Wanted to do a performance rebuild on my KZ1000-K2. Originally, I was planning on just doing the top-end myself. I’m a new-car dealership technician with 30 years’ experience – and I’ve assembled and repaired more engines than I care to mention. But I was referred to Pit Stop Performance in Orlando, FL, understanding they could perform a quality complete rebuild, and they specialize in classic Japanese muscle engines.
The bill was almost $5k, and it looked great in the crate, but here’s what I’ve learned since then:
Within the first 100 miles the oil leaks began. It leaked at the generator cover, clutch cover, gearbox cover, RS crank cover, and the oil pan. The cover leaks were caused by engine paint on all the gasket surfaces, combined with the use of inexpensive thin paper gaskets. I cleaned all surfaces down to the aluminum, and used OEM gaskets to make the repairs. During the process I replaced the oil level lens in the clutch cover (couldn’t read the oil level because the lens was installed backwards).
Next, the head gasket started leaking oil, significantly from the oil passages. Tried re-torquing the cylinder several times, but that didn’t help at all. At the same time I noticed small leaks beginning at the engine case-half seam.
While attempting to tune the carbs the engine wasn’t running quite right, so I performed a cylinder leakdown test, and discovered about a 25% leakage past the intake valves at two cylinders.
The head gasket oil leak, combined with the leaking valves, required me to teardown the top-end and send the head, cams, block, and pistons to a reputable machinist I work with here in the Dallas, TX area.
He informed me that the combined .004” warpage at the head, and .006” warpage at the block, along with the aftermarket one-piece head gasket coated with an unknown sealant, was the cause of the head gasket oil leak. He machined the block and head to correct the warpage.
The valve seats were not cut concentric with the valves causing the compression leak at the two intake valves. He cut all seats and lapped in the valves to correct.
At the same time we noticed significant scoring at a number of the camshaft journals and bearings. The machinist, while cleaning the cylinder head, found some kind of blasting media (grit) inside the oil galleys feeding the camshafts. He cleaned out the media, polished the cam journals, and I replaced all the camshaft bearings to correct that problem.
The pistons, rings, and cylinder walls were also scored. The machinist believed this could be caused by insufficient cleaning of the cylinder walls after honing. I keep wondering if the blasting media may have been a part of this problem also. The correction was re-honing the cylinders, polishing the pistons, and replacing the rings. The machinist also noted that the engine paint on both the block and head washed off completely with gasoline, even after full curing at the hottest areas of the head.
As part of the original rebuild the air/pollution passages leading to the cylinder head exhaust ports were supposed to have been plugged off, but they were not. My machinist completed that also.
Re-painted and reassembled the top end with OEM gaskets and O-rings (no sealant), and she’s now running well with no oil leaks – except the case-half seam. Right now I don’t have the time or energy to pull the engine again, split the case, and repair this final oil leak. But I’m confident the cause is again engine paint on the seam surfaces, and the use of the unknown sealant. I can see the hard sealant at parts of the seam, and it’s definitely not a silicone liquid gasket which is used in almost all aluminum-to-aluminum non-gasket engine sealing applications.
In the beginning Pit Stop Performance was sending me the OEM gaskets while I repaired the first oil leaks, but when I asked for reimbursement for the machinist and parts bills for the top-end, I was offered only a fraction of the cost, which wasn’t worth accepting. In reality, the machining, parts, time and labor for everything I’ve done to repair this engine has exceeded what I paid for the rebuild. And I still have to pull the engine, split the case, and re-seal the case halves.
I just wanted to explain what I’ve been through, while trying to be nothing more than factual about the whole thing. I’m hoping to help fellow enthusiasts avoid the loss of time and money this has cost me. Bottom line; I should have done it myself.
But, after all is said and done, I think I still I have a pretty cool KZ.
Let me know if you have any questions. I have pictures of everything, and it’s not pretty.
