Saving a '81 KZ750-E

Here I am, trying to be careful. Those unwanted nicks will get weld beads when the bracket is welded back on. Glad it's on the inside of the muffler.

I will gain about 3/8" clearance with this welded back in this position.the rest will come with bending the mount bracket, and shaving down the bolt heads. Some percussive material movement was required for the closer nut to fit. I will have to shorten that mounting bolt before installing.

The muffler is off at the weld shop. Once I get it back I will start changing the bends on the hanger bracket. Time to move on to the next step. Since I was in such a hurry to test fit the exhaust, I failed to notice a lack of thread engagement on the cylinder head nuts. I purchased APE studs of of Z1E, and the nuts as well. I'm thinking maybe you need a longer APE stud to use with their nuts? I torqued the studs into the case per instructions, so I don't think they are threaded in too far. Some (not all) are slightly less than one stud diameter on engagement - not good. I may be taking the head and block back off (almost positive, actually).

I put in a call to technical support at APE Racing Parts. They are looking into the issue and will call me back. I am suspecting the part number on the Z1E site is not the correct length. They list these studs as fitting both the KZ650 and KZ750. APE will get to the bottom of it and let me know, but it looks like I will need to buy longer studs regardless. I think I have lost track of how many times this bike has kicked me in the ass... :sick:

I did use the washers under the head nuts, but those would not account for the amount of shortage there is. And the head was fly cut, making it shorter (only a marginal amount for clean up).

APE has great customer service. They researched it and called back in the less than 15 minutes. I have the correct studs and head nuts. Apparently when I cleaned up the cases and ran a tap in the case holes to clean them up, it opened the threads slightly, enough to wear they will thread in too deep. They recommend using a ball bearing in the case holes to prevent the stud from going in too deep. That won't work on all locations as some are tapped through into the case interior. I guess it's time to buy a new base and head gasket as it's going back down to the block.

Hindsight being 20/20, I probably should have measured and recorded the OEM stud heights prior to removing them... oops.

Skidmark wrote: Hindsight being 20/20, I probably should have measured and recorded the OEM stud heights prior to removing them... oops.

Shrug it off. Just keep looking at that beautiful bike begging to be finished. You will have an awesome bike once it’s done...

It's only a "mistake" if you do something wrong TWICE. The first time is a "learning experience."

Good luck

Skidmark wrote: APE has great customer service. They researched it and called back in the less than 15 minutes. I have the correct studs and head nuts. Apparently when I cleaned up the cases and ran a tap in the case holes to clean them up, it opened the threads slightly, enough to wear they will thread in too deep. They recommend using a ball bearing in the case holes to prevent the stud from going in too deep. That won't work on all locations as some are tapped through into the case interior. I guess it's time to buy a new base and head gasket as it's going back down to the block.

because not all the holes are blind the stud bottoms out where the stud threads end not on the bottom of the hole. You could tap the hole to china and the stud would assemble the same way, as long as you didn't counter bore the hole nothing should change. Either APE formed their threads too long, you have the wrong studs, or (what i assume is likely) you installed the studs in the wrong locations, they do not all assemble at the same height.

as long as you don't tear or deform your gaskets i personally would reuse them if they haven't been through a heat cycle.

we've all been there. it took me like 5 trys to assemble my first kz1000 engine. a litany of stupid mistakes.

I do have them in the correct locations. All of the studs are short by approximately the same amount. APE confirmed I have the right length (p/n) for this engine. My mistake was installing them too deep. I torqued them in, and used loctite. I believe there are two studs that are not in a blind hole, probably the two that require o-rings at the base of the studs. There was a lot of debris at the base of the studs, and some of them came out with some minor difficulty. That is why I went back with a tap and cleaned up all the threads for the studs. APE suggested this is why they threaded in deeper, and easier, than normal. I just chased the threads to clean them up - I did not cut the threads deeper. I was careful not to cut aggressively with the tap. I am hoping the loctite doesn't cause me too much trouble removing them. I was thinking I may be able to back the studs out without taking the cylinder block off, but I am nervous about the two that have o-rings at the base and if backing them out while the o-rings are compressed might damage them. If that would work the base gasket would be fine.

You cannot install them too deep. the installed height of the stud is set by the length of the thread on the stud. the studs bottom out where the thread terminates on the stud, not the bottom of the blind hole, thats why the OEM studs have the bump above the threads that go into the cases. There is something else going on.

Being an aftermarket stud, the bottom thread is more than likely longer than stock. I verified all of the studs were the same length as the factory studs.