Can anyone tell me what type of Yamaha this engine is from?

[mal180]

I bought this engine today for a buggy i am going to make and belive its a yamaha 250cc 2 stroke?? but can any one tell me the model it is because i need a wiring diagram because the wiring in a mess and engine is not sparking!

https://i39.tinypic.com/10562ab.jpg
https://i42.tinypic.com/sdo9yo.jpg
https://i44.tinypic.com/11h3nsm.jpg[/img]

[Teflon-Mike]

I'm not SURE, but the metal sprocket cover & cable operated servo, suggests a road bike, not an MX machine, while the 124cm2 on the barrel would hint its a 125.... TZR?
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[mal180]

I just googled that and certainly the speedo and stuff is the same as a tzr indeed! So you think its a 125 any way i can check for sure? P.s thanks for the reply

[Pete.]

I'd say TZR except they didn't sell the powervalve version as standard in the UK. It's certainly a 125 as it says so on the barrel.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[mal180]

Thanks as i say the pics on google seem to be the same, what is the powervalve as i have no idea and have to try and get this engine going I have also posted this on several other forums with no reply so thanks alot for helping me out!

[Bomberman]

I'd say it's a 2RK TZR - the cylinder head on mine has the same 2RH marking. I don't believe the engine changed across the models so any TZR wiring guide should be fine.
That said, it could have come out of a DT of course.

Ah! Remembered this; https://www.djunreal.co.uk/bikedocs/Yamaha.TZR125.87-93.DT125.88-02.Haynes.Service.Manual.pdf
Wiring diagrams at the end
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'Allo! My name is Inigo Montoya, you killed my father, prepare to die!
'89 TZR 125 - '94 GPZ500s - ZK3 GSXR600 Alstare

[mal180]

Thanks bomberman! That bit that the throttle cable goes into not the carb the other bit has two rubber pipes coming from it what are those?

[Kickstart]

Hi

2RH is the model code for the early TZR125.

While UK ones were missing the setup for operating the power valve the bits were sold as a kit for full licence holders. Think the same engine was also used in the RDZ125 (late UK RD125 fitted with the TZRs engine).

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Bomberman]

On the left of the cylinder head? That's the powervalve servo (edit, not servo just the valve :p) - that Haynes won't help you there as the UK bikes weren't fitted with them.

Thieved straight from a wiki on powervalves;

YPVS-Yamaha Power Valve System
YPVS Yamaha engines, Yamaha Power Valve System: Yamaha engineers realized that by altering the height of the exhaust port they could effectively change the engine power delivery thereby having optimal power and torque across the entire rev range, so it was that the YPVS was born. The valve is of a cylindrical design running across the top of the exhaust port, it is turned by a servo motor controlled from a control box taking information from the CDI (and other locations). The valve is a slightly ovular shape. This changes the height and size of the exhaust port at different engine speeds, maximizing the available power at all rev ranges. opening up firstly at 3k rpm for low end power, gradually in between 3-6k, fully opening at 6k rpm for maximum power,on most 125cc. It was fitted to all of the later models of the RZ/RD two-stroke road bikes (125, 250 350 and 500 cc), the TZR range.it was also added to the DT(125lc 2/3) range after 1984 (but was locked closed to comply with UK learner regulations until the(R) in 1988-04 which had a fully functional YPVS valve) the dt125r has a better design of engine,although not much altered in speed, just more reliable than its predecessor. The YZ series of motocross bikes has a mechanical power valve which is activated at RPM speed . The YPVS is only found on the liquid-cooled bikes not air cooled versions. Yamaha have also used a guillotine version in some of their later models such as the TZR250R SPR model..
Yamaha was actually the first company to produce consistent results with their YPVS in their race bikes. The 1977 OW35K was the first race bike to incorporate the power valve system and it won the Finnish GP in 1977. The Kadenacy effect was harnessed and controlled to a point that gave Yamaha great advantage over all the other manufacturers throughout the late 70's and into the mid 80's. The first street bikes with YPVS were the RZ/RD350 YPVS (LC2-onwards), and RZ/RD500 GP Replica in 1983-84. A
____________________
'Allo! My name is Inigo Montoya, you killed my father, prepare to die!
'89 TZR 125 - '94 GPZ500s - ZK3 GSXR600 Alstare

[Pete.]

Did you remove the plug? If not, going by the state of the fasteners I'd suggest pulling off the top and inspecting the internals. You might find rusted bearings and rings.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[mal180]

THanks guys this is all great help, going by the wiring diagram i am missing a servo motor?? Does anyone know where this should be on engine or is it a seperate component? That could be the reason for no spark? I will take it of and give it a good inspection/clean!

[Kickstart]

Hi

It is a separate component and would have been bolted to the frame, also a separate control unit I think.

The engine should run fine without them though

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Bomberman]

See here https://www.ebay.co.uk/itm/Yanaha-Dt-125r-Dtr-Tzr-125-3-Wire-Servo-Power-Valve-/150787715794?pt=UK_Motorcycle_Parts&hash=item231ba5f2d2#ht_500wt_1287 but it looks like you've lost it. Engine should run without, as most TZRs (in the UK anyway) never had them.
____________________
'Allo! My name is Inigo Montoya, you killed my father, prepare to die!
'89 TZR 125 - '94 GPZ500s - ZK3 GSXR600 Alstare

[mal180]

So even although i dont have this "servo motor" it should still spark and run? I Could also have a coil problem because i have changed plug and still nothing! This engine has been sitting for a while so i need to give it a little tlc.

[mal180]

Thanks BM didnt see your post before i posted last post

[mal180]

Sorry to be a pain but also on the bottom pic there is a plastic cover with the two rubber pipes coming from that what is that pipes for?? They appear to have just been chopped off?

[Kickstart]

Hi

Do you have the cdi unit?

Given how rusty everything is it wouldn't surprise me if the stator is also a rusty mess.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Bomberman]

That's your two stroke pump under there.
____________________
'Allo! My name is Inigo Montoya, you killed my father, prepare to die!
'89 TZR 125 - '94 GPZ500s - ZK3 GSXR600 Alstare

[mal180]

@Keith yes every thing else appears to be there i will have a look at stator aswell, Cheers

@Bomberman I take it this bike had a seperate tank for the 2 stroke oil?? Am i able to just mix it and put it in the fuel tank because i got no other bits other than the bare engine and speedo/dash

[Bomberman]

[mal180]

Good stuff, I have been wanting to buil a buggy for ages and this engine came up today for 50qiud and i thought i might as well thinking it was a 250cc lol but if i can get it going i will just use it! So if i have any more problems i know where to come cheers for the help guys! PS what mix of petrol to oil is it?

[Bomberman]

[mal180]

That was ok because i was going to ask about power valves as well! I will google again

[Kickstart]

Hi

If you run premix you will need to seal up the feed for 2 stroke oil into the intake, run a reasonable amount of oil in the fuel (I would guess at 33:1) and run larger jets in the carb. Also probably remove the pump and blank off the hole for it.

Easier to just source a 2 stroke oil reservoir.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[mal180]

yes Keith i was just looking at them and they ain't that expensive! Tomorrow i will redo the wiring and check the stator and hopefully i will have spark if not i will have to start checking coil etc! There is a lot of block connectors and stuff hanging around but hopefully that's for lights etc that i wont be needing for my buggy! I will be back on with a update cheers for all help guys!