V-Force Reed Valve pang Kawasaki KMX 125
ano pang v-force reed valve and makasya sa kmx125?
v-force, got no idea. got your pm. is that a bore out, 140-175?
replacing the reeds, i think, will not increase the topspeed but will give you the power you like anywhere in the power band. there is this dual stage valves ( i read in magazine) that offers broadband ,but i have not tried it. he.he. medyo mahal paglaruan.
the way i squeeze power from my kmx:
1. always de-carbonize the pipe
2. clean air-filter
3. right sparkplug gap
4. clean carb
5. let the engine gargle gas
if you live near taytay i can offer you a deal, i will de carb your pipe for 3 brown bottle..how's that
i wish i had my house close to you sir, pareho kse tau ng hilig, kmx saka ung brown bottles. hehe sarap. wag lang pagsabayin
I tried some aftermarket reed valves in a Honda CR500 once without any overwhelming evidence they made any difference at the drag strip. But I did try smoothing an extra OEM reed cage's ribs and picked up 1/10 of a second in back to back drag strip runs! The bike went 12.35@107mph
What kind of power do you want from a reed/reed cage mod? Drag race power? Trail riding power?
rgon bro, how do you de carb the pipe? do you have a shop? takot kasi akong pakialaman KMX ko pero minsan pag hatawan nawawalan sya ng power sa dulo ng rpm...
Originally Posted by greenback
ano set-up bike mo?
stock lang po, dunlop tyres and yrs tune pipe and arrestor, do u think po na makkatulong sakin ung reed valve???
Originally Posted by greenback
wika nga "depende" sa application.
originally posted by Roalndo Alunan.
qoute: What kind of power do you want from a reed/reed cage mod? Drag race power? Trail riding power?
if you're just curious with the feel (of the effect) of having a racing reed valves in your engine and money is not a prblem go for it
in playing around the track, i just stay in the powerband and would not mind
downshifting when cornering and would not mind either if the engine is growling. i just make sure that there's enough oil that will lubricate the cylinder wall. are you into maarat trails or motox trax?
nde po, regular rider lang po ako. but i am also interested sa trail riding.
ei rgon bro, sorry 4 d late reply. yung reed valve ko nakita ko parang me binali na mga metal support (by the previous owner) para siguro lumakas, pero di kaya mabali yung plastic nun pag napuwersa? ala rin syang filter anu ba alternative kasi 900 petot yung bagong filter.
Originally Posted by rgon
nga pala, nagpatune-up ako sa kservico taytay last saturday at nakita na durog pala yung mga ring, me tama ang piston at pati yung block! ngayon kailangan ipa-sleeve ko yung block kasi maluwag na at medyo oblong nampucha kaya pala parang mahina na sya, mahirap i-start at laging lunod! (di kasi exclusive sa akin ang KMX ko) bumili na ko ng piston, rings, sangkaterbang gasket at pina-sleeve ko na yung block (16k daw yung bago eh) next sat ko pa makukuha sa YRS.
tanong: totoo bang hindi na sya magiging kasing lakas ng dati? balak ko pa naman ikarera... hu hu hu...
hello po mga chief.... pardon me for butting in.. I recently acquired a used KMX 98 model... took the top end out replaced new rings , head gasket and clutch plates and a YRS arrester only mated to the stock expansion chamber..changed the rear sprocket to a 52 teeth ( stock is 48T) power now is OK pero parang kulang siya ng low midrange power, pero once na past 6k rpm talagang humihiyaw.... me paraan ba na lakasan ang mid power ..kasi i find myself downshifting 2 gears just to keep the revs at it power band.. i ride mostly sa street lang po ... looking to learn some trail riding kaso hadn't got a chance pa.. BTW ( nalinis na po ang mga carbon sa loob ng pipe and sa ex port and KIPS ko.. hope you could share some tips po .. salamat.
SUNDAY RIDERS CLUB
am waiting also for some mods done on a kmx125.
mods collected from this thread and previous threads
1.YRS arrester (accs)
2. rear sprocket to a 52 teeth ( stock is 48T) (accs)
3. boyesen reed valve (rls)
tanong ka sa kalookan may 5k "DAW" na brand new kmx125 cylinder.
yun pa-sleeve medyo ala ko balita sa performance after ng sleeving.
boss chief Rgon,
ok po ba ang Boyesen reeds and 28mm carb? nag tanong ako medyo mahal and reeds nasa 2K na.. carb nasa 4k ano po ang opinion niyo?
SUNDAY RIDERS CLUB
narinig ko sa trails okey naman daw yun big carb pero yun reeds ala ko balita lalo na doon sa dual-stage. hindi ko pa nasusubukan ang magpalit ng reeds at carb kasi nga may kamahalan. magandang set-up na yang bike mo for the trails of mt. maarat. tingin ko segunda okey pa yan sa pinakamatarik lalo na pag may buwelo.
nasa baba nabasa ko sa isang site na itinuro ni E.R.
BASIC TWO-STROKE TUNING
By Eric Gorr
Changing the power band of your dirt bike engine is simple when you know the basics. A myriad of different aftermarket accessories is available for you to custom tune your bike to better suit your needs. The most common mistake is to choose the wrong combination of engine components, making the engine run worse than stock. Use this as a guide to inform yourself on how changes in engine components can alter the powerband of bike's engine. Use the guide at the end of the chapter to map out your strategy for changing engine components to create the perfect power band.
Although a two-stroke engine has less moving parts than a four-stroke engine, a two-stroke is a complex engine because it relies on gas dynamics. There are different phases taking place in the crankcase and in the cylinder bore at the same time. That is how a two-stroke engine completes a power cycle in only 360 degrees of crankshaft rotation compared to a four-stroke engine which requires 720 degrees of crankshaft rotation to complete one power cycle. These four drawings give an explanation of how a two-stroke engine works.
1) Starting with the piston at top dead center (TDC 0 degrees) ignition has occurred and the gasses in the combustion chamber are expanding and pushing down the piston. This pressurizes the crankcase causing the reed valve to close. At about 90 degrees after TDC the exhaust port opens ending the power stroke. A pressure wave of hot expanding gasses flows down the exhaust pipe. The blow-down phase has started and will end when the transfer ports open. The pressure in the cylinder must blow-down to below the pressure in the crankcase in order for the unburned mixture gasses to flow out the transfer ports during the scavenging phase.
2) Now the transfer ports are uncovered at about 120 degrees after TDC. The scavenging phase has begun. Meaning that the unburned mixture gasses are flowing out of the transfers and merging together to form a loop. The gasses travel up the back side of the cylinder and loops around in the cylinder head to scavenge out the burnt mixture gasses from the previous power stroke. It is critical that the burnt gasses are scavenged from the combustion chamber, in order to make room for as much unburned gasses as possible. That is the key to making more power in a two-stroke engine. The more unburned gasses you can squeeze into the combustion chamber, the more the engine will produce. Now the loop of unburned mixture gasses have traveled into the exhaust pipe's header section. The gasses aren't lost because a compression pressure wave has reflected from the end of the exhaust pipe, to pack the unburned gasses back into the cylinder before the piston closes off the port. This is the unique super-charging effect of two-stroke engines. The main advantage of two-stroke engines is that they can combust more volume of fuel/air mixture than the swept volume of the engine. Example: A 125cc four-stroke engine combusts about 110cc of F/A gasses but a 125cc two-stroke engine combusts about 180cc of F/A gasses.
3) Now the crankshaft has rotated past bottom dead center (BDC 180 degrees) and the piston is on the upstroke. The compression wave reflected from the exhaust pipe is packing the unburned gasses back in through the exhaust port as the piston closes off the port the start the compression phase. In the crankcase the pressure is below atmospheric producing a vacuum and a fresh charge of unburned mixture gasses is flowing through the reed valve into the crankcase.
4) The unburned mixture gasses are compresses and just before the piston reaches TDC, the ignition system discharges a spark causing the gasses to ignite and start the process all over again.
The cylinder ports are designed to produce a certain power characteristic over a fairly narrow rpm band. Porting or tuning is a metal machining process performed to the cylinder ports (exhaust & transfers) that alters the timing, area size, and angles of the ports in order to adjust the power band to better suit the rider's demands. For example, a veteran trail rider riding an RM250 in the Rocky mountain region of the USA will need to adjust the power band for more low end power because of the steep hill climbs and the lower air density of higher altitudes. The only way to determine what changes will be needed to the engine is by measuring and calculating the stock engine's specifications. The most critical measurement is termed port-time-area. This term is a calculation of a port's size area and timing in relation to the displacement of the engine and the rpm. Experienced tuners know what the port-time-area values of the exhaust and transfer ports should be for an engine used for a particular purpose. In general, if a tuner wants to adjust the engine's power band for more low to mid range he would do the following things. Turn down the cylinder base on a lathe to increase the effective stroke (distance from TDC to exhaust port opening). This also retards the exhaust port timing and shortens the duration and increases the compression ratio. Next the transfer ports should be narrowed and re-angled with epoxy to reduce the port-time-area for an rpm peak of 7,000 rpm. The rear transfer ports need to be re-angled so they oppose each other rather than pointing forward to the exhaust port. This changes the loop scavenging flow pattern of the transfer ports to improve scavenging efficiency at low to mid rpm (2,000 to 5,000 rpm). An expert rider racing mx in England would want to adjust the power band of an RM250 for more mid to top end power. The cylinder would need to be tuned radically different than for trail riding.
Here is an example. The exhaust port would have to be raised and widened to change the port-time-area peak for a higher rpm (9,000 rpm). For either of these cylinder modifications to be effective, other engine components would also need to be changed to get the desired tuning effect.
Cylinder heads can be reshaped to change the power band. Generally speaking, a cylinder head with a small diameter and deep combustion chamber, and a wide squish band (60% of the bore area). Combined with a compression ratio of 9 to 1 is ideally suited for low to mid range power. A cylinder head with a wide shallow chamber and a narrow squish band (35-45% of bore area) and a compression ratio of 8 to 1, is ideally suited for high rpm power.
There are many reasons why a particular head design works for certain types of racing. For example; a head with a wide squish band and a high compression ratio will generate high turbulence in the combustion chamber. This turbulence is termed Maximum Squish Velocity, MSV is rated in meters per second (m/s). A cylinder head designed for supercross should have an MSV rating of 28m/s. Computer design software is used to calculate the MSV for head designs. In the model tuning tips chapters of this book, all the head specs quoted have MSV ratings designed for the intended power band changes.
There are two popular mods hop-up companies are doing to crankshafts; stroking and turbo-vaning. Stroking means to increase the distance from the crank center to the big end pin center. There are two techniques for stroking crankshafts; weld old hole and re-drill a new big end pin hole, or by installing an off-set big end pin. The method of weld and re-drilling is labor intensive. The off-set pin system is cheap, non-permanent, and can be changed quickly. In general, increasing the stroke of a crankshaft boosts the mid range power but decreases the engine's rpm peak.
The term "Turbo-Crank" refers to a modification to the crankshaft of a two-stroke engine, whereby scoops are fastened to the crank in order to improve the volumetric efficiency of the engine. Every decade some hop-up shop revives this old idea and gives it a trendy name with product promises that it can't live up to. These crank modifications cause oil to be directed away from the connecting rod and often times the vanes will detach from the crank at high rpm, causing catastrophic engine damage. My advice, don't waste the $750!
In general a small diameter carburetor will have high velocity and a good flow characteristic for a low to mid rpm power band. A large diameter carburetor works better for high rpm power bands. For 125 cc engines a 34mm carburetor works well for supercross and enduro and a 36 or 338 mm carburetor works best for fast mx tracks. For 250 cc engines a 36 mm carburetor works best for low to mid power bands and a 39.5 mm carburetor works best for top end power bands. Recently there has been a trend in the use of air-foils and rifle-boring for carbs. These innovations are designed to improve air flow at low throttle openings. Some companies sell carb inserts, to change the diameter of a carb. Typically a set of inserts is sold with a service of over boring the carb. For example; a carb for a 250cc bike (38mm) will be bored to 39.5mm and two inserts will be supplied. The carb can then be restricted to a diameter of 36 or 38mm.
Think of a reed valve like a carburetor, bigger valves with large flow-areas work best for high rpm power bands. In general, reed valves with six or more petals are used for high rpm engines. Reed valves with four petals are used for dirt bikes that need strong low end and mid range power. There are three other factors to consider when choosing a reed valve. The angle of the reed valve, the type of reed material, and the petal thickness. The two common reed valve angles are 30 and 45 degrees. A 30-degree valve is designed for low to mid rpm and a 45 degree valve is designed for high rpm. There are two types of reed petal materials commonly used, carbon fiber and fiberglass. Carbon fiber reeds are lightweight but relatively stiff (spring tension) and designed to resist fluttering at high rpm. Fiberglass reeds have relatively low spring tension so they instantly respond to pressure that changes in the crankcase, however the low spring tension makes them flutter at high rpm thereby limiting the amount of power. Fiberglass reed petals are good for low to mid power bands and carbon fiber reeds are better for high rpm engines.
Boyesen Dual Stage reeds have a large thick base reed with a smaller thinner reed mounted on top. This setup widens the rpm range where the reed valve flows best. The thin reeds respond to low rpm and low frequency pressure pulses. The thick reeds respond to higher-pressure pulses and resist fluttering at high rpm. A Boyesen RAD valve is different than a traditional reed valve. Bikes with single rear shocks have off-set carbs. The RAD valve is designed to redistribute the gas flow to the crankcases evenly. A RAD valve will give an overall improvement to the power band. Polini of Italy makes a reed valve called the Supervalve. It features several mini sets of reeds positioned vertically instead of horizontally like conventional reed valves. These valves are excellent for enduro riding because of improved throttle response. In tests on an inertia chassis dyno show the Supervalve to be superior when power shifting. However these valves don't generate greater peak power than conventional reed valves. Supervalves are imported to America and sold by Moto Italia in Maine.
The exhaust pipe of a two-stroke engine attempts to harness the energy of the pressure waves from combustion. The diameter and length of the five main sections of a pipe, are critical to producing the desired power band. The five sections of the pipe are the head pipe, diffuser cone, dwell, baffle cone, and the stinger. In general, after market exhaust pipes shift the power band up the rpm scale. Most pipes are designed for original cylinders not tuned cylinders. Companies like MOTOWERKS custom computer design and fabricate pipes based on the cylinder specifications and the type of power band targeted.
Silencers come in all sorts of shapes and sizes. A long silencer with a small diameter enhance the low to mid power because it increases the bleed-down pressure in the pipe. A silencer with a short length and a large core diameter provides the best bleed-down pressure for a high rpm engine. Too much pressure in the pipe at high rpm will radically increase the temperature of the piston crown and could cause the piston to seize in the cylinder.
The flywheel is weighted to improve the engine's tractability at low to mid rpms. There are two different types of flywheel weights, weld-on and thread-on. A-Loop performs the weld-on flywheel weight service. Steahly makes thread-on flywheel weights. This product threads onto the fine left-hand threads that are on the center hub of most Japanese magneto rotors. normally the threads are used for the flywheel remover tool. Thread-on flywheel weights can only be used if the threads on the flywheel are in perfect condition. The advantage to weld-on weights is they can't possibly come off.
External rotor flywheels have a larger diameter than internal rotor flywheels so they have greater flywheel inertia. Internal rotor flywheels give quicker throttle response.
AFFECTS OF THE IGNITION TIMING
Here is how changes in the static ignition timing affects the power band of a Japanese dirt bike. Advancing the timing will make the power band hit harder in the mid range but fall flat on top end. Advancing the timing gives the flame front in the combustion chamber, adequate time to travel across the chamber to form a great pressure rise. The rapid pressure rise contributes to a power band's "Hit". In some cases the pressure rise can be so great that it causes an audible pinging noise from the engine. As the engine rpm increases, the pressure in the cylinder becomes so great that pumping losses occur to the piston. That is why engines with too much spark advance or too high of a compression ratio, run flat at high rpm.
Retarding the timing will make the power band smoother in the mid-range and give more top end over rev. When the spark fires closer to TDC, the pressure rise in the cylinder isn't as great. The emphasis is on gaining more degrees of retard at high rpm. This causes a shift of the heat from the cylinder to the pipe. This can prevent the piston from melting at high rpm, but the biggest benefit is how the heat affects the tuning in the pipe. When the temperature rises, the velocity of the waves in the pipe increases. At high rpm this can cause a closer synchronization between the returning compression wave and the piston speed. This effectively extends the rpm peak of the pipe.
HOW TO ADJUST THE TIMING
Rotating the stator plate relative to the crankcases changes the timing. Most manufacturers stamp the stator plate with three marks, near the plate's mounting holes. The center mark is the standard timing. If you loosen the plate mounting bolts and rotate the stator plate clockwise to the flywheel's rotation, that will advance the ignition timing. If you rotate the stator plate counterclockwise to the flywheel's rotation, that will retard the ignition timing. Never rotate the stator plate more than .028in/.7mm past the original standard timing mark. Kawasaki and Yamaha stator plates are marked. Honda stators have a sheet metal plate riveted to one of the mount holes. This plate insures that the stator can only be installed in one position. If you want to adjust the ignition timing on a Honda CR, you'll have to file the sheet metal plate, with a 1/4in rat-tail file.
The latest innovation in ignition systems is an internal rotor with bolt-on discs that function as flywheel weights. PVL of Germany makes these ignitions for modern Japanese dirt bikes. Another advantage to the PVL ignition is that they make a variety of disc weights so you can tune the flywheel inertia to suit racetrack conditions.
MSD is an aftermarket ignition component manufacturer. They are making ignition systems for CR and RM 125 and 250. MSD's ignition system features the ability to control the number of degrees of advance and retard. These aftermarket ignition systems sell for less than the OEM equivalent.
TIPS FOR BIG BORING CYLINDERS
In the mid nineties, European electro-plating companies started service centers in America. This made it possible to over bore cylinders and electro-plate them to precise tolerances. This process is used by tuners to push an engine's displacement to the limit of the racing class rules, or make the engine legal for a different class.
When you change the displacement of the cylinder, there are so many factors to consider. Factors like; port-time-area, compression ratio, exhaust valves, carb jetting, silencer, and ignition timing. Here is an explanation of what you need to do when planning to over bore a cylinder.
Port-Time-Area - This is the size and opening timing of the exhaust and intake ports, versus the size of the cylinder and the rpm. When increasing the displacement of the cylinder, the cylinder has to be bored to a larger diameter. The ports enter the cylinder at angles of approximately 15 degrees. When the cylinder is bore is made larger, the transfer ports drop in height and retard the timing and duration of those ports. The exhaust port gets narrower. If you just over bored and plated a cylinder, it would have much more low end power than stock. Normally tuners have to adjust the ports to suit the demands of the larger engine displacement. Those exact dimension changes can be determined with TSR's Time-Area computer program.
Cylinder Head - The head's dimensions must be changed to suit the larger piston. The bore must be enlarged to the finished bore size. Then the squish band deck height must be set to the proper installed squish clearance. The larger bore size will increase the squish turbulence so the head's squish band may have to be narrowed. The volume of the head must be increased to suit the change in cylinder displacement. Otherwise the engine will run flat at high rpm or ping in the mid range from detonation.
Exhaust Valves - When the bore size is increased, the exhaust valve to piston clearance must be checked and adjusted. This pertains to the types of exhaust valves that operate within close proximity of the piston. If the exhaust valves aren't modified, the piston could strike the valves and cause serious engine damage.
Carb - The piston diameter and carb bore diameter are closely related. The larger the ratio between the piston size and the carb size, the higher the intake velocity. That makes the jetting richer. Figure on leaning the jetting after an engine is over bored.
Ignition Timing - The timing can be retarded to improve the over rev. Normally over bored engines tend to run flat on top end.
Pipe and Silencer - Because only the bore size is changed, you won't need a longer pipe only one with a larger center section. FMF's line of Fatty pipes work great on engines with larger displacement. Some riders use silencers that are shorter with larger outlets to adjust the back-pressure in the pipe for the larger engine displacement.
if you want to know more about (your) 2-stroke machines, and harnessing its (kili-kili) powers for a specific type of riding condition, e.g MX or trails, read thru rgon's references posted above...
rgon's a real 2-stroke guru....read thru and find out why...
what you just did is called streamlining the bridges (ribs you might call them) of the stock reedcage which reduces turbulence & improves laminar flow past the reedcage, it's standard practice for a hardcore 2stroke tuner.
Originally Posted by RolandoAlunan
when you tried aftermarket reeds how much thickness did you use? if you have gone too thick then you'll lose power almost everywhere in the rpm range, i have tried different thickness ranging from .25mm all the way to .50mm carbonfiber reeds & my high revving 70cc dragscooter performed best with .25mm to .30mm carbonfiber reeds, any thicker the reeds won't open far enough to give an area for an effective flowrate for high rpm operation.
bigger engines don't need thicker reeds they will benefit more using thinner reeds made of carbonfiber sheets, the engine response across the rpm range will improve significantly.
HONDA CBR 600RR track bike
Yamaha Aerox MHR Team 70cc track scooter
now at Taytay Rizal
btw i have VFORCE3 (Moto Tassinari) reedvalves for my Yamaha Jog dragscooter it's the only one here in the Philippines, it performs way better than my old Malossi MHR VL14 reedvalve, i had virtually zero blowback from the carb unlike the standard MHR VL14 which only perform best when changed with new reeds, with the VFORCE3 i always get consistent engine performance b'coz not only did it eliminate flutter at high rpm it also improved engine response at lot to mid engine speeds thanks to it's additional area.
when they tested a modified MHR VL14 reedcage vs a standard out of the box VFORCE3 for the Yamaha on a chassis dyno the VFORCE3 outperformed the VL14 by 1hp...........ACROSS THE ENTIRE RPM RANGE.
with the VL14 it only started making power at 9000rpm up till 13500rpm where it falls down flat but with the VFORCE it started pulling down as low as 7000rpm all the way to 14500rpm! talk about a linear powerband.
the amount we paid for the VFORCE3 was very worth it, 1hp may not seem like much but for a small racing engine where a fraction of a hp can mean a difference between 1st & 2nd place 1hp is a big gain for a bolt-on piece.
HONDA CBR 600RR track bike
Yamaha Aerox MHR Team 70cc track scooter
now at Taytay Rizal
hey nice info, pre!
Originally Posted by Modular Overrev
the YZ i got from jody is now equipped with a VForce 3, but i haven't jetted for it after the installation.
i got advice to step down leaner, from the stock pilot jet of 40, i should try to bring it down to 37.5 or 35 (1 to 2 steps down). i'm also having spooge problems. i used repsol 2T before, and now switched to motul 800 2T at ratio of 28 : 1, or 35 ml motul 800 2T for every 1 liter 95-octane leaded gasoline.
i'd rather jet properly for my current 2T mix in solving the spooge issue than reduce my engine oil pre-mix concentration to 40 : 1 or 50 : 1, which is a common rider's mistake.
any further advise, please...have you tried using the JD jetting kits? or could you recommend some you have tried?
hmmm i think you could be using a 2stroke oil with too thick viscosity, have you ever tried Motul 600? it's also a great oil & it's ok to use for premix & autolube, you could also have jetting problems, running it too rich causes the temps on the carb to run cold & that makes the oil emulsify into "spooge", you could also try running a different brand or type of gasoline, if it doesn't detonate on 93 unleaded then that is what you should use but test it carefully at first give the throttle a smooth roll on until you reach wot & listen for detonation.
HONDA CBR 600RR track bike
Yamaha Aerox MHR Team 70cc track scooter
now at Taytay Rizal
yeah, maybe the 28 : 1 gas : oil mixture is the culprit why there is always spooge coming out of the exhaust even though my plug is already 1 step hotter from BR9EV, went BR8ES. another reason could be that i haven't properly jetted the bike, yet to compensate for the hotter temperature, 32 to 35 degrees celsius.
Originally Posted by Modular Overrev
will experiment on going down 1 to 2 steps leaner on the pilot jet, as stock production bikes always come in with larger size jets, making them little richer. won't touch the main jet in any case just optimize the A/F mixture thereafter....then will let you know any findings.
won't reduce the 2T oil mix, however...
Originally Posted by m7zednalfs
ported 135 ba yan bro?
malata ung sa cuzin ko na ganyan...but pls send your info,bka sau ok at lumakas..baka may sira lng sa bike ng cuzin ko...dito samin kc may available na 200cc topend for kmx..15g daw..nyways,gudluck sa races
bro yung akin naka sleeve sa 135 pero malakas pa din sya,,
2005 YZ 125
Re: V-Force Reed Valve pang Kawasaki KMX 125
Salamat sa forum na ito. I need to resleeve my KMX 125R stock said the mechanic at YRS. roblem is 6,900 plus ang singil..Will use daw piston ng DT 125. Mas mura ba sa Caloocan?Advise naman po. Street use lang pero gusto ko rin pang trail. Ano po kaya magandang gawin...piston na 135 brutus, DT125? or standard KMX? nalilito lang...Thanks.