Pocketbike Tech Page

Seeing the total lack of instructions regarding carb setup and other minor tips on the internet, I decided it was time for this page...

New Tech:


Click here for:One-piece rim tire install New!

Click here for:DM 50cc conversion New!

Click here for:17.5mm carb guide

Click here for:18mm carb guide New!

Click here for:Reed box adventures New!

Click here for:Polini 911 Tech Tips

Click here for:The Muffler Contraption


Kevlar Clutches  (this is something I found on the minimotoclub forum):

Bizeta shoes (lightweight) 

Weights None 
Springs 2.0mm 
Flats 39 

Weights Standard 
Springs 2.3mm 
Flats 26 

Weights Large 
Springs 2.5mm 
Flats 16 

Polini shoes 

Weights None 
Springs 2.3mm 
Flats 27 

Weights Standard 
Springs 2.5mm 
Flats 22 

Weights Large 
Springs 2.5mm 
Flats 18 

Remember these are just starting points and will need to be varied according to where the power 'comes in' on
your particular engine, normally between 8,000 and 9,000 revs. There are many permutations of springs, weights
and tensions. Borrow a rev counter if you don't have one. 
Large weights are made by grinding down the face of 8mm bolts to appx. 2mm. Cut off the bolt thread so that it
protrudes out of the back of the shoe (crank side) by a few mm. 

When adjusting the spring tension it is important to start with both springs just 'nipping'. To do this start with
the springs loose and gradually tighten the nut until the spring is barely twistable using your fingers. If you can't
do this, you can use a thin feeler gauge to 'nip' on between the shoe and back plate stop. You must then
concentrate when counting the flats on the adjusting nut, to make sure the tension is even on both springs. 

Some people are lucky and their clutch requires no bedding in. We recommend a new clutch drum as old drums
inevitably have wear grooves in them, which prevent the Kevlar shoes bedding in properly. The new drum will
last indefinitely as the Kevlar only polishes the surface (anyone who has had an old drum shatter will realize it's
a good investment anyway, at only 18.) You don't have to be gentle bedding in these clutches. 

Before it's 'bedded in' this material sometimes gives a 2 stage effect where the clutch comes in, then slips, then
comes in again. This is only temporary and wears off over the first 10 or 20 laps. Then it's gone for good. 

The performance of both Polini and Bizeta based shoes is identical; there is no 
reason to use Bizeta. I use Polini. 

To date we have one competitor whose Kevlar clutch has lasted 11 months at appx. 4hrs running per week. In
that time it has only needed to be adjusted 4 times! Think of the time you have wasted fitting and adjusting
ordinary shoes. 

Some doubters suggest that there is not enough 'Bite' out of the corners with Kevlar clutches, this means their
setup is wrong.

DM tips:

Do yourself a favor and install a steering damper (the Polini damper fits-  Amy at microbikes.com sells a complete kit with necessary hardware).  The bike will handle much more stable, and you'll thank me later.  


Polini brake levers do fit the DM bikes.  They pull more cable, so you'll have a stuffer feel, but they will stay in adjustment longer, as you have more leeway as to how loose the cable gets before you lose braking.


Mossbarger reed spacer-  Anyone who has tried this product says it's a free lunch-  more low end and midrange power, with no loss of top end.

Initial results seem encouraging, but we'll see when I get out to the track.  The bike's running rich when cool, so I'm hoping it's spot on when hot.


I made a custom mount for the tachometer as well.  It fits into the spare mounting hole on the front fairing bracket:

Notice the unit sits closer to the front in the second picture?  That's because I shortened the mount.  The longer mount vibrated too much.  I used a simple garage door mounting strap wrapped in duct tape- it's a bit soft, but it's a breeze to work with.


I have a few thoughts for custom items in the works- more to come later.

Other minor tips:

Solder the ends of the brake lines if they aren't done already with a cheap soldering iron and any kind of solder (be sure to flux the wire first).  This keeps the ends from fraying.

Grips can be helped on with a bit of water. Make sure they are fully set before riding- I have some nice bicycle 'wet grip crash' stories to share sometime.  Hairspray works too.


Chain Lube:

WD-40 sucks.  Don't use it- it dries out in 3 laps.  PJ-1 sucks-  it's a dirt and crap magnet.  I'm using pro-gold chain lube- it seems to work fairly well.  The odd thing is, the best chain lube I tried (though it does fling)  is simple 80W gear oil.



I hope you enjoyed my tips page!

Be sure to visit the TECH FAQ from Pocketbike.com for other useful information.


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