Smoking and what do or not do about it

Twinstar Joined: Sep 13, 2009 Posts: 32 Location: Conn.

Borderline technical question but not quite.

I have an 82 900F which I bought about 12 years ago and which I use as a commuter, mostly. She has 56955 miles on her and is pretty much mint. Since the day I got her, she would smoke a little on startup, particularly if the last run wasn't the day before. No big deal.

Now, she smokes quite a bit on startup, and also quite a bit on any swift change in RPM, either direction. And probably is smoking all the time. Seems like valve seals. It's been a couple years since I did a compression test so that needs to be done, I know.

The bike runs beautifully other than a very slight bog at 4000 which I haven't been able to dial out. What to do? Pull the motor, or just blow some smoke? I have other bikes to ride, but an engine rebuild would take me most of the summer, and I'd miss the 900.

Posted: Sun Feb 12, 2023 7:58 pm

Your valve stem seals are toast - this is typical. The good news is that a full rebuild isn't necessary to replace them and SteveG, one of our members, wrote up a nice how-to on replacing them without pulling the heads.

I have plenty of Viton seals in stock if you decide to do the job yourself.

Twinstar Joined: Sep 13, 2009 Posts: 32 Location: Conn.

Oh wow, ok, I found a couple posts, not SteveG's, but others where the seals are being replaced without pulling the head. So, that's great, thanks for pointing that out. Of course the manual says pull the motor, pull the head, etc.

I can totally do this, send me a msg if you want, I'll buy some seals.

This is great - it's Feb 12 in CT and I just put 20 miles on the bike. She was unbelievable in the cool air. I was kinda cold.

Well, clutch slipped a few times between 6 and 7, but that's not a big deal. If I can do a few weekends of work and then ride and not have to pull the motor for a whole season, I'm pretty happy.

Posted: Mon Mar 20, 2023 2:31 pm

Mine was smoking a bit a while back. It never really bothered me as the smoke was behind me and the bike ran great. Then one day I had to stop on the side of the road and wait for a fellow rider to catch up. Turns out he had to pull over and puke as he was breathing in all that (mostly invisible) smoke behind me. Well that changed my mind and after some research I came up with a plan.
Removing the motor turned out to be hard in my mind but too easy in real life. Just needed some consumables to put it all back together.

Anyway good luck and hopefully this helps you out.
https://www.cb1100f.net/modules.php?name=Forums&file=viewtopic&t=79570&highlight=valve+seals

Cool

Twinstar Joined: May 08, 2019 Posts: 39 Location: BC

You're probably due for a full top end refresh, check compression obviously but id bet you have a lot of carbon buildup and possibly leaky valves from the oil seeping in.

Posted: Sat Apr 08, 2023 2:44 am

I think Bucko was actually the first one on this site to change valve stem seals without removing the head and write it up, back in 2010.

It might be comforting to read more than one point of view.

https://www.cb1100f.net/modules.php?name=Forums&file=viewtopic&t=54761