Exhaust smoke, tapping noise, compression test

[Guest]

Edit: Please see my next post (#3)

So my bike 'smokes' out the pipes a bit, but it can only be seen when it's dark and there's a light shining on it. It's kind of amazing - I really can't see any smoke whatsoever during the day, but in traffic at night it's kind of embarrassing. I'm wondering, since it's not visible in the daylight, what kind of smoke it actually is. Anyway, there's definitely more out the left side than the right. However there's also a broken bolt in the #1 exhaust header with a definite small air leak (potentially the cause of left side backfires?)

Before fixing, the bike leaked a lot of oil. I've replaced a bunch of gaskets and am down to almost no oil drips, with the exception of the (breather cover gasket?) which could be seeping a little oil under the tank. I've put ~300 miles on the bike with quite a bit of spirited riding, so I feel like left over oil should have been burned away. Oh - actually these pipes weren't originally on the bike so they shouldn't have had much in them to burn away.

The second part of the question is about a tapping noise I hear after the bike is warm, coming from the general area of #4 intake cam cover. It sounds like a steady light tap with a hammer on the inside of the chrome cover. The valve clearances have been checked/adjusted and the carbs were synced, albeit running on 2 cylinders and needing a re-sync. I don't know if this is related to the (cam chain tensioner?) but I did replace the usual maintenance items on that thing when we shimmed the valves.

My real question here is, what is the urgency of addressing either or both of these - can it wait days or months? I can't say how many miles are on the bike because it's got a different gauge, and has apparently been in a wreck with probably a decent amount of replacement parts. I'd say it's generally in good shape - the seat, frame, wheels, etc all look pretty decent, but it's hard to know what's original and what's hiding under aftermarket paint.

[Dogma]

If it's not using a lot of oil, I wouldn't worry about light smoke. Does it smell like oil or unburnt fuel?

Does the tapping only happen near idle? Is it perfectly steady, or does it miss a little?

[Joe Garfield]

Since I've been thinking about the smoke, I checked my oil after riding to work today (checked it after work, cold, on the center stand) and found I've gone from the max to min lines in ~250 miles or so. Also the backfiring is getting pretty bad (coming from both sides, more so on the side w/o the exhaust leak). So I picked up a compression test kit on the way home, and failed. FWIW: carbs have been completely cleaned and restored, valves adjusted, and new petcock installed. The readings are (dry / with oil):

Results (cold, throttle closed)
1) 60 / 80
2) 105 / 135
3) 60 / 80
4) 70 / 85

Results (hot, throttle open)
Min) 120 / 140
Max) 145 / 185

Since starting this thread I learned how to properly do a compression test - pressure went up to acceptable levels when hot with no plugs and throttle open.

In addition to this, I've got a broken exhaust header bolt which is now leaking, a twisted front end (I think I can fix with parts I have, but not sure since I tried once already), and I'm still fighting oil leaking under the stator cover gasket (which is getting better and I'm thinking/hoping it's the starter O-ring and stator wire gasket).

I've had so much fun riding for the 1 week I've had it running and am a bit disappointed to put it back up on blocks. I was starting to think it might not be worth the continued effort, but as I typed the above it doesn't sound quite so bad - especially considering there's not much else I want to ride that I'm willing to pay for.

Where do I go from here? And should I stop riding it?

[Cipher]

Are the valves properly adjusted? Did you do the comp test with throttle WFO?

[Buffalo Bill]

If you want to do something about this and not spend hardly any money.
Check all the valve clearances, and buy some shims, no biggie just be detail minded.

Replace the piston rings, take off the head (after shimming the valves to spec), check the cylinder walls (hope there ain't no scoring), lift the cylinders off, hone just enough to take the polish off and put new piston rings on the pistons. Add new gaskets everywhere and reassemble. Getting the pistons into the cylinders is tricky but I figured it out. Not expensive.

If the cylinders are scored up and worn, they have to be re-bored to fit new oversize pistons with new rings to match. I'm not up to date on the cost.

[Joe Garfield]

Ok I feel like an idiot. After reading more about how to do the test, I did it over with the bike warm, plugs out, and throttle open:

Dry (range): 120-135
Wet (range): 140-185

The valves (shims) have been adjusted. My guess is the valve seals haven't been touched. Do these new numbers warrant new rings? And/or does it make sense to just do the rings if I do the valve seals?

[tkent02]

Your numbers are fine. Ride.

[Cipher]

Does it make good power on the road? If it does I would drive it hard for a few hundred miles.

[Joe Garfield]

Does it make good power on the road? If it does I would drive it hard for a few hundred miles.

Hell yeah it does! And I can certainly do that. I'll get the carbs synced and see what I can do about the exhaust leak, hopefully that will help with the backfiring and I'll put up with the smoke for a little while.

[Cipher]

There may be oil residue left in the packing material of the exhaust pipes.

[Joe Garfield]

If it's not using a lot of oil, I wouldn't worry about light smoke. Does it smell like oil or unburnt fuel?

Does the tapping only happen near idle? Is it perfectly steady, or does it miss a little?

• Good question about the smell - I'll pay closer attention to it.

• The tapping is perfectly steady, loudest at idle but frequency coincides with engine speed - as the engine revs up, the tapping gets faster and seems quieter (I think I can hear it when riding - there's a peculiar 'zing' but it could be something else). And it seems louder when hot.

Here's what the plugs look like. 1-3 all look the same (white), #4 is dark. Note that most of the smoke is out of the 1-2 pipes.

I guess the big question for me is what to do about the exhaust leak (broken manifold bolt). I feel like it needs to be fixed before a carb sync, but feel like a carb sync is needed before I ride much more (if I'm running lean). If the head comes off to fix the bolt, I'll use that opportunity to do valve seals, etc but obviously will lose riding time.

[Cipher]

You are not running lean if the plugs all look like that.

[Joe Garfield]

Something's weird with the attachment function. I changed it to show Plugs 1-3 are white, only plug 4 looks dark.

[Steve]

In that picture, I would rather have MY plugs looking like #4 than #1-3.

.

[Cipher]

There are two pictures now.
Yes they look lean