Timing layshaft...

[koko64]

What do you think you'll do? Make a project of it or pick up another 800 motor?

[Dirty Duc]

It's a project... because I need another one of those.

Big 2v crank will be the extent, though.  870, here I come (after I do a few other things).

[Speeddog]

I built a DS1000 motor with custom rods a while ago.

A mock-up determined that the rods would hit everything they possibly could.....
....so the rods were even more custom after I rounded off the shoulders and cut a bit off the heads of the rod bolts.

I understand the attraction of rebuilding your motor the way you want to, and the frustration with the price of replacement engines.
If you can do all the labor in-house, that tilts the table a lot in your favor.

The 800 does have the lowest deck-height pistons amongst the small-case motors.
From your "870", I'm assuming you're targeting a DS1000 crank.
The additional stroke is 5.5mm, but you only need to deal with half of that, 2.75mm.
One way is to use a 'base gasket' of sufficient thickness, thus lifting the head and cylinder.
That introduces issues of exhaust and intake system fitment.

The larger issue is cambelt length.
I don't think the 600/620/695/750/800 belts will allow that much.
The 696 belts *may* work, they're longer, but may not be too long.

You'll need studs from a big case as well, they're a bit longer.

Big issues for splitting the cases are removing the alternator rotor nut, clutch hub nut, and primary gear nut on the crank.

Biggest issue for the DIY is getting the primary gear off of the crank taper.
They are generally quite securely mated, and the access for a generic puller is not good.
Your local dealer or well-equipped independent Duc wrench will have the factory puller, best to do it that way.
The puller is a very serious piece, and fairly priced for how nice it is and how well it works, but not worth the coin for a one-shot use.

Do your best to clean the engine as much as possible before opening up any of it.
And the usual.....
Take pictures and notes as you go.
Bag and tag parts and fasteners.
Put the bagged and tagged parts in plastic storage totes.
Finally, keep animals and children (of all ages) away from the work area so they don't fuxxor things.

[Dirty Duc]

From your "870", I'm assuming you're targeting a DS1000 crank.
The additional stroke is 5.5mm, but you only need to deal with half of that, 2.75mm.

I read that elsewhere, and promptly forgot that it applied to my plans.  I read somewhere else (someone was stroking a 996) that 1198 rods are 122.5mm, that puts the deck height at only 1.25mm higher.

That's only three base gaskets... and I'm only finding small case gaskets in 0.4mm.

One way is to use a 'base gasket' of sufficient thickness, thus lifting the head and cylinder.
That introduces issues of exhaust and intake system fitment.

The larger issue is cambelt length.
I don't think the 600/620/695/750/800 belts will allow that much.
The 696 belts *may* work, they're longer, but may not be too long.

You'll need studs from a big case as well, they're a bit longer.

Thanks for the tips!

[brad black]

1198 rods are small end located, so you'll need some pistons to suit.

[Dirty Duc]

1198 rods are small end located, so you'll need some pistons to suit.

Ah.  That does pose difficulties.

On to plan W.