125 - 2 Stroke stuff

  • That is a great book. Very interesting read about tuning. And direct informative advice about the 2stroke. I recommend it too.

    Wow really, Always thought the DT ratios were pretty good. Good spread. Just a thought when the bottom end is due. Gearbox needs a referb, Used to not clutch up alot.

    It is a little un-wise to think we can be better than Yamaha. I appreciate this more than ever after Re-reading Bell's 2T Tuning'. The DT is a very nice piece of engineering on it's own. Excellent attention to creating a very user friendly product. I like how smooth these Yamaha engines are. Great design. Used to get 50ish,Mpg.

    Given me food for thought..I will go ahead with it. Think it will end up a 142cc by the end. Still need to De-coke the Dep Expansion pipe. It's the little things, it is caked up too fook.

    True. I am creating work for myself. I've got a tiny budget. It's meticulous. It's all about making it that little bit more special on pipe' on a Summers day.

  • I'm currently running a mikuni tm32, boysen dual stage reeds, 2x 5mm reed block spacers, custom inlet, athena 170 kit with 3mm port timing correction, custom stainless exhaust and 14-50 yz 520 sprokets and the difference over standard is remarkable loads more low down torque and a lot more quicker through the gears but run out of gears top end against my rs125 the dt Is quicker but on my gearing the rs would be better top end

  • @chalkey46 Your's is a little beast. Yeah those RS's go on much longer. I'm not far off you, got a 13-55 520 YZ drive. Shorter gearing over Standard. Probably only good for about 65-70 But it's alot of hillclimbs round the Cotswolds. Get the wheel up n all that. Quicker between the gaps in traffic haha.

  • Yeah fairplay Chalky hats off to you on that build. For me that's what I loved on the old forum and why I like forums. The uniqueness in peoples builds just can't be captured on Facebook. And I know the type on Facebook and it's not quite what I would like here. A more close knit community of DT enthusiasts who break the mould in innovation.

    Love.to see more pictures and what not!

  • Going to borrow a Dyno over Easter. See what's what. Just out if interest really.

    Shiny Red is just down the road from me.

    Thought I would share these vids. not to take too much away from them, just an interesting comparison and look at these claimed BHP figures.

    It's a TZR4DL with a 4FU barrel/head and extensively modified. Pretty interesting results.

    22.34 BHP@10147.3 rpm
    11.58 FT/lb torque @10108.8 rpm

    30.12bhp @11228rpm



    Thought about a swap ages ago. I like those old 4FU TZR's, Flat top pistons and better heads, more racey, but never interested in using a Nikasil barrel on the DT. Bit unnecessary, even though they have superior heat dissipation and arguably better friction characteristics.

    Interestingly, 14.3 ft/lb of Torque by their modified TZR. More than this RS. I know which one I would have.

    The MK1 RS. The only one to buy. Future purchase. They never looked as good after 1997.


    I'm all for the Yamaha 125's, but the MK1 RS is just better. Prefer one over a Mito.

  • That's not a true mk1. The true mk1 is the futura. They are the best looking. Agree though the chesterfields are very nice.

    I have a post on the 4fu barrels having owned a few of them myself. The 4FU heads actually have a restrictive combustion ring in them. Should be on this forum if you want to have a look.

    The rs was claimed 26bhp out the factory. And as we know deteriorate rapidly if left unmaintained. No doubt about the stock porting work on the rotax engine. They are far superior to thay of the 4fu and reflext more like the sp barrels.

    Dynos vary bhp from dyno to dyno. However I would take 30bhp tzr as a very very very well tuned bike. Someone has spent a lot of money on that one.

    Ultimately I look at the facts as they are presented to me.

    Aprilia rs125's are still raced in championships today. A lot of them in fact. I am yet to see a Yamaha TZR on thr track, and if I did I would put money on it being a sp not 4fu.

    And I would imagine the main rival to the RS is not the tzr but the tz instead. And the tz is an incredible bike! The 250's claim around 65bhp! And I know a chap who has one who claims they are a little less but still savage!

    Ultimately what evidence do I have. I am going on what I believe in having stripped both engines down. Rebuilt botb and tuned both. I have GoPro footage of my tzr belgarda engine against an Aprilia rs125 that my brother bought from a breakers yard.

    Fair enougg my tzr engine was in a dt. But it was portee witb a nice pipe and zeeltronic ignition system. It didn't lose by a hair, I got thrashed.

    So I have experienced both ends of the spectrum. I personally have come to realise perhaps the road bike engines are not the best for tuning. But they are still cracking bikes and nothing takss thay away from them.

    Would like to see an sp in the flesh and compare that to an rs. But ultimately the availability of an rs is what attracts me thr most. Knowing parts are accessible and tuning is there. The sp is a beast, but if that block goes then it's bye bye bike!

  • Do you mean the Aprilia AF1? I supppose it is the MK1. Forgot about that actually. But it's not in the RS series. The RS replaced the AF1. The Futura is the Series 3 AF1. They look pretty tasty from about 1991 onwards.

    TZR was never a competition design, that's the difference between them. Rotax does win. An RS has a much nicer chassis to start with.

    TZs are cool. 00's TZ125s are good for 42+bhp@75kg dry, It's a pure race bike. RSGP vs TZ, That's a good question.

    TZ ftw.

    A 2003 'Road Race' spec TZ250 was rated at 93PS@102kg dry weight from Yamaha. Mad! 90+bhp. Not far off a the YZR GP factory bike at the time

    TZRR vs RS I can't say which one is a better street bike, but on the track I'd pick a Rotax.

    Tuning potential is there in both engines, but the Rotax is a superior design for output already.

  • But it's not like Yamaha don't know how to build savage engines. Your tz example is prime case of that.

    I would say the futura is the genesis rs. Even though not called an rs. Its engine, frame and other components are the same. But I know what you are saying.

    If I could buy a crisp mk1 or futura I would. But they are few and far between. Plus the later rs models, whilst severely down on power, are better spec. Power can be restored.

    Yammy is a good manufacturers. Even Aprilias are high spec. For me, if we are going ftw stylie, has to be Honda. But I am a Honda fan boy. I have see first hand Hondas reliability and production. The Ultimate Honda RS125 yes sirie please!

    And a good point raised to me the other day. Okay the Honda Civic EP3 type r. I love them. Beautiful machines, not as fast as my starlet mind you. I was in a 150'000 mile ep3 being thrashed within an inch of its life. I shit you not. No exaggeration, the person I was with doesn't care about breaking things. Maxed out in 4th he dropped it into 3rd. And you could feel the driveshafts snap back from the compression. The car is still running.

    Hats bloody of to the lads in Swindon assembling those cars. Keep up the good work as the builds of Hondas are insane. Love Japanese quality standards!

  • Agreed, Honda ran the RS125 to a 130mph in a test. Honda make engines!

    Been around the older B series Honda's, EG6 and DC2s. Man knew a DC2 Type R that was running to nearly 12k! The old body shells are proper wafer thin, I'm sure those bread van' EP3s are better quality over all, but damn, mechanically, those older DOHC B18s are incredible. Honda engines can go moon miles, with a healthy thirst for oil, a bit like Wankels, they remind me of a 2stroke, NA weapons!

    Hats off to the Japanese, excellent engineering and just little racers out the box. I proper rate Honda's to.

    I like Japanese stuff in general, studying the language too, good fun. I never feel a true love for Japanese machines. They have less character than European stuff, never feel as special. I'm into to industrial design so I'm always thinking the feeling and statement of objects. Maybe they work too well?. I digress, love machines, love em all.

    I need a late 1980's Husqvarna WR and I'll be sorted. And a Japanese car to actually get to work no questions asked.

  • See I disagree. I think European machines have nothing to be desired for. The Germans invented the wankel engine. Saw no profit in it so left it. But the Japs saw the potential. Sure it mixes oil like a two strokw. And it has one power cycle to every rotation, like a two stroke. But they also make serious power like a two stroke. What innovative do the Europeans do that the Japs didn't do first, and cheaper. Look at late 80's Mercedes introducing features into their luxury models. Then look at what Honda and toyota introduced to their boggo models a few years later for cheap.

    Again a good example is subaru with the boxer engine. While they may be fuel consumptious and low on power. They are different than your conventional european design.

    And of course wonders like hondas vtec.

    There are only a few European manufactures that I rate. Volvo, and SAAB.

    You should have a look at Saabs innovative svc engine. 1.6 was pushong 220 bhp and saab claimed it would easily make 300 with still very good mpgs. The Americans bought saab and scrapped the svc. But I guarantee if that was a jap design or sold to the Japs they would have released it. Even if it flopped lol.

    Audi are raving over their new TFSI models. Turbo supercharge cars. Their flagships. But oh wait, Didn't Nissan already do this, 30 years ago...to their Nissan Micra!

    Japs all the way.

    I would love to learn their language. Is it hard?

  • Oh and Honda lmao. Have you seen their 5 cylinder GP bike that dominated the series. Their four stroke out raced all the other two strokes on the track!

    This was back when Honda, or rather the Japanese, didn't have the quality controls they have in place now!

  • You have to admire the Japanese tenacity, mainly there ascendency as an Industrial super power during the 1960s. They have pretty much just copied us folks in the Northern hemisphere for years, but yeah, they have made technology work for them, and subsequently the rest of the world.

    Japan sacrificed alot to be a competitive world power, there products innovated the cheaper market, and they dominated for years. Still do I think.

    Think the Germans pioneered the 2 cycle engine 30s to 1950s, used it for a bit.. Sachs built engines. Nice product made was the now quite famous Messerschmitt KR200. But euro cars and bikes dropped the 2stroke and it's design for the Japanese to lap up and invest into. And conquer massively.

    Haha, Japanese technology all the way, certainly more willing to actually produce the wacky and no conformist solutions. Nissan's innovation history is epic tbf.

    Japanese is quite hard, I'm just reading and writing it so far, It's simple, but broad with lots of modifying elements in speech and description. It's so different, it's refreshing and just pushes my curiosity.

    Try it. Helps out watching all the Best Motoring - Hot Version and Option NSTC stuff ✋

    That Honda GP bike is beast. New discovery

  • Back to a DT.

    I'm taken with this insanity. Saw this one a while ago. Now I appreciate this utter madness.
    This KR1 Hybrid death machine is just silly people. This one is a bike to shit your mates up.

  • I don't quite know what to make of that to be honest.

    It seems a little vulgar. Is that supposed to be a dt frame and rear arm. Like the wheels and underslung but perhaps the colour to me is a no no. Plus yhe conventional forks.

    Engine looks tasty though!

  • It looks horrific. Just a mad one. Not a fan of the Straight pipes on Supermoto's. I have to admit. The look is out of function with the chassis. Can't imagine eliminating the off-road ability completely, it's so fun, even on 17s .

  • Underslungs look sick lol. You won't like my bike when it's done then. Handmade underslung pipe will be fitted on mine. The wrap around pipe does inhibit performance and I was looking for a few more ponies. Plus hopefully it will be different.

  • Yeah they are certainly easier to make, and slightly better road race performance.

    Found this picture I took of my DT, 2 days after getting it on the road. Deep summer time in the woods, never been better.

    The rust is now an issue on my bike. Think she will be sorned off this year and boxed up.

    A full rebuild will take me a long time around studying. Got some new paint scheme ideas for it. And a special top end.

    1989 YZWR 250 , Blue on White is dope. Seriously want to design my DT around this brute.

  • @Darty yeah rust is a killer lol. That is a nice coloue scheme! Would make for a. Awesome colour scheme if you can get the right graphics to go with it!

  • http://www.ebay.co.uk/itm/Yamaha-DTR-125-Full-Aliuminuim-Swing-Arm-Rare-Item-/121900673515?hash=item1c61d8a9eb:g:TsYAAOSwe7BWyI5S

    Yamaha DT200R Swingarm! If you're not sure just compare the welds to the steel 125R version. It's legit.

    Alloy part of the same dimensions as the steel DT125R version. Straight swap. saves some much needed Kg's.

    Pricey as fuck, this can't go to waste, someone snatch it up and get building with it!

  • @Darty Good spot. If I hadn't just dropped my swingarm off at the coaters I would have snapped this up!

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