macbig2k1 builts his own 5-valve-engine

[macbig2k1]

Salut mes amis,

I decided last year to build my own engine for the TW.
The base for "my" engine is the original gearing and gearbox (crankcase) from a TW125. And I will use as "Top End" the cylinder, cylinderhead and piston from a YZ/WR250F.

The basic idea was a watercooler TW engine.
I have now nearly all parts for the conversion.
One thing is sad, the cylinderhead is without valves and springs. But I will not use the too expensive titanium valves (price for a set [5], over 500 EUR), I will install a fitting set steel valves with springs.
A original Keihin carb is too expensive for me, I would have to pay 800-900EUR for it. I will use a cheaper Mikuni carb, but I don't know which one (at this time).

I started the same topic in the US TW200-Forum (link) and in our German TW125 forum (link) to get more input (problems that I haven't seen).


Here are some pictures:


- YZ/WR250F cylinderhead (without valves and springs)
- YZ/WR250F cylinder
- 76mm std. sleeve



The crankcase with the bigger bore for the 76mm sleeve. Thanks to christddel for the hint with a bigger sleeve.



You can see here the difference between the YZ/WR250F and a TW200 cylinder.



And now from the side.
I know, the iron sleeve is too long. The sleeve will be cutted later to the correct length.



You can see, the cylinder/sleeve fitts perfect into the crankcase.



I have to close the internal oil pipe from the TW cylinder, because the WR/YZ250F cylinderhead does have a external oil pipe.



A guy from the US forum asked "Do you have enouth space for the timing chain?"
I think, this picture can show you very good, that it could fit very well.


I know that the original clutch (4 or 5 disks, 4 springs) is not good enouth for this power. And I found the solution for this problem, it's the 7 disk and 5 spring clutch from a DT125 (max. 24hp). These bikes does have the same clutch: TDR125, TZR125 (max. 33hp), TZR150, DT200, WR200 (max. 31hp), SDR200, YFS200 (quad), DT230.
I've ordered a special clutchset from EBC, it's a racing kit with all needed disks (friction and steel) and stronger springs.


There are still a lot of things to do.
My saying: "A problem doesn't exist, just a solution has not found."

[nico-dem]

little bit crazy but i'm sure that it will work 

[Namna]

Il manque une possibilité de réponse :
"Cela devrait fonctionner"
La course est-elle modifiée, ou gardes-tu l'embiellage standard ?
Les points les plus délicats seront d'assurer le graissage et le refroidissement correct pour garantir la longévité.
D'autre part, le CDI de la TW a-t'il les bonnes caractéristiques en terme d'avance à l'allumage ?
En tous cas, c'est un beau projet, félicitations 

[george-le-yeti]

ouah ca va tiré sec !! 

[T2vv]

Il manque une possibilité de réponse :
"Cela devrait fonctionner"
La course est-elle modifiée, ou gardes-tu l'embiellage standard ?
Les points les plus délicats seront d'assurer le graissage et le refroidissement correct pour garantir la longévité.
D'autre part, le CDI de la TW a-t'il les bonnes caractéristiques en terme d'avance à l'allumage ?
En tous cas, c'est un beau projet, félicitations 

Cette possibilité de réponse ne manque pas puisque celà VA fonctionner...

De mémoire il me semble que l'on peut jouer sur l'avance a l'allumage, Christddel l'a fait il me semble quand il a modifier un arbre a came.

[macbig2k1]

@ Christian
The solution for fixing and the cooling oulet from the cylinder is not so complicated. I will use a alu adapter plate with all needed holes and threads for the crankcase and cylinderhead and with the outlet for the hot water.
5mm for the timing/distribution chain?!? No problem, we can remove a bit from the crankcase (see marked area):


And a solution for the waterpump is also found. I will install a pump on the generator side and the sprocked will be mounted on the rotor.
My engine pro knows a very good company for carbon parts. Mybe they will make a new carbon generator cover with an integrated water pump.



@ Namna
> gardes-tu l'embiellage standard?
qui, standard

> le graissage
Pas de souci.
d'autres pignon pour pompe à huile

> D'autre part, le CDI de la TW a-t'il les bonnes caractéristiques en terme d'avance à l'allumage?

[Namna]

Quelle cylindrée obtient-on avec ce cylindre et la course d'une 200 ?

Which cubic capacity do you obtain with this cylinder and the vilbrequin of TW 200 ?

D'autre part, sur la photo, on dirait que les pignons d'arbre à came sont plus petits. Faut-il aussi changer le pignon sur le vilbrequin ?

In addition, on the photograph, it seems that the pinions of camshaft are smaller. Is it also necessary to change the pinion on the vilbrequin ?