RD200 yamaha classic racer

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RD200 yamaha classic racer

Hi I have just built a RD200 racer and need advice on tuning the motor. Any help appreciated.

Whats the problem?When you say tuning do you mean standard tune or gaining performance.The ports will need opening up a bit.Performance reeds and expansion chambers (exhaust), carb rejetting.

Hi dooffle9 I want more hp , so far I have skimmed .5 mm off heads opened the holes in the pistons and fitted expansion boxes re jetted up to 100 on main and 70 on pilot the little bike has livened up a bit but has a bad flat spot from 4500 to 6000 but will then rev up to 8500. I live in south africa so can't just go out and buy racing parts like reeds so have to work with what I have . What do you think about taking a mm off the top of the piston at ext and transfer ports ?

raise the needle to sort your mid range

Hi bim I raised the needles up but the flat spot got worse. I have now filed 2mm off the piston crown at exhaust and transfer ports to advance timing the bike now revs to 9500 and has more power but the flat spot is still there from 4500 to 6000 I got advice to close the plug gap to .025 because the higher comp from .5mm head skim was killing the spark and the flat spot got smaller now it starts at 5000 to 6000 go figure ? But at least its getting better. I am now looking at expansion boxes tuned to the new exhaust port timing hope I'm on the right track ?

The new expansion boxes are on the bike and were tested A,OK giving power from 7500 to 9500 there basic sizes are tuned length to 9000 rpm at 930mm with 198mm stinger pipe the header dia is 35mm to 70mm at mid section and 16mm stinger pipe dia the motor is a twin 200cc with ext port duration of 194* I think the motor is now tuned to a point where any more port tuning it will become to unreliable remember its a 37yr old air cooled motor .....or is there a boffin out there who thinks I could squeeze a few more hp ?

Good God ! Where is everyone ? Am I the only member of this site or are you guys simply ignoring me ???

I don't think their (all two of em) that bothered?? Shame really.  Go buy a book and learn is my advise, download two stroke tuning e-book torrent for free

Graham bells book is a good onehttp://thepiratebay.org/torrent/5161227

Hi geo thanks for your response but not bothered ? Why would anyone join a site like visor down if they couldn't be bothered to discuss posts concerning motor tuning, I bet every guy who owned a bike has at sometime wanted to fit a part or do a modification to make it go faster, its what's owning a bike is all about. Thanks for your info but I have read Bells book years ago, I started my racing career in 1967 with a suzuki T20 & a yamaha TD1C & now retired & living the good life on the sunny west coast of south africa. My hobby is to build classic race bikes, fish, sail & play golf. Oh! And to try to find a site frequented by bikers who could be bothered. BTW I got the expansion box calculations for the little RD200 from Graham Bells book, hahaha so you are on the right track, try to keep it up. All the best George

Hi Doofle , Bim and Geo well guys I had my little RD200 screamer out on the track this morning and had a ball there were no 125s or 250s to compare my bike with possibly a good thing as at 60+ I'm not up to dicing into the corners with bunch of teenage Rossis but did find my way around the short circuit with out falling on my arse. The big lesson was the lack of a close ratio box to keep the motor in the now very narrow power band of just under 2000rpm from about 7700 to just under 10000 and with a wet clutch I was not to happy slipping it to boost revs but as I don't plan on taking on the young guns on there Aprilias I can live with the old box. I have tried to post a pic of the little bike but it won't work ?? But who could be bothered anyway well that brings to a close my report on the little RD.

Nice little story boertjie and I'm glad you (sort of) got it right.However, with reference to the previous comments regarding lack of interest, it's not really a lack of interest it's more a lack of knowledge. Kids nowadays buy parts to tune bikes and cars and aren't interested in filing ports, tuning spannies, sorting out a set of points, or rebuilding a carb. They have no reason to. As modern bikes and cars get more  and more complicated to the point of you needing to plug a computer into them to diagnose faults the maintenance is becoming more and more replace rather than repair. So the fettling of old stuff will, I'm afraid, be left to the elder generation.

Hi falcorob this is my second attempt at posting I have trouble working this bloody cel phone hahaha so would be a bit lost tuning rossies bike but timing is timing and big ports make big hp even with all the tuned cyl that are available over the counter the new generation will still try to do a mod or two just to get one better than the next guy so just for the hell of it I will keep on looking for ways to make my little rd go faster I will keep this forum posted on any new mods that work the failures I will keep to myself after all I don't want people thinking I'm an old twit cheers for now george

Funny that - I've just turned 32, but didn't really count myself as the "elder generation" just yet :-/

Hi tappy...after a lifetime of buggering around with bikes the main thing I have learnt is age doesn't matter, if anything it has kept me young..at heart anyway. A few months back @ Killarney our local racetrack in cape town we got visited by the international classic TT revival series run by mick grant, the event drew record crowds never seen @ national races. The highlight of my day was to spend time chatting to jim redman who @ 80 years young was parading a 250 honda4 alongside a young steve plater of isle of man fame. Jim even remembered the last time he & I along with a young guy called hailwood raced together in the Rhodesian GP in 1968 Mike Hailwood won the race Jim retired after leading for four laps with an oiled up plug and I came in 15th not a great result but in great company anyway here's to a great sport that has no age limits

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Ok I know this thread is months old but I stumbled across it. Close to 30 years ago a friend built up a RD200 to road race. The expansion chambers were off of an RD125 or TA125. The cranks rods pistons were Yamaha KT100 parts. At one point it was pulling 14,000 RPMs. The problem was the starter generator would do the crank in..........just to darn heavy. I think the KT100 ignition will work from what we were told way back then. Other things I vaguely remember is the forks were TA125 , reed blocks were YZ80 and carbs were RD350 (28mm??)

I know it's not much but hope some of it helps.

Hey TCG125 thanks for the info do you possibly have the port timing of the 14000 rpm RD200 motor I have got the bike going OK got A Graham Bell's book that is a great help. I have since got a 2nd bike a RD135 it is a little rocket my email is thewenmans@gmail.com mail me if you would like to see pic of the two little bikes of join me on face book where I have posted pic of the rebuild of the 135

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Hi all interesting stuff that someone still interested in playing with the old RD200. I am just in the process of trying to build one from NOS parts. Also gonna tune a motor and make some nice pipes.

Hi PFP I just got in from 5 laps around the 2.2 km street circuit near my home on the little RD200 I have a set of pipes designed and built in my shed that work ok with the port mods the bike is a pleasure to ride after I have gone threw a big learning curve helped with Graham Bells book on two stroke tuning and Ferry bowers advise on weight saving its nothing like the TD1c and the TD2 Yamaha's I raced in the 60s and early 70s but still a fun bike if you want to see pic mail me and I will post some to you also if you want tuning info I can put it up here or mail it to anyone interested

Hi Boertjie, How did you finally get on with tuning your RD200? I'm working on an RD200 bottom end with RS200 barrels as we're not allowed to use reeds in CRMC class. I'm looking for single ring race pistons, any suggestions? Gareth.

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