xs400 rebore

[Bondy]

I am thinking that increasing the cc on my xs400 but I am unsure if this will achive anything. Here is that plan so far.
The current bore and stoke is 69.0mm x 52.4mm. I am looking at getting two SR250 pistons. SR250 bore and stroke is 73.5mm x 56.5mm from what I can tell. rebore the the XS400 Cylinders out to 73.5mm. If this works out it will get a bore and stroke of 73.5mm x 52.4 which if my maths is right brings the cc's up to 440cc. If I can find a set of con rods that will bring the stroke to 56.5. which is an increase of 4.1 mm will that the cc's out to around 500 cc.

If someome have the measurments for a SR250 pistons so that I can see if this will increase the stroke from 52.4mm.

there are other tuning tricks that are going to be done polishing rockers and other parts. and a lighting with an aim to improve performance and top speed.

if anyone things that this is going raise any issues and what factor should I take in to account if I go down this road.

Cheers Bondy

 

[Nuno]

The con rods don't change the stroke...you have to change the crankshaft to increase the stroke.
Why not use 2 pistons from an XS 650? I don't remember the bore but I remember that should give something around 480cc on an XS 400 crankshaft.

Anyway...I was thinking about the same thing for my XS...what year is yours? Mine is a '82, one of those with DOHC and the monoshock.

 

[crazypj]

I have fitted 1mm OS GS500 liners and pistons (75mm) into XS400 for a friend.
You can use sohc or dohc XS400 as pistons are the same (2 valves/cyl)
I'm pretty sure the stock liners are too thin to bore more than 2.5mm OS, you need to fit new ones.
XS650 pistons are 75mm but too long for XS400

 

[Bondy]

The con rods don't change the stroke

sorry about that I must have been having a brain fart at the time of writing.

Mine is a SOHC 81 special.

I will have to have a look at the liners in my engine, However I am looking at getting another full top end so that I can play around with the ports and the rockers and maybe the cams.

Is there anyone around that has done any performance work on the SOHC xs400 if so can they pass on some of the magic that they performed and what was some of the out comes of the work regardless of if it was a not as successful.

Cheers

Bondy

 

[Bondy]

Here is a pic of a mock up so I could get an idea of how the seat would look once it was finished and that the foot controls didnt bash in to my exhausts.

I will post some other pic in the next few days with the fibre glass seat on so that I get a better idea

Cheers

bondy

 

[crazypj]

Mine is a SOHC 81 special.

I will have to have a look at the liners in my engine, However I am looking at getting another full top end so that I can play around with the ports and the rockers and maybe the cams.

Cheers

Bondy

I've got a complete head you can have cheap.
Don't have a cylinder though