So Close!...
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Cleaned out the carb and found bubbles of water still present in the bowl and around the main jet. Power is back to ‘normal’ though it still doesn’t want to rev freely up to and beyond 7K. I’ve got a few plans forming in mind, including swapping out another CDI I gotten (wish the original fitted had markings!) unplugging and ‘pinning’ the power valve to see if there’s a difference…
I’m really not sure about the crank after 20,000 miles of riding while missing at low throttle. The bearings are ok but that doesn’t mean that the Conrod is true…
I do have another good crank and casings, ect that I’ve been planning on building a ‘new’ bottom end lump. I just need to be able to focus on it without other problems stacking up 🫠
Remember to check the power valve servo closer, it appears to be opening at 7000 . But could be higher…
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@SpookDog From the digital readout it was reaching about 85 degrees then cooling down to 80 then spiking. So it would fluctuate around 80-85. But one day I made it literally a mile after leaving home and it went to 110. So I turned back and removed it and its been perfect ever since. Just takes a while to warm up.
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80-85 is the absolute wide open temp isn’t it it should open at 60-5. Definitely sounds like the stat failed to me, especially if removing it solved the problem. I’ve got a couple known good spares if you want to try one before paying out for something you think might not work…
Is your temp probe on the head or radiator or?
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Remember to remove flywheel cover and check rotation for any play/noise at TDC or during rotation. A random tapping/knocking noise has appeared during tick over since removing the oil pump/replacing clutch side main seal. Or since water in carb cut out episode…
Also fit rubber mounts and P clip mount to exhaust…
PS remember to turn off the lights when adjusting the carb, the drag caused by them is significant…
PPS didn’t remove the oil pump!!
Piston was a tight good fit when assembled. Am getting Tappety sound at TDC when turning flywheel by hand. Will check more through the exhaust outlet when pipes off for rubber mounting… -
@SpookDog said in So Close!...:
Cleaned out the carb and found bubbles of water still present in the bowl and around the main jet. Power is back to ‘normal’ though it still doesn’t want to rev freely up to and beyond 7K. I’ve got a few plans forming in mind, including swapping out another CDI I gotten (wish the original fitted had markings!) unplugging and ‘pinning’ the power valve to see if there’s a difference…
I’m really not sure about the crank after 20,000 miles of riding while missing at low throttle. The bearings are ok but that doesn’t mean that the Conrod is true…
I do have another good crank and casings, ect that I’ve been planning on building a ‘new’ bottom end lump. I just need to be able to focus on it without other problems stacking up 🫠
Remember to check the power valve servo closer, it appears to be opening at 7000 . But could be higher…
I saw you post and recently had a similar problem developed in my bike,remove your spark plug and test by touching somewhere on the engine,healthy spark is orange in color,mine was lighlty blue to white.Changed the ignition coil with a used working genuine one.Run's fine now.
My sympton's was hesitation to rev after 6-7k but was clearing and had full power after around 9k.It'looked like a carb problem and did 2 rebuilds with different jets.Sometimes had misfires but not at the same rpm's. -
Cheers bud, I will check it out…
Does anyone know how to find the CDI markings numbers to year? I’m sure I saw a page once that listed all the years of CDI and when they changed by their marked numbers. Also which ones were the least restricted? Any help is appreciated
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@SpookDog said in So Close!...:
Cheers bud, I will check it out…
Does anyone know how to find the CDI markings numbers to year? I’m sure I saw a page once that listed all the years of CDI and when they changed by their marked numbers. Also which ones were the least restricted? Any help is appreciated
…CDI 3NC no restriction,I ve revved up to 13500rpm on the road.
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Really? What year bike? Mines a late 1988 (28mm flatslide) that came without the servo (3 wire) I’d like to know what I should have or can use. My CDI has no marking. I think I can use any 3 wire servo-CDI, but: Nothing is ever easy!
I’ve actually got a 3nc-00 93n CDI I brought for £25-30 off of fleabay. Has 10 (or 11 counting looped black wire) wires, just checked it out! I only hope it works!…
Got a 4hw CDI as well… -
@SpookDog said in So Close!...:
Really? What year bike? Mines a late 1988 (28mm flatslide) that came without the servo (3 wire) I’d like to know what I should have or can use. My CDI has no marking. I think I can use any 3 wire servo-CDI, but: Nothing is ever easy!
I’ve actually got a 3nc-00 93n CDI I brought for £25-30 off of fleabay. Has 10 (or 11 counting looped black wire) wires, just checked it out! I only hope it works!…
Got a 4hw CDI as well…It's a 1990 model as far as I found,3 wire servo, 3NC-00 cdi,28mm flatside carb.Registered here in Greece at 1993 but came as a used bike from another country,not European.Although it says 4BL on the frame.
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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! …
