Just changed the piston rings and valves in my bandit. Its smoking a bit - which I expected but how long should I leave it before I check the valves again? I realise the valves need time to set in.
Also its the first time I’ve done this kind of work on my bike, its all good and as it should be apart from the smoke.
How long have you run it in “smoking mode” Tel?
It was half hour yesterday and half hour today. I asked a mechanic at a local garage and he said it might take a week or so depending on use, apparently it needs to build up carbon around the valves.?
Did you hone the bores?
Yep, should it not be smoking that much then?
The smoke should have gone pretty quickly once it was warmed up fully. If you replaced the valves did you replace the valve guides and oil seals ?
Edit to add unless there is a lot of oil accumulated in the exhaust ?
Yep, pretty much complete change over old for new. Including plugs.
Assume you also lapped the new valves in with grinding paste ?
Yep and did the leak test too. I cant think what it could be. I doubt there could be that much oil left in the pipes from before - when it was burning a lot of oil, one of the piston rings was knackered.
As you can appreciate it’s hard to tell without seeing the bike but I’d expect any smoke to have gone after 5-10 minutes. It’s basically oil that you have used on assembly being burned off.
If you have honed the bores, replaced the rings, valve guides & seals and lapped the valves I wouldn’t expect too much in the way of smoke.
Is it blue or white smoke Tel?
Thanks for your help guys.
It’s got a slight blue look to it, which I know is oil. I thought that as it previously burnt a lot of oil that there would be a bit of oil in the pipes and can?
Also what is usually black dust on the inside of the can is a thin layer of moist black oil.
Possibly but it wouldn’t be smoking until the engine was hot enough for the pipes to be scalding hot.
Does it smoke straight away?
Yeah, starts with a puff, then only smokes on acceleration. With a little when it stops. No smoke when just ticking over.
I’d be inclined to beg, borrow or steal a compression tester before running it again.
Why’s that? There is plenty of compression. I have taken it down the road, and it rides great.
What’s the possibilty you broke a ring instaling the block back on? I know how fiddly that was on my gixer cos it sounds to me you should have deffo stopped burning oil by now. The only reason valves need time to settle in is purely for clearance settings, they shouldn’t leak either past the lip if they were lapped correctly…and the stem seals should seal straight away. Any oil that is burnt off during initial start up is residue from the build, this should clear almost straight away. Smoke on acceleration can be due to rings…likewise smoke on the overun is stem seals. You say ‘changed’…how bad was it smoking before?
I suppose it is possible a ring broke, it seemed ok - and it wasn’t smoking as much as it is now - guess I’ve got to open it up again.
Before you do that I would check the compressions, that might at least give you a clue to which cylinder is the problem. Sorry to ask more questions but did you check the bores to see if they had been worn oval ? I’ve had that before on a high mileage car engine.
A cylinder leakage test rather than compression will tell you if it’s a ring or valve issue without any stripping 
To me it must be ring/piston/bore area for it to be oilgetting past. I’m presuming you have rings right way up, in the right order and overlapped as they suggest for your lump :unsure: some have tapered edges etc 
Always hard to diagnose what someone else has done :blink:
