Engine Dismantling: cannot remove cylinders!

Hey, all.

I took a little while off my '82 650 Seca project, because things are always coming up. I'm ready to go again, fully back-in-action with a new workbench in my garage so I don't have to 1) lean over the engine on the garage floor, and 2) fill my basement with carb cleaner fumes. The whole thing's in one location now.

Anyhow, following the service manual, I'm working on dismantling the engine to the point where I can hone the cylinders and change the rings. Trouble is, the cylinders won't come off. In my service manual, it says:
1. remove front cylinder holding bolt
2. remove cylinder
Sweet, except it doesn't budge at all. I've tried tapping at it with a rubber mallet, I've tried (lightly) prying with screwdrivers of several sizes, and then with a crowbar.

Is there something I'm missing? Is just the gasket between the block and the cylinders holding it on? Or is there some obvious step I missed?

-Los

 

Common problem. Make SURE you have all the cyl hold down bolts undone Hunt for them just to be positively sure.
What invariably happens is the Cyl hold down studs aquire a coating of Rust and this interferes with the cyl castings when you try to pull it up.
This can be so bad that the studs have to be cut off.. Neither easy nor fun to do! And be v carefull with these studs as Yama for Gawd only knows what reason made these studs with a much shorter threaded end (into the Case) than they did in 250 cc machines.. in short the damned things are way to easy to strip/pull out.
With care and genuine patience you can deal with this.
Ain't old clapped Bikes Fun ?

 

If you look at a parts diagram for your engine you will see that there are the 12 studs (nuts removed from the head). There's one short stud front and center that you need to remove the nut from the engine case. Once these 13 nuts are removed you have to break the seal of the cylinder gasket and four oring seals that are at the base of each cylinder.

There are also 2 collars plus orings that seal the outer two studs right side, as they are used to supply oil up to the cylinder head. I don't think they offer too much resistance to breaking the cylinders free.

The biggest resistance I believe is going to be the 4 large orings at the base of the cylinders as they get press fit into a lip in the crankcase as the cylinder is bolted down.

Good luck and be gentle with the prying, don't want to break any cooling fins off.

 

It don't come easy.
The Cylinders extend down into the Block almost three inches. There's a gasket and O-rings working against you.

Heep the Block Removal Force as close to Vertical as possible. If you get one side to lift ... break the opposite side, next.

You also have the Pistons and rings to deal with. Place the Pistons at the Half-stroke so all the upwarb force isn't negated by a pair of Pistons on the Down-stroke ... it helps.

 

Not sure about the 650 engine but on the 900 once I had the head off and had located (eventually...!) the single front nut/bolt at the centre front of the barrels (attaching it to the crankcase) it was still a bit of an effort to loosen the barrels up in order to lift them from the main part of the engine.

Maybe they were taken apart once before and some sort of sealant might have been used in addition to the gasket to ensure oil tightness?

I'd also gently try a rubber mallett and wood block on the barrels to see if it loosens them (aiming upward) - watch that you don't damage any fins.

I'm presuming that with head off, the front chainguide has been removed and that the rear cam chain guide is not interfering with the removal...and also, what about the cam chain tensioner. I'm doing this from memory here but just checking that you've stripped it back to bare essentials before trying to remove the barrels.

 

Thanks for the tips, guys.

All (13) nuts are off... the upper chain guide is out, the chain tensioner is out. I've been step-by-stepping it with the service manual in front of me, so I think all the prep work is done.

Looks like it's just a matter of time. And patience.

I'll post with progress.

 

Any luck getting the cylinders off?

I've done two and they were both a PITA to get off. One took me and the boy over half an hour and much swearing and the other over a hour with four of us trying to get them off with more swearing and extreme violence (you would cringe seeing the effort it took).

They (cylinder blocks) get stuck on the threads of the studs and the plastic tubes on the unthreaded part of the studs. Keep it as level as possible, be careful not to break cooling fins and don't be afraid to bash the **** out of the block!