So Close!...
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@MadGyver
Thank you bud! That’s the best info I’ve been able to find about early dtr RPMs’ and I’ve been searching!
…IMO, My bike feels like it’s reaching its max rpm with the valve closed before the the servo opens up. I’m thinking that if the servo opened 1000rpm earlier it would be a smooth transition. I could well be wrong though!
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@SpookDog said in So Close!...:
@MadGyver
Thank you bud! That’s the best info I’ve been able to find about early dtr RPMs’ and I’ve been searching! …IMO, My bike feels like it’s reaching its max rpm with the valve closed before the the servo opens up. I’m thinking that if the servo opened 1000rpm earlier it would be a smooth transition. I could well be wrong though!
…For smoother operation search also the reed valve major component for that,see at my project topic for some info,down to the last posts.
My bike was very ok until 8K but after that was explosive almost burnt my clutch disks.It revved really hard and instantly to the 12K with the boyesen dual stage. -
@MadGyver
Cheers bud, will do…One thing I’ve noticed with the stainless steel exhaust is it kinda ‘rings’ at certain revs, like a bell. It’s quite strange to get used to. I thought it was engine noise at first…
Anyone else get that with HR or other stainless pipes?…PS another question: does the CDI tell the power valve when to open? Or does it just provide RPM info and the servo is hard wired to open at a certain RPM? This is 3 wire servo’s only. I understand that dtre 5 wire servo’s can be programmed if you have the right aftermarket ignition system, but doubt it’s relevant to early, pre 1996 models…
PPS is there a manual for after 1993 TZRs? I have a Mikuni 28 flatslide (Yamaha, with the 12*deg slant & coolant pipes) that has different 1mm cutaway slide, needle jet & tube, ect, internal setup. I was told it was from a 4dl iirc, but I’d like to learn more about it properly…
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@SpookDog said in So Close!...:
PS another question: does the CDI tell the power valve when to open? Or does it just provide RPM info and the servo is hard wired to open at a certain RPM? This is 3 wire servo’s only. I understand that dtre 5 wire servo’s can be programmed if you have the right aftermarket ignition system, but doubt it’s relevant to early, pre 1996 models…
On 3-wire servo systems (3BN, 3NC and 3MB) the CDI just sends engine speed information to the servo via the black/yellow wire (i.e it pulses once per crank revolution like the crank sensor on a car). Inside the 3-wire servo there's a small onboard computer (just a PCB) which interprets this and decides how far the valve should open at a given engine speed. This is the reason the 3-wire DTR servos are so expensive and difficult to find (IIRC almost every other YPVS- and EXUP-equipped Yamaha runs on the 5-wire servo system where the CDI takes care of all this and the servo is just a servo like the ones you get on a radio-controlled model).
I once bought a 3NC where the 3-wire servo did its cleaning cycle when switching on the ignition, but didn't respond to engine speed; a replacement servo cured it meaning the PCB has two separate circuits, one for the cleaning cycle and one for engine speed. If you apply 12v to the black and brown wires with the 3-wire servo removed from the bike altogether, it still performs its cleaning cycle (brown is +ve main feed from the ignition switch on Yamahas). I once watched a Suzuki mechanic use a piece of test equipment to simulate an RGV250 revving to over 14000rpm to test powervalve operation (the electronic tacho was displaying the rpm and the plugs were sparking and everything even though it wasn't actually running). Zeeltronic ignitions come wired for either 3- or 5-wire servos; they advise running a 5-wire because it's more tuneable. There's also a guide on their site showing how to turn a 3-wire servo into a 5-wire (this allows you to remove and store the PCB and return the servo to a 3-wire if you ever want to go back to the stock CDI).
Not sure about the CDI for the earlier round slide carb '88 bikes (I think they're etched 3BD but I've never seen one) but the flat slide carb 3-wire servo CDI units are either 3NC or 3MB and the wiring is:
3NC
Black/yellow female bullet
Blue/yellow female bullet
Black/white female bullet
Orange female spade
Blue and sky blue female 2-pin connector
Black and white/red female 2-pin connector
Black/red and green/white male 2-pin connector3MB
Black/yellow female bullet
Blue/yellow female bullet
Black/white female bullet
Orange female spade
Blue male bullet
Black male bullet (2 black wires into one terminal)
Black and white/red female 2-pin connector
Black/red and green/white male 2-pin connector3NC and 3MB engines are mechanically identical, both should rev to around 10.5k stock but I found the 3MB to have a lot more power at the same engine speeds; the 3NC still went well, was fun to ride, revved out OK etc. but there's certain places on my regular rides (steep hills etc.) where the 3MB just keeps revving whilst the 3NC runs out of puff leading me to suspect the 3MB ignition advance curve is different. Unfortunately 3NC and 3MB looms are also different meaning you can't just bung a 3MB CDI on a 3NC bike (hence my decision to opt for the Zeeltronic/5-wire servo setup on my 3NC which has now been sold).
This could be for a number of reasons; my 3MB is the highest mileage DTR anyone has ever seen with nearly 70,000km of Paris commuting racked up but when I replaced the head gasket not long after buying it I measured the bore to be standard 56mm leading me to suspect the previous owner had the engine rebuilt (possibly with a non-OEM head gasket) just before selling it after umpteen rebores. And interestingly I changed the head from a 3BN to a 3MB at the same time and it made no difference (i.e it was fast even with a 3BN head). But I've owned two sub-6000 mile French import 3NCs (a '93 and a '98) and they both felt exactly the same. And all three bikes ran stock jetting (including having the power jet connected) according to the Yamaha France parts lookup where you enter your VIN number and they tell you the jet sizes for that particular bike by part number.
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Thank you, this is the good stuff that I need to know. I have another 3 wire servo that opens & closes much (3x slower, I thought the motor was fubar) slower than the one I’ve fitted to my 88. I’m going to try fitting it and see if it opens at something useful to me. I remember reading that some open as late as 8K+ (tzr) & some as low as 6-7…
I noticed no performance difference between the MB & BN heads either, at all. The 3bn was actually a lower CC (measured with liquid) than the MB which would make it higher compression! Go figure
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@SpookDog This geezer seemed to have differing opinions.
https://yamahaclub.com/forums/topic/20583-de-restricting-my-dt125r/?page=6
And noted his 3MB head made more compression measured with a guage than the 3BN. I know others also remarked at how they noticed more mid-range.
Years ago when I was a wee lad and I went from a restricted CDI to green & black wire earthed and eventually to a Zeeltronic ignition system, I noticed no performance increase. It was only when I went back to stock ignition when my CDI developed a fault that I really appreciated how good the Zeeltronic was, then earthed the Green & Black wire to be surprised at what a difference it made.
The thing is, the difference might be quite small and hard to detect, it's not like slapping on the 170 kit and increasing the displacement by 30%+
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What’s your take on the Romeu Henrique pipe (or any stainless steel pipe) Do you get a ringing/humming at certain revs or speeds? Like a cross between ‘blowing across a open bottle top’ & one of those weird metal bowls that ring when you rub around the rim…
PS, on the MB v BN front, I don’t think there’s any real difference between them, not enough to call one ‘performance’ and the other ‘restrictive’ or to even argue about anyways. I think maybe it (the 3bn) seemed like a good idea at the time, but didn’t stand the test
Either way, I’d always pick the 3mb head if given the choice! … -
Sweet! New thing!…
Speedo has stopped working, happened all of a sudden. Cable is good, stuck a small screwdriver in the bottom of the speedo and spun it and the needle goes up, so I’m guessing it’s the impossible to find gear at the wheel. What are the chances of it failing all of a sudden with no warning? I would of expected slow failure as the cogs teeth gave up the ghost? Strange thing is the speedo bulb went at the same time
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@SpookDog the speedo drive at the wheel is quite a common failure on these. With the cable removed from the clocks you can spin the wheel and check if the inner moves. They are still available new from Fowlers for about £50. Strange that the bulb stopped working same time but surely that has to be a coincidence?
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Yeah, the hub drive has failed, it did have a bit of a needle wobble at 50-55 before for a while, as I’ve now remembered! My bad memory is the main reason I document so much info in this thread. I used to rite it down on bits of cardboard (aka my work bench) and pads, but I was always loosing them or forgetting to date them…
I checked the cable was sound then removed the speedo, put a bit of tape on the end of the top inner and checked to see if it was spinning, alas it was just sat there, useless as me
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There’s a tiny pin that holds the brass insert into the gear housing (that the speedo cable screws onto). Has anyone ever taken the worm drive out? I can’t see if it’s a tiny Allen grub screw or a press pin that needs to be drilled out? Anyone help?…
The worm drive has seized on mine and I want to take it out and free it off…
The worm drive (that the cable fits into @ the hub) has seized solid, the ring gear is intact, but the 3 tabbed/pronged ring has had the tabs bent down on it. If I can dismantle the worm gear and get it turning again I can save the unit. It’s just getting out the pin/grub screw thing so I can remove the brass threaded cap (that the speedo cable screws to) and get to the worm drive/shaft… -
@SpookDog It's a hollow roll pin that holds the worm drive into the speedo drive housing. I've repaired a couple of plastic ones, IIRC I drilled a small hole into the housing from the inside enabling me to tap out the pin (I think I might have even made something smaller in diameter than my smallest punch to do this). Then once I got it all apart and freed off I used a split pin to keep it all together on reassembly. Also bought a load of shims the correct ID/OD as the worm drive eats into the plastic as it rotates. And you can get the seal where the unit fits onto the wheel hub from a bearing shop, I think Ashley Bearings in Poole are pretty good. Well worth replacing as they leak sometimes, and you can get ones with a garter spring (better than OEM) meaning you can really pack the unit with grease once it's fixed.
An aluminium one might be more difficult as there's potential for the roll pin to seize into the housing so maybe a bit of heat after you've drilled it?
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Ashley bearings, in parkstone sill going? I wish I’d known that before. Cheers bud…
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This is the pin holding in the brass threaded coupling
You can see it’s possible to drill from the rear but it’s such a small diameter. If I do drill it from the rear I could use what’s left of the pin and drift it in with a micro punch afterwards…
I would rather mend & resurrect the original part just because I’m a mean, stubborn git! Besides these genuine aluminium parts are going for fucking ridiculous prices! Some people have no (or @ least less than me) shame! I’ve seen nearly £120 asked for
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I’m assuming that the brass coupling has a groove in it that the pin ‘bites’ into?…
PS: no input on the stainless steel pipe? I hope I haven’t caused offence! I know that I can be quite abrasive sometimes when I drink the Brew. Please, just don’t take it personally. I’m tetchy with the World in general, not specifically
not on purpose, anyways 
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@SpookDog Yes there's a groove in the brass coupling for the pin to retain it. If you can get the roll pin out intact it would be perfectly in order to re-use it IMO, although it might not fit as tightly as when installed by the factory hence my decision to use a split pin the same size.
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@SpookDog Like this, looks neat enough but it can always be taken apart again if necessary. In hindsight I could've used an M3 CSK screw from the RC car box but that would have meant countersinking the housing to match and being plastic, I wanted to disturb/mutilate it as little as possible
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Wow, so that’s what a clean one looks like?! Cool, when you said it was plastic and you drilled from the inside, I thought something else…
