Fouled plug

KZ Gurus, My bike has been running pretty crappy lately. 1979 KZ 1000 LTD. Pulled the plugs. Number 4 plug fouled with oil. Not good. Could it be time for a refresh on the top end? Bike has almost 30,000 miles on it. Runs bad at low rpm's. Better at higher rpm's. What exactly is involved in a leak down test? How does that differ from a compression test? Showing my ignorance I know but need answers. Could I just need new valve seals? Need input please.

Have you done a compression test? Engine warm, Ignition off, plugs out, and throttle open?
Leak down test: Applying air pressure to the cylinder, at Top Dead Center of the firing stroke. There will be 2 gauges commonly, 1 for the in-coming pressure set to 100psi, then 1 for the amount that the cylinder holds/ leaks. If your motor was perfect/ fresh then you would be looking at 10% or so on all 4. Then since it is used, it could be way bad, only testing will let you know. If say 25%, thats not the end of the world, but you are losing compression or course. Listen to where the Air is going, Oil Cap, Exhaust, Intake. Possibly a valve adjustment could bring a cylinder up some.
oil could very well be from the valve stem oil seals, and while you could get the tools for changing them with the head on, if the compression and leak down tests are showing problems, then a tear down would be best. At least rings and a valve job.
If the oil ring has a problem controlling oil, it will not show up on either test.

Leak Down:



Compression:

What test would tell you if the problem is a valve-stem seal, and what tool would facilitate removal of the seal without removing the head?

Removing the spark plugs then looking down in the hole, crank the motor and look at the back of the valves head. All built up with oily black carbon? Then stem seals, but you could have loose fit between the stem and guides. Stem seals them selves are pretty easy to do, its getting the spring retainer locks off and back on. There are some great tools out there for it, some are a lever and cylinder with a window in the side. Then there are these later Quick Change Tools. Someone posted links before for those awhile back. Do a search, it should come up, I can't remember who it was. I posted a tool from Feebay, cgi.ebay.com/ebaymotors/Universal-OHV-OH...&hash=item2a14424507 but there was another from Toyota or BMW or something. Looked very interesting, one hand, one movement. never used one, always the lever cylinder with window. This:http://cgi.ebay.com/ebaymotors/valve-spring-compressor-tool-Toyota-Honda-Nissan-Etc-/290557199623?pt=Motors_Automotive_Tools&hash=item43a68f0507

daveo wrote: What test would tell you if the problem is a valve-stem seal, and what tool would facilitate removal of the seal without removing the head?

Typical exhaust smoke for a few moments after first starting a cold engine.

Good Fortune!

Took the bike by a guy that works on old Kaws today. He said if the top end needs "refreshed" i.e. new valve seals, grinding,lapping etc. all new gaskets. New rings, cylinder honing, carbs cleaned, 3-4 days and $1000 to $1100 bucks. Sound outrageous or not? Having trouble finding decent old school bike mechanics near Nashville.

as with any estimate get a breakdown or parts and labor, but yes $1K if you take it then pay on pick up. But get what parts are included and a labor cost per job, Itemized. Make sure that things are going to be done correctly, any feedback on this guy/ shop that you can relate to?

KZ1979LTD wrote: KZ Gurus, My bike has been running pretty crappy lately. 1979 KZ 1000 LTD. Pulled the plugs. Number 4 plug fouled with oil. Not good. Could it be time for a refresh on the top end? Bike has almost 30,000 miles on it. Runs bad at low rpm's. Better at higher rpm's. What exactly is involved in a leak down test? How does that differ from a compression test? Showing my ignorance I know but need answers. Could I just need new valve seals? Need input please.

With half-way decent maintenance and absent serious abuse, 30,000 miles is barely broken in.

Compression test can indicate weak compression.

Whereas a leak down test can better pinpoint exactly where the compression is being lost, such as a particular valve failing to seal and/or compression leaking past piston/rings into the crankcase, or sometimes a leaking head gasket. Basically, uses an air compressor to add air pressure to the combustion chamber, and then determine how long it takes for the compression to dissipate, and listen to where the pressurized air escapes (exhaust port, carb intake, and/or crankcase vent.)

Would invest $10 in a set of thickness (feeler) gauges and 4 brand new NGKB8ES spark plugs.

Assure valve clearances are within specs.

Perform a proper compression test.

Visibly observe fat blue sparks on plugs. A weak orange spark indicates weakness somewhere in the ignition system

Lube the ignition timing advancer and check its function under a strobe type timing light.

Assure ignition timing is correct.
Does bike have the older points style ignition? If so, service the points (dress and gap the contacts, use strobe type timing light to assure correct ignition timing, and adjust if necessary).

Assure air filter is fresh and clean, not over-oiled, and that the air intake isn't obstructed by something stored under the seat.

Blackened spark plug might be partially attributable to fuel fouling due to improper mixture, inadequate compression (for whatever reason), or inadequate spark (for whatever reason).
Add some Seafoam to the gasoline, and run a tankful.
However, carbs might require adjusting and sync, and possible dis-assembly for thorough cleaning, as to which many owners have found themselves capable of doing.

Runs bad at low rpm's. Better at higher rpm's. --- often results from imperfect -- usually dirty -- carb pilot circuits. But may sometimes result from improperly adjusted pilot screws.

Old hardened valve stem seals often leak oil and cause temporary exhaust smoking upon initial starting of a cold engine. This common condition isn't serious and usually clears up pretty quickly within a mile or so of riding. Most owners just postpone installation of new valve stem seals until there's some other reason to remove the head.

Enjoyment of these older bikes largely depends on an owner's ability to maintain them without spending inordinate sums on the common more simple maintenance items as noted above.

While an engine might indeed require more intense attention, imo too many engines are prematurely "torn down" and "overhauled", at least where the above items haven't been already addressed to improve compression, spark, timing and carb function.

In any event, a leak down test is recommended before tear down.

Took the bike by a guy that works on old Kaws today. He said if the top end needs "refreshed" i.e. new valve seals, grinding,lapping etc. all new gaskets. New rings, cylinder honing, carbs cleaned, 3-4 days and $1000 to $1100 bucks. Sound outrageous or not? Having trouble finding decent old school bike mechanics near Nashville --- After assuring valve clearances are within specs, if the leak down test indicates the above work is warranted, the quoted price for "competent" repair work seems very reasonable, imo.

Good Fortune!

Motor Head wrote: Removing the spark plugs then looking down in the hole, crank the motor and look at the back of the valves head. All built up with oily black carbon? Then stem seals, but you could have loose fit between the stem and guides. Stem seals them selves are pretty easy to do, its getting the spring retainer locks off and back on. There are some great tools out there for it, some are a lever and cylinder with a window in the side. Then there are these later Quick Change Tools. Someone posted links before for those awhile back. Do a search, it should come up, I can't remember who it was. I posted a tool from Feebay, cgi.ebay.com/ebaymotors/Universal-OHV-OH...&hash=item2a14424507 but there was another from Toyota or BMW or something. Looked very interesting, one hand, one movement. never used one, always the lever cylinder with window. This:http://cgi.ebay.com/ebaymotors/valve-spring-compressor-tool-Toyota-Honda-Nissan-Etc-/290557199623?pt=Motors_Automotive_Tools&hash=item43a68f0507

Dang, these tools are pretty cool! Watching the video for the second tool, it seems like the valve would fall down into the combustion chamber when the keeper is removed. Can someone explain why the valve stays in place?

First the piston being at Top Dead Center, the valve will only move a short distance. But what is the preferred method is to "Hold" the valves in place by using compressed air in the cylinder. This pressure holds the valves against their seats. There are other ways to accomplish this also. Small soft cotton rope can be used down the plg hole to "Fill" the combustion chamber. You Must have the motor on the compression stroke so both valves are closed, if not you can bend a valve. Rolling the motor back off of TDC to install a few feet of the rope then rolling back to TDC. If TDC is not found be close to the mark, or remove a bit of the rope.

Excellent info, Motor Head thanks!