All stock 1978 kz1000, when do they need valve job

Hi folks, when you're out scouting for your next project how many miles do you expect on the odometer of a bike you're looking at before you say 'That many miles means I need to ask the owner if he's ever done a valve job.'

I guess it depends on how hard the bike's been ridden.

Assuming an adult-owned kz1000, late 70s vintage, if you saw 30,000 miles on the odometer would you figure on doing a valve job in your decision on Buy/Not Buy?

Probably not a fair comparision, but cars don't need valve jobs till over 100,000 miles I reckon. However they are water-cooled too.

I would say 30K would be about right. All the bikes I have owned had about 20K and were getting tired with the exception of my 79. It had 25K on it and was as fresh as the day it was born.

My 76 900 has 50k on it and it is still fine.

My '77 KZ650C1 has 49,000 miles and it's still fine too. Ed

otakar wrote:

My 76 900 has 50k on it and it is still fine.

650ed wrote:

My '77 KZ650C1 has 49,000 miles and it's still fine too. Ed

Guys, thanks for that, I figured that these valve jobs would be odd if they were needed *too* quickly -- the reason is, if you figure 10,000 miles a year driving, that would mean we'd be doing valve jobs on 3-year-old bikes from manufacturers who did pretty fair jobs at design and manufacturing. Japanese cycle and auto designing and manufacturing is unquestionably highly regarded these days.


QUESTION FOR 650ed and otakar:

When you do your valve adjustment checks, is there a way to avoid hit-or-miss when you're doing shim selection for out-of-spec gaps between shim and cam lobe?

What I mean is, with 50,000 miles I suspect you guys have had to do valve adjustments by putting in different shims along the way. And I suspect that you've encountered cam-lobe-to-shim clearances that are less than .05mm, which is the minimum allowed gap.

How do you go about ordering shims efficiently, that is -- when you measure valve clearance and the gap is out of spec on the low side (less than .05mm) how do you know which next shim to choose to install at that valve?

I realize the FSM has the table you use but the table only works if you can read the current gap accurately and I can't do that.

I can't measure an out-of-spec valve clearance below the minimum allowable gap of .05mm because I can't find a feeler gauge that will measure small gaps less than .05mm.

So when choosing the correct smaller shim, how do you guys choose it, if you are unable to know if you have, say, .03mm of clearance, or .02mm of clearance, etc. -- you can't measure that small of a gap without super thin feeler gauges below .04mm which don't seem to exist.

Or are you guys doing a 'hit-or-miss' approach?
I need to do a re-shim on a bunch of 'below-minimum-.05mm-gap' shims on my 1978 kz1000.

I need a bunch of thinner shims because my gaps are worn below the .05mm minimum gap but I don't know if I should order the next size smaller shim, or the next-next smaller shim, etc. so I'm confronted with hit-or-miss shim ordering.

Them shims aint cheap. But I am. :silly:

I've got 67,000 on the KZ650 I ride most currently and it still runs fine and never had the head off it. Uses zero oil still.
About the shims, all you can do really is take an edjucated guess at size. You measure less than .05mm, try spinning the bucket with your fingers. If it spins you know you have between 0 and .05mm so figure what spec you want to adjust to. Mostly .10-.15mm is good, so if you subtract 2 shim sizes theoretically the clearance on the 0-0.05mm valve would now measure between .10-.15mm right where you want it.
If the bucket does not spin, you have zero clearance and unless someone has recently been fooling with the valves, chances are going down 3 sizes would be the first guess.

RonKZ650 wrote:

I've got 67,000 on the KZ650 I ride most currently and it still runs fine and never had the head off it. Uses zero oil still.
About the shims, all you can do really is take an edjucated guess at size. You measure less than .05mm, try spinning the bucket with your fingers. If it spins you know you have between 0 and .05mm so figure what spec you want to adjust to. Mostly .10-.15mm is good, so if you subtract 2 shim sizes theoretically the clearance on the 0-0.05mm valve would now measure between .10-.15mm right where you want it.
If the bucket does not spin, you have zero clearance and unless someone has recently been fooling with the valves, chances are going down 3 sizes would be the first guess.

Thanks Ron, excellent advice there, I'm a complete newbie regarding 'correct shim replacement' and the 'spinning the bucket' idea is GREAT.

Thanks.

newOld_kz1000 wrote:

Hi folks, when you're out scouting for your next project how many miles do you expect on the odometer of a bike you're looking at before you say 'That many miles means I need to ask the owner if he's ever done a valve job.'

I guess it depends on how hard the bike's been ridden.

Assuming an adult-owned kz1000, late 70s vintage, if you saw 30,000 miles on the odometer would you figure on doing a valve job in your decision on Buy/Not Buy?

Probably not a fair comparision, but cars don't need valve jobs till over 100,000 miles I reckon. However they are water-cooled too.

The shop that did my first valve job was contracted to service the KZ1000 police bikes and he said their normal interval was about 20k miles. maybe they beat theirs harder than average. Bikes cook the valves and valve seals earlier than cars because air cooled engines have very high temps in the valve areas.

Mine got maybe 45k on the original valves but that was a lot of short city riding in there. Longer typical rides is less stressful on the engine.