Sunken valve guide on J-head?

The J-head removed from my engine has one exhaust valve-guide extending downward about 1/4" lower (compared to the other three), when viewed through the exhaust port.

Is this a serious problem, and typically what cost to have repaired?

daveo wrote: The J-head removed from my engine has one exhaust valve-guide extending downward about 1/4" lower (compared to the other three), when viewed through the exhaust port.

Is this a serious problem, and typically what cost to have repaired?

I've fixed 3 of them in the last 3 months that were like that. I just finished an ELR head that had a really bad one in #3 exhaust port.

You might get by with some plus .004 guides. You can get plus .025 guides and the special tool to ream the hole for them.

When you assemble the head, get some 8mm * 2mm O-Rings to put over the exhaust guides. You install them before you put the spring cups and seals.

You also need to get all that carbon off the guides before you drive them out. If you don't, you'll gouge up the guide bores.

Cost depends on what the condition of the valves & guides. That can't be determined until the head is taken apart and inspected. Here's some particulars.

If the faces on the intake valves are cupping, which is common on those heads, it's best to replace them rather than reface them. There's no assurance that the refaced valve will hold up with no lubrication in our fuel today. Usually, it's the intakes that cup and not the exhausts.

There are some cheap aftermarket valves available but you get what you pay for. I tend to shy away from those and put stainless valves in. Guides were cast iron in those heads. The remaining guides may or may not be useable....just depends.

Thanks Larry,

Is there something you could suggest doing (or not doing) to prevent this from happening to my replacement head, which checked out to be in excellent shape.

daveo wrote: Thanks Larry,

Is there something you could suggest doing (or not doing) to prevent this from happening to my replacement head, which checked out to be in excellent shape.

It's just a manufacturing defect. The guide bores were loose and the guides sunk. It's common in J heads. That and cupping intake valve faces. A head can be in bad shape valve wise but the bike still runs OK. A pretty good way to tell if you have cupping intake valves is to check the shim sizes. If the're down there in the 225 range, the valve faces are probably cupping. The smart, most cost effective move is to disassemble and inspect a head before bolting it on an engine. Correct any problems up front and save the cost and head aches of pulling he head again later on.

Thanks again Larry,

Would you say that OEM Kawasaki valve (intake, and guides) weaknesses are reason to baby a J-motor?

Am I a little too rough on the engine, by holding fourth gear perhaps a little too long...and winding her out?
She just seems to want more than I'm putting to her, especially now with a V&H header and low-mileage head. She wants it, baby!

daveo wrote: Thanks again Larry,

Would you say that OEM Kawasaki valve (intake, and guides) weaknesses are reason to baby a J-motor?

Am I a little too rough on the engine, by holding fourth gear perhaps a little too long...and winding her out?
She just seems to want more than I'm putting to her, especially now with a V&H header and low-mileage head. She wants it, baby!

Just don't miss shifts when you're twisting it hard :laugh: If the other head doesn't have any sunk guides by now, it probably won't ever have any. You can put one cam at a time in the head and bench shim it before you put it on. If the shims come out on the low side of the range, get a valve job done. If money is tight, you can go with K&L valves. They're pretty cheap.

Great reply, thanks!

The head on the bike now was original to a (low mileage) 82 KZ1100A, and everything about it is crisp, especially the threads. After comparing the two, I think the early heads received more attention to quality and detail. The problem-one was original to a 94 Las Vegas police bike, which likely took a beating before I got it. Just about every bolt hole had been, or needed repair.
Well, it worked for a year and a half.

I really appreciate your response.