Kohler SV730 vs Kohler ZT730

[bullet bob]

Guy, got quite a problem brewing here with the daughter-in-laws' JD Z520A. Dealer 'worked' on it last year to the tune of ~$1100. Long story short, somehow oil leaked out of engine & she blew up. Dealer steps up & puts in a new engine. Only problem is, the holes to mount the engine don't align. Rear 2 do, front is off about 1/4". So they apparently 'angle in' the front 2. 80 hours later, after having other problems, we notice the engine is flopping, again. Front 2 bolts are missing. Dealer takes a look, then decides to try Loctite. Yes, I know. Daughter mows once for 4 hours, bolts are out. Technican explains that the threads in the block are oblonged now.
Now, the reason for my heading, the dealer replaced the original Kohler SV730 with a ZT730. They say they couldn't find a SV but this ZT comes close. Obviously not close enough. So, I contact someone who sells Kohlers, he asks me what is the spec #? I don't know, don't have the old engine!
So, I guess I'm looking for either a way to match up a ZT730, spec # 3043 to what might be the equivalent in a SV, or if anyone would know what SV engine I need. The JD is probably 20 years old. Any help will be greatly appreciated.

 

[StarTech]

I could say what idiots but that not going to help. All they had to do initially to drill mounting holes in correct positions; although, the ZT730 series is a replacement for the SV730 and the mounting holes should had lined up properly as both had the same 10" bolt circle. But doesn't mean the holes are in the same place on the circle. And even now they can drill out and Heli coil the mounting holes. Something you couldn't easily do on the SV. And they should be using serrate flange head torqued to spec not just hand tighten.

Both the SV and ZT uses 3/8 self tappers. The problem is the ZT has less meat persay for threads. It recommend that you Heli coil back to 3/8-16 threads approximately 1 inch deep provided they are not too mess or if there is enough material left at the mounting go to M10 x 25. Either way the Heli coil tap would need to be a bottoming tap which is not part most kits but as a separate tap. And it not cheap. I know as I got a 3/8-16 Heli coil bottom tap inbound here that was $41 plus shipping. Now max hole size is 25/64 for the 3/8-16 and 13/32 for M10-1.25(fine thread) or 10.5mm for M10-1.5 (course thread). As said it depends how much material is left to work with.

SV


ZT


It appears the original engine was a SV730-0023 superseded to ZT730-3023 but that engine is NLA now.

 

[bullet bob]

Wow. Great info there ST! I'm going to show this to the 'techs' as I feel they need all the help they can get. I was going to suggest something about a helicoil but was afraid I would be talking over their heads. I won't even tell you about the comment he said about running the impact gun until he hears /feels "the 'slam' so he knows it's tight." Again, aluminum threads............

 

[StarTech]

Aluminum and Impacts just asking for problems especially if it is like the one I have here that only starts hammering around 80 ft-lbs.

My lord that why they publish torque specs which I believe is only 35 ft-lbs or at least that the 3/8 bolts on the Z525.

And yes you may have been over his head if it like some of the JD techs here.

 

[Tiger Small Engine]

I could say what idiots but that not going to help. All they had to do initially to drill mounting holes in correct positions; although, the ZT730 series is a replacement for the SV730 and the mounting holes should had lined up properly as both had the same 10" bolt circle. But doesn't mean the holes are in the same place on the circle. And even now they can drill out and Heli coil the mounting holes. Something you couldn't easily do on the SV. And they should be using serrate flange head torqued to spec not just hand tighten.

Both the SV and ZT uses 3/8 self tappers. The problem is the ZT has less meat persay for threads. It recommend that you Heli coil back to 3/8-16 threads approximately 1 inch deep provided they are not too mess or if there is enough material left at the mounting go to M10 x 25. Either way the Heli coil tap would need to be a bottoming tap which is not part most kits but as a separate tap. And it not cheap. I know as I got a 3/8-16 Heli coil bottom tap inbound here that was $41 plus shipping. Now max hole size is 25/64 for the 3/8-16 and 13/32 for M10-1.25(fine thread) or 10.5mm for M10-1.5 (course thread). As said it depends how much material is left to work with.

SV
View attachment 69642

ZT
View attachment 69641

It appears the original engine was a SV730-0023 superseded to ZT730-3023 but that engine is NLA now.

Plan B, use longer bolts with nuts and run bolt through and tighten with nut. Never use an impact in a case like this. Hand tighten with socket wrench and use Loctite with clean bolts.

 

[bullet bob]

So

Plan B, use longer bolts with nuts and run bolt through and tighten with nut. Never use an impact in a case like this. Hand tighten with socket wrench and use Loctite with clean bolts.

So you're saying that the bolts just don't go into the block but go through?

 

[StarTech]

Well, IF Tiger actually did his research he would know that is impossible. I actually called my RBI Kohler Tech support to verify these are not thru holes and the size of the screws used in the holes initially which were 3/8-16 self tappers. Actually I was mainly checking on the screw as the SV had 8.5mm holes and the KT has 9mm holes which means less material for the self tappers to bite into for threads. Otherwords the screws if over tighten can pull out easier.

Personally I think it going very difficult to use thru screws since would require drilling thru holes and then mounting the sump/oil pan/closure plate and reassemble the engine while this is attached to the mower's engine plate.

I wish posters would stop just throwing things out just to hear their head rattle or in this case the keys rattle.

Here is the location of the mounting screw holes.

 

[Tiger Small Engine]

Well, IF Tiger actually did his research he would know that is impossible. I actually called my RBI Kohler Tech support to verify these are not thru holes and the size of the screws used in the holes initially which were 3/8-16 self tappers. Actually I was mainly checking on the screw as the SV had 8.5mm holes and the KT has 9mm holes which means less material for the self tappers to bite into for threads. Otherwords the screws if over tighten can pull out easier.

Personally I think it going very difficult to use thru screws since would require drilling thru holes and then mounting the sump/oil pan/closure plate and reassemble the engine while this is attached to the mower's engine plate.

I wish posters would stop just throwing things out just to hear their head rattle or in this case the keys rattle.

Here is the location of the mounting screw holes.

View attachment 69646

I was not saying on this particular model engine that using bolts and nuts instead of self tapping bolts would absolutely 100% work. I am on this forum to help people, not get berated by you.

 

[MParr]

An expensive lesson learned.
If the clowns at the John Deere dealership ever gets this straightened out, fire them and find a competent repair shop.

 

[StarTech]

I was not saying on this particular model engine that using bolts and nuts instead of self tapping bolts would absolutely 100% work. I am on this forum to help people, not get berated by you.

You know better than just throw something just to increase your post count. All you did took a wild guess without even looking up the engine info. That is like telling you to replace all eight spark plugs when you got a two cylinder engine.

But the Damn problem is resolved as I am deleting all links to this forum and will not post any further comments or help. At least take the time to properly research things so I post as accurate info that I can. The Loony Tunes here can have it.