Topic: Intermittently smoking

[Coredozer19]

Started it up (cold start) it’s smoking out of the left banks. I warm it up. Drive it and it stops smoking. Drive it a few more miles down the road and it starts smoking again from both pipes. Fresh rebuild. What is wrong with my bike? 1973 Honda CB350F.

[eigenvector]

Cold start smoke can be oil leaking past the valve guides. 

Did your fresh rebuild include new valve guides, if not that's what I would suspect.  Personally unless compression was low smoke on a cold start doesn't bother me.  If they were new valve guides I'd be bothered though.

As for it coming back - you didn't indicate whether or not you shut off the bike before that second leg of your trip.

[ekpent]

 Could be that the second wave of smoke comes on when the pipes get hot enough to start burning off some oil.

[dave500]

seems to be a few posts of fresh built 350/400s smoking?

[Coredozer19]

Yes I am having a handful of problems. I’m getting frustrated. I did not replace the valve guides and the motor was sitting for 38 years untouched

[Coredozer19]

I know the first go around I put the oil scrapers in backwards so the engine was burning oil pretty good. So the pipes are coated I’m sure. I put a brand new set of plugs in it when I got it legal. Maybe 60 miles on them now. Hopefully they are clean. If not I’ll do a compression test and see what I get. If that checks out good then it is the valve seals right?

I also have red gasoline. The tank liner is red and it seems to be leeching into the gas. I dont know if that would cause it to smoke.

Also I noticed like I said after I let it sit on the side stand all day when I got back to the shop to ride home it was smoking from the left bank. Which could be because the oil stays up in the valve train on only that side if the bike is leaned. The other bank would have leaked back down into case due to it leaning right?

I just want to figure out what’s wrong. I’m tired of these smoke problems. I just want to ride it :,(

[Coredozer19]

What’s the CI kit? And I didn’t replace the valve guides

[danyo]

CI kit - pistons and rings from japanese seller on ebay - cruzinimage.

Sent from my SM-N900T using Tapatalk

[eigenvector]

Worn valve guides are why it's smoking on start up (probably).  Normal for an engine that old and unless it's excessive not really a big deal - what's excessive?  Beats me - the local refinery points to you as to why there's so much pollution in the air?

[Coredozer19]

Okay so I’ve decided that I’m not messing around at all anymore. I am going to put a brand new ring kit in it and new valve seals.

Can anyone point me to the right direction of a good kit for a top end job. I don’t care about money.

I need a head gasket and a lower jug gasket. And I need the valve seals.

Anything else anyone can think of that could be causing the oil in my cylinders?

[Coredozer19]

Are the valve guides not the silicone rubbers that come in the rebuild kit. The bike only has 5k miles on it. So if it’s a wearable item I doubt it’s worn.

[dave500]

they look like this,if the guides are worn new seals might hold for a while but will get distorted as the valve stem cranks over,old seals go hard and fail to flex to help seal,if they are the stock ones they'll be hard.

[dave500]

worn guides WILL cause oil use and smoking,you need to find an engine rebuilder/machinist who gives a #$%*,these are a small engine and need attention to detail,they cant be slap happy.

[Coredozer19]

Only the left bank smokes on startup and then once it warms up both smoke when I bang the throttle. Could this all be because of the valve seals. Or could I have a ring bore issue aswell?

[Deltarider]

You could try an oil that makes the rubbers swell a bit more and supple, like Castrol's High Mileage.

[Coredozer19]

I’m just gunna pull it apart and replace the piston rings and the silicone seals.

Where should I get new rings from. I want something reliable.

Where should I get the seals from?

[Coredozer19]

Confirmed. I can see the oil coated on the intake valve where it shouldn’t be.

[dave500]

have a look at the guide and valve stem wear aswell.