How easy is it to rebuild a 8v K100 head.
Needs valve guides replacing and valves reseating (I think)
Anything else I should be doing please?

That depends on whether you have rebuilt a head before. It's very doable for an amateur mechanic.

Follow whatever manual you have for dismantling. Give it to a local engineering place to get the head skimmed/planed and the valve seats re-cut, They might do the guides for you too and lap the valves if you are unsure how to do it.

"Refitting is the reverse of the removal proceedure" as they say in the Haynes . Use a good quality torque wrench.

Use a full gasket kit whilst doing it and I would be having a good look at doing the timing chain and/or guides whilst at it.

The real issue is determining why did it go? Until you have determined that it may be a false economy putting the overhauled head back.

Thanks for the response.

There's nothing wrong with it except being 35 years old. The valve guides were worn and need replacing.

The head has been stripped just need to get new valve guides and reseat the valves (I think)

What parts should I replace while here?

Chewbacker wrote:Thanks for the response.

There's nothing wrong with it except being 35 years old. The valve guides were worn and need replacing.

The head has been stripped just need to get new valve guides and reseat the valves (I think)

What parts should I replace while here?

You only need to do the valve seats if they are worn beyond re lapping. The last one I got done was a k11 - I got the ports all soda blasted which smoothed them out a good bit too. not quite ported and polished but a nice clean up and free airflow.

I would do the valve guides, valve seals and check all the valve edges to make sure they are all ok to go back in.

Thanks 88. Should I also replace the valves if the vales guides were worn. I'm very conscious of how much each one is!!

Shame that James & Harmer up at Fleetsbridge seem to have disappeared. They used to make Guzzi valve guides for me - far cheaper than going out to Motomecca at Ferndown Industrial and buying OEM.

Dai wrote:They used to make Guzzi valve guides for me - far cheaper than going out to Motomecca at Ferndown Industrial and buying OEM.

That may be part of the answer you seek.

Until the day I needed three valve guides in a hurry and went up to Motomecca. After some fiddling around with the computer and digging in plastic bins there was a hiss of indrawn breath.

'We've got some in the bins but I can't sell you them. Not on stock control you see'.

Somewhat pissed-off I finished my (shop supplied) coffee just as [REDACTED to protect the guilty/innocent] lined up three valve guides on the counter.

'I did say I couldn't sell you them...'

If you are asking us for what would we do with the head off, then Yes New guides, valve inspection, (by that I mean stem length avareage 111mm stem dia wear limit 6.950 normal 6.975 and valve head runout  sort of rim buckle ovality, the seat detail will tell some of that) Guide internal limit is 7.1mm
I'd have the combustion chambers CC'd and the Port volume equalised. How fussy am I? Yep. But it can pay dividends.

Spring checks and collet check.

My reckoning is if you have to go in there then make it worth your while and finesse the thing to combustible perfection. No one cylinder should do the lions share of the work when your finished. you may even get the engine to equal the throttles factory volumetric sync. That would ensure an incredibly smooth  idle and running engine.