Frequently Asked Questions : Yamaha RX Series

I am starting this thread in hope of helping fellow 2-strokers & newbies in the world of 2-strokes. I will start with very commonly asked question & later will add more information as & when possible. Right now restricting the topic to Yamaha RX series only.

1. I am looking for some serious performance mods for my RX what are the steps involved?

Ans:Considering the case of a stock RX135 4-Speed, the top speed is around 95-100Kmph. Lot of modification is required for even incresing the top speed by 10Kmph & yes it does cost a lot of money & energy. The bike setting can be classified in general as below:

Stage 1: This is the first step to porting. Main work is on exhaust port & BHP increase is to approx. 14. With every BHP gain there is approx., 5Kmph increase in Top End. A 14BHP bike will do around 110Kmph with stock exhaust. This setup is ideal for stop & go traffic. One can easily smoke all the known 150cc air-cooled 4-strokes with this setup within city limits & sometimes even in highways.

Stage 2: Its for those who need more grunt & more top speed than stage 1. The BHP level will be around 16 for this case with an Expansion Chamber. Good power to take on bikes like RTR160, P180. Top speeds may be around 120-122Kmph.

Stage 3: Now we are talking some serious porting business here. The exhaust, trasfers & the inlets are all touched upon & use of a bigger carburettor. Matching expansion chamber makes it complete. Speeds can go as high as 125-130Kmph & enought to take on bikes like P200, ZMA.

Fully Blown Street Legal: The port levels are almost the same as stage 3, or maybe slightly tweaked. Use of some imported connecting-rod, Imported Pistons, Imported clutch plates, 90/100Kit with matching CDI, Better & slicker imported tyres (Ex., Michelin or IRC), bigger carburettor assembly, Iridium spark plugs, fiber reeds (optional), front disc brake assembly (for safety), better rims (Ex., IRC, HH), Synthetic 2-T Oil (Ex., AGIP, MOTUL). The chasis still remains of normal RX135 & weight of the machine will now be around 100-102Kgs. This is the max possible modification that can be done with a fully blown setup. The BHP will be around 18-19 (max) with top speeds in between 130-135Kmph.

Now anyone boasting about RX doing 140 or even 150Kmph, then its not street legal anymore. Its more into drag settings (which will not be discussed here) & not for city or highway usage.

Note1: Please note that the above procedure is very generalized & it may differ from case to case. Please do some study on what you need & get it executed by some thoroughly professional Tuner who knows what he is doing.

Note2: As the power (BHP) increases the Top speed increases but the acceleration drops (Initial Pick-Up). And after a certain port setting there is no further increase in Top Speed & the torque capability starts to reduce further.

Note3: It is highly recommened to have a complete engine rebuild with original parts (OEM-Original Equipment Manufacturer) before considering a stage 3 or Fully-Blown setup for your own safety.

2. I need 40+ Kmpl Fuel Economy from my RX135. How do i do it?

Ans:Expecting 40+ Kmpl from an RX135 is a little tricky, but can be done. Kindly note that this is possible only with 4-speed bore kits (4TL00). All you need is the original Bore kit in absolute stock condition & bit of lean tune in carburettor, a stock exhaust system (Big Catalytic type is perfect for this) & riding sane. Follow this pattern:

1st Gear : 10Kmph
2nd Gear : 20Kmph
3rd Gear : 30Kmph
4th Gear : 40Kmph

Try to ride within 40-50Kmph in top gear for most of the journey & i am sure 40Kmpl + will be easily done. Additionally you can opt for 5th gear (overdrive) for lesser strain on engine & slightly more FE.

Note: Dont expect these results on a 5-speed bore kit (4TL10). A 5-speed kit is rated at 14BHP & was more for power, you will be lucky if it returns a practical value of 35Kmpl in B'lore riding conditions.

3. What is the ideal time for replacement of cylinder kit or rebore option?

Ans:Considering today's riding conditions (Read: Ripping) a 4-speed bore may last around 50,000Kms if not modified & a 5-speed bore may last around 35,000Kms. Highly modified cylinders last anywhere between 10,000Kms to 15,000Kms under ripped conditions, assuming the bike was regularly serviced, Good 2-T oil, correct 2-T oil flow etc.

The indications are poor throttle response, more sound coming from cylinder, rings sound. As per the availability replace the cylinder kit or go for an upsize piston (rebore). For RX135s, original ART pistons are available upto 2nd O/S (0.5mm) & hence it is wise to make use of it.

4. Which is the best 2-T oil for my bike?

Ans: There is no definate answer to this question. There are many oil brands available & also in option of not being synthetic or fully synthetic. Common brands such as Castrol (2T, Jettex), Pennzoil 2T, Shell, Agip, Motul, Servo, Mobil are all good. Its better to experiment first & then stick to one.

Personally i have used all the above brands & 2Yrs back i shifted to Synthetic Oil & use AGIP as its always available with my tuner. So depending on the availability & pricing pick your choice.

5. How to improve the lighting of my bike?

Ans: It depends on what is the brightness you are looking at. If you want to compare it with a car's headlight (Single ofcourse), then best option is to go for a reputed 90/100Kit with a 90/100W Headlight bulb for best output. Stator Coil rewinding with higer turns is another option, but the result may not always be as good as the 90/100 Lighting kits.

Please contact your local tuner who can do this job for you or source the kit from a reliable source & get it fixed.

6. I want to convert my RX100/RX135 4-Speed to 5-Speed. How do i do it?

Ans:In the present market condition there are 2 options:

a. Use a 5-Speed Conversion Kit comprising of 3rd, 4th & 5th Gear wheel, Main Axle assembly, Shift cam assembly. Rest of the stuff can be re-used from existing 4-speed gearbox.

b. Use a complete 5-speed gearbox assembly (No longer available in YASS). Try to import a RX-K 5-Speed gearbox (the gear ratios of 3rd, 4th & 5th are little different as compared to Indian 5-Speed GB) or try a used Indian 5-Speed GB.

Shifters can be purchased brand new from ASS or major automobile stores.

7. I have a RX135 5-Speed, can i use a 4-speed bore (4TL00) in it & have similar performance?

Ans:Depending on the availability, yes. A 4-speed bore will give you more torque & excellent city ride with low end grunt. It will also return more FE. Replacing the cylinder kit & correct tuning should do the job. As an option carburettor assembly can also be used of a 4-speed.

Answering second part very specifically, a 4-speed bore & 5-speed bore can never have similar performance even if the BHP levels are the same. Both were designed with a different intent.

A 4-speed bore is rated at 12BHP at crank & the 5-Speed at 14BHP at crank. You will need to modify the 4-speed cylinder by porting the exhaust to bring it upto 14BHP. This is what is stage 1 porting in case of 4TL00 kits. The top-speeds will be the same as a 4TL10 kit, but a ported 4TL00 kit will get there faster. It is the inherent characteristic of the cylinder that makes it produce more starting torque. This is the reason 4TL00 kits are more preferred in Drag racing, where not only the top speed is important, but hitting that top speed within 400Mts is of more importance.

8. I have an RX100 & would like to convert it to an RX135 5-Speed. What is the procedure ?

Ans: An RX100 has a displacement of 98CC & an RX135 has a displacement of 132CC. So it would be right to assume that the cylinder kits are different, but the trick here is, there are many other components that are different. Let us look at it one by one:

a. Piston-Cylinder kit of RX135 (4TL00 or 4TL10, both will do)
b. Head Assembly of RX135 (4TL5, 4TL00 or 09L, all 3 will do)
c. Carburettor Assembly of RX135 (4TL01 by Mikuni or UCAL Mikuni)
d. Complete Indian 5-Speed Gear Box assemby OR Conversion Assembly OR Close Ratio GB of RX-King (Imported)
e. Crank Shaft Assembly of RX135
f. Engine Bearings (Advicable to change as the entire engine is being rebuilt)
g. Reed Valve Assembly of RX135
h. Sproketing of RX135 5-speed, 15/38
i. Painting Scheme of RX135 5-Speed (Optional)
j. Clutch bell assembly may be changed if not in good condition, highly recommended along with pressure plates & clutch plates.
k. Spark Plug (Make & model as per owner's manual, optionally NGK Iridium can be used)
l. 12V Electrical System
m. Lighting Kit & Associated CDI of RX135 (Optionally can use After Market stuffs available at your own risk)
n. Exhaust assembly may be re-used of RX100 or can fit chrome type exhaust of RX135.

There you have it, full conversion to RX135 5-Speed.

9. What is the best tyre sizes for RX Series?

Ans: Following are the recommended tyre sizes for below models:

a. RX100 : 2.50 x 18 Front & 2.75 x 18 Rear
b. RX135 4-Speed : 2.50 x 18 Front & 2.75 x 18 Rear
c. RX135 5-Speed : 2.75 x 18 Front & 3.00 x 18 Rear

Optionally one can go for 3.25 x 16 in Rear wheel, there is no known advantage except for better asthetic appeal & reduction in height of the bike.

10. How to check if the 2-T oil supply pump is working or not ?

Ans: The 2-T oil is supposed to mix with petrol for combustion & it helps in lubrication in the cylinder area. Inadequate supply of 2-T oil can cause major siezure of the engine, sometimes even with crank bottom siezure. It is very essential to have a track of this 2-T oil flow periodically. This is the procedure:

a. On the LHS of the bike (Gear Shifter Side) we have the 2-T oil tank, which can hold approx., 1.1Lts of 2-T oil. There is a peep view available for RX100 (It even has a guage), RXG, RX135 & directly looking at it will give a fair idea of how much oil is present. You may want to bend the bike as well to check if the level is enough. For RX-Z there is a oil level measurement & indication on Tachometer for the same.

b. Now we know that there is enough oil in the tank, but how to make sure it is flowing & doing its part. There is small 2-T oil pipe connected on RHS of the carburettor assembly, you should disconnect this pipe after the bike start up. Keep revving the throttle & wait for the oil to ooze out, if it doesn't even after say 30 secs, then there is something worng either with the pump or there may be some leakage with the pipe or vacuum in the whole system. Get the bike checked with nearest service center & get it get the problem rectified.

c. If you are in the middle of a trip & something like this happens, kill the engine, let it cool down & drive very slowly to the nearest petrol pump, go for an oil mil for around 3-4% & then proceed.

d. On a long trip, you may always want to use around 2% oil mix with petrol (Shell bunks have these facility of direct mix) just to be on safer side.

11. I am looking for a big-bore project for my RX135. How to proceed?

Ans: Big-Bore essentially means a cylinder of Higher displacement. For an RX135 with existing sleeve one can go all the way up till 2.00mm, i.e a 60mm piston. Going beyond this point on the existing sleeve will hamper the performance. Always remember, fitting a larger piston alone will not bring the desired power level, you may want to follow the steps mentioned in question no.1 for details. Pistons like TOP, TOP PRO etc are readily available, if you are looking for extreme performance then 'ART' will be way to go & try some Imported Racing Pistons.

For an RX100 one can opt for a RX115 Piston (available in Pakistan).

12. How can i prevent rusting inside petrol tank?

Ans: A healthy petrol tank is the key to reliabilty of your machine. A through petrol wash is recommended once a year & even if you are using 2-T oil pump, please top up with some oil directly with petrol to avoid any further rusting. If the rust is beyond treatment, please replace the Entire Petrol Tank assembly for your own safety.

13. What are the various aftermarket upgraded available for RX series?

Ans: There are many upgrades one can have depending on personal choice & money. So may cause harm to your bike's overall performance, some may improve them. So what i am suggesting below are to be treated as optional items only & intented to be reviewed & used at own risk.

a. Performance Air Filter (Ex., K&N, Pipercorss, UNI, Custom)
b. Ignition System (Ex., PVL, Ravi-Nagesh, Custom)
c. Gear Box (Ex., RX-King, DT125, Custom)
d. Disc Brake Assembly (Yamaha Gladiator, Honda Unicorn)
e. Tyres (IRC, Michelin, Dunlop)
f. Expansion Chambers (Proton, KRP, Custom)
g. Connecting Rod (DT125, RX-King)
f. Reed Valve (Boyesen, VForce, RX-King, RZ-Series)......All these will need modification in Inlet Port.
g. Spark Plugs (NGK Iridiums)
h. Headlight Bulbs (Philips, Osram)
i. Rims & Spokes (Union Cycle, Hero Honda OE, Yamaha OE)
j. Handle Bar (Suzuki Shogun OE, RD350 OE, Sports Handle Custom)
k. Indicators (Suzuki Shogun OE)

14. What parts are recommended to be stocked if i have plans of keeping my RX for a very very long time.

Ans: It is always recommended to keep spares for your beloved RX as the production has stopped completely back in 2004-2005. Below are some mandatory & optional spares which needs to be kept for your own safety, please purchase them as & when available, don't wait for prices to come down, this is Yamaha RX we are talking here, not some Mobile Phone. The list goes below, some may seem optional, work on your instincts & decide.

a. Piston-Cylinder Kit (4TL00 or 4TL10, whatever available) - 1 No
b. 1st O/S & 2nd O/S '4Y2' 'ART' Piston Kit - 1 Each
c. Connecting Rod Assembly - 1 No..............2YA rods are no longer available, hence importing 4Y2 is an option.
d. Clutch Bell assembly with matching Primary - 1 No
e. Reedvalve Assembly - 2 Nos
f. Manifold Rubber - 4-5 Pieces
g. Exhaust Assembly - 1 No
h. Petrol Tank - 1 No
i. Oil-Pump - 1 No
j. Engine Bearing (LH & RH) - 1 Each
k. Packing Kit - 1 No
l. Side Panels - 1 Each

15. Can the Malaysian RX-Z 6-Speed Engine Parts be used in Indian RX-Z or RX135? If not then what options do we have?

Ans: The Malaysian RX-Z 6-Speed Bore x Stroke values = 56mm x 54mm & the displacement value come to 133.056 Cm3 & the Indian RX-Z or RX135 Bore x Stroke values = 58mm x 50mm, resulting in displacement of 132.157 Cm3.

Hence we can see that the diplacement values are similar, i.e 135Cm3 or CC (rounded off) & this is what causes the confusion among many Indian RX-Z/RX135 owners that they can use the parts from RX-Z 6-Speed. But if you notice carefully the Bore x Stroke values are different & hence it has resulted in two completely different engines. Except for some body parts such as Headlight assembly, Disc setup, nothing from the engine is a direct fit for our Indian RX-Z.

In a nutshell, stay away from procuring Engine related parts of RX-Z 6-Speed as they will burn a huge hole in your pocket & also nothing can be used on our Indian counterpart. So it is complete waste of money & time !!!!

The only other option to use Imported parts are that of Malaysian/Indonesian RX-King or Brazilian RD-135. The original "4Y2" parts of these are also very hard to find, but you may get them if you are lucky. These are direct fit to all our 135CC RX models.

16. What are the standard sproketing details for Yamaha RX series? What needs to be done to achieve higher top-end & likewise higher pickup?

Ans: Below are the sproketing details on Yamaha RX series

RX100 - 15T / 39T
RXG - 15T / 37T
RX135 4-Speed / RX-Z 4-Speed - 16T / 34T
RX135 5-Speed / RX-Z 5-Speed - 15T / 38T
Kindly note that Pick-Up & Top Speed are two different dimensions of performance tuning. One can't increase both simultaneously, that is against the law of nature.
To achieve higher top-end, reduce the sproketing in the rear by decrement of 1 & so on. For ex., a stock 5-speed has 38T in rear, to achieve a little higher top-end one can opt for 37T in rear. Also by increasing the front sproket helps. Please try it practically to feel the difference. Make sure not to overdo the sproketing or else there will not be any torque left in top-gear. You will be waiting for the powerband to open forever!!!!!

To achieve increased pickup (for ex., 0-60kmph timings), increase the sproketing in rear, overdoing this will limit the top-speed of the machine.

If you are planning on using 35T & 36T, they are not available in market, you will have to custome build this one. The problem in heavily modified motors is they are unable to run on 16T/34T sprokets anymore, especially if it is a 5-speed, there is huge drop in speed in 5th gear & hence we need to go in for 35T or 36T or 37T which ever is available & finally decide on which set-up is best for the bike.

17. What is the procedure to install a Speedometer + Center Panel + Tachometer on regular RX as compared to RX-Z?

Ans: Below are the items which need to be added. Kindly note that the Yamaha RX-Z came with factory fitted Tachometer & is mechanical based & not electronic based like in Shoguns & Shaolins.

a. Speedometer
b. Center Panel
c. Tachometer
d. Speedometer Cable
e. Tachometer Cable
f. RPM worm Kit
g. 5-speed or 4-speed Clutch side cover having provision for RPM cable inlet
h. RX-Z Meter Bracket
i. RX-Z central Locking System

Hope you enjoyed the read