Is it easiest to just remove the pistons with the jugs on a Ztu?

[Case1951]

I'm not an MM guy, so learning these engines. On a ZTU.. I was going to remove the jugs for a valve job and was thinking of doing the piston rings too.

Is my thinking right that you unbolt the rod cap, then unbolt the jugs, then lift the pistons right off with the jugs?

Will a standard wrench work when reassembling the rod cap or do you guys use a torque wrench? Thanks

 

[CraigWis]

That is how you do it. Unhook the Rods from the crankshaft. If you can push the piston up and remove the Jug
MM advertized that you could rebuild that Engine by sitting on a chair

 

[Case1951]

That is how you do it. Unhook the Rods from the crankshaft. If you can push the piston up and remove the Jug
MM advertized that you could rebuild that Engine by sitting on a chair

Thanks. That is what I needed to know. Stupid question, do you advise using a torque wrench during reassembly or will tightening it all back down with a standard wrench be ok? Thanks

 

[JOCCO]

What Craig said I don't think you can get the pistons out the bottom. Put pistons back in then put jugs on. No need to remove jugs just to due valves.

 

[CraigWis]

It has been over 10 years since I had one apart. I think I had Torque spec to tighten it down with

 

[JOCCO]

Yes use normal torque wrench and get specs out of book

 

[Case1951]

What Craig said I don't think you can get the pistons out the bottom. Put pistons back in then put jugs on. No need to remove jugs just to due valves.

I guess I should have mentioned, the first jug is leaking oil bad where it meets the crankcase. I am guessing the gasket is shot? So, it has to come off to replace that gasket. I'm just thinking while it's off, maybe inspect and replace rings as well. Just an idea

 

[JOCCO]

I guess I should have mentioned, the first jug is leaking oil bad where it meets the crankcase. I am guessing the gasket is shot? So, it has to come off to replace that gasket. I'm just thinking while it's off, maybe inspect and replace rings as well. Just an idea

Yes my guess is gasket. Ring set was 80 at Otto engine works gasket set online at napa 68 dollars.that engine is very similar to an r stroke is longer.

 

[molinegb]

Block gaskets pretty simple to make. Blocks have to come off to get pistons out..

 

[Ill John]

I guess I should have mentioned, the first jug is leaking oil bad where it meets the crankcase. I am guessing the gasket is shot? So, it has to come off to replace that gasket. I'm just thinking while it's off, maybe inspect and replace rings as well. Just an idea

If you're going to replace the rings. you'll need to clean up the ridge at the top of the cylinder, that operation alone might cost more than the rings and gaskets. Just a thought

 

[Case1951]

If you're going to replace the rings. you'll need to clean up the ridge at the top of the cylinder, that operation alone might cost more than the rings and gaskets. Just a thought

Like I said, I don't know these engines very good. I was mostly just going to do rings since I would be right there at it. Might turn into more than I bargained for. If I only took the jugs off, didn't remove the pistons at all, when it came time to put the jug back on, after replacing the gaskets, would I need compress the rings when sliding the jug back over them?

 

[CraigWis]

Like I said, I don't know these engines very good. I was mostly just going to do rings since I would be right there at it. Might turn into more than I bargained for. If I only took the jugs off, didn't remove the pistons at all, when it came time to put the jug back on, after replacing the gaskets, would I need compress the rings when sliding the jug back over them?

Take the Jugs with the Piston in them Off. Not Much room to use a Ring Compressor with the Conn. Rods still on the Crank

 

[Case1951]

Take the Jugs with the Piston in them Off. Not Much room to use a Ring Compressor with the Conn. Rods still on the Crank

Will do exactly this. Maybe I should clean & work with the valves and just skip rings for now. The pistons move freely so maybe it would be ok to run it as it is? Been sitting a long time. The only reason I wanted to do rings is just being this close to it

 

[JOCCO]

If you're going to replace the rings. you'll need to clean up the ridge at the top of the cylinder, that operation alone might cost more than the rings and gaskets. Just a thought

It won't for me and if it was that bad you would be into reboring.

 

[Ill John]

Like I said, I don't know these engines very good. I was mostly just going to do rings since I would be right there at it. Might turn into more than I bargained for. If I only took the jugs off, didn't remove the pistons at all, when it came time to put the jug back on, after replacing the gaskets, would I need compress the rings when sliding the jug back over them?

yes, the same as any piston ring setup only you would need a compressor that you can take apart once the rings are inside the cylinder

 

[Alan K]

Just to add, if you do decide to do the cylinders, the bottom of the cylinders are tapered for installation of the piston / ring assembly. Just compress the ring slightly when you wiggle the piston and it will go in the cylinder, then do the next ring. The edges of the rings can be a little sharp so don't cut your finger when compressing them.

 

[Case1951]

Just to add, if you do decide to do the cylinders, the bottom of the cylinders are tapered for installation of the piston / ring assembly. Just compress the ring slightly when you wiggle the piston and it will go in the cylinder, then do the next ring. The edges of the rings can be a little sharp so don't cut your finger when compressing them.

Great information! I have the head off already. I am working on unbolting the jugs right now as well as the rod caps. I think I will let the machine shop worry with compressing the rings and getting the pistons back inside the jugs, then hopefully when I pick it all back up, I can just put the jugs back on and connect the rods to the caps again.. I have a service manual coming to get all the right torque specs.. I'd rather just pay the machine shop a little extra $$ and know the pistons are back inside safe and I didn't hurt anything from ignorance

 

[Alan K]

Great information! I have the head off already. I am working on unbolting the jugs right now as well as the rod caps. I think I will let the machine shop worry with compressing the rings and getting the pistons back inside the jugs, then hopefully when I pick it all back up, I can just put the jugs back on and connect the rods to the caps again.. I have a service manual coming to get all the right torque specs.. I'd rather just pay the machine shop a little extra $$ and know the pistons are back inside safe and I didn't hurt anything from ignorance

If you do re-ring the pistons and don't remove the top ring groove in the cylinders, I have always heard to use an extra block gasket when reassembling. This raises the blocks up enough that the new rings don't hit the groove from the old rings. After you get the blocks on and tightened down, turn it over by hand to make sure it turns over ok. Also when reassembling, leave the blocks just snugged down a little and install the head and torque it first. This squares the head to the blocks. Then you can install the water manifold and intake / exhaust manifold and tighten the blocks down the rest of the way. The blocks don't have to be tightened down too much. If they are you will squish out the gasket.
Just to add, make sure and have them install new expansion plugs in the blocks.

 

[molinegb]

If you do re-ring the pistons and don't remove the top ring groove in the cylinders, I have always heard to use an extra block gasket when reassembling. This raises the blocks up enough that the new rings don't hit the groove from the old rings. After you get the blocks on and tightened down, turn it over by hand to make sure it turns over ok. Also when reassembling, leave the blocks just snugged down a little and install the head and torque it first. This squares the head to the blocks. Then you can install the water manifold and intake / exhaust manifold and tighten the blocks down the rest of the way. The blocks don't have to be tightened down too much. If they are you will squish out the gasket.
Just to add, make sure and have them install new expansion plugs in the blocks.

Extra gasket will decrease compression.

 

[Alan K]

Extra gasket will decrease compression.

Not by that much. If it isn't used you risk breaking a ring or the piston. MM I believe, had a service bulletin on using an extra gasket for this purpose. I was also told this by a couple of guys who used to work in MM shops back in the 1950s and 60s.