TOPIC:

Hi Guys

So I made the mistake of building a leak down tester. Here are the results, engine hot:

1 - 85%
2 - 72% - Hissing from Crankcase
3 - 70% - Hissing from Crankcase
4 - 85%


Hot Compression test piles on the prognosis:

1 - 130
2 - 120....Add oil and get 125
3 - 117.....Add oil and get 125
4 - 135

As per a previous post, I have to pull the head this winter to do the valve seals & was planning on doing a complete refresh on the valves at that time.

Now I see I am loosing compression down the cylinder walls.

I have never been anywhere near valves, rings, honing, boring etc.. Its all new to me.

So my question is: what do you guys, who have been there before, think I will find down there based on these numbers.

Or...what is the probability that I will get away with new rings and a hone to refresh the crosshatch? Should I expect (and save) to bore / replace pistons?

What say you, hive-mind?

Thanks
Chris

1977 KZ1000-A with about 27,000 miles.

Your mileage is still pretty low and gaining only 5-8psi when adding oil to the cylinders seems to confirm that you still have a pretty good seal on the piston rings. Personally I wouldn't touch the bottom end. I also think your leakdown tester might be a little pessimistic

I'd venture a guess that you will get to double your current mileage before you need to think about the piston rings or bores, and given that it took over 35 years to get to the current mileage you've got some time before you need to think about this all. You'll probably find yourself in there for something else before the next 35 years pass anyway

Your leak down numbers are very bad. Have a good engine builder measure the pistons and the cylinders. If you are lucky just the rings are dead, they are 37 years old! If you are not lucky the pistons rings and cylinders are out of spec. Count on replacing all of the cam chain rollers and bits too.
Let us know what you find.

Just a tiny bit of thought would convince you the rings are good and the valves need adjusted.
The oil added to the cylinder seals the rings right? After all, that's the reason for adding oil to the cylinder, to seal the rings and determine if it's the valves leaking. Any oil added will make the compression increase as there is always at least minimum leakage through the ring gaps, and that's what you are seeing. Failure to see a significant increase in compression after adding oil means the valves are leaking, unless there's a huge hole in the piston or the piston is missing.
Hell, if there's no rings at all and you add oil you'll get a huge increase in compression (seen that done also).


Adjust the valves and re-test, it is easy and cost you next to nothing.

My advice is based on personal experience doing hundreds of compression tests over the last 50 years, sometimes multiple times in one day just to prove a point.

I'm done and probably won't check this thread again.

Thanks Guys

Once I have the head off Ill decide the next step. I am thinking I can do a partial inspection of the cylinder wall without pulling off the block.

Chris

So the bottom line is that you simply want to pull the engine apart whether or not there is a problem that requires such action. That's ok, I guess, but it seems like a waste of time, money, and energy to me. I would rather just do a normal tuneup, including adjusting the valves as needed, and ride. Let us know if you get the engine running again after taking it apart. Ed

I said in my initial post I have to replace valve seals. That's why I am considering pulling the head. I could try using compressed air or rope to hold the valves closed,

But with compression variation from 135 to 117, it seems like its worth pulling the head and at least addressing that while I am there.

FSM says lower service limit is 100 psi (being less than the existing 117 which is within specs ).

If the engine hasn't been run regularly for quite some time, a few hundred miles may loosen things up enough to produce even better compression figures.

Likely the valve seals are hardened from age and oil exposure regardless of the low mileage, and would produce some exhaust smoke momentarily after starting a cold engine, which usually stops smoking when the seals warm up after riding a few miles.
This is a common condition with these bikes, and I suspect that most owners elect to wait until something else more important needs doing before pulling the head, at which time the valve seals may also be replaced. And pulling the head will likely entail the additional expense of replacing the head gasket.

The momentary exhaust smoking due to hardened valve seals usually doesn't noticeably affect the crankcase oil level between scheduled changes.

Good Fortune!

70% on a leakdow test, that engine is very tired. Take it apart and measure the pistons and cylinders. When I see that much leakage there is always a problem.
I understand Kawasaki made sure all of their test bikes held over 95%. If one returned from a magazine test with more leakage then that it was retired.

Thanks Patton / All

I was really focused on the 135 - 117 spread as a problem, but it looks like a consensus to leave the thing alone. If i cant stand the start up smoke Ill use rope to change the seals.

Glad I asked!

Cheers
Chris

80B4 wrote: 70% on a leakdow test, that engine is very tired. Take it apart and measure the pistons and cylinders. When I see that much leakage there is always a problem.
I understand Kawasaki made sure all of their test bikes held over 95%. If one returned from a magazine test with more leakage then that it was retired.

Urk...I sensed a "consensus" too soon it seems.

chconger wrote: ...was really focused on the 135 - 117 spread as a problem, but it looks like a consensus to leave the thing alone. If i cant stand the start up smoke Ill use rope to change the seals....

Yes, the 18 psi spread does exceed the 14 psi service limit as noted in the FSM.

Although I suspect that many large Kaw 4 riders are cruising happily along either unworried about or blissfully ignorant of similarly out-of-spec spreads.

However, assuring the valve clearances are within specs, plus riding a hundred or so miles, might reduce the spread (perhaps by freeing up the rings).

27,000 miles seems very early to need rings, and age alone hasn't affected the wear index.

It's unlikely that the extra 4 psi spread could do the running engine any physical harm.

Good Fortune!