Thread: 79 CT70 Oil dripping from air cleaner box

Just got a "new" 79 ct70. Wouldn''t start so I repalced condenser and points adjusted gap, etc. Now runs great but does not idle without a little gas. No foam air cleaner in air cleaner box. I have one on order and hope that will help with idle.

In the meantime, after a few minutes of running around, oil begins to drip from the front edge bottom of the air cleaner box. Is this normal and will the new filter absorb the oil?

Thanks
Kevin

Have you tried adjusting the idle? `79 is right at the beginning of the emission era for bikes and that makes for some minor weirdness, as you have seen. I don't recall if your model has an idle airbleed adjustment, but that'd be the first thing I'd try, followed by the curb idle screw. There's a good chance that the pilot jet and/or pilot circuit have some blockage. When you open the throttle slightly, the main metering circuit begins flowing fuel and a <very fast> idle can be maintained. As for the oil drip, as I recall the crankcase breather tube vents into the airbox on `79s. A new airfilter element will absorb oil...up to saturation. Then thre drippage will return. Sounds like this bike sat for a long time, thus some carb blockage and excess blowby aren't surprising. You might check the compression. If it's low the upper end may need some freshening. There's also a chance that if the cylinder walls are only slightly rusty from sitting (with a valve open) that the rings might re-seat with some additional miles.

You'd do well to pull the RH engine cover and clean the oil spinner. That'll let you see how clean the inside of the motor is (or isn't) and you'll be better able to gauge the overall condition of the motor.

Must just be old oil from previous air filter left over. There is no other reason for oil to drip out of airbox. Previous filter must have been overoiled.

I think Racerx has you on the right path here. This model bike had the first emmision control system for the CT70's. There is a tube running from the rear of the engine casing to a breather separator, then two tubes from the separator. One goes back to the air filter canister, the second into a small storage tank and finally to a drain tube.

There should be a plug at the end of the drain tube. Take it off and make sure everything is drained out. Then wipe out the inside of the air filter canister and when you put the new air filter in it, use a filter oil like K&N that is red in color. That way, if/when you start dripping again you can look to see if its red (from the air filter) or brown (from the engine) via blowby or weak top end.

As for the carb, there is only the throttle idle screw that can be adjusted. The pilot screw is set from the factory so unless someone took it off, it shouldn't need adjustment. Probably a good carb cleaning is in order.

i had a pitted exhaust valve oil mist a k&n to the point it dripped and stained my nice paint on the side cover.the bore was ok but the valve was beat.i found it when i did the 88 kit.

Thanks for the suggestions. I drained the crankcase breather tube near the back tire- it was like lancing a boil!

I won't turn the idle adj screw until I get the new air filter in.

Another question on oil- I tipped the bike straight up and the oil level comes up to the bottom of the threads in the hole for the cap. Could this be part of the issue? Looks like too much oil.

Thanks again.

Originally Posted by kevhed

. . . .
Another question on oil- I tipped the bike straight up and the oil level comes up to the bottom of the threads in the hole for the cap. Could this be part of the issue? Looks like too much oil.

Thanks again.

I have to assume that you have the screw in dipstick, right? Here's the drill straight from the Honda manual:

1. Start the engine and operate until warm. Stop the engine.
2. Support the motorcycle upright on level ground.
3. Check the oil level with the filler cap/dipstick.
4. Do not screw in the cap when making this check.

You have the right idea, standing it up straight. When you set the dipstick in, the oil should be in the XXX portion of the dipstick. It sounds like yours is too full which is likely to be contributing to your oil blow-by issue, if it's not the sole source of your problem. I concur with RacerXs recommendations to clean out the oil spinner, and to ride it a while and see if things improve. It's amazing how resilient these little engines are. Mr. Honda's engineers did it right.

-kevin

p.s. Great name you've got there.

Originally Posted by P.C.

i had a pitted exhaust valve oil mist a k&n to the point it dripped and stained my nice paint on the side cover.the bore was ok but the valve was beat.i found it when i did the 88 kit.

Did you mean the intake valve? Worn intake valves are far more common and allow reversion. If the intake port & manifold are blackened, odds are there's a tuliped intake valve causing it. In really severe cases, the carb throat can be blackened past the choke assembly. I suspect that the oil mist was actually air filter oil dissolved with gasoline mist.

i did replace both valves.i cant remember how bad the intake was..i do remember the exhaust valve was pitted.since i did the 88 kit,no drips yet.the drips were ''gold'' like motor oil.

Thanks for all the help. It appears it was overfilled. Last change was probably a full qt. Drained the oil (black as soot) and managed to clean the spinner. Inside looks pretty good- not much sludge at all.

Question now- Clymer references an "oil screen" and shows it in an illustration. I have a 79 CT70 3 SP auto and did not see the screen- even when I got down to the spinner. Did I not go far enough or doesn't this bike have one?

Kevin