XS400 Parts & Machining??

[Thund3r]

Initial Teardown of my 1980 XS400G Special ii is showing that the jugs will need an oversize bore on them ( I have measurements at points of 69.05mm which to my understanding is over the .02 mm limit listed in the factory manuals). With that in mind I have 2 initial questions:

1. Where is the best place to find .25mm over pistons and rings? (I have found some pistons on Ebay but have been struggling to find rings)
- my search has found that ring Piston PN should be 2L0-11635-00 or 2A2-11635-00
- and ring PN should be 2A2-11610-10-00 (+1 O/S or .25mm)

2. Any recommendations for Jug machining? or should I go at it myself with some ball hones? I am in Norther OR/Southern WA for reference.

In other notes I already have a "complete" gasket kit which I am sure I will need to get more gaskets than are in the kit but its a start.

Any advice and pointers is appreciated!! Cheers.

Also I stumbled accross this ebay kit... which considering NOS parts almost add up to the price of this is it worth it?

https://www.ebay.com/itm/2560550017...0xbEc2OhEJpgvnVlyG1Rnr8Q==|tkp:Bk9SR-TTlLX9Yw

 

[Philymoves]

Hopefully someone with rebuild experience chimes in, but were you able to get any compression or leakdown numbers before the engine teardown? Was the bike previously running? What lead you to the rebuild? Curious to follow this as I would like to look into my top end, but I think from what I have seen, getting oversized pistons means spending a bit of money.

 

[tstidham]

I had to replace my cylinder head due to a crack and low compression in the right cylinder but I just did a rering. I only ball honed the jugs and reused the pistons as is. They were a little loose but I just wanted to ride. It burned some oil initially but once the rings seated in, it's been running fine ever since.

 

[Thund3r]

so couple of points

• the bike was not running when I bought it, and already partially disassembled (upper half) without pistons (so I need to get pistons anyways)
• Jugs/bore themselves have some surface corrosion, assumedly from sitting, which at minimum needs to be removed
• Also based on my measurements of bore diameters the upper parts of the bore are over spec (based on how I read the factory manual which is 69mm with a +.02mm limit?) with measurements ranging from 69.02 - 69.05mm

so based on that I am debating to just ball hone it and throw it back together with factory pistons fingers crossed? otherwise my interpretation of the "right way" to do it would be to do a full over bore to 69.25mm with corresponding pistons and rings.

 

[CaptChrome]

am debating to just ball hone it and throw it back together with factory pistons fingers crossed? otherwise my interpretation of the "right way" to do it would be to do a full over bore to 69.25mm with corresponding pistons and rings.

I would do the quick and dirty job myself. It will be cheap and if things don't turn out to your liking, you can still do it the "right way." Also the wear limit on the cylinders is 70.10 mm, so there is a lot of meat left to play with. If you have to bore the cylinders, I would first see what size pistons/rings you can get and let that be the deciding factor of bore size in order to give you the 0.030 – 0.050 mm clearance between the piston and cylinder.