[Rpmfly1]

Yp250 manual

https://www.manualslib.com/download/656596/Yamaha-Yp250.html

 

[ronnydog]

I built a TW 250 from a TTR225 4mm stroke crank 71 mm piston carburetor off a raptor 250, Bike has a lot Of low end power and top end power still running no well leaks love it

 

[DougDotyTW200]

I read your whole thread this evening, great work !!

 

[Rpmfly1]

Another tip for high rpm missfire is a one or two step colder plug to help retard detonation with lean mixtures!

 

[molochnik]

The information contain herein is one of the main motivating factors to join this forum. @macbig2k1 , thank you for the parts lists...also a thanks to elime for chiming in when necessary.
I may, perhaps, be reviving a necrothread but this is the sort of stuff that is always useful/of interest to those of us inclined. It saved me from asking "can a stock 200 crank be stroked, and if so, how much?" and then suffer the humiliation of the standard replies of search, etc.
I intend to put a conservative stroker motor together once I find a Tdub for myself (I'd rather not experiment with Mrs. Molochnik's). I like the idea of not having to worry about fuel when out in the boonies - on the TAT there were many cases where I could only get 87 gas and was thankful that my DR will run on whiskey, if need be.
I've not seen this level of technical info so far down in the weeds on any other forum yet. Big thanks to all who've posted their triumphs, tribulations on this most ubiquitous question!

 

[ArcticJeff]

Are we sure the heads are all the same?
I just took the head off my 200 and diameter of the dome is 67mm. I have a 225 cyl I'm going to put on it, would I not want the dome to have a diameter of 70mm?

Does someone have a 225 head that they could measure the diameter to compare?

Thank you

 

[CasperHammerly]

I am a bit confused about the last bit of this "but than you have to use the first oversize (71.50 mm) "

is he referring to oversized piston? I am looking to do the 10.25:1 Wiseco piston, and planning on using a YFB250 71mm cylinder. I am using a TTR225 bottom end.

220.5 cc / 229.6 cc

• 71 mm piston with 8.7, 9.5:1 or 10.25:1 compression ratio
• original cylinder can be used, but needs new 225/230 sleeve

OR
- 225/230 cylinder (70.00 mm std. bore)
OR
- 250 cylinder (71.00 mm std. bore) can be used, but than you have to use the first oversize (71.50 mm)

 

[CJ7Pilot]

I think he's assuming that if you find a used 71mm cylinder, you'll likely need to hone it/bore it out to 71.5mm, in which case you'll need an oversized piston.

If you find a brand new 71mm cylinder, or have yours sleeved with a new 71mm sleeve, then you won't need an oversized piston.

It might be easier to find a 70mm cylinder, and bore it out to 71mm.

 

[WECSOG]

I just bought an early '80s XT250 jug and head with the intention of putting it on an XT225 bottom end, which I already have. I don't have it in hand yet to measure, but I found some specs listing the early XT250 bore as 75mm and the same stroke as a TW200. With a 0.5mm overbore, that will be about 260cc with the 58mm stroke, assuming it works.

 

[elime]

TW200 stroke equals 55.7mm.

 

[macbig2k1]

I just bought an early '80s XT250 jug and head with the intention of putting it on an XT225 bottom end, which I already have. I don't have it in hand yet to measure, but I found some specs listing the early XT250 bore as 75mm and the same stroke as a TW200. With a 0.5mm overbore, that will be about 260cc with the 58mm stroke, assuming it works.

The XT250 cylinder will not fit on the TW crank case, because the engines are totally different.

 

[Lapdi]

Hi Basti,

could you please do a big list for the 125 as well?

ps: tomorrow I'll fly in Germany for some business 😎

 

[macbig2k1]

Hi Lapdi,

please, not "Basti".
Please take a look on my online shop. There you'll find some example calculations for engine conversions.
For example here's the link 125 to 240 cc for VIN code DE01:

TW-Parts.com - Tuning-, Zubehör- und Ersatzteile für Yamaha TW125, 200 und 225

Greets,
Sebastian

PS: My normal fulltime job is in a car workshop. TW-Parts.com is my after work job, for this reason I don't have that much free time.

 

[Lapdi]

Hi Sebastian,
Thanks a lot. Do you have contact for new bikes import from USA?

ps: sorry for Basti, I work in Gemany and it is very common. 🙏. Respect.

 

[Ski Pro 3]

Hi Sebastian,
Thanks a lot. Do you have contact for new bikes import from USA?

ps: sorry for Basti, I work in Gemany and it is very common. 🙏. Respect.

I Googled Basti. In America it is a type of enema. No wonder Sebastian doesn't care for it! Ha!
(In Germany, Basti is short for Sebastian)

 

[Lapdi]

Good evening guys and happy Easter,

I found again another bike, this time is a 200 but no engine.
Question: the 125 cc engines are much easier to find here in Italy; how much can I re-use to bring it to 200? Make it sense or is better to struggle for find directly a 200cc?

ciao 😊

 

[macbig2k1]

I Googled Basti. In America it is a type of enema. No wonder Sebastian doesn't care for it! Ha!

In Germany, Basti is short for Sebastian

That's true, but connected with some bad memories.

 

[macbig2k1]

Good evening guys and happy Easter,

I found again another bike, this time is a 200 but no engine.
Question: the 125 cc engines are much easier to find here in Italy; how much can I re-use to bring it to 200? Make it sense or is better to struggle for find directly a 200cc?

ciao 😊

You can use the crank case and gearing.
But you have to change:

• crankshaft
• cylinder
• cylinder head
• clutch (change/modify)
• carb kit

-->> You'll find all information on the engine conversion site.

 

[macbig2k1]

Do you have contact for new bikes import from USA?

No.
The TW200 2008 and newer isn't street legal in Europe.
The exhaust emission regulations are too strict.

 

[Lapdi]

I know the issue about the emissions but here in Italy there are a lot of 200 and some agencies offer import service for this bike🤷‍♂️