Topic: Cylinder Install Tips - Broke 2 Rings Already

[Mandic]

Well I am a car guy, new to heavy mechanical work on motorcycles.  This CB750 engine has been my mortal enemy for a while now.  While trying to drop the cylinders on my 836 F2 engine last week I broke 2 rings.  One was an oil rail, the other a second compression ring.  My Dad(helping) actually broke the compression ring, how I haven't a clue.  That said, does anyone have tips for getting this thing together? 

I don't have a compressor that will work for this application at the moment.  I have been using my fingers and screw drivers to squeeze the rings together and slip the cylinder over the pistons while doing so.  Obviously it hasn't worked out so well.  I think the ring broke because I got ahead of my Dad and he tried to force things too much. 

Currently waiting on replacement rings and contemplating what my next plan of attack is.  I moved away from my Dad/friends so the mechanical help I have here is lacking quite a bit.  My friends in Austin will help but don't really know what is what when it comes to this stuff.

[bollingball]

Good old hose clamp better than nuttin

[MCRider]

I noticed you used the word "force". Uhuh. Even without clamps the cylinders will drop on without force, gravity alone, if you take your time and work the rings in. That is assuming they are stock and have the full taper on the bottom of the cylinder sleeve? But that takes a lot of fingers to do.

Tips are to use strips of wood under the piston skirts to hold them level. Proper size you may need to rip them down to size.  Also oil up from the inside of the cylinder so it flows down onto the piston head and the rings.

But best is to use hose clamps. Get some as close as possible to the diameter of the piston, 2.25 to 2.5 in I think. You don't want a lot of tail sticking out of the clamp. Also if the clampislarger when youscrew it down itloses its perfect circle and presses unevenly on the rings. Don't put the buckle of the clamp on an end gap. Tighten them down snug, then back off enough that you can just turn them. Oil first on the rings and lands.

More tips I'm sure in the Search function of FAQ.

[Mandic]

Thanks, hose clamp was an idea we had before and one I think I will attempt.

This is an 836 motor with cylinders bored by Cycle-X.  I don't know how much of a taper there should be, there is one but not a big big one.  Force is what my Dad did that broke the one compression ring.  He can fix things, but finesse is not his style, ha. 

These are far from just dropping on though.  I checked gaps and the pistons and all, every measurement checks out.  It is just a bear to get everything to slide together without the cylinder wanting to cock to one side or the other.  That seems to be where the big issue lies.  Keeping everything level on the way down.  If one side gets ahead of the other you are just about jammed up and have to start over.

Searching didn't net me much of anything(I searched the general forum though).  I swore just a few weeks ago someone posted a topic with almost the exact same title as mine as well.

[MCRider]

Yeah, not much taper left on an 836, that makes it harder. I'll search and see what i can find.

[MCRider]

Here's a good thread. Seems doing 2 pistons at a time is an option. Tapping on the block from above is allowed  if you're sure therings are in.

http://forums.sohc4.net/index.php?topic=169.0

Search on "piston Ring Compressor". That's where I found this and lots more. Hit the "home" button first, in the blue bar across the top. You'll get a better search I'm told.

[Mandic]

Yea I have discovered over time that searching locks you into each forum you are in(sort of).

I have been doing 2 cylinders at a time and do find it easier.  Starting with the inner ones since they are harder to get to and the outsides seem easier.  I will get it, just going to take patience.

[tweakin]

I instal all 4 pistons into the cylinder then push them slightly up inside.  I then rotate the engine so the inside rods are up and then pull down the inside pistons just enough to get the pins in.  Then I rotate the engine enough to work on the outside pistons.  If working alone use rages yo hold up the cylinder or have a buddy help.

i have found this way to be the easiest way, IMO.

[Toxic]

Ya hose clamps for sure but make sure you don't tighten them too much.  Just enough to compress the rings flush to the piston sides.

But what really helps is at least two buddies, one on each end of the block to slowly lower it as you work the pistons up into it.

No such thing as too much lube.

[kaceyf2]

+ one with tweakin, worked for me too.

[turboguzzi]

cut some wood pieces that will hold the block at higher level than the mid pistons @ mid stroke, and feed the mid pistons UP & INTO the block by rotating the crank.

sure, you are starting at the deep end with a big bore and very little chamfer to lead in. just mounted such a kit now and its definitely harder than stock. and still, didnt use clamps, or whatever, just fingers and strategic pushes in the right spots with a long screwdriver.

it defientely requires finesse and lots of patience, so if your dad is not the type, do it by yourself, its really doable.

TG

[CB750F2]

+ 2 with Tweakin. Ensure that you have the inner piston pin circlips in place before you connect the connecting rods to the pistons. Once the piston pins are in place then it is easy to install the outer piston pin circlips. Also ensure that you seal the crankcase with rags just in case you drop a circlip. Hasten slowly. Pat

[turboguzzi]

+ 2 with Tweakin. Ensure that you have the inner piston pin circlips in place before you connect the connecting rods to the pistons. Once the piston pins are in place then it is easy to install the outer piston pin circlips. Also ensure that you seal the crankcase with rags just in case you drop a circlip. Hasten slowly. Pat

that's cheating!

[bollingball]

Next time you start to install see if you can get your DAD to make a beer run or get supplies

[Mandic]

Hose clamps and plenty of oil.  Did it alone, and it went smooth.  Took a while of slow progress but I got it on and smooth.  Thanks guys!  One step closer to getting this bike roaring again!

[JScottB]

Hose clamps did the trick for me however the problem I ran into when putting the cyls on my 550 was the part of the clamp 180 deg from the screw kept wanting to go in with the piston and jamming it. It was a delicate balance between the clamp being just tight enough and being too tight. The 550 ended up a success with no broken rings or scuffed pistons however I didn't want to run into the same problem when I installed the cyls on my current 750 project so what I did was weld 3 small tacks spaced 120 deg from each other on the top edge of all the clamps to prevent them from wanting to slide up the bore with the piston. This was tricky because even with quick bursts with my mig welder it was tough to keep from blowing a hole in the thin clamp. With that said the end result was 4 hose clamps that didn't look all that pretty due to the tacks but they worked perfectly. I also used wood shims under the pistons.

[MCRider]

Hose clamps did the trick for me however the problem I ran into when putting the cyls on my 550 was the part of the clamp 180 deg from the screw kept wanting to go in with the piston and jamming it. It was a delicate balance between the clamp being just tight enough and being too tight. The 550 ended up a success with no broken rings or scuffed pistons however I didn't want to run into the same problem when I installed the cyls on my current 750 project so what I did was weld 3 small tacks spaced 120 deg from each other on the top edge of all the clamps to prevent them from wanting to slide up the bore with the piston. This was tricky because even with quick bursts with my mig welder it was tough to keep from blowing a hole in the thin clamp. With that said the end result was 4 hose clamps that didn't look all that pretty due to the tacks but they worked perfectly. I also used wood shims under the pistons.

Great explanation of exactly what happens. And a good idea for fixing it.