Low compression, Valves or Rings?

Hopefully someone can help. I am new at this so any help would be appreciated. I bought a 79 KZ1000 LTD with 36000 miles on it. It runs really rough, bogs down when trying to accelerate and will not idle (even when warm) unless partial choke is applied.

Spark looks OK (its blue, not orange), I installed new plugs, checked the air filter, cleaned the carbs and changed the oil and filter. It had the wrong oil filter in it (small, I believe the filter was for a 81 KZ).

After cleaning the carbs, I started it up and noticed that there was air pressure coming out of the crankcase breather. That didn't seem right so I bought a cheap tester to check compression. Here are the readings I got.

cyl#1 dry ~125 wet ~155
cyl#2 dry ~80 wet ~155
cyl#3 dry ~100 wet ~180?
cyl#4 dry ~110 wet ~155

The wet readings were taken after adding 1 tablespoon of motor oil to each cylinder. Any ideas? Could it be valves or is it more likely rings? I will check the valve clearances tomorrow.

Also, does anyone know where I can find help locally. I live in Tracy,Ca (central california) but am close to the San Francisco Bay Area.

Thanks
Ernest

with the wet change and blowing out the breather its definately rings.
id help you fix it but im 1500 miles away

When you took the compression readings did you have the throttle held wide open? That's very important.
How long has it been since the bike really ran regular day-to-day? I ask as I think if a bike sits for a long time, the rings stick and it could be a reason for low compression. My 650 had low compression when I first got it, and it hadn't run for a few years. After a few hundred miles of regular riding, all my cylinders went up about 10-15 lbs, and a low cylinder came up even with the other three. I think the rings were a reason. But my engine had 9,000 miles, not 36,000 like yours.

Concerning your bogging and running with the choke, you may have an air leak in the manifolds, or the jetting may not be right for the current intake/exhaust system. Do you have the stock air filter system and exhaust, or aftermarket?

Does the exhaust smoke at all?

Post edited by: OKC_Kent, at: 2006/08/01 10:28

OKC_Kent

Yes, the throttle was wide open when I checked the compression.

I believe the bike sat for less than a year.

The motorcycle is completely stock. The carbs have 102.5 main jets and it appears that the accelerator pump is not working. It is definately running lean. The plugs are almost white.

No smoke from the exhaust.

LTDRider, it sounds like the compression is low, but you may still not need to replace the rings. I had a LTD with 110 dry and it ran really well and I rode it often. It sounds like you have two problems to troubleshoot, carbs first then rings.

The carbs may need to be cleaned if they sat for a year or so. Gas turns to crap inside the carbs and this could account for the problems you are having. If it's rideable, you may want to make sure the tank has fresh gas and put in some Seafoam additive. It may clean up the carbs.

Secondly, the rings may be stuck to where they don't seal well. I put Seafoam in my oil on my 80 LTD 1000 and it helped free the rings up as I rode it, over a period of a month or two. IT's not an immediate fix.

Hope this helps, send us more info and we can help.