Unicorn GSX1200S: Yoshimura ST-1 Camshaft Installed! Unleashing the True Power of the Oil-Cooled Inazuma

I’ve been thinking maybe I should start doing YouTube videos… but I’m short on equipment.
Tripods and dollies just get in the way…
And cheap tripods wobble all over the place… It’s a headache.
I finally went ahead and ordered something (*´ω｀*)

So, today I installed the Yoshimura ST-1 camshaft.

Sometimes they rust and won’t come off

By the way, the timing is off, but that stepped bolt on the front of the head cover

sometimes rusts and won’t come out.
If it feels stubborn…
spray some lubricant through the gap loosen → tighten → loosen → tighten
If you only loosen it, you’ll strip the head cover threads.
If you end up needing a helicoil insert, that means dropping the engine, so be careful when removing bolts.

This time it came out fine though.

Adding restoration elements to routine maintenance

When the bike is clean at the component level, the final result looks better too.
We work quietly with the spirit that love saves bikes.

Once the top is off, the cam comes out smoothly

We’re not doing anything extreme, so let’s move right along.

The front cam chain tensioner can be replaced in this state .
*The rear one is fixed to the crankcase, so it can’t be replaced in this state

No cracks and good flexibility . *We’ll replace it anyway.

Rocker arms get replaced at the same time (*´ω｀*)
The cam and rocker arms are a couple that go together.

First time? The cam sprocket’s elongated holes aren’t long enough?

I have great faith in Yoshimura cams.
Sometimes valve timing adjustment isn’t even needed~ That’s incredible.
That said,
if I make the cam sprocket with elongated holes, I can adjust more precisely .
I mill elongated holes front and back by at least 5° every time .
Today was the first time I encountered elongated holes that weren’t long enough~ So that’s a thing~

It’s not a bolt-on cam; some adjustment is necessary .
Next time I’ll mill about 8° front and back.
The surface hardening makes elongated holes a bit tedious.
So I’m removing the intake cam.

Remove again, re-mill → measure → done

Sprocket machining and valve timing adjustment.
That’s how the Yoshimura ST-1 cam got installed (*´ω｀*)
Now we can enjoy the true 1200cc oil-cooled engine.

Now it’s just closing the cover.

Surprisingly tricky: the automatic cam chain tensioner

I’ve experienced this too, but at the very end “Okay, who skipped a link?”
This is so frustrating.

You have to be really careful,
because when you fully release the spring and close the cover, the momentum can make the intake cam chain skip a link.
At that moment “Huh?”
Do I have to remove the cam again? That’s the flow you end up in… Here’s the prevention method

Use a bolt to push by hand. Adjust gently by hand.
It’s surprisingly useful… When you want to add just one more link! It’s perfect for that too.

This works even better with a GSF1200.

I thought I’d seen a used one lying around, but I didn’t find one (*´ω｀*)
Next time we get a chance to replace it, it’ll advance the timing a bit and make a subtle difference.

33120-19C20

Head cover gasket—no liquid sealant needed

If liquid sealant gets into this groove, it’s really a pain.
Oil leaking = gasket degradation is what I think.

But I think some models like the CB1100 SC65 do use sealant,
so each manufacturer’s philosophy gets ingrained in their technicians.
I think it’s best to avoid anything that causes headaches down the road.

The spark plug base was rusty, so I replaced it.
I don’t want to regret later wishing I’d changed the plug back then.

For carbureted bikes, standard plugs are preferable
*Iridium plugs are best avoided unless you’re really confident.
If you foul an iridium plug, it’s hard to recover = you’re stuck on the road.
That’s the tendency.

The rest is just fine details, so we’re almost done.