Oversize replacement pistons? Could these work

[esmith87]

I have been searching for different pistons to replace the almost obsolete xs400 pistons. After looking through a lot of part diagrams I stumbled on these guys.

KAWASAKI KLF250 Bayou 03-11 Piston

They look very similar to the xs400 OE pistons, but run a slightly lower compression height, as they are slightly dished in the center. 8.9:1, I think. They even have a 16mm wrist pin. Could these work? Does anyone have a KLF250 bayou in the back yard they could break down and check these against an xs400 piston. These only come in standard and .5 OS though. And they are hella cheaper than Yamaha pistons.

Please input in you can on this thread. The future of the XS400 depends on it!

 

[Scorpio1963]

The only way to find out is get the specs from each piston bore and height including skirt.You want to make sure the skirt on the other piston isn't longer than that of xs400 piston.Worst comes to worst you can take the piston to a machine shop have the skirt shaved off and the piston balanced.

 

[salisride]

essmith did you look more into these pistons ? whats the stock od on these ?

 

[esmith87]

They are a 69mm piston. and I believe there is one oversize available. I am not sure if the valve reliefs are in the correct locations. These are the closest thing I have been able to find to our XS400 pistons that is currently being manufactured. I just can't afford to purchase one at the moment (new or used) for a visual inspection and a proper measurement. I still am interested in looking into this more, just need some time to do so.

 

[Lester]

Hi guys,
this thread interests me a lot as I am in the process of rebuilding my 400 sohc engine (4G5) I am an engineer by trade and would gladly do the machine work necessary to try to make these pistons work. I am finding the cost and availability of the Yamaha units far too expensive to use and would welcome nay attempt to find an alternatve solution.

Hands up any like minded engine builders?

lester

 

[salisride]

im tring to big bore my 400 maybe using 650 sleeves and pistons

 

[xschris]

How will you be able to fit them in the cases?

 

[Lester]

I had thought about resleeving so that I could use the existing pistons but have been told that it is not possible to do this due to the way that the original manufacturing process. Not confirmed by any expert on the subject but he advises that the original sleeves are slotted on the outside of the sleeve and the alu cast around them. I know where I can get sleeves made but would need to have this confirmed first.

Are the 650 pistons any less expensive /readily available?

Pleased that I'm not alone on this topic.

Lester

 

[xschris]

The 650 stuff won't work for the 400.

 

[Scorpio1963]

Exactly if you want a bigger bore engine then modify your fram and put a 650 engine in it

 

[HoughMade]

im tring to big bore my 400 maybe using 650 sleeves and pistons

Good luck with that. Please let us know how that goes.