Topic: Smoke coming from No.3 header

[spmc]

Hey all! So had some smoke coming from the front of the bike, and being that I've had a slow oil leak for a while now and haven't been riding as much as I'd like I thought it was just the accumulation burning off the case, but come to find out it's actually coming from the no. 3 pipe. I just did an oil changes so while I did that I changed the exhaust gaskets and that didn't seem to fix the problem. So then I thought maybe it's gas and I need to change the plug, did that, seems to still be wet, with the flange bolts on either side of the collars looking wet after a ride.

So seems like it's not the exhaust gasket or the spark plug... any other things I should look into? I assume wires and caps? Guess I could test that with the old plug outside the engine to confirm it's delivering the spark... but any other advice is welcomed!


1977 CB750f2

[fizzlebottom]

Is it oil or gas?

[Stev-o]

Is the exhaust leak at the head where the header attaches?  If yes, are you certain you removed the old gaskets??

[spmc]

90% sure its gas since it's more clear and wetter if that makes sense, though the fact that I have a slow leak at the jugs kind of makes it hard to be certain as a lot of the case in that area is full of grit and grime related to that.

And yes I for sure removed the old gaskets... it kind of puffs out from under the collar on revs when I first fire it up then it just kind of generally smokes from that area after a ride. But the pipe from that cylinder do feel hot so that's what's got me a little confused.

It would also help if anyone who's seen/experienced blow by on one of their bikes tell me what they saw/noticed to see if I'm seeing the same things.

[Scootch]

Doesn't seem that #3 cylinder is firing. How is that plug? Is it getting spark? Maybe a bad plug wire or cap?

[fizzlebottom]

That's what I'm thinking. If the pipe isn't getting hot, then that cylinder isn't firing. If the carb isn't the problem then I'm betting that theres no spark. Need to confirm you have spark in that cylinder.