First Time Bike Rebuild: Thoughts?

[Scorpio1963]

Yikes man the one side of the head doesnt look very good.Might need some machine work done there.You can definately tell inside the cylinders where they were crusted up bad.I dont think those pistons would clean up well either they would probaly be pitted up pretty bad.The cylinder walls dont look that bad so you could probaly get by with a good hone job.Dont use a stone hone either if you attempt this.Get the ones that have the beeds on them they do a better job.The stone ones just remove the glaze while beed ones will give you that criss cross pattern.Keep us updated with lots of pics.

 

[maxholland1]

I got the valves out, but they look real dirty. How do they look?

 

[Arclight88]

I recommend getting a Dremmel tool and a supply of wire brushes and cleaning all of those parts. It may well be that the head and valves clean up OK. Mine did.

 

[maxholland1]

I got the parts cleaned by a machinist. But he says that the holes in the head are too worn down to work properly. What do you think?

My options now are a) find a working engine OR b) buy a new head and cylinder with pistons and hope they work

Ideas? Advice? Perspective?

 

[drewpy]

holes in the head?

those are valve guides, you can buy valve guides anywhere and with superior material than 30 years ago.

its simple for an engineer to heat up the head and knock in a new guide. the valve guide needs reaming to suit the valve

 

[xschris]

I think your best bet is to find another engine that runs good. With the money it will take to get that top end working right your better off.

 

[16VGTIDave]

I agree with Chris. The first pic shows the sparkplug hole is wrecked and the valve seats are pitted beyond recovery. If nothing else, a new head is going to be cheaper than fixing that one.

 

[bcware]

If it were me I'd probably try fixing it just to see what happens.

A spark plug repair insert costs like $25 with all tools included.

I'd lap the valves and see what happens.

Maybe it will clean up or maybe it won't. I like doing that sort of things anyway; it's up to you!

 

[xschris]

The valve stems and that one valve seat looks totally shot. The jugs look like they will need more than a hone to fix but that is just my 2 cents

 

[bcware]

I didn't really notice the scrapes in the jugs. Yeah, maybe buy another

 

[Scorpio1963]

I almost bet if you did a real good job honing the cylinders with bead hone they would turn out pretty good.I have seen worse inside car engine blocks and honed them out.Heres what I would do get a stone hone and clean all the glaze out then redo it with good bead hone.They will look good as new.If you can get chrome molly ringsTo use on the pistons the engine from the head down would be good.The head is messed up though,replace it with your new gaskets your engine should be good to go.

 

[maxholland1]

Great! Thank you for all the advice. It has been really helpful.

I have found a cylinder block+pistons and the complete head from a 1977 XS400. Is that compatible?

Mine is a 1980XS400

 

[bcware]

I think so long as they are both SOHC they are compatible. I believe the differences you'll find involve timing and the related wiring; the 1977 will have points. I am not sure if a 1980 has electronic ignition or not.

I am not sure if the gearing or transmission is different. That could be sorted out if it is the case, but I don't want you to be surprised if it is.

 

[maxholland1]

Awesome. I will post pictures when I pick it up.

 

[bcware]

Check this out first: http://www.xs400.com/forum/showthread.php?t=7652&highlight=electronic+points+swap

Ok, I think I've sussed it out.

To convert the 1977 motor to electronic you need to:

Add another wire from the charging system to the tci
Remove the points and replace with your electronic timing piece

To convert your bike to use points:

Replace your 3 ohm coils with 4 ohm coils
Modify the main harness in some way (not sure what needs to be changed, but something definitely will)

 

[xschris]

All you will need to do is swap your old parts from the 80 to the 77. The extra wire is on the 77-79 bikes because of the points. The 77 head will be 9.2:1 compression ratio where the 80 has 9.3:1 but you wont notice much if any difference. If the 77 top end has a cam use that one. 77-79 cams had a little longer exhaust lobe duration than the 80 had.

 

[maxholland1]

Great. Everything matches perfectly. Here are pictures of it:

 

[maxholland1]

I finally got the oil filter and front brake off. Any thoughts on whether it needs to be replaced?

 

[bcware]

Ditch the old pads.

Clean the brake caliper and possibly replace the seal.

New oil filter cover o-rings usually come with every engine gasket kit.

 

[xschris]

Make sure you use the matching rocker box for the new head.