What was I thinking!…
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Yeah, I know. It’s just while it’s apart and all…
You should see the stanchions that caused this
…Weird thing: my rotor has something ‘inside’ it that rattles back and forth. Sounds like a single ball bearing or washer, but it’s behind the magnet ring it’s doing my head in. WTF?!…
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I really wanted to. I’ve even thought about making or buying a vapour blaster if possible. It’s just time, availability and money. They never seem to come together
…I did it the old fashioned way, with a toothbrush and elbow grease
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Though you wouldn’t think it’s clean to look at it!! But I never put an engine together if it’s got grime and loose crud on it that can contaminate the interior…——————————————————
Edit: Just saw my first SDR200, it’s on fleabay. What a gorgeous little bike!…
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@SpookDog said in What was I thinking!…:
Anybody got a spare clutch cable bracket? The one that bolts onto the base of the barrel, that they want to part with?…
Also, do RE’s have a third cable running from the power valve servo to the oil pump cable?
No? Why would the RE have a third cable going from the servo to the oil pump cable?
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@Calum I thought only 250cc+ Yamahas had the third cable from the YPVS servo to the oil pump, so I looked at the 4FL TZR125R on Yamaha France and sure enough, it's shown as part of the throttle cable!
It's known as a "see-saw linkage" and its purpose is to further increase the oil delivery rate when the YPVS opens and the bike comes on the pipe as this is a high load application when the engine needs a lot of oil. It was fitted to the TDR and TZR250 parallel twins and probably the Reverse Cylinder and V-Twin TZR250s as well.
I was very surprised to see this on a DTR-derived engine, I guess this combined with the strange looking ignition advance curve and plated bore as standard all point to the fact that the TZR125R is meant to rev a lot higher than the 10,500rpm you can expect from a well-sorted stock DTR.
https://dt125r.co.uk/post/30119
Interestingly the original 2RH TZR125 which was released in 1986 was also well-known to rev to around 12,000rpm when derestricted, and whilst they didn't have a plated bore the 2RH cylinder and head did have a weirdly enormous water jacket, I mean they were roughly the same physical size as a Suzuki TS250X top end or something like that. Looking at mates' TZRs as a youth I always thought it looked a bit out of place sat on what were basically DTR crankcases (the TZR125R plated cylinder is outwardly the same as a 3MB DTR cylinder IIRC). I think this was an attempt to achieve the required heat transfer into the coolant for those kinds of engine speeds without the expense of a plated bore as this was fairly new technology in the motorcycle world in the mid 80s.
I must admit I was never a fan of the 2RH engine, I knew a few people who made them quite fast but they had a weaker clutch than the DTR, and also a particularly horrible front sprocket retention using one of those little locking plates and two M6 bolts like a C90 step-thru meaning if you buy a 2RH TZR125 to restore today, you can pretty much guarantee a knackered output shaft. And very low compression for some reason, whenever someone let me have go on one I thought it had blown up just kicking it over. Yamaha made some intelligent mods to make it strong enough for DTR use.
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Yep, it does look like it gives the pump a boost when the power valve is open.
Mine isn’t a 2RH though, it has a 5 spring clutch and is stamped 4HW. Looks like an RE engine but was made in 1993-4. IE: electric start & reversed rotor. Also oil pump is ‘same as’…
From the little reading I found it seems like Yamaha were touting +30bhp @ 11500 rpm (IIRC!) This was with a 4FU barrel and a 30 or 32mm dellorto though. Mine has a 28mm Mikuni sized inlet rubber mount, and more telling a carb to air box rubber that fits a 28mm, not a dellorto which has a much bigger inlet mouth. So I guess there were different iterations…
This bike is a bit of a dark horse because of the really low production run. PITA really
especially for spares! 3XV (body panels) & 4FL seem to share some parts…I need to get two new power valve cables. They’re about two foot long! Any help appreciated! I’ve looked and can’t find any…
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@SpookDog No it won't be a 2RH engine, these were (thankfully) only fitted to the original TZR125 which looks like this:
The TZR125R with the Dell'Orto carb was the Belgarda version which was manufactured in Italy, I'm not altogether sure what the other differences are between that and your bike. And yes, not many TZR125Rs were sold even though it was officially imported by Yamaha UK (the type you have with TM28SS carb, 3XV bodywork etc.) which means even fewer were properly derestricted.
Powervalve cables, well this is a fantastic opportunity to take a look at my home-made YPVS cables post as this should work with any YPVS-equipped Yamaha:
https://dt125r.co.uk/post/28693
Whereabouts on the bike is the servo located? If the cables are this long as standard, this bike more than any other could benefit from inline cable oilers, and MTB outer gear cable is sold by the metre.
I don't know much about these but as more details emerge it's beginning to look like Yamaha wanted this bike to compete directly with the Cagiva Mitos etc. of the day and put a lot of R&D into adapting the DTR engine to achieve this.
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I never removed the servo but it looks like it goes on the right hand side. Kinda under the throttle and behind the radiator. Hidden by the fairing…
The adjusters snapped off clean to the PV housing. I had to snip off the nipples to separate it all. So they are prime candidates for resurrecting
With new adjusters and yes! oilers! Or maybe new all through if I have the resources …It doesn’t have the 41mm sp forks or even the gold ally ones fitted to the other R bikes. These are steel tubes. Upgrading should be straightforward. I just hope bushes are easier to get for the Paioli (sp?) forks
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Wow! I didn’t realise that the hard chrome on forks could take so much wet’n’dry action! Gave them both a good going over with 800 grit to get rid of the puckered edges of the pitting that is so sharp it cuts the seals up badly. Now it’s smooth to the touch, but I have a lot of bad pitting over both stanchions from the seal line down. Especially bad at the seal line. Next I’m going to clean out the pits with a diamond tip dremel tool, then I’m going to fill them with chemical metal…
Seals still haven’t turned up, I’m going to have to get another parcel fired off…
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It's interesting to read about the YPVS oil pump action.
All I will say is, the Cagiva/Aprilias don't inject more oil on pipe. So I don't see the need for this capability. The pumps on those engines are Japanese Mikuni oil pumps and they seem more than up to the task of delivering enough oil.
Also, the RD350s don't run them either, even when highly tuned the stock oil pump flows more than enough oil!
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Getting it together, bit at a time…
The back barrel studs are longer on this engine. I’m thinking maybe a guide bracket fits under the nut…
One thing I always do now is clean all the engine casing/ect thread holes with a tap and the bolts with a die. I even clean my nuts now
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What?! It’s a racing plug! A lad sold it to me along with a 350 main jet to make it go faster! See the way it’s straining to go forwards faster?
That or it stops dust & acorns falling in the barrel
I wish I’d took pics of the piston in the bore, such a sweet fit. I love PJME freshly rebores!…
Thankfully I found a clutch bracket in my bits box, along with the PV & housing that I don’t remember buying
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Filled and sanded
I am not recommending anyone do this !
That said, if I close my eyes and run my fingers up and down I can’t feel anything untoward at all! Before it would of grated a lemon…
Just waiting on another parcel of fork seals to come, the first one got itself lost in transit. That and some aluminium silver spray paint and zinc primer to finish the swingarm and (bolt on) frame down tubes. Then I can mount the engine and move towards getting it running
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about it. An air of ‘solidity’ in knowing that it’s tight…
