Oil Usage

[Z-Rex]

I am looking at a 79 CBX, it is in great shape with 12,000 miles, but it is using quite a bit of oil - 1 quart every 300 mile!
The owner thinks it is valve guide seals.
Anybody here have any comments on whether he is right, and on the cost to have it repaired?

Thanks,

Loren

[EMS]

Provided the previous owner(s) did not do anything stupid and maintained the bike well, 12,000 miles should not cause the rings to be worn. The rubber of the valve shaft seals ages and becomes hard and brittle. This is indeed a problem area for bikes this age, even if properly taken care of.
Maybe you can narrow it down a little. Does it smoke out of both pipes?
Can you do a compression/leak-down test?
If it is the guide seals, the replacement would involve removal of the head. Most probably, the oil leaking into the combustion chamber has formed a crusty residue around the valve seats also and they should be cleaned and refinished. Nothing you can't do yourself, really. Just a little care and effort required. And a service manual!

[Don]

If it truly only has 12K on it (very hard to really tell, and looking over the "rest of the bike" will tell you LOTS more than the odometer will) I suspect he may be correct on the valve guide seals, but then, you're the one "placing the bet".

Assuming just seals would fix it, and that you can't install them yourself, you'll need to shop around in your area, as the cost to get it fixed could vary by a bunch - If you're needing a "number" to negotiate with, I'd go with $500 to $750. I suspect if he could have it repaired for that amount, he would have done it a while back, as it would have increased the value of what he's trying to sell by more than that . . . . .

If it was me (and I just did LOTS of shopping, and bought a CBX about 3 weeks ago) I'd make him an offer on the bike after it's been repaired - If that's not possible, I'd plan on it being at least $500, and possibly a good bit more, and go from there.

Don

[Z-Rex]

Thanks guys

btw, it is only blowing smoke when cold, no smoke from the pipes once it warms up.

[Terry]

I have it on good authority (Mark SR71CBX) that especially the early Z models have rather poor oil rings. Mine has 30K and does use oil but doesn't smoke at all, cold or hot. Compression is fine and the carbs are synched, it just uses oil. Hopefully your 79 isn't in too bad of shape.

[sr71cbx]

Z-Rex,
Did that speedo say 12,000 or 72,000?Usually,oil consumption that high is indicative of the oil rings allowing oil to pass by the upper two rings,and EMS is also correct in saying that guide seals are also a contributing factor.If you decide to purchase this machine,you may want to haggle with the owner pretty aggressively on the price ,as you could be looking at $500 to $1000 easy to do the top end.

[E Lee]

It's the motor, the motor, the motor!
If it helps from a rookie, I just came into this obsession with the X. I made every mistake you can think of; to make a long story longer I've spent so much money on this bike, the motor, I can't turn back now. The can of worms can cost you way more than a healthy deposit on the latest and greatest "03". Eventually I will have enough parts to have an almost new motor Big Bore at that. Don't just think it's one thing and you are done - figure the worse case and that's where it ends up - seals, valves, guides, rings, pistons, machining, gaskets, did I just say $1.5K in parts not including labor or lower end! example valves $26 ea.!
The X is soooo coooool! SPEND A LITTLE MORE TO GET A GOOD ONE -- OTHERWISE PLAN ON THOSE EVENINGS IN THE GARAGE WRENCHING WHEN EVERYONE ELSE IS RIDING!
Later,
Ed
PS. Mark M. thanks for helping me keep my chin up!

[CBXzREG]

Did the owner clean up the bike before you saw it? Could be the oil is escaping from the camchain tensioner bolt on the front of the engine cases. Mine's doing it at the moment. Apparantly its a simple case of changing the "O" ring but I'm gonna wait til it gets a bit warmer before gettin' down on the cold concrete!

Anyone else had this problem before?

[Z-Rex]

I spoke to the local shop that I use - their view was that if you had the head off to do the valve seals you might as well replace the rings while you were at it.

Their estimated cost including parts, labour and taxes was $1,200 Cdn.

Sound about right?

[Don]

No CBX with 12,000 miles on it (or 22,000 for that matter) should need a ring job.

I'd be all for determining, 1.) How many miles the bike really has, and 2.) Exactly what's needed to make it "right" - Preferably before I made a firm offer on it, and certainly before I bought it.

If you can't do this, I'd look at other bikes - From what you describe of this one, I think I'd forget about it anyway, and find another (better) example in my price range.

Don