TOPIC:

Got my top-end back at last and would like some tips on aligning the pistons with the cylinder block? I have a plan for the #3 and #4 cylinders but 1, 2, 5 and 6 I am still pondering and I am feeling a bit under qualified at present. I was planning to make piston ring compressors from split pvc pipes and clamps (I think Pete may have given me this idea). As usual all tips and comments are welcome.

Anyway here are photos of the before and after of the head.

I'm no fond of the "PVC" idea because I feel the sharp edges on the rings could scrape or shave small pieces of the PVC and trap the shavings between the rings when the pistons are in the cylinder.

I have heard of members using gear clamps to compress the rings and I'm concerned that the engagement grooves in the clamps could damage the sealing face of the rings and or the bottom edge of the clamp could marr up the sides of the piston. Also, the gear clamp will probably not cover all three rings at the same time.

Another method commonly used is to cut 1-1.2" wide strips of brass shim stock (probably .005" or .008") and cut to length to wrap around the piston and then put the gear clamp over top. The wider shim stock will keep the shim stock from gouging the side of the piston and the smooth surface of the shim stock will not damage the ring faces.

My preference is to just use my fingers but I also do a couple of things first.The bottom edge of the cylinders has a 45 degree chamfer on the piston bores to assist with installing the cylinder over the pistons and that chamfer really inhibits the effort when using the clamps. As the rings come out of the ring compressor be it the gear clamp or the bras shim, the ring will not be in the true bore but in the chamfer area and for that reason, I don't use ring compressors.

So the first thing I do is prep the cylinder bore chamfers. I take a piece of 400 wet and dry sandpaper and using oil as a libricant, smooth the sharp edge where the chamfer on the bore and the bore meet so that I can't "feel" a sharp transfer between the bore and the chamfer. Then clean up the cylinder bores with Laquer Thinner (thank you Scotch) then wipe the bores thoroughly with engine oil. That's the cylinder prepped and ready to install. Put it off to the side for now.

Next install the cylinder base gasket. I use Permatex super high tack gasket sealant. It's a brush on product. brush it on the gasket and the crankcase and let it tack up. Then install the gasket. Now the gasket is on BEFORE you get the cylinder on and realize you forgot the gasket (ask me how I know)

Next, get cylinder 3 and 4 at top dead center. Really important that they are at the top and not just close to the top.

With an oil can, squirt oil on the 3-4 pistons and work the oil into the piston rings and down the sides of the 3-4 pistons.

Position the piston ring ends on 3-4 pistons as noted in the service manual.

Now the fun begins. Place the cylinder on the studs and lower down until the 3-4 pistons are resting on the cylinder bores. The trick now is to compress the top ring on each of the 3-4 pistons one at a time and encourage them into the bores. The first part is to get the back side (as opposed to the open side) of the ring started in the bore and then using your fingers start squeezing the rings into the piston lands while watching the ring ends. If you've wet sanded the bore chamfers like I suggested, you can actually rock the pistons slightly and get the piston ring backsides in the bores and rock the piston and just watch the rings compress into the piston lands as you rock the piston and the cylinder will drop down to the second ring. It's facinating watching this happen.

So you carry on and following the same practice get the second rings engaged, then the oil rings engaged. the more rings that engage the more likely you'll have to apply a little pressure on the cylinder to get it to drop down. At this point, you should now have 3-4 pistons engaged in the bores.

Now you need to rotate the crank and bring 2-5 up so you can repeat the process. oil the rings and piston sides, align the ring ends and engage the pistons. Then repeat for 1-6 pistons.

Before finally engaging the cylinder down on the cranckcase, remember to apply your gasket sealer on the base gasket.


That's how I do it. Hope the thoughts help .
KB

Yep - pretty much exactly as Kawboy said but I will add it is much easier with 2 people working from each side of the bike.

Also helps if you have fingernails to help compress the rings into the chamfers, or a couple of small flat bladed screwdrivers to poke them in (like the hobby screwdrivers).

Go easy and take your time.

+1 on the friend to help, also taking the edge off the chamfer & using your fingernails to feed the rings in. In the manual it states to position the ring gaps at even intervals to maintain compression but they move gradually around the circumference of the ring groove in service anyway. Certainly a lot easier to ease those pistons in with the ring gaps all in the same place anyway I did a compression test after it was all bolted together again & it was fine.
This was me & a mate doing the same job some years back:

Phil,

The last time I saw that photo many years ago I asked you for the name and contact details of your interior decorator ........and I am still waiting !!!!

LOL

Pete F
UK

Wide zip ties are your friend. The nylon won't scratch anything, and as you slip the bores over the pistons it will push the ties off as the rings go into the bores.

I had to supplement mine with a bit of thin plastic because the ties weren't quite wide enough, but between the ties and the bore taper, it worked (solo) magnificently.