1978 KZ650 Bike Build

DoctoRot wrote:
the Z1 hub is different from the KZ650. also KZ650 has a 17mm rear axle. im sure it could be made to work.

Thanks for that info. Luckily the wheels are the same size so I know it will fit. The only mods I can see are to tie the brake lever into the foot pedal and to attach the torque bar.

There has been some damage to the tranny cover...possibly from a snapped chain. At some point some PO tried to repair it to prevent leakage. I need to strip the repair and examine the crack to see if it's OK, or maybe try to replace the cover. If you look closely you can also see that the top bolt on the sprocket shroud was snapped off. Also, when removing case bolts I noticed that one was broken on the threads, so will have a stud to remove when I get the cases apart.





Photos below show another, more serious problem. The engine case is cracked on the left side of the lower engine mount. One photo shows if from the side and the other from the bottom. Any opinions on whether this is weldable? I may have to scrap the project if it cannot be properly repaired. I have the cylinders off and they look OK, as do the pistons, but still need some measurements to ensure everything can be re-used.

To properly weld a crack you need to grind material away exposing the entire crack. Then it can be refilled with weld. If all of the crack is not exposed and welded, it can continue to migrate through heat expansion and vibration. That looks like it may not be easy to save. The crack looks like it runs pretty deep.

Thanks for your thoughts Skid. Fracture mechanics was my specialty in university so I have a good understanding of how the crack can propagate. From what I saw the crack is indeed quite deep.

That crack is repairable but the amount of time it will take to weld and then machine will make the repair fairly expensive. Its probably cheaper to find a new engine, or the very least new cases. Big ol' bummer. I went through something similar no long ago on a early GSXR frame.

I kind of thought that might be the alternative. There are lots of cases on ebay for less than $100 not including shipping but photos only show so much. I'll take the case to a welder and see what he says about repair price.

Cases are apart. I had to pull the pistons off in order to pull them completely apart. Two bolts were broken by the PO when he re-assembled the engine. One is an M6 case bolt and one is on the pan. Both are broken flush so I'll leave them to an expert to extract. All of the bolts so far felt really tight. I am guessing the PO over torqued them.

More damage noted to the engine. The first photo shows where the underneath left side top engine mount was welded at some point in the past. and the second photo shows where a piece broke off the clutch hub and was welded. I suspect the bike was in an accident sometime in the past and suffered serious engine damage. The frame doesn't show it though.

A lot of permatex was strung out along the inside of the cases and would have likely plugged the strainer at some point. Transmission looks to be in good shape.

Mikaw wrote: Here are the counter sprocket covers. If they fit one is yours.

If they are not 650, then I’d appreciate it if a member can identify them.

- I believe these are 77/78 KZ1000 covers

Injected wrote:

Mikaw wrote: Here are the counter sprocket covers. If they fit one is yours.

If they are not 650, then I’d appreciate it if a member can identify them.

- I believe these are 77/78 KZ1000 covers

I do not know what they are from, but they are not from a KZ650. Below is a picture of the KZ650 cover. Ed

I agree they are not from a (K)Z650. Not sure at the moment what they might be from.

Here are pics of outside and inside of it.

Injected wrote:

Mikaw wrote: Here are the counter sprocket covers. If they fit one is yours.

If they are not 650, then I’d appreciate it if a member can identify them.

- I believe these are 77/78 KZ1000 covers

Definitely not. This is a '78 KZ1000:

I agree. Not a 77/78 kz1000.

My guess is they are a 79/80 mk2 kz1000 covers. The 81 and later J model had an added undercut.

Wow that must have taken a serious hit. Looks like there are many more cracks, possibly some you cannot see. might be better to cut your losses on those.