[Desertwndrr]

I'm hoping that I can get a little help. I am going to be tearing into my motor on a 2003 TW200 so that I can diagnose a little knock that I have. Since I will be pulling the top end apart I'd like to bump the HP a bit and install a 225 or 230 cylinder. Nearest I can gather, the 230 cylinder requires the cases to be bored out a bit. Does the XT225 cylinder require machining? Also, if I am going to be able to install the larger cylinder and piston will I still be able to use my head or will I have to change the head out as well.



I've tried to read as much as possible but it all seems to conflict a bit at times. I wish there was a single guide to parts exchanges for this bike.



Thanks in advance for any help that you can give.

 

[TWrider]

I'm hoping that I can get a little help. I am going to be tearing into my motor on a 2003 TW200 so that I can diagnose a little knock that I have. Since I will be pulling the top end apart I'd like to bump the HP a bit and install a 225 or 230 cylinder. Nearest I can gather, the 230 cylinder requires the cases to be bored out a bit. Does the XT225 cylinder require machining? Also, if I am going to be able to install the larger cylinder and piston will I still be able to use my head or will I have to change the head out as well.



I've tried to read as much as possible but it all seems to conflict a bit at times. I wish there was a single guide to parts exchanges for this bike.



Thanks in advance for any help that you can give.

There are two types, late xt225 are nikasil, every other 225/230 is iron...it is by far easiest to use a 225 head...200 head needs slight mods. The cases do need to be bored...you will end up with 215cc, the power increase is negligible, but there do seem to be more piston offerings in the 225 size. Keeping it 200cc is easiest.

 

[Desertwndrr]

Thanks. If it was drop in I was going to go with the 225 cylinder and HC piston. Since it takes a bit of work I think that I'll just stick to stock. Still would like a bit more power though.

 

[christddel]

No problem to install a piston cylinder 225.

I have done several engine TW125 125 To ---> 231-236-243.

Just, we must enlarge the passage of sleeve in crankcase.

And the head cylinder is the same on 200-225-230



My Maximal Bore...Cylindre 225, Sleeve XT250, piston YZ250F

 

[indigo]

OK this may be a nutty question ... what does it take to turn a 200cc into a 125cc? A thicker sleeve and same head or different head?

 

[uktw125]

OK this may be a nutty question ... what does it take to turn a 200cc into a 125cc? A thicker sleeve and same head or different head?

TW125 has a different cylinder as when you want convert the other way you have to press out the 125 sleeve then bore the aluminium casting to accept the 200 sleeve, the crankcase mouth is also smaller so you could not fit a 125 cylinder into a 200 bottom end. The crank has a shorter stroke and the valves in the head are smaller.

It is much easier to convert a 125 to 200 though because you can remove metal to make things bigger but not add metal to fill the gaps.



I guess you were only wondering rather than actually planning such a conversion. As an aside the TW125 is much more common in Europe and especially the UK because of the licensing laws for learner riders.



I hope that helps you.

 

[christddel]

OK this may be a nutty question ... what does it take to turn a 200cc into a 125cc? A thicker sleeve and same head or different head?

Hello,

But why make this change? It's strange ...



But, to change a 200 by 125...

We must change the crankshaft,

Change the cylinder with the sleeve

Change the engine cylinder head

The carburetor can stay, if we place smaller jets

 

[lizrdbrth]

No problem to install a piston cylinder 225.

I have done several engine TW125 125 To ---> 231-236-243.

Just, we must enlarge the passage of sleeve in crankcase.

And the head cylinder is the same on 200-225-230



My Maximal Bore...Cylindre 225, Sleeve XT250, piston YZ250F

How well does this bore deal with the heat, what are you using for head gaskets, and does the YZ piston have the same pin diameter?

 

[indigo]

I guess you were only wondering rather than actually planning such a conversion. As an aside the TW125 is much more common in Europe and especially the UK because of the licensing laws for learner riders.



I hope that helps you.

Yes, more wondering than anything else. There are so few real motorcycles that are small bore/cc's here in the USA a super economic gas sipping TW kind of made me pause for thought.

 

[christddel]

How well does this bore deal with the heat, what are you using for head gaskets, and does the YZ piston have the same pin diameter?

Hello,

The piston pin is 16mm the same as on TW200-225,

I place a crankshaft 200, as amended to 64.5 mm stroke (working Macbig TW-parts)

The head gasket is made from a sheet (1mm) aluminum hole of 77.5 mm

Under the cylinder we must put a plate 4 mm thick ....

And extend the distribution chain 2 links.

Is to make just a TW 300 cc

 

[TWrider]

Hello,

The piston pin is 16mm the same as on TW200-225,

I place a crankshaft 200, as amended to 64.5 mm stroke (working Macbig TW-parts)

The head gasket is made from a sheet (1mm) aluminum hole of 77.5 mm

Under the cylinder we must put a plate 4 mm thick ....

And extend the distribution chain 2 links.

Is to make just a TW 300 cc

So the head bolt holes becomes part of the combustion chamber?



I suppose that's one way to get a few extra cc's...and flame harden your bolts at the same time

Or is that the pic of your base spacer?

 

[christddel]

So the head bolt holes becomes part of the combustion chamber?



I suppose that's one way to get a few extra cc's...and flame harden your bolts at the same time

Or is that the pic of your base spacer?

Hello,

Yes, It is the pic of your base spacer...

 

[qwerty]

300cc of TW goodness!