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Old 11th June 2009, 23:26   #1
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Default RX dirt bike mod. (vintage scrambler)

Hey Guys,

This is my first foray into this community, feels great to be here.

Let me get started right away , I have always wanted to do a serious mod job
and finally, here's my chance. I have purchased a 96' model RXG for this purpose, I intend to go for a vintage scrambler type look (eg. Yamaha Dt-01, google it to get an idea)

I am taking it step by step, first the suspension, wheels/tyres and frame then the body work, lights, electricals and paint job and finally the engine, exhaust and other performance add-ons. I would first like to explain what I have in mind. I am no engineer so please dont look for anything elaborate , I am more of a design guy, so I need it to look the part but performance wont be left out either.

Front end :

I intend to lift the front end by 3.5 inches and fit a 19" block tread pattern tyre, give it a wide handle bar and disc brakes with a single pod tachometer alone (Race style). A tiny round headlamp with a small fly screen and a slightly lifted front fender (enfield type). So here's what I have bought till now.

1. Pulsar 150/180 fork assembly
2. Pulsar's T-clamp
3. Pulsar 150/180 disc brake kit and hub
4. Rajdooth's 19" front rim
5. Dunlop block tread tyre (3.25/19)

Rear end:

At the rear I want to lift the swing arm by 2 inches, give it mono shocks, a wide button tyre (3.50/18), a curvy rear fender that juts out of the frame and a tiny rectangular tail light and a number plate holder below it.

1. Unicorn's swing arm
2. Monoshocks
3. Drum Kit
4. Ceat secura tyre (3.50/18)
5. Pulsar 180's Rim

Frame:

Other than the suspension mods i am fitting a V-shaped brace at the center of the bike on either sides. It will extend from just before the rear shock mount to the axle where the swing-arm fits to the frame and then rise up from there and connect to the frame just below the point where the fuel tank meets the seat. I am fitting this piece for both strengthening the frame and for aesthetic appeal as that area looks really empty once the Unicorn's swing arm's fitted.

Body work :

I have a wacky idea for the fuel tank, thinking of getting a scrapped yezdi roadking's fuel tank and chopping it off horizontaly just an inch from the bottom and then flattening the underside of it. The side shields are goin to be standard but the Rxg monogram's coming off, it will be a smooth piece. The fenders are going to be custom made based on the DT-01 and I am planning to make a seat plate on the same DT-01's style , probably use the same yezdi's seat plate and lift it at the rear.

Engine:

And here's the fun part . The barrel's goin to be rebored to fit a 145cc imported piston, rings and its goin to be ported to match an underseat expansion chamber (motocross style), An RD 350-carburettor if I find one or an after-market 26mm Mikuni (the standard one's a 24mm....I think), a 5-speed gearbox , 5 plate clutch assembly, boyzene reed valve, a Quick-throttle
and finally sprocketing for outright acceleration.

So thats about it, I have started work on lengthening the front forks, the wheels are being trewed and once that is done I will strip the bike, fit it and then fit the swing-arm and mono according to the stance required and so on and so forth.

I will be posting Pics very shortly and guys if you have modded your bikes in this manner (anything related) please feel free contribute. Any suggestion will be helpful as I am sure I will come across quite a few hurdles.

P.S: The reason I am doin the engine finally is bcause I am residing in Hyderabad and I dont trust anyone over here to fiddle with 2-stroke engines, so I will be shipping it to chennai for the engine work .

Wish me luck guys

Cheers.
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Old 12th June 2009, 01:21   #2
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If you want a vintage scrambler look then you need to retain twin shocks.

Also I think the Yezdi rear tire is the one to go for. This is a very popular mod for rally RXs along with longer travel rear twin shocks.
You can try fuel tank from Explorer.. might just work out fine.

Make sure you paint it white with red accents to complete the DT look.

Last edited by Mpower : 12th June 2009 at 01:22.
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Old 12th June 2009, 01:57   #3
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Hey thanks for your views but Im only shaping the body parts like a vintage scrambler, the suspension parts are goin to be modern. The RX's swing-arm's too flimsy and weedy so it might flex with the big rear tyre and there are no shocks twin rear shocks available in the market that has long travel and I dont like the sort of mod most people do to increase it (weld an additional piece at the top or bottom of the shocks), also I think the yezdi's 16" rims are too small for the bike. I have a few paint schemes that i am working on, one's the yellow and white with black blocks like the Kenny roberts style GP yamaha bike or the whit and red of the lucky strike suzukis or full mtallic black with chromed mud guards and red pin stripe on the fuel tank. I think the explorer fuel tank is a little too angular for the 60's look
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Old 12th June 2009, 03:09   #4
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good stuff i like ur ideas . big tyres are good for real scramblers . yezdi tyres make sense only on a full RX bases twin shock dirt setup . 19 - 18 inch combo sounds good . might make it a little high tho incase ur short . carbs i would suggest u go with a PWK or a TM series . U want instant throttle response on ur RX and an RD vm28 will not give u that as per my experience . im not sure about the boysen reeds either , look up the net and see what kinda reed dirt trackers prefer for their 2 strokes . i only hope u get the mountings rite for the mono shock. thats the only major tricky bit in this project i guess . which tuner are u sending u engine to in chennai btw ? i also suggest u get a square headlight like the rxz and a sqaure fairing for the headlight . like the 80s scramblers .

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Old 12th June 2009, 15:14   #5
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hey thanks 2-strokejunkie, i like the fact that u like my ideas. I am really not going to be using it as a dirt tracker so outright performance is not my goal. its mostly going to be used on regular roads so the above said add-ons should do i guess, I'll be happy if I got 24 - 25hp out of it. but i will give those carbs a shot, any ideas where i can find one. Hey and do you know what sort of problems i will face when fitting the mono? And real sorry bro, my mech does not want his name to be revealed, all i can say is that he runs a race team with 2 group-c (unrestricted RX 135-100) spec racing yamahas in it and has a good reputation over there.
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Old 12th June 2009, 17:51   #6
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Quote:
Originally Posted by nitro.1000bhp View Post
do i guess, I'll be happy if I got 24 - 25hp out of it.

runs a race team with 2 group-c (unrestricted RX 135-100) spec racing yamahas in it and has a good reputation over there.
YOu think, its easy to get 24 - 25bhp (true) and keep it street reliable? U need to do a radical build to strike the balance of reliability and that much of power. U are talking about twice of what an RXG pumps in stock.

FYI, Group C is not the unrestricted class, its indeed limited by a great margin over Group B. Group B is the fully-unrestricted class(however class limits apply) and 2-strokes are only raced as Group C.
4-strokes fall under the group B category.
Another point is, there is no local tuner from chennai except for R&R brothers (Raja and Raju) to stand the might of the TVS factory and the Yamaha team. Others are too slow to even come close to the factory bikes.
You figure this out now,
The TVS factory shaolins pumps 28-30bhp on the dyno and are the fastest in the pack(they have the best equipment level and refinement), closely matched by pacer's Yamaha RX135.
The others are way behind in the race, right from the start line. If these race bikes even developed 25bhp at the track, they would not be left that far behind. Let alone you getting 24-25bhp as a daily ride. Out of the actual pack, half the 2-strokes will end up in a blow-up in a lap or two.
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Old 12th June 2009, 21:46   #7
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CHILL man, y do u sound so tensed, I AM doin it up with R&R brothers and in fact I raced a bike on the circuit that he had done up and thats why i am so confident about the power output, reliability will be an issue but if the oil levels are right its manageable.
And for YOUR instance group c is not the only 2-stroke class, there's group D and novice class too. I am from chennai dude so please dont bother preaching to me, Raju had done up my own RX 135 some time back and a lot of my friend's RDs too.
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Old 12th June 2009, 22:06   #8
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correction : No one really knows how much power the factory TVS shoguns and shaolins put out as they have never really revealed the dyno charts. So its anybody's guess unless you are an insider. But the general assumption is that they put out anywhere close to 35-37 bhp, and thats how they can manage a top speed of 170 kph. So my friend tuning a 2-stroke engine for high power is really not that difficult if you have the right kind of parts in the right hands. Its not rocket science but at the same time its no cake walk either.
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Old 12th June 2009, 22:30   #9
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The problem with most local tuners is they really don know squat about 2-stroke tuning, they simply make the inlet & exhaust port bigger and fit an exhaust with no caliberations. The ports need to be bigger but the angle and smoothness of the ports matter a lot and then the exhaust needs to be an exact match. So a lot of math work needs to be done and only the most knowledgeable tuner can make it wok to perfection. And then comes the carbs, jetting, reeds sprocketing ....etc. Skill is second to wisdom.
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Old 12th June 2009, 22:33   #10
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Quote:
Originally Posted by nitro.1000bhp View Post
correction : No one really knows how much power the factory TVS shoguns and shaolins put out as they have never really revealed the dyno charts. So its anybody's guess unless you are an insider. But the general assumption is that they put out anywhere close to 35-37 bhp, and thats how they can manage a top speed of 170 kph. So my friend tuning a 2-stroke engine for high power is really not that difficult if you have the right kind of parts in the right hands. Its not rocket science but at the same time its no cake walk either.
You dont have to get so worked up dude, take a chill pill.
I spoke about the point to which you said Group C is an unrestricted class. Who spoke about Group D. Dont you say that only chennai boys know racing.
FYI, I've raced in group D and I'm building group B spec engines.
No-one knows about the TVS factory figures true, but I'm not anybody
FYI I've even seen the dyno chart of the Rx135 group C bike as well. If you saying its putting out close to 35-37bhp, thats utter rumour.
The factory bikes have never gone past 147kmph(on the speedgun on the back-straight and MRF arch) in the chennai track. 170kph is what those bikes are geared for and can theoritically achieve.
If you believe tuning a 2-stroke for high power output and striking reliability is easy, its high time you striked reality. If you put each of these tall claimed engines on a dyno, you'll know the truth. reliability in a 2-stroke engine is not achieved by merely maintaining oil levels. Just saying that 25bhp is too high to aim for a street reliable build. I dont understand why the sudden rise of adrenaline in you.
Having said that, a good 20bhp package in an RX can be a daily ride.
My post is not to ridicule you, but only to point what you quoted earlier about the group C and 25bhp part.
All the best with your project.

@2StrokeJunkie - I guess you got to know who the tuner is now
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Old 13th June 2009, 00:53   #11
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well I think I got worked up because of the tone you used at the the begining of your reply
Quote:
Originally Posted by fieroid View Post
YOu think, its easy to get 24 - 25bhp (true) and keep it street reliable?
Henceforth start off a bit subtle and then explain yourself. Its a bit rude otherwise. Still nevermind, I will work on the said power output, you are right I guess, 20hp should strike a good balance , thanks for your views.

cheers mate.
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Old 13th June 2009, 11:21   #12
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haha some friendly 2 stroke smoke flying around the place eh

yea joel i guessed as much . vivek's garage was another possibility , no news from tetrac from a long time .

dude nitro i donno how u will manage with button tyres on a ported and piped setup running on the tarmac . i dont like the feeling of the rear tyre spinning out everytime i down shift but to each his own . i think all u need for a reliable setup is

4 speed or 5 speed barrel ( scrambler id say go with a 4 speeder )
5 speed or RXK gearbox
PWK or TM ( check with raja raju themselves or maybe joel can help )
Mono shock again RnR are the best people to consult ( hows about the TZ125 mono and swing arm ? )
and not to forget a well designed pipe .

that said figuring out ur squish , porting and compression along with jetting and designing a good pipe are the tricky parts reliability being the main issue . if u havnt picked up a KnN as of yet then id suggest a UNI they work nice too . When ur down in Blore do come and check out some bikes here . I think blore is a good place to build dirt bikes , better than chennai IMO , chennais CBE good for circuit bikes .

otherwise dunk the mono shock and scrambler wishes .

just do the same stuff on an RX135 chassis . put on a rally handle bar , high grade aluminium rims , good IRC rubber , shogun seat , rally handle bar and probably a R15 or RTR stopping power on the front . will handle awesome and go pretty fast too ur only worry about cosmetics then will be mostly on this " Quality of Paint " .

Last edited by 2StrokeJunkie : 13th June 2009 at 11:24.
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Old 13th June 2009, 13:16   #13
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Hey wats the difference between the 4-speed and 5-speed barrels, like i know the latter is more powerful but any idea abt the ports. I am trying for the RXK's gearbox only and I am not even considering the tz125's monos, my cash reserves have almost depleted already so i'll stick to my original plan. And about the last part

"just do the same stuff on an RX135 chassis . put on a rally handle bar , high grade aluminium rims , good IRC rubber , shogun seat , rally handle bar and probably a R15 or RTR stopping power on the front . will handle awesome and go pretty fast too"

Everybody has done this, I want to do something different. I want the bike to look good and perform well.

cheers.
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Old 14th June 2009, 20:58   #14
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5 speeds open up later compared to 4 speeds . kinda like the HT LT concept in RDs . 5 speed head , gearbox and carb are also different .
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Old 14th June 2009, 21:15   #15
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If the 5-speed opens up later than the 4 then wont the 4 be a better choice wen you need more acceleration ??
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