TOPIC:

76 Kz900, 1015 block, new pistons & rings.

Took her for a 50 mile ride this weekend to see how the rebuild came out. Now have 107 mile since the rebuild.

The bike has a 4 into 2 setup and is throwing out what I would call "fairly heavy" smoke from the right side pipe. So I definately have a problem with either #3 or #4. Constant clouds of smoke which you can clearly see behind you in the mirror. Maybe a little heavier under acceleration.

All the plugs are burning very black but I think thats an indication of the needles on slot #3 and they probably should be on slot #2. No oils residue evident on any of the plugs. Wet shiny black residue at the end of the right pipe.

My conclusion is that I could have a broken ring or I could have a blown head gasket?

If I had a head gasket blow between say the chain cavity and #3 pot, would the intake stroke pull oil into the cumbustion chamber which would then burn?

Any ideas would be most appreciated. Thanks.

have a tried a compression test yet?

Wire, Not yet. Only have a very cheap E-bay compression tester but hopefully it will at least show me which pot is low evebn if it doesn't show me the correct psi(S). The low one is what I'm looking for. Unfortunately, I am obviously going to have to take it back down to at least the head gasket.

What do you think of the possibility of the oil being sucked in from an oil passage rather than a broken ring? If I had a broken oil ring in either #3 or #4 would I be hearing any slap?

have you tried adjusting the carbs yet,what color smoke?

Yikes!
I have had that problem #'s of times while using an old exhaust on a fresh motor.
Sometimes heavy smoke out the tail sometimes light.
But after a couple hundred miles the smoke would eventually clear up.
I think that was due to older pipes having build up of oil throughout the system , and the fresh motor is putting out some serious heat burning out all the crap.
This could be your case .
But for now check the compression and listen for any noises , but most of all keep check of the oil level to see if the motor is indeed the culprit .

Post edited by: intimida2or, at: 2006/04/10 20:25

OK, Here's the deal. #1,2,3,4 = 129lbs, 122lbs, 124lbs, 130lbs.

Very interested in the newly built engine w/old pipes theory. I reaaaly want this to be the case but I fear not? Did you have smoke you could see in the mirror for 200 miles? Tell me this is it.

What else? could I get these readings if I broke an oil ring and it's just laying in the groove? Did I forget to put one of the valve seals on?

Any ideas? Thanks.

Im no help on the motor ideas, but as to the bigger and better motor with old pipes, I had one idea. before you go tearing down the top end, try taking off the exhaust and try cleaning it out with something. maybe a degreaser or rinse it out with gas (make sure to dry it out after!) or some other solvent maybe? it should be pretty easy to do, and would eliminate a potential problem before you spent a lot of time wrenching.
Scott

those numbers are awfull close.maybe pull the exhuast and look in exhuast ports .if it is pumping out that much oil that port should look pretty nasty,do you have differant exhuast you can try if ports look clean?

BARNEYHYPHEN wrote:

OK, Here's the deal. #1,2,3,4 = 129lbs, 122lbs, 124lbs, 130lbs.

Very interested in the newly built engine w/old pipes theory. I reaaaly want this to be the case but I fear not? Did you have smoke you could see in the mirror for 200 miles? Tell me this is it.

In a word yes.
I did have a really smokey exhaust that was visible when i was on the street.
It wasn't bad enough to see at 70 on the freeway but definetely smokey on the street for a few hundred miles.
Mine completely cleared up after 400 miles .
Some pipes are worst off than others i've noticed.
You'll know for sure if you can't keep oil in the motor!

Intimida2or, you're giving me hope buddy. For anyone who cares, the above mentioned compression readings were taken on a totally COLD engine with all plugs removed at full open throttle. I haven't yet done the compression test on a hot engine. My feeling is that the HOT engine readings would be highter. Also haven't yet tried doing it with a squirt of oil in each plug hole.

So the readings so far are a good baseline.

pull the exhaust off and fire it up. you'll see exactly what cylinder is doing the smoking if it isn't oil residue in the exhaust. if it isn't jetted right i would get it there and fast. if it is really rich 200 miles is enough to destroy you engine. your compression readings look pretty even so my guess is that you have a leaky head gasket.

KL250, Thinking along those same lines...What I was going to do next was remove the mufflers but leave the four separate header pipies in place. Then fire her up and see if either #3 or #4 still smokes. My thinking is, NO smoke = muffler residue. SMOKE = problem further up the line.

Just a thought but if it turns out to be still smoking, without the mufflers and the smoke is coming from #3 I'm going to check the Tach drive seals and the tightness of the #3 exhaust gasket. Tach leak down into #3 hole, past a lose gasket, burning off in the header?

I'll update as soon as I have any news.