How fast is a Yamaha RD50dx?
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- Опубліковано 18 тра 2022
- It's time! To finally do a speed test with Kenny!
Does it truely have 6.25 hp?
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One of my first ever ‘real’ bikes.. (with gears not rev n go).. no way it could do 100kmph under normal use, however back then there was a 65cc kit available (still had 50cc on the head though 😬).. and if you change the carb and remove the exhaust baffles you could just get it to a 100 kmph ‘but’ buy a decent socket set because you would break the piston once every couple of weeks.. thing revved so high it just kept shattering the piston heads.. fun times.. always carried a plug socket under the seat as the plug would foul ‘a lot’.. good memories thx fir the video,
Glad you liked it! I know there are a lot of people claiming big numbers on stock bikes, however no one has a stock one anymore and still aren't reaching 100km/h. It's still a very fun bike with a lot of potential. I'm trying to improve it everywhere I can without doing major changes like changing cylinders.
Back in the early 80's as teenagers using very primitive handtools, my friend and I used to tune up the 1981 DT50 which had the identical engine as the RD50. In stock form, it would go about 80 km/hr top speed. We enlarged and widened the boost port. Secondly, we raised and widened the exhaust port. We used carbon fiber reeds. Thirdly, we milled the cylinder head for higher compression ratios. We installed a 22 mm mikuni carburator. Lastly, we installed a store bought tuned expansion chamber. We reached speeds of 110 - 115 km/hr. Now with much more knowledge and more professional tools, 120 km/hr plus speeds could be obtained but only for straightline racing as the RPM would be in the 15000 RPM. Good for Drag racing.
I don't think a mill is a primitive tool?
Also the 1981 RD50 is not the same bike as an RD50DX. Very different engines... The models after the DX were much easier to tune.
There are a lot of stories of RD50s going 100km/h, some even claim to reach that with stock bikes, however I have yet to see one do it... Even modified ones..
@@VintageGarageYT We did not use a Mill for the cylinderhead, but we used a Sand Paper placed on a flat piece of glass. By passing the cylinder head over the sand paper, we were able to lower the cylinderhead combustion chamber volume. The other tools we used were hand files, Dremel drills and stones. The regular RD50 cylinder was cast iron and it made less horsepower than the RD50 DX which has an aluminum cylinder. The RD50 DX is much more efficient both volumetrically and thermodynamically than the RD50 cylinder. As long as you "Understand" the Engine Dynamics, you can "easily" get these RD50 and RD50 DX above 120 KM/HR. I used to design and built my own expansion chambers. We were not your average teenagers back then, but we built plenty of two strokes 50ccs: Suzuki AP50, Suzuki GT50, Yamaha FS1, Yamaha RD50 (steel barrels), and Yamaha DT50. These were mopeds from 1977 to 1981. Again, I need to point out, you just have to understand the engine dynamics of engines. For instance, one of my stock Yamaha 1981 DT175 has a factory Engine Crankshaft Horsepower rating of 16.5 HP. I opened up all the ports (Transfer, Intake, Boost, and Exhaust) in the "Correct" pattern. Installed an expansion chamber exhaust from a Honda CR125, installed a Mikuni 32 mm Carburator and then placed the bike on a 2 wheel automotive Dynojet Dyno for horsepower testing. It Dynoed at 22 WHEEL Horsepower which is equal to about 26 Engine Crankshaft Horsepower. Original factory powerband was from 6000 to 10000 rpm. After the modifications, the powerband was from 8000 to 14000 rpm. Again, you just have to have a good understanding of engine dynamics and you can gain lots of horsepower with two strokes.
@@boengsnel With all due respect but you aren't making any reasonable comparisons. I know how 2 stroke works and how you can make power on them, but you compare tuned and modified engines to my stock one. Also that was not the point off this video.
I believe you and your stories about making more power, I will go that way on a bike someday, but here I was testing a bone stock RD50DX. I'm also not testing top speed, I'm doing a 400m run to calculate usable power. This bike might do 80kph in 5th, I don't know because it takes way too long to get there. There's no usable torque to even get into the power band with some wind on the front. There are a lot of stories, even some here in the comments, of people claiming high speeds on stock engines, but no one has any proof. The very few RD50's ive seen in the wild are all modified, so sure these engines have good potential, but I'm willing to bet a case of beer my FS1 is faster stock for stock because it has more usable power. The DX might win in a drag race that takes 2km, but when is that ever happening 😅
Appreciate you sharing your adventures from your youth.
This kind of experimenting is huge fun. There are all kinds of ways to improve on something that was deigned by the factory to start up and operate in any climate or altitude in the world.
I have a Portuguese Casal SS 50 moped (with pedals from the early 70's), it has 6.7hp stamped on the engine plate. It is awaiting a restoration and I have never ridden it, but I have heard that the Casal's were some of the very fastest mopeds of the time. You have a great collection there. :)
Also the 5th gear issue could be the final drive ratios of the chain and sprockets perhaps??, maybe go down one tooth on the front sprocket or up one or two teeth on the back sprocket to make it rev out in top gear. I have a 1970's Suzuki GT 185 as well and with shorter gearing and expansion chambers, ram air filters and bigger jets (and a very mild DIY port tune) it would rev out in top at around 90mph and was great fun to ride.
@@thesunreport Hello and big thanks! Already went 2 teeth down on the back sprocket, but maybe more is needed. However I am struggling with the carb so I have high suspicion this is holding the bike down still. Working on a solution as we speak 😀.
Ive also heard rumours on Casals but never saw one, let alone ride one so I'm curious as well! Definitely let me know how it goes when finished!
You’re very lucky being in Europe and having access to so many of these 50cc bikes. And awesome channel, keep up the great work.
Thanks man! Really appreciate it! I do consider myself lucky, we have a lot of cool stuff here!
Where are you from? Not many 50s around?
Originally from Brooklyn, NY but now in Miami. There’s a good amount of puchs and tomos mopeds but any occasional rd50 or ts50 or even mb5 is listed for way too high of an asking price😑
@@freddie6234 ah I see. Dont you guys have the rd60? Those are non existant here
So true. We had really slow 50cc bikes here in the States. Honda Express was the most popular when I was 15. When I was out of Highschool my roommate had a Kawasaki AR 80. It was fast for a very small bike.
My schoolfriend at the time had a red one of these. Compared to my Yamaha TY50 it had no low down power and a nasty dip in the powerband below 6000rpm and ran very good from 6000 and up. I convinced him to take it back to the dealers for them to have a look. The dealer drilled some holes in the airfilter box and fitted larger jets. After that intervention this bike was transformed.
On good days it ran 130km/h on the clocks
130 seems way too much. They probably messed with the clock then 🤣
Ive also tried riding without the air filter connected, but it didnt change anything. Im looking into a new carb because my suspicion is high that someone messed with it.
I had one, back in the days, with a little passion but stock 12 mm carb and modded airfilter, it did over 90 km/h when I was Lucky! Modified piston, slightly modified cilinder and head. But overall, pretty stock!
Not being rude, but modified piston,head and cylinder is far from stock in my opinion 😅.
Pretty stock would be nothing more than change a carb. Im doing some investigation on this one though, there might be something off after all.
Yeah finend a new rd video
Haha more to come!
I got 102km/h lying flat on the tank one cold morning (dense air) riding down the motorway. There was probably some speedo overread but still a good 95km/h as claimed. I had a few minor mods like bent back reed stops and polished ports but nothing that would have made a huge difference. Weight of the rider was of course a big factor so my weight as a 16 year old would have allowed me to get a better top speed than an adult would get. They were fantastic bikes - best 50cc available at the time.
Not saying you're a liar, but there are many claims, yet no one has any proof of a bone stock rd50 doing those speeds. They are always modded in some way and even then no one has any hard proof (video+ gps) of it.
Also this was a 1/4th mile test. Top speed was irrelevant at that time cause it took waaaaaaay to long. And as you mentioned, with some wind it wouldn't even get there. All my 1/4th mile tests are normal riding conditions and bone stock.
Nowadays the bike gets up to 75-80 km/h and at a reasonable speed too, but it has a different carb and HPI ignition, so far from bone stock again.
There was a guy in our town with a yamaha Rd50dx in 1980. I had a Zündapp ks 50wc with Drum Brakes and both run around 95 km/h flat The Yamaha was defenitly not tuned! You can find tests from German "Motorrad, where Rd50dx was tested between 90 and 95kn/h in the net. Ten years ago I had a Rd50Mx with the ysr 50 motor from 1982. It run 75 km/h when i got it. Somwhere in the net I found the ignition timing for the ysr and mine was set wrong. With this change it did 80 and was much faster in acceleration. I changed the sprocket and: 90km/h. In an Article from 'Motorrad' was a description of how to set the timing for the old Rd50dx. Many used the wrong setting from Rd50M and had no Power. Maybe that's your problem
I recently received the article from another follower with those tests. Very interesting article!
As far as I remember the ignition was set correctly, but later on I swapped it for an HPI ignition. Recently though the piston destroyed itself so it no longer runs, sadly enough. I was still looking for the missing power.
Also these were short acceleration tests doing a 400m sprint, not a top speed run. It did go 75-80 when going all out on a long road
É muito linda mesmo 😍
Muito linda!!!!!
Yamaha won't have over geared the bike so that leaves two possibilities, either the engine is not running correctly or someone has messed about with the gearing. Your calculated BHP would indicate that the engine is 'sick' (not in a good way!)
Just for something fun to do a couple of years ago I purchased a basket case of a Honda MT5, they were restricted to 30 MPH in the UK, I had one 40 years ago when I was 16. Anyway I've thrown all my 2 stroke knowledge at my 'new' MT5, it's doing an easy 55 MPH (88 KPH) even through I weight twice as much as I did when I was 16. The powerband on my bike is also pretty narrow, 7500 to 9500 RPM, because of this I've replaced the stock 5 speed box with a 6 speed box from an MTX 80.
In the meantime I did find some small things that could've been improved and some of them did help. The biggest one being swapping the mikuni carb for a dellorto. I have big suspicion the original carb has been tampered with. I'm suspecting the needle and the emulsion tube don't match. I have some new carbs to test, but I'm making some plans to actually make my own small dyno so I can properly test it! But I'm lacking some time currently. I'm slowly gathering parts and ideas to complete it 😁
Salut le kenny roberts belge! Ta yamaha est de toute beauté, j,adore cette déco des 70's 👍🙂🤘🏁
Merci bien! Moi je l'adore aussi! 🤣
Real science 👌
A real dyno would be more accurate and would give me definite results, but at the time of making this I did not know of any dyno's close. Now I know there is one, so perhaps in the future we put it on a real dyno
@@VintageGarageYT keep doing it your way fella, much more unique and entertaining in a UA-cam world of “same old”
@@neoquest2012 Thanks man! Really appreciate that!
80cc dirt bike motor swap would be awesome 🤔👍🤠👍
Nooooo 🤣
Not in an RD. I have other plans.of swapping stuff 🫣
Soo beautiful 👌 if it only could rev out on the 5th gear the results would have been much better. Maybe a smaller pinion gear next try. Love the video mate 👍
Thanks, yeah i have been playing around with gearing, this is allready one size smaller. Perhaps another one might help 😁
How is your fizzy doing?
My Yamaha TY 50 with same engine but only 4 speed (as DT50) + Kit Malossi 60cm3 + high compression cylinder head + sawn off piston skirt + expansion chamber reworked = 85 km/h followed by a car. Don't forget a big detail in tests: we were teenagers, we had to weigh 50-60kgs with all our muscles!
Seems reasonable! A TY50 is also on my 'want to have' list. They look like a lot of fun! Weight off the bike and rider have a big influence on the smaller engines!
@@VintageGarageYT Pure chance, Sunday at a big collection of classic cars, there was a TY 50 (my last video at 15 seconds) fully restored with original condition, a magnificent job. We discussed mechanics, the bike belongs to his wife who wanted the same as when she was 14 years old. He told me that there were only 7 left in the world in this state.
@@partis2288 that's awesome! Not many ty50 are around in general. The bike was not that popular back in the day, so sales were slacking.
@@VintageGarageYT I just have one last question that I couldn't find answer to when I was teenager. DT-TY 50 is 4 speeds, so I wanted to put the 5-speed gearbox of an RD, but I never found any. Are engine cases of TY/DT 50 the same as those of the RD?
@@partis2288 they should be the same as the RD50 M model. The DX like mine has a 5 speed, not sure if the M has 4 or 5 speed, never rode one.
The DX engines have an engine code starting with 353. They also have the aluminium cylinder which is highly desired
Yes, there is probably something wrong with it. A Zundapp 6.25 is much, much faster. The top speed was kind of like a 2.9hp Zundapp, if you changed the gear ratio.
Been playing around with it. It reaches 80kph now. I think wouldve done that also at the time of the video, but it just took way too long.
Interesting video. Honestly I don't trust most people claiming amazing speed and acceleration stats. I'm french and into mopeds and it's the same story: few people are objective, most just inflate numbers. When we were teen me and my brothers had many performance parts and we did our best to put an end to all the exagerated stories we heard about moped performance.
Anyway back to the topic. You probably have found it already but if if you look for "ZSEFT- ZUNDAPP le grand test des meilleurs Kleinkrafträder" on the web, you'll find a serious german test where they compare 50cc.
Here what they find for the yamaha 50rd: 4,96 hp at the rearwheel, 0 to 70kmh 15,9, topspeed seated 80,4 kmh (prone 90,8 kmh). May be they had a top shape rd and yours is a bit "tired".
One factor to keep in mind is that the size and weight of the rider has a substancial influence on the performance. Japanese test riders were probably more like 170cm tall and 60kg.
Yeah you are completely right! Nowadays everyone is superfast on claiming big numbers on these small engines, but in reality its a whole different story. No one can actually back it up. Mine is indeed a bit off and I've found some improvements allready. Have not found the test you mention. Will have a look at it!
I just read the article! Very interesting! I wonder how they achieved 77kph while riding duo. I think mine would go backwards when I have a passenger 🤣🥲
You and vintage garage and most or all friends around you guys know very little to nothing about HOW TO MAKE A 2 STROKE FAST 😂😂😂😂 for 40 years already every 50 cc from Japan the professional mechanics CAN MAKE IT GO 100 VERY EASY. But ofcourse you have never seen it in your life, in your garage, in your streets , 😂than it seems like a bluff. I feel so sad for you and it really hurts me to read your comments. I am 52 and you talking about stuff we did when we were 18. And still you didn't figured it out. Right now I have a rd50m standard engine, standard ignition, 42mm cylinder 2w1japan(ported), cylinderhead 42.5 (bell-ported)3klep membrane polini, 16mm mikuni japan(original ), racepipe , 3clutchplates. @12000rpm, 100km/hour in under 400meters, EVERY GEAR IS VERY POWERFULL AND CONSTANTLY IN TOP RPM WHILE SHIFTING, WHEN YOU SHIFT 5TH GEAR .... BLAST😊😊😊. LEARN TO DO IT OR SHUT UP, BECAUSE... WE... SEE ...A .... DOMBO.
UUURGHHHH
The 50cc HONDA MB5 had 7HP, and hit 53 MPH flat out.
Awesome! Will have to find one to make a test on 😁
Beste ik heb van mijn 16 tot daags voor mijn 18 jaar met dezelfde dx gereden, die van mij reed altijd 100 km/u tot aan het rood(10000 t/m). Heb 40000 km gedaan in 2 jaar tijd en heb tegen alles gereden wat er op markt was, Niks kon mij volgen of het was ook een dx. Uw dx draait niet goed en er zal wel een reden zijn waarom die aan 9000 toeren dood valt, heb de mijne 2 keer moeten door laten gaan naar 12000 toeren omdat er een camionet met oranje streep mij wou inhalen, toen reed hij zelfs 120 km/u, ze hebben mij niet kunnen snappen.
Zo'n verhalen hoor ik wel vaker. Ik ken er heel weinig die het ook effectief waarmaken. Ik zeg niet dat je liegt, maar ik moet het eerst zien voor ik het geloof.
De mijne is volledig gereviseerd en correct afgesteld. In 5de was hij niet vooruit te branden. Misschien dat hij wel heel snel gaat in 5de in hoge toeren, maar als je er niet geraakt ben je er niet veel mee. 😁
@@VintageGarageYT yamaha rd 50 dx 353 topspeed Deze klinkt wel heel anders dan den uwe. Aja nog vergeten te melden dat er bij mij een Fostham carrenage op stond
@@filipd.2976 Bedoel je dat filmpje gefilmd op de tellers? Het is van zo'n lage kwaliteit dat je er eerlijk gezegd weinig van kan maken. Geen idee of die ook origineel is.
Ik heb er 2 gehad tussen mijn 16 en 18, en zat in een club van RD50DX. De zaterdagavond gingen wij vanuit Oostende naar Blankenberge met als doel de eerste te zijn bij aankomst. Wij reden allemaal tussen de 105 en 120km/h. En zoals u zegt, deze in het filmpje is slecht afgesteld. Oorzaak kunnen de tandwielen zijn, valse lucht, doorblazen van de pakking, te kleine sproeier, uitlaat binnenin die niet gekuist is, aanslag op de piston, versleten segment enz....wie weet wat, en het is leuk om uit te zoeken en gemakkelijk om eraan te werken
Idd, destijds kon niemand met een andere 50cc ons volgen. Ik had een vriend met een RD50DX die 16000 rpm deed, mijne 12500. Topslenheid ooit behaald met achterwind 121op de teller, mijn vriend 126.....Grts 👍
Can u plz tell the cost of this bike 🙏
Sorry it's not for sale
A bike like this (in good condition) in the UK would be around £3000 - £5000 I would guess. :)
Depends on the weight of the rider too....
Exactly. Weight is a huge factor with these small engines
It seems like the squish is not good it should be around 0.7mm also try to play with the jetting a stock RD50dx is always faster then a fs1
Ive tried many different jets and ive concluded the carb has been messed with. Either the needle or the needle jet does not match. Im in the works for making another manifold to mount a dellorto D-slide carb.
Squish is 0.8 if i remember correctly
@@VintageGarageYT the squish is on the highside but still within tolarance if its really 0.8mm dont know about the dellorto why not buy a replacement mikuni?
@@mr.whiskers6273 I will definitely recheck squish, thanks for the tip.
Finding the correct replacement seems tricky. Not sure if the remakes are any good?
And I have a spare dellorto laying around. I heard the D slide is pretty good, so I wanted to try it 😁.
All about learning 😁
Are you allowed to go that fast along a cycle lane?
45 is the legal speed, so I went a bit over 🤭
Drop a tooth on the gearbox sprocket.That'll make top gear usable.
Yeah i changed the gear ratio a little bit. Now its also running a HPI ignition and reaches a nice 80kph. There is more in there, im playing around with some different carbs
mijn rdm gaat 45KM/H ongeveer in 2e maar valt al dood in 3e en berg op gaat niet hahah, denk dat ik me koppelingsplaatjes eens ga vervangen en een kleiner voor tandwiel en groter achter
Oei die vertanding lijkt inderdaad veeel te hoog! Wat zit er nu op van tandwielen?
@@VintageGarageYT heb geen idee, op zicht wel heel klein achteraan vooraan weet ik niet maar ik schat ook weer te groot, staat ook een 22mm dellorto op dus is een pittige setup :D
@@TeaserGaming 22mm op een standaard cilinder? Of is er aan gewerkt? Dat lijkt me ook veel de hoog. Standaard moet daar een vm16 op toch?
@@VintageGarageYT heb geen idee hoeveel cc, of wat er allemaal aan gedaan is hahah
@@VintageGarageYT maar idd, standaard zit er een Mikuni VM16 op
ooh yes he easily went over a hundred.
especially the RDX with chrome cylinder, different exhaust and different carburetor, different nozzles. remove all unnecessary clutter. (turn signals, fenders, mirrors, different handlebars for an aerodynamic position)
Throwing a bunch of parts at it, might indeed get it over 100. But this was a stock test.
Yes, don’t forget the optional rocket pack!
Fantic caberlerro 7.2 hp would do over 60mph…FS1E was 4.5hp
Yeah I've heard a lot of stories about the fantics, need to get a hold of one!
My honda xl70 could sit on very close to 80km all day long
Never ridden an XL, I hear they are ok bikes?
@@VintageGarageYT they were it was a 1973 model
@@bigears4014 awesome! They do look great!
😂😂 that's a very lazy rd50m(x) , I got a 42mm piston/cylinder ported, 16mm mikuni japan, racepipe,5 speed, 3clutchplates ,103km in just under 400meter, very badass powerband ,5th gear is very very powerful. It's not difficult to do, in fact very very easy, I always wondered WHY it's so difficult for some people to make them fast. Easy to make very vast-> ->
1: rd/dt50m(x) 42mm-45mm
2: mt/mb50(x) ,, ,,
And all 50cc older japan 2stroke. Want to see ?
They are good platforms to tune, but that's beside the point of this video. The point was to test a bone stock bike and these were the results. Throwing parts at 1 bike and comparing it with a bone stock one isn't really a good comparison is it?
those people were probably 16 and less than 50kgs weight
Most likely yeah. I'm definitely not that anymore 🫣🤣
Gearing is too tall. Drop one tooth down on gearbox sprocket to allow the engine to enter the powerband in top gear.
I changed the gear ratio after. This was the original stock ratio. Also has an hpi ignition now and it actually gets to it powerband now at top gear
You have a very slow RD50 - mine pulled in 5th. You also need to get out of the wind. There is absolutely no ways the FS1 was faster than the RD50 - all RD50s ran rings around the FS1s
My fs1 wouldve beaten the RD in acceleration anytime at that point in time. Now the bike has some mods and it will probably be a closer call. Might have to redo the tests.
The speed of the FS1 and RD50 depends on the date and in which country the bike was sold. The FS1E was sold in the UK from 1972 to 1977 with the ability to reach about 75km/h. The RD50 was introduced in the UK in 1978 or 79 and from the start was restricted to about 50km/h, as was the FS1M which was a restricted version of the FS1E. All of these models can be modified so that they will go much faster than they did as sold. The RD50 in this video is much faster than this model in its standard form as sold in the UK. Not many of the restricted bikes were sold in the UK until 1979 because dealers had bought in large stocks of the unrestricted models and registered them before the restriction law came into force on 1 August 1977. For some years after 1977, 16 year olds could still legally ride the unrestricted models provided that they had been registered by 31 July 1977. This was later changed in the UK because 16 year olds can only get a licence for Category AM, which is defined as being constructed so that it cannot exceed 45km/h. This means that the unrestricted old mopeds are not Category AM and are now in the same position for driver licensing as a 125cc bike.
You need to be flat on the tank for speed runs…sitting up like a sail is no good…lol
I had one of these…restricted to 30mph…utterly criminal waste
Yeah I came across some restricted ones. Luckily they are pretty easy to derestrict
100km/h is easy with a RD50!
Learn to tune!
Lol, prove it.
@@VintageGarageYT try a smaller sprocket on the engine, 5th gear is too much to get up to good RPM.
@@lasdop ive been messing around with the gearing before. But im having some carb issues now that need solving
It's starving for more air in 5th, take off air filter and try again.
I can't anymore, my FS1 was confiscated by the police in 87.
I ran way over 100 km/h!