Yamaha RX-S 100

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Cerberus73
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Yamaha RX-S 100

Post by Cerberus73 » Thu May 12, 2011 2:54 pm

Took a trip to local bike breakers, intending to buy some mirrors to fit my cub and see if they would check it over for MOT which is due in a month, he was happy my wee bike should pass the MOT, might need a rear boot, but hey i expected that, and a new numberplate cos my current one is cracked.

Was talking to him trying to get him to flog me one of his Honda Chaly's he has... and in passing just happened to ask if he had any small strokers, bingo... 1989 Yamaha RX-S100, last MOT'd last yr, has a Suzuki GS125 front forks and disk brake fitted... but soon change that, eBay should come up with the right bits. bike has low compression so needs a rebore.. standard for a old stroker really. 22 quid piston will sort her and a hr or 2, when done up this little bike will do 75-80mph if done right, can be bored up to 135cc that will make her do 85-90, i will try get a 125 barrel and head so its still learner legal. this will be my "big bike" lol well for more dual carriageway type journeys, i plan to do this as a project, i will sell the Suzuki front end to recoup the cost of the RX front end i need to source.

Im taking delivery of her tomorrow or early next week, im looking forward to doing this wee bike, and i will stick some pics up of the bike as bought and along the way. dunno if this will be of interest to us cubbers?

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Cerberus73
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Re: Yamaha RX-S 100

Post by Cerberus73 » Fri May 13, 2011 6:16 pm

well took delivery of my ring ding ding bike today, here she is in all her grubby glory.

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I also got another Suzuki GS125 rear wheel, cush drive, sprocket carrier, and brake backing plate to fit, as i think i will be keeping the front disk, with proper tuning and work, these little bikes can do 85+mph.... to much for a small drum brake to cope with i think, i will be getting her taken out to 115 or 125cc, a expansion chamber exhaust, bikini fairing, powder coating the frame, swingarm and cast wheels, vapour blasting the engine cases and head, and hopefully a cafe racer type solo seat, and a new paintjob, and better rear shocks, maybe uprated front springs as well. and new front and rear mudguards, new boots of a more modern pattern, she will be my lightweight blaster... ring ding ding ding... lol

while i was at breaker getting the rear wheel he dug out for me, there was a guy on the grubbiest, tattiest looking blue sq lighter cub there ive ever seen on the road, headlamp was taped in place, seat looked mouldy, plastics cracked, chipped, and frame a combination of blue and orange, sounded like a bag of nails as well, i felt sorry for the poor thing and asked if he would part with her, he wouldn't... shame poor wee bike, apparently it had just passed its MOT :O

The breakers also kindly donated me a honda express moped for doing the local "moped marathon" at the local annual bike show, my sisters man is ex forces, so we wanna do it for erskine veterans charity, only problem moped is missing parts of the automatic tranny, so i need to hunt one down between now and mid july as the race takes place in early august, so if any of the guys here have a spare engine or parts to fix this one for a honda express NC50 (not the crappy city express) moped drop me a PM

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ll81
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Re: Yamaha RX-S 100

Post by ll81 » Fri May 13, 2011 6:52 pm

She's got plenty of potential, do you really think you can get 85 mph out of it? Will be cool if you do.

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Cerberus73
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Re: Yamaha RX-S 100

Post by Cerberus73 » Fri May 13, 2011 7:13 pm

they do 75-80ish as standard, so with a spanny chamber, better brakes, lose some lard of her (and myself :P) and a few cc more of a rebore, yep 85+ can easily be achieved, one advantage to 2 strokes, easy to tune for speed, and cc for cc produce a lot more power than a 4 stroke... just not quite as reliable, but hey thats why i own a cub... reliable best of both worlds :D

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Black Sheep Radical
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Re: Yamaha RX-S 100

Post by Black Sheep Radical » Fri May 13, 2011 7:50 pm

That looks grand, but we really need to see pictures of the Honda Express :D

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Re: Yamaha RX-S 100

Post by aliengravy » Fri May 13, 2011 10:08 pm

Pictures of everything :D :D he he!

That looks like a nice bike!! And it sounds impressive..... I will be watching this thread :D

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Cerberus73
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Re: Yamaha RX-S 100

Post by Cerberus73 » Fri May 13, 2011 11:40 pm

i told the blokey at breakers to put the express to the side until i can see if a engine can be sourced, after all no point taking the wee bike if i cant find a motor cheap enough on time, after all the poor things get thrashed to point of exploding during these things, so everything is done on the uber cheap, beg, borrow, or steal... after all its to raise cash not spend it. we have set a total budget of £100 for our racing season, including fuel, 2 stroke oil etc, idea is to do away with oil injector pump, use premix for reliability, cant go wrong if its already in there!, better variator weights, stronger springs, and a 70cc head if i can find one, they are about! i already have pit bike front forks, disk brake, handlebars, levers, footrests, and rear n front wheels, i may have to get a relly in the engineering trade to "mod" the rear swingarm to take the 10 inch wheels with knobblies, after all its a park we thrash them round and by 3rd lap it is a bog, i also intend mounting a pit bike tank for fuel as the idea is endurance, so longer can go between pit stops, more laps we cover... strategy is less pit stops over all out speed, and hopefully reliability will be improved as well. if i cant find a motor the idea of the charity run is pretty dead in the water, its just the fact i saw the express in the breakers that got me thinking... moped marathon!

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Re: Yamaha RX-S 100

Post by cruncherkid » Sat May 14, 2011 1:10 am

Hi Cerberus, have owned an RXS myself, AND the earlier RS100 and 125 (also a YB100 thrown in for good measure) back in teenage years along with a variety of Suzuki GP100's and 125's, now if that little fella is standard i can promise you a top speed of 65-70mph before tuning with a skinny bloke on! I was from a family with not a lot of money, so i had to make do with these air cooled 'commuters' while the real posh kids had the power valve 125LC's, the 125TZR's and the RG125 Gammas, stuff i couldn't afford, and no way would the bike ever have a hope of keeping up....and you could kill it trying.......

Cruncherkid

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Cerberus73
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Re: Yamaha RX-S 100

Post by Cerberus73 » Sat May 14, 2011 10:25 am

they can be taken out to 175cc with parts swapping, 175 is available with early air cooled DT175 head and barrel, piston, only thing need to fit the DT conrod as small end of RXS is 14mm, and DT its 16mm, crankcase needs opened up by about 1mm to let the DT barrel drop on, stud, exhaust, for 125 all you need to do is use +20 RX115 piston (asian market model) and since the liner of the 100 RXS is meaty, it can be bored out easily, just means not much more left to go on liner, so ill source a spare head n barrel, there cheap, and use it to bore out to 123cc (RX115cc piston +20, with RXS100 bore n stroke)... if i want bigger id need to go down the DT175cc head n barrel route. as long as she does the speed limit with a few mph in reserve.. im happy

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