Installing Pistons.

[squares5]

Does it matter if I put the the Pistons in from the bottom or the top of the cylinder. I'm rebuilding my 76 xs650. Bought a complete kit from xs650 direct with the bigger cooling fins. I'll be looking for quite a few tips as I go. Do put the Pistons on the connecting rods and try to bring the cylinders down which sounds like it could be clumsy and awkward. Or do I put the cylinders down with a wood block hold them up and put the Pistons down through the cylinders, and the put the wrist pins in.

 

[I am Carbon]

It doesn't matter
I put mine in from bottom it's a bit easier jugs are chamfered.

 

[Downeaster]

I guess either way would work, but most folks (at least the ones I know) put the pistons on the connecting rods first then slide the jug down over them.

Putting the wrist pin circlips in is enough of a pain in the ass when you have as much clear working area as possible, having the jugs in the way would just make it that much worse.

Tip: Stuff rags/paper towels around the pistons and rods while putting the clips in. For when, not if, you drop one. You don't want to be fishing them out of the crankcase.

 

[Brian902]

You have lots of good ideas there already.

We did a BSA 650 last year by putting the engine up on it nose, transmission up and slid the cylinder on a block of wood so we could slowly feed the pistions into the bottom of their bores. Heavy cast cylinder hard to manage when dealing with rings that break easily. Don't ask how I know.

Yamaha has cylinder studs that would make it even easier. But hard to hold engine in that position so studs are horizontal.

Most use blocks under the pistions to hold them up and ease cylinder down on top. Best done with two people if you are not experienced. Rings break with a snap.

The champher at the bottom of the cylinders can be smoothed out so the transisition to the cylinder is smoother making it easier to insert pistion and rings.

I filed mine with a round file until you could barely feel the transition edge. Piston never gets this far down the bore so no worries when filing.

 

[I am Carbon]

I would also install the cam chain guide before putting the jug on.
getting the guide centered

The first engine I did I put it on after i got the jugs on. can't really get the guide centered in tunnel .
I use a chain hoist to install jugs.

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[retiredgentleman]

Great video by Carbon, as usual Yes, the lowly popsicle stick as humble as it is, is an excellent ring compressor.

The following method makes installing the cylinders/pistons very easy.

On the bench, install the inner wrist pin circlips into both pistons at the same time you install rings and then put the pistons fully into the cylinders from the bottom.

Install cylinder base gasket. Rotate the engine to stand on its nose, so that the cylinders/pistons can slide onto the studs horizontally. Slide the cylinders/pistons down the studs,feeding cam chain as you go. I used a clamp to hold the conn rods just below the cylinder bottom. Tap the pistons down until holes line up for the wrist pins. Install the wrist pins and outer circ clips. Remove clamp and slide the cylinders fully into the crankcase. Rotate engine so cylinders are vertical again. Carry on with front camchain guide, camshaft/bearings etc.

With this method, you're not fighting with the weight of the cylinders and less chance of the camchain falling downward.

 

[member3480]

Here is the way I have been doing it for over 30 years and cannot count how many rebuilt motors.
There is nothing wrong with putting pistons in cylinders and then putting wrist pins in and clips. BUT if you screw up and the clip pops out and goes into bottom of motor you are screwed if you cannot get it out. You have to pull sump plate and try to get it out with a magnet ... I have done it this way but I shove rages in motor so pin cannot go in there.
Now with that said here is what I do works all the time and the same as if you had a ring compressor the right way to do it.
I put both pistons on rods oil up the rings and pistons and just use two HOSE CLAMPS that you buy at your local auto parts and close the rings in the hose clamps just enough that the clamps can slid. Put the jugs on and slowly push down past the wrist pins and unloosen hose clamps and you are done. WORKS everytime

 

[CDNTX650]

I do it the same way as daddyg. Fast and easy.

 

[chizler62]

The fastest, easiest with minimal chance of damaging parts is IMO.

ASSY rings and then pistons on rods. Use piston forks or even two pieces of platic or wood to hold each piston. Rotate crank to lock pistons. Slide jug on pulling chain up when posiible.

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[denisducati750]

Some great ideas here fellas! The horizontal approach to avoid the weight and allow slow mating of the two makes a lot of sense. Thanks heaps for your help! Slug.

 

[Jan_P]

Gentlemen.
I have done this a couple of times ca 4 -5 times over the years
Some info here as I did this a few days ago.
Putting on clips especially on the inside ..
was difficult so I put pistons and clips on first.
I tried with hose clamps and thin sheet metal -- not working.
First time I ended up ruining the base gasket.
Perhaps it would have worked but I ordered a new one.
Second time I used a ratchet and a socket of the right size
On the right side of the engine
The socket on the crank Nut and the shaft of the ratchet going against
kick axle. leaving it there . In this manner the crank is fixed ( pretty good )
and crank was not able to rotate .. Pistons not able going down and hitting the
gasket again.
So then with the crank motion locked .I slide the cylinders downwards
Be careful so it dont fall down and break the new rings
I have done that once. There was some resistance that suddenly disappeared.
Most likely the bolts not centered at top but more so lower.

Plenty of oil. In the cylinders
As mentioned there is a taper on the cylinder. At the bottom
I positioned the Pistons at a small angle against the cylinder.
Making the back of the rings enter and not the front.
I used a wooden stick ( in my case an artist paint brush back )
to push in the rings. Into their grooves.
And used my fist to hit the Cylinders topside. No tool needed.
And not hitting hard.
Doing that step by step on Right and Left piston side . from back forward.
On both pitons. Gradually
Gradually a larger portion of the rings enter the taper if not the cylinder.
And at the end --- perhaps a little harder with the fist it went in
Oil again .
And then a rubber mallet on the Top. Still no hard blows.
I am no Mechanic so if there are obvious faults in this.
Please disregard it.
But this is the way ill do it next time. It went so good this time.

I dropped the cam chain all the way through the engine , One part Hanging out at the bottom when I was about to
put the joint in.
I am not sure if everyone knows it .But it is possible to pull it up again
with a thin steel wire from the bottom up .. with a closed loop ..at the upper end of the wire
The other in the chain end
Pushing that up .. so it can be seen from the upper side.
From that upper end Using a thicker steel wire like a fishing hook .
Hooking the loop and pull it up.
I took a while but it is possible.