Forum Corner

  • moppet/DT125 SM/story

    Check out this bulld, if you have not already seen it.


    I have been looking into Porting options for the 3MB00-P, Wondering exactly about these claimed BHP figures I've found over the Net. I'll quote, Factory stock Yamaha TZR125RR 4DL Y-2 - around 23-25 BHP. Couple of dyno's prove that, Seems about right. I can't imagine pressing anything more out of it without a completely Re-worked cylinder. With minor induction improvements to follow.

    Looking at the porting on the 3MB00-P it's very sedate (being a production road bike of course)

    The Gilardoni Barrels were Re-worked in Italy and present the holy grail SPR. Claimed these SP's could make 28hp. Pretty much a race bike. Must have some impressive Boost porting and Transfer arrangements. And they do. The exhaust port is extreme. Found some pics on here to illustrate. Really interesting. HP figures are useless unless your road racing competitively. So got to think about what is practically, realistically a fast tune.

    Made some plans for an aggressive Mid range' barrel. with a TM32. I can't see there being enough 'Signal' with my PWK36 in a expectable range. Yamaha - Mikuni. Made for each other.

    Hmmm. And it does fit. Standard Reeds are pretty up to it for light tuning.

    Inquired on a WR200 Cylinder, Cylinder Head, Piston, and YPVS drum. With some life in it. £400. Alot. Would be Performance Issues sorted really.

    Just use the internals into your block. if you run a later CDI model. It is a WR200 engine (3XP)s. They have quite Racey Porting actually, An endeavour I cannot afford.

  • Ahh the SP.

    Yes what a bike. The banana swingarm ftw. I don't know why but the higher spec bike all run it so it must be lol.

    So the 3MB00P i have I sent to Mick Abbey for porting. It came back bigger exhaust port and gas flowed ports. Even with my setup which is pretty much everything I will not be hitting 20+ bhp. I will get it dynod one day and we will see.

    Ultimately the dt was never meant to be a racer. Try as you will. Do some subtle mods, I highly recommend the zeel it will make the biggest change throughout the rev range and good price for the money. I ran it on stock 3mb and p can't say I noticed a flying difference.

    Then you want a good exhaust, dep gave nice performance but terrible build. I cannot comment on any other but I hope my underslung will be superior.

    A good carb, can't say I noticed a difference but I am sure it will.

    And well worth getting the head squish band since that is only 30 quid and it's where you will make or break power.

    Chase power all you like, that bike is not a racer. You should be more interested in torques on a bike like the dt. And the Athena kit should deliver that. Poorly I might add. But it does deliver.

    The SP barrel. Well it is and it isn't special.

    Sure it's a limited production run barrel with beautiful porting that you could only get from remoulding the barrel.

    But it's no better porting than an RS125 barrel of which there are thousands. Or the YZ porting of which there are thousands.

    The rs wins because it's a road going bike. My brother has both. And always thought the YZ would make for an epic ride and he is sorely disappointed. Sure it's great up to 50.

    My point being that if you wish to persue high power, do not be tempted bt shelling out a small fortune on a barrel because it's a direct fit and rare.

    The wr200 is a good example and I believe a zeeltronic is available. Maybe. Can't remember.

    The dt can deliver great performance as you say in mild tune. The tzrr Belgarda sp no doubt ran 28bhp it was a superb motor. Something Yamaha could replicate today if they so wish. It was nothing special in terms of power output only in terms of production.

    Love this topic and I did once wish to own the sp barrel. But quite frankly it simply isn't worth it. Even my setuo with a portes 3MB i wouldn't do again since it wasn't worth it.

    The zeeltronic wins every time of that wow factor. The noticeable difference is obvious.

    If you want high powered dts then engine transplant.

    I remember Scrimustang working on a yz125 top end swap which would be well worth a look into! Parts more freely available and barrels are cheaper.

  • True, never going to be a stonking' racer. Certainly room for improvement. Needs more punch to get through the gears

    Don't want a Terribly expensive DT without any low range get up. I've got short gearing for an SM setup, Revising the induction and Barrel should raise the Top end enough. Think there is a bit more to be had with a 3MBP. I really plan to play hard on it. Not used for much else.

    Would like to SM' setup an KTM EXC 200 instead, but it's more fun offroad.

    I'd say my standard DT, with a revised Airbox and Jetted properly and Dep is probs around 18hp. They are 17-20hp de-restricted. New. Definitely will be interesting to see your's on the Dyno.

    Looking at lighter Crank shafts, Nothing fits. There's a nice modification. I know the TZRRs are a little better.

    I'm really looking forward to playing with the Ignitech. Wish I left my old gearing on there. I was never far off finding 85mph (prone) on a flat and windless day. Bloody sketchy on the old' front end.

    I've not seen much on using a YZ barrel. But I do believe a 1987-1989 YZ125 barrel would fit'. because they were 'case reed' and look to line up on a DT/TZR crankcase. Transfer ports line up sort of as well. I had a look at it a while back. The Power valve drive is on the other side on the YZ barrel. I deemed it to be alot of arseing about. Could work though.

    If an SP barrel came up for sale. I'd probably buy it. Not for it's potential, it would just be sweet to have one. A bit of Yamaha 125 history.

    @calum btw Do you run the TZRR gearbox?

  • Yeah I know what you mean. I have been down that road before and look at the possible ventures. My DT was running a nice power output but it was never faster than my brothers rs125. But I never had it spot on.

    Honestly don't waste money on the sp barrel. Last one I saw.sold for €700's and it was climbing hard.

    That's the one. Scrim was working on would love to know how he got on! I am sure he wouldn't have been far off!

    But for the price of onw of those barrels it would make a viable solution. However bigger is not always better.

    My advice to you would be to pick up Graham Bells Two Stroke Performance Tuning and that will tell you most of what you will want to know.

    I genuinely think for power gains you want a transplant for power unit. But that's my opinion. If I worked harder I bet there would be more to had out of it. I shall see when I rebuild the bike in the next couple of weeks where I was going wrong.

    Yes TZR box, again wouldn't recommend it. Was nothing special at all. Worse in fact haha! Sixth gear was pathetic and I guess designed to just push the bike that little further.

    Dt gearbox should be all that's required and just the right sprockets.

  • I will say though, love the thought and what not. And if you want to do it fair play.

    Only just saying I have spent X amount here with nothing substantial. I have spent enough on that bike now and if I had my time again those would be what I would do.

    Barrel porting is an art and imo the manufacturer got it right. A little here and there that cures obvious faults are perfect. But overly porting a barrel that Yamaha spent millions developing is unwise.

    Just my experience on the matter and hopefully it helps derive a good solution. If we find something makes a massive difference then great.

    As said I think a YZ barrel has that potential, but there are a lot of factors that affect performancr, not just bigger ports.

  • 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. 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 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 .