Legend
Joined
Jan 10, 2009
Messages
3,382
Reaction score
46
Location
Melbourne
I think a simpler explanation of sprockets would be good, people who don't know how it works might not fully get what you said ?

smaller front = acceleration lose top speed
smaller rear = top speed lose acceleration
and vice versa
for the trail riders, having top speed orientated gearing makes 1st gear useable, helps for obstacles/hillclimbs
 

thump*140

Mini Riders Legend
Joined
Aug 20, 2008
Messages
2,840
Reaction score
63
Location
adelaide
I think a simpler explanation of sprockets would be good, people who don't know how it works might not fully get what you said ?

smaller front = acceleration lose top speed
smaller rear = top speed lose acceleration
and vice versa
for the trail riders, having top speed orientated gearing makes 1st gear useable, helps for obstacles/hillclimbs

edited, and done! :D
 

DvDRip

Mini Riders Legend
Joined
Jan 10, 2009
Messages
3,382
Reaction score
46
Location
Melbourne
anyone know a good online store for pitties??

DHZ on ebay is the best, there's also Just Ride, KDF and a few others

thump maybe you could add some info on where to source parts to the guide?
 

roost666

Mini Riders Legend
Joined
May 13, 2008
Messages
3,005
Reaction score
20
Location
Tassie
DHZ on ebay is the best, there's also Just Ride, KDF and a few others

thump maybe you could add some info on where to source parts to the guide?

there is already a stickied thread on mini bike shops
 

thump*140

Mini Riders Legend
Joined
Aug 20, 2008
Messages
2,840
Reaction score
63
Location
adelaide
there is already a stickied thread on mini bike shops

^^^^ that's why i left that one alone... plus ebay links tend to become out of date very rapidly...

plus i cant do everything for those that seek info... ha ha...
 

Latest posts

Top