2013 Suzuki AX100 Modifications

Here are the specs on this Suzuki and what modifications are needed to perform better:
* 100cc two stroke engine (50mm bore, 51mm stroke, 100mm connecting rod)
* 20mm Mikuni carburetor (92.5 main, 20 pilot, 4D08 needle, 2mm slide cutaway)
* case reed induction (I replaced the steel reeds with a fiberglass one I made)
* spark plug NGK B8ES. (I put in a NGK BKR8E1X iridium plug which made a noticeable improvement)
* 120 psi cranking cylinder pressure
* steel cylinder liner
* 4 speed (shift down for a higher gear which was really hard for me to get used to since it is opposite of most bikes)
* 9400 RPM max
* 115 KPH max
* drum brakes front and rear
* 2.75x18" tires (I eventually put on a 90/90-18 Dunlop "Mystic" tire on the rear which is about a 3.25")
* comfy seat
* expansion chamber is header/diffuser/silencer instead of header/diffuser/baffle/silencer but the silencer gets restricted in flow with time and limits top speed more and more
* power delivery is smooth and somewhat linear like a 4 stroke
* power is sufficient for two 150 lb people on board
* port durations: exhaust 169°, transfers 124°, boosts 124°
* piston is dual ringed with the locators on the exhaust side (strangely enough)
* automatic oil injection (which I don't use because its oil delivery rate is based mostly on throttle position and not RPM. Premixing the oil provides more consistent protection.)
* very little engine vibration
* good gas mileage (around 30km per litro)
* shifting was terrible till I replaced the oil. still sometimes it pops out of 3rd gear into a false neutral and sometimes won't shift to 3rd. (It got much better after 6000km.)
* instruments: speedometer, low engine oil light, neutral light, turn signals lights
* handlebar choke lever
* front fork angle: 27 degrees (which is a bit too steep to handle really well)
* front fork travel: 3.5 inches
* rear wheel travel: 2.75 inches. Very stiff springs. Letting the tire almost touch the rear fender I measured that any replacement shock should have at least a 24.5cm (9.75") compressed length from eye to eye. You can figure out that length by subtracting the exposed shaft length from the extended shock length.

 I figured out the max RPM by counting the crank revolutions per wheel rotation in each gear. (1st gear: 27, 2nd: 17, 3rd: 13, 4th: 9). Here are the speeds at 9400 RPM: 1st: 39kph, 2nd: 61kph, 3rd: 80kph, 4th: 116kph

With my new timing light I found out the idle ignition timing is around 18 degrees BTDC and advances to 23 with more revs and then finally starts to retard around 6000 RPM to around 5 degrees BTDC. It needs a CDI with a normal progressively changing timing with peak advance around 3500 RPM.

Engine head temperature at the spark plug with everything stock other than me replacing the head gasket with high temperature silicone is 315 degrees Farenheit going 80kph in 4th gear on a summer day.

I measured the eye-to-eye shock length at 12.25" with 2.75" wheel clearance.

If you modify your engine then I would like to know what you did and what the results were.

my email: health@dragonfly75.com

My timing light died and so while waiting for another one I installed a high voltage ignition coil (from a Kawasaki KX) and my replacement KDX CDI. The idle jumped up from 1800 RPM to 2010 just from the ignition system change, probably due to a stronger spark. Riding it the mid range power was better after I gave the new CDI more peak timing advance. Vibration became slightly more above 6000 RPM. Since mid range RPM timing with this CDI is now more retarded I think the dynamic compression in that range is now less and so to bring it back to where it was (for less vibration like before) had 1mm lathed off the head which gave around 150psi. That was perfect and now it runs even smoother than before! I doubt that many people know that dynamic compression plays an important part in engine balancing. Engine temperature increased just a small amount from the compression increase. It is just as easy to crank over also.

Let me know if you want to buy an adjustable CDI from me for $75. The perfect fitting high voltage coils are any motocross coil from EBay with 55mm bolt hole spacing (look for Honda CR coils which are the best coils) or the $50 HT55 from Electrex in UK. I can sell you a moderately good high voltage coil for $25, the same type I'm using now on my AX100 along with this CDI. Shipping via certified mail is $25.

$20 piston/rings std size (A100 piston will also work if you cut some off the bottom of the skirt)
$15 gasket set
6v 25/25W headlamp (with BA20d base)
instrument panel lamp (T3-1/4 26MM 10MM 7V 3W)
6v 10/3W taillight lamp (Stanley A4854H)
turn signal bulb (6.5v 10W)
$18 13 tooth front sprocket  or $22 14 tooth (stock) sprocket
$9 front brake shoes
BR8EIX Iridium spark plug (for the best plug for this engine)
I have bought the piston and gaskets. I got 2 pistons and one of them had its piston locator pin receed which allowed the top ring to wander around on the piston and I was lucky that its ring end didn't snag a port. The head gasket from this set is thicker and lowered my 155psi to 135 which was OK because I put it on before making my exhaust pipe a true expansion chamber which increases the dynamic compression from 6000-9200 RPM. This gasket is metal/fiber and looks like it should seal better than the stock aluminum gasket. I bought the front brake pads to see if they improve the braking power and they did.

Also CMS in Great Britain has a full listing of AX100 parts.

MZMiami in EBay also has AX100 parts such as complete cylinder/piston kit for $40.

Kenton makes a copy of the AX100 and is called the NX100. I'm not sure what years it was made but here parts for Kenton are readily available so I will ask the parts store.

My final evaluation: If you are looking for a 2 stroke street bike then look to see if a new or used Yamaha RX100 (or 115 or 135) is available. It has a full reed valve, better forks, and 5 speeds (which means a normal expansion chamber can be used which will give better power than my AX100 design because of a normal RPM spread between gears). The AX100 has a terrible gearbox, only 4 gears, terrible suspension, and low power due to a restrictive reed valve. And its instrument panel makes a terrible clunking noise every time you hit a good sized bump.

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