Topic: Smokey smokey smoke.

[Reganator]

I thought everything was great... but now there is trouble in paradise.

I purchased my 71 cb750 with a 72 engine late last year.  It's been out of commission for at least a year but possibly longer.  I very recently got it up and running, and I've put something like 40 miles on it maybe.  It's a little slow to warm up, but it generally starts quite easily once it is warm. 

Earlier on I replaced the oil and cleaned out the oil pan.  Presently, it's running Casterol 10w40.  This evening I replaced the plugs.  The notorious cylinder 2 had an NGK plug in it that was significantly older than the other three plugs.  It's lettering was actually blue rather than black.  Anyway, it had been smoking earlier when I was riding it, and it's continued to smoke some as I've ridden it around this evening.  I would call the smoke a white / grey color.  It doesn't seem to have a distinct smell, maybe a little gas, maybe a little oil, and it doesn't leave any residue on your hand so far as I can tell.  Additionally when we opened the oil tank to check the oil some smoke or steam came out of it as well.  This was after a short ride, maybe 30 minutes, as fast as 40.

So... what does the forum think is the culprit for my smoking issues?

Oh, also possibly worthwhile, running a kerker 4 into 1 with stock size 105 (75 CB750F carbs) mains (115 is on the way) and air mixture is 1 out.  Turning out farther seems to make the smoke worse. 

I have no good ideas.... maybe switching to 20w50 is in order?  Any help would be great, I have an oil leak to track down....

Please tell me my valve seals aren't shot... please?

[bjbuchanan]

Run the bike more to refresh the seals. As long as it doesn't get hot to where it shudders, wants to die, falls flat on its face like it is seriously overheating ride it. Some heat cycles usually puts life back in to the seals so they swell a bit and work like they should

My replacement engine sat for a yr or two and pissed oil out of the exhaust when I got it running. A reasonable amount of seafoam in the gas tank and tiny bit in the oil (that I was planning on changing) and it came back to life in no time.

When engines sit moisture accumulates. You are burning off all that crap, plus other random junk from the acidity and sitting. Don't be a sissy haha

[Reganator]

Ride it I shall.....

For awhile anyway, keeping a close eye on the oil and an ear to the valve cover, before doing anything drastic.  I was just looking for other theories.  The smoke didn't appear until the second day I actually rode the bike... it also seemed like the air mixture wasn't without meaning... but it certainly didn't eliminate it.  I'll get it up to highway speed soon and for a good run in the hopes that I'll burn out some of what time left there.

[HondaMan]

Often the oil rings get sticky after a long 'sit'. Like BJ says, some riding can make that better. If it does not get better, there are several options, but most of them require the engine out, sitting on the floor...

Check the compression, write the numbers down somewhere (and remember where?) After it has about 1000 miles on it, check the compression and compare the numbers again.If it is improving and you don't have oil drooling down the front of the engine, ride on while the sparkplug fouling isn't too expensive.

Sometimes, they just need to be awakened: mine sat for 5 years when I had cancer and healed, smoked and spit and generally complained when I woke it up. A year later, it was fine. The compression started about 80 PSI across the board: now it is over 110 (at 140k miles, that's not bad!).

[Reganator]

Sounds... Ok to me!

Really not wanting to do an overhaul just yet.  It was actually my plan to keep my ear to the ground for a cheap basket case or loose engine in any condition to gradually rebuild and then swap in as need or want and time dictated, so I'm really hoping I can keep this engine in and running for a bit.

I have not checked the compression.  Will that require any special tool, or is the one that O'Reiley's rents out useful for this? 

[Reganator]

Just thought I'd give an update.  Took the bike on two short rides today.  First one smoked a little but somewhat better, just took it out again and it barely smoked at all.

Looks like my 2 stoke is turning back into a 4.

[bollingball]

mine sat for 5-6 years. Smoked like a train after about 100 miles it was just fine. When it does stop and I think it will I would change the oil & filter again.
Ken

[Reganator]

Thanks for the reinforcement.  That's the plan.  When I get a new (or new to me anyway) car or (now) bike I always do a short oil change.  I'm wanting to switch it over to the 20w50 anyway.  In the process of getting it started we also managed to flood it a number of times as well.  Those days are behind us but I'm sure that there was some fuel that leaked down into the oil as well, so all the more reason to change soon.

Thanks again for the help everyone, looks like I lucked out this time.  Just have to kill that brake squeak and change my tires and I'll be completely done. 

BTW, any opinion on Dunlop Roadmaster TT100s?  Got a set that I'm planning on putting on right away.

[HondaMan]

Thanks for the reinforcement.  That's the plan.  When I get a new (or new to me anyway) car or (now) bike I always do a short oil change.  I'm wanting to switch it over to the 20w50 anyway.  In the process of getting it started we also managed to flood it a number of times as well.  Those days are behind us but I'm sure that there was some fuel that leaked down into the oil as well, so all the more reason to change soon.

Thanks again for the help everyone, looks like I lucked out this time.  Just have to kill that brake squeak and change my tires and I'll be completely done. 

BTW, any opinion on Dunlop Roadmaster TT100s?  Got a set that I'm planning on putting on right away.

If they are the old-style true trigonometric (i.e., V-shaped carcass profile that is taller than wide), they are the perfect match for the CB750 steering geometry. Best-handling tires I ever had on my 750! Hard to find lately, though. I have been using the Avons for most of the last 15 years because the 'true' TT100 tires went away in the late 1990s. The TT100 tire profile was made for Isle of Mann racing when the 750 was duke-ing it out with the world's best in the late 1970s and 1980s. I used them exclusively until I got married and started carrying payloads bigger than they could manage at spoke-wheel tire pressures (i.e., 45 PSI or less), then switched to the Avons for their road grip and durability. The TT100 perfectly matches the departure ('lean') angle of the 750 chassis, and it fits perfectly with the short 3.75" trail when pulling up out of a deep corner. This prevents line changes at high speed, lets you 'loft' the bike when flipping from one side to the other easily, too, as the sidewalls are wider than the vertical footprint, so you can really haul it up and down the sides. In fast twisties, they were unbeatable!

The ones I have seen lately (since 2004) are Japanese Dunlop knockoffs of the original British version. They do not have "S"-rated rubber and don't have the unique V-profile carcass. They just have the old K81 tread pattern and a marketer behind them. I hope yours are better than that: I recently heard that Brit Dunlop was going to make them again (and drooled...).

[Reganator]

In that case, how do I tell if they are the originals as some new old stock or the Japanese knock offs?  Any way to identify?

[trueblue]

The other thing to think about if it is white smoke is a misfiring cylinder.  Fuel that has partially burned gives a black smoke, but fuel that hasn't burnt gives a white smoke.  If all 4 header pipes are getting hot then I would just ride it, but if one is significantly cooler you have a misfiring cylinder .

[Reganator]

I'm pretty sure 2 was misfiring until we finally got the proper socket to replace it 2 days ago.  That plug, as noted above, was significantly older than the other 3 the bike showed up with.  PO hadn't changed it for.... Well a time period I shudder to speculate on.  Anyway, we've been checking the headers and now that pipe seems to be warming up like the rest.  Unfortunately, it's still got just a little smoke.  I'm going to check it again today.  It's fairly cool here as well so I'm sure I can chock some of it up to being water vapor or something.  That's a byproduct of combustion correct?  Where is my damn chemistry book...

[freeze]

Was the oil you used in a sealed new container? sounds like moisture in your oil being vapored off by heat.

[trueblue]

With perfect combustion you combine HydroCarbons with Oxygen to produce Carbon Dioxide and water (H2O), but no piston engine can produce perfect combustion due to a number of factors.  This results in the production of nasties like Carbon Monoxide and even Nitrogen, which is normally inert, gets pulled into the mix to produce oxides of Nitrogen, these are what cause the smog layers over larger cities. 
Back on topic, if it is blue it is oil, if it is white it is either steam or unburned fuel, if it is black it is partially burned fuel usually caused by a rich condition or really bad timing.  I would ride it and see how it goes, take it on a good long run at high speed to evaporate any moisture out of the oil and also help to free up any stuck rings .

[Reganator]

The oil I used was new and completely sealed.  I suppose it could be moisture there, but it seems unlikely.  It's also been very very rainy here over the past couple weeks, so maybe that could have contributed.  We're honestly turning into the damn rain Forrest here. 

I'll see if I can maybe get a picture or video of the smoke.  I still say it looks white / grey, but it's kind of hard to say.  I don't know how blue burning oil is.  Like I said, I'll take a picture.... Maybe a video.  I know it still isn't running perfect, but maybe that would help give you guys a better idea of what, if anything, I should do.  It is improving though.

[heffay]

Ride that thing!  40 miles and 40 mph max is insufficient.  Get it out on the highway and blow the cobwebs out of it, as they say. 

[trueblue]

If you want to see what the colour of the smoke is, hold a large sheet of white paper up and look at the paper through the smoke, in a well lit area

[Reganator]

Ok, I think I'm almost 100% certain my smoke is I burned gas.  With my header wrap, dirty engine, and slight oil leak before it was difficult to tell, but now the wrap is done smoking, the engine is cleaned up, and the oil leak is stopped, which leaves gas as the main smell.  I might still make a video.  Anyway, the bike seems to be running very well, and the smoke is most noticible / only seems to be present when the bike is idling. 

So, whatcha think?  Adjustment to the idle air screws?  Maybe the needle?  Why would a bike with stock jets and a 4 into 1 run on the rich side?  Doesn't seem to make sense... Air screws are one turn out, when we tried closer to 2 we got some pre detonation or spark knocking as my friend was calling it....  No idea...


EDIT:  Serriously though, I live in a hippy dippy neighborhood.  While I love both the bike and the neighborhood every time I'm at a red I'm surrounded by a cloud of fossil fuel stuff and I can feel them judging me and somewhere I hear the ice caps melting....

[flybox1]

Ride that thing!  40 miles and 40 mph max is insufficient.  Get it out on the highway and blow the cobwebs out of it, as they say.

+1!
 done this yet?  with a little seafoam in your gas, it might help to seal any valve guides.

only proper plug chops will tell you if you need to make needle clip and air/fuel screw adjustments.
i live in one of those neighborhoods, too.  laps to 'dry' my pipe wrap always get stares, but no calls to the FD, yet 

[Reganator]

I'm not unwilling to try the seafoam solution, but I haven't yet.  I'll maybe try it and get started on those plug chops. 

I've been riding it around more, but I haven't gotten it up to interstate type speeds just yet.  It's not like I'm some sort of pansy that's afraid to get on the interstate on a motorcycle for the first time... Ok maybe a little, but if you were from Saint Louis and had seen the way people drive around here you'd be scared to death of the interstate as well!

In all seriousness though, plans to do that tonight are unfolding.  I have a question about that though...  What's the difference between doing 40 in 3rd at 4 to 5 k rpms (not sure if that's right, just going from memory for a hypothetical, just follow me for a second) and doing 70 to 80 in 5th at 4 to 5 k rpms?  It seems like as far as the pistons and the environment inside the engine is concerned it would be the same thing.  Just reasoning this out here, every possibility I'm off, and if so I accept my mistake but would like to know why... Guessing it would be somewhat obvious.

[flybox1]

uuum..its more fun!   
JK    its the RPM's that you're looking for, here. 
these bikes like to run, and 4-8k rpm is their wheelhouse.

[Reganator]

4 to 8 it is...

My friend and I were just discussing and tinkering.  We moved idle screws 1/4 of a turn in, they are at 3/4 out now...

I omitted something that may be of interest.  I just realized that my carbs hail from a 75 CB750F model... I'm wondering if this might be part of my issue.  Is it possible these carbs may simply give up to much gas at idle?  I'm not sure what to think of this little situation...  The CB750F came with a 4 into 1 stock... mine has a 4 into 1 Kerker...

You fine folks think I'll be able to make these carbs work?  I wouldn't think there would be that much difference between the K and F engines, but then again I don't know for sure...

[trueblue]

The big difference is at a higher speed there is more load on the engine due to the higher wind resistance and taller gear.  A higher load will push the rings harder against the bore and make them bed in/free up quicker, but don't lug the engine.

[Reganator]

Got it true blue, that kind of makes sense.  Unfortunately after cleaning up other smells this really seems to be gas now, and with my F0 carb on a K2 engine, it sounds like I'm going to have to do some experimenting.

[Reganator]

Ok, I started over on this issue with videos and pictures and better information.  Still not quite there but I'm getting closer. 

New thread with video, audio, and pictures and better info is here:  http://forums.sohc4.net/index.php?topic=121045.0