The International CBX Owners Association

I parked one of my 79 "X's" in 2008 after two attempts to get the #1 cylinder to stop burning oil. I have discussed the bike before but was vague because I was new to the CBX so I will add as much info as I can think of this time:
The oil leak into the combustion chamber is enough to foul the plug after 15 or 20 minutes and if I remove the plug and look in there is a drip of oil running accross the piston. If I remove the #1 coil wire it stops smoking immediately. The first overhaul I cleared the carbon from the pistons and replaced the valve seals and it still smoked the same so I parked it and shopped around for another head and cylinders (overkill). I found a head off a totaled 82 bike with under 500 miles and picked up a reconditioned cylinders from our Ole' Pal Louis that was like new with standard bores honed and ready to go. I neglected to replace the valve seals because the oem ones looked and felt new. Needless to say the bike smoked from #1 still so I parked it until I can figure things out. I am pretty thorough usually but I can't know this one out. Relating to the assembly, the cam chain that connects to the crank is tighter with the replacement head and cylinders so maybe someone can state why that is and if I need an 82 chain or what? I did rotate the crank to make sure the chain was wrapped around the crank sprocket properly.

Do a leak down test, if you hear air escaping from the exhaust its valve related, air through the breather or oil fill cap its the piston, rings.

There's nothing at all different about the late and early camchains. If everything is seated correctly you should have normal adjustment range. You did remove all the slack from the tensioner?

Are you absolutely sure you are oil fouling #1, even after the top end swap? If you have replaced the head and cylinders/pistons and #1 is still fouling - it can't be oil. My guess is you have a very rich #1 carb. Maybe the primary and secondary mains are switched? I can't really tell from your post whether you have actually swapped the parts yet.

Dave

Yes, the replacement head and cylinders are on the engine and when it smoked upon start-up I pushed it into the storage room and left it. The smoke coming from the cylinder is oil not fuel and the plug had accumulated enough goo during a 20 minute ride to close the gap and foul. The reason I parked it after the second attempt was because I was totally stumped. This time I am putting the engine on a stand so I can relax and take a close look as I go. Maybe I broke a piston ring but I can't imagine that much oil getting by one ring and what about the oil running across the top of the piston? That sounds like oil dripping from above. Is there a way to salvage the new head gasket, I am tired of buying new ones and this one was only on a running engine for a few minutes? Before doing the first valve seal replacement it only smoked if I got on it or reved the engine but now with the new top end it smokes all the time.

I've heard of cracks in the head casting that would allow oil in the combustion chamber, but what's the chance of 2 heads doing it on the same cylinder? Also, it's very possible to break a ring if you don't have the right ring compressor, but again, what's the chance of it happening on the same cylinder? What did you find with the old cylinder? Any evidence that #1 had an obvious problem?

As Jeff said, a leakdown test is in order here to see just what you have going on. A quickie compression check might show something also.

Dave

......what's the chance of 2 heads doing it on the same cylinder?

EXACTLY!!!! You just summed up in one sentence the reason I parked the bike a year and a half ago. To be honest, I was surprised after replacing the valve seals on the old head and it still smoked but I was stunned when it smoked from #1 after replacing the head and cylinders. I will try to get a leak down tester next month and do that test as well as a compression test and this fall when I pull the engine off I am going to keep this string updated in case someone else runs into the same thing.

I always have a suspicion about the seemingly frequent cases of # 1 cylinder smoking. Bike on sidestand, leaky fuel valve washing the lube off the cylinder, not enough for hydraulic lock. Over a period of time, what cylinder would it effect ? Number 1...Nothing to prove my hypothesis but as I said, a suspicion... Valve seals ? Naaaa.. #'s 1 & 6 are out in the breeze compared to the others...

I have a leak down tester ordered so I should be able to confirm whether it is the head side or cylinder side soon. I lay in bed at night running through the possible causes for the smoke and always wind up back at the piston because it is the only thing I didn't change out. That would explain the drip of oil running down the face of the piston when I look through the plug hole after running. Maybe a pit in the casting that was exposed when I cleaned the carbon off. I think the valve seals are ok since there is no smoke from 2 thru 6 and if the rings are intact and located properly it would leave the piston as a suspect. Is there enough internal engine pressure on the down stroke to force oil thru a crack or pit in the piston?

CBX engine by nature of it's design has very little crankcase pressure...however it is quite feasable that oil could find it's way through a crack or plit.... Not sure what you mean when you say "the drip of oil running down the face of the piston" ?

.......drip of oil running down the face of the piston when I look through the plug hole after running.

After the last rebuild and test run I shut the engine off, pulled the spark plug out and looked into the combustion chamber with a small flashlight and saw a drop of oil running down hill on top of the piston.

This ones a tough one that does point to the item ( piston) not changed, however, do you have all the cylinder liner base O-Rings in ?...It's a long shot.

That is a little hard to remember but I think I wasn't able to get the old ones out. But still, it only leaks from number one. Next time around the engine will be on a stand and nothing will be left to chance. I am replacing the piston.

Good luck & keep us updated....

Where can I get a new standard piston? None on Ebay and Bike Bandit shows none available from Honda. Tim's only offers sets.

Nils has put an excellent list of CBX parts vendors, I would try there first twine....I checked David Silver & his are 25 tho ovesized !