Topic: help installing head on motor

[Bonesaw]

Ok for the life of me I can't figure this out. I can't fit a ring compressor under the "jugs" when I'm lowering them down onto the pistons. How does one put the cylinder head back on the motor?

[Terry in Australia]

OK mate, a couple of things first, you are asking how to install the cylinder block, not the cylinder head, yeah? What model bike?

The car type ring compessors are too big and bulky for our bikes, so try some hose clamps instead. Use some wooden blocks beneath the centre two pistons (#2 and #3) to hold them up above the engine cases as your assistant holds the cylinder block over the pistons, while you guide them into the bores, then once they're in, guide them onto #1 and #4.

Come back to us if you need help torqueing down your cylinder head and installing your cam, cam chain, rockers etc. Cheers, Terry.  

[Bonesaw]

lol yeah used to working on cars. Cylinder block. 1978 cb750K.

The manual isn't much help, it just says work can be "facilitated" by a SST ring compressor.

I've got the 2/3 pistons sitting right at the lip and the rings are lined up, do i just "tap" them in lightly with a rubber mallet? I don't have any hose clamps that large at the moment, but can get the "screw" type tomorrow at autozone

[adamlwvdc36]

Honestly, ive rebuilt 2 of these motors and have never used a ring compressor.  squeeze with your hands and slip them in place, they will go.  Then, yes, rubber mallet gently down into place

[MCRider]

Honestly, ive rebuilt 2 of these motors and have never used a ring compressor.  squeeze with your hands and slip them in place, they will go.  Then, yes, rubber mallet gently down into place

If the bore is stock there is a good size taper on the bottom of the sleeve that will let you do this, avoid a ring compressor. If its an overbore like an 836, pretty tough without hose clamps ala Terry.

Oil the rings lands and the bottom of the sleeves a little to help.

[davesee]

the wood blocks idea is right on. the hose clamp idea is sound, but i spent more time fighting with them than anything else. nor was i very good at getting the rings in with my fingers. i had a helper (who knew nothing about bikes) who go the rings in by hand first try every time.

[Bonesaw]

ok i'll try getting a helper before I go buy a compressor (beer is cheaper than shipping these days).

before I try that, the manual didn't say anything about which way the pistons go on. I just want to confirm with you guys that the circles on the one side of the pistons go towards the exhaust? I didn't notice that there were any markings on the pistons until after I took them off and cleaned them off, too much caked on carbon.

[wrenchmuch]

There should be a small triangle in the top of the piston. This points forward or towards the exhaust port.

[Bonesaw]

no triangles. There's a divot in one side which looks like clearance for a valve, and a circle on the other side

[Terry in Australia]

Yeah mate, some pistons have triangles or arrows pointing towards the exhaust, and others have circles, either way, you're correct. Cheers, Terry.

[MCRider]

If there is only one divot for valve clearance it would be for the intake as it opens more and is larger diameter than the exhaust.

If the divot is offset, remember the valves are offset too. So the piston must match the valves.

That is, the #1 intake is offset towards the inside, the #2 intake is offset towards #1. Same with 3 & 4 so the divots in the pistones must match.

Some pistons come with 2 divots overlapping so the pistons can go in either hole.