1982 Xj 650 seca problem with engine head

Hi everyone!

I have such issue:
Saw that 2 seats on engine head is damaged, photos attached.

So I have a few options :

• -to buy and instal a used head
• - to fix old one by specialists with welding and polishing, etc. (not cheap)
• - simply polish and leave it as it is
• - just live it as it is and install back

Do not know when it happened and and how long it’s been working with this damage.

Please help me to choose best and cheachpest option.
Or if I install from other mc, for expl 1982 xj650 MAXIM or 1980 xj650 Maxim, will it fit?

And guide me through the effects if I install my old head with/without just polished seats, what could happen.

Thank u and Cheers!

 

That's not seats, it's cam journal bearings. What's the cam look like? What's the opposite side (top) bearing look like?
I'm guessing not good. It's either been very hot or running on low oil pressure, or both. I don't advise welding and remachining, nigh on impossible to get right, you need to do some old fasioned fitting with a good cam, scraper, carborundum paper, maybe a sacrificial cam and some lapping paste. It's very close to scrap, but worth trying to save it.

 

Thanks, I didn’t know what is the right name for those badboys.

The top side looks not that bad. Has a few scratches but definitely not so critical.

It was of low oil preasure&overheat. Already changed oit pump and cleaned oil channels.

Pls specify what do u mean by What's the cam look like?

 

He means the part of the cam (journals) that sit into those parts of the head that are galled up. Do those parts on the cam look chewed up or do they still have a nice machined looking surface

 

Those cam jounals are done. Any scratches are bad, and all of the journals are critical. Don't put it back together as-is.
You have two good options.
1. Buy a used head.
2. Have all of the cam journals machined to take replaceable bearing shells.
Option #1 is the most economic.

The cams are probably fine, but may have streaks of aluminum stuck to them. Muratic acid will remove the aluminum without damaging the cam. Use nitrile gloves, and in a well ventilated area use a rag with the acid on it to wipe the aluminum off.


How long did it run with the low oil light on,
You may need to check the crankshaft bearings, and have a look a the piston rings.

 

Thanks for your reply.

Actually the oil light was blinkin a few times but never was ON..

Already bought a crankshaft with bearings too..

Pistons and cylinder surprisingly in a good condition

But if I just take off around 1/3 mm of damaged surface and polish it, will it work or not?

 

A 1/3 rd of a millimeter? 12 thou for old Welshmen like me. Now ask yourself, when the cam journals wer line bored (maybe even honed) at the factory, what would the tollerance have been? Half a thou or thereabouts I would expect?
And when running, how thick would be the oil film forming the bearing on which the cam runs? I don't proffess to be an expert, but 1 1/2 thou or thereabouts would seem about right, given the bearing clearance would be around 2 thou.
Now, if you remove any metal at all from one journal bearing, what happens to the cam, spinning away in the other, previously alligned bearings? The answer is that where there used to be a bearing, there now is none - effectively.
So, unless you can clean up any high spots from ally gouged out and deposited on the bearing surface, and at the same time ensure the bulk of the surface still remains, the job is scrap.
I have, in the past saved heads by scraping, lapping and surfacing caps, you really need a sacrificial cam, as well as some luck and knowledge. In your case I would recommend looking for another head, as k-moe recommends.

 

Just be aware the oil light is quantity not oil pressure. Worst case find another complete used engine to either swap in or for parts for your present engine.

 

No. That will open the tolerance up even more (it's already too big, with too much surface damage, just looking at it) and a oil wedge will not form. While the engine will run after you do that, you'll end up ruining the cam in short order (and likely in a quite spectacular way. Be sure to video the event if you go that route).