Author Topic: Another smoke thread: 71 Honda CB (Read 2917 times)

zerodaydave · « **on:** July 14, 2016, 07:44:21 AM »

My bike is producing white smoke both on idle and when revving. I will post a video soon.

I know the different colors of smoke and what it could mean: white = water/coolant (coolant not applicable here), white/bluish = oil, black = fuel. The smoke is definitely white. It also doesn't linger around to long. I have seen water pour out of the exhaust before when I start my bike depending on the day but the smoke is consistent. I'm sure it was water as I put some on my fingers and checked/smelled it.

I have pulled the plugs and they all look normal (tan). One could argue that they might be running slightly lean but nothing to serious. They are not oil fouled. I checked each one for spark against the case and they are good.

I also replaced the piston rings about 6 months ago. So I'm not sure that would be it either.

I have seen water pour out of the exhaust before when I start my bike depending on the day but the smoke is consistent. I'm sure it was water as I put some on my fingers and checked/smelled it.

I'm also not losing any oil. I have been checking the bike every time I ride.

I'm at a loss. What should I be doing?

chewbacca5000 · « **Reply #1 on:** July 14, 2016, 07:53:12 AM »

I have had bad white smoke problems when I ran a MAC turnout type exhaust. The problem was that the mufflers took a really long time to heat up causing condensation.

That said on all the 72 and earlier year models you will always get some smoke when you rev due to no oil seals on the exhaust side. This does not bother me as the early year iron type guides last a very long time.

Can you post up some pics of your exhaust?

Also do you have new float needles and seats? What are they set at? I buy the 2.0 replica from 4into1.com and set them to 25mm. That seems to work out pretty good for me.

I am thinking it is the ehxaust can or fuel level is too high.

zerodaydave · « **Reply #2 on:** July 14, 2016, 08:32:35 AM »

Pics are attached.

I haven't replaced the needles. Everything is at spec per the manual. Minus the jets (120).

The smoke is persistent. No matter how long I ride. I would say it gets a little better the longer I ride but it is still present.

chewbacca5000 · « **Reply #3 on:** July 14, 2016, 08:56:08 AM »

Try lowering the fuel level by raising the floats 1mm. I know it is not easy pulling the carbs on that bike, but that is all I can think of. Could be rings too. I lean toward too much fuel.

b52bombardier1 · « **Reply #4 on:** July 14, 2016, 09:16:53 AM »

Have you tried a tank of no ethanol fuel?

Rick

Sent from my SAMSUNG-SM-N900A using Tapatalk

chewbacca5000 · « **Reply #5 on:** July 14, 2016, 09:42:10 AM »

Post up a pic of the other 3 pipes. Are they all the same as number 4. I am with Cal on the plug chops. Something is not quite right.

zerodaydave · « **Reply #6 on:** July 14, 2016, 09:56:16 AM »

Here's a better shot of the exhaust.

Quote from: calj737 on July 14, 2016, 09:02:12 AM

Exhaust pipe says you're burning pretty hot. Might want to tune the carbs a bit closer to actual based upon plug chops.

Yo Cal!

Can you explain this or point me in the right direction so that I can start looking this up? I did just sync and clean the carbs a few days ago. And yes there was the same amount of smoke before I synced the carbs.

Regarding piston rings. When we opened up the bike because of poor compression in one cylinder we replaced all of the piston rings. This was like six months ago. Can it really be the rings?

zerodaydave · « **Reply #7 on:** July 14, 2016, 12:20:27 PM »

Here's a video. It's pretty bright outside but you can somewhat see it. I'm going to pull the plugs tonight and make sure that after the sync the bike is running a little richer versus lean. I'll post a pic of the plugs tonight.

Also I should add that the bike backfires when I completely close the throttle in 3rd gear from 4k-5k rpm.

chewbacca5000 · « **Reply #8 on:** July 14, 2016, 12:58:47 PM »

You need to pull the plugs at different throttle positions then hit the kill switch an coast to a stop.

This is the only way to get a good reading.

Most people advocate going Wide Open Throttle (WOT), hit kill, coast to stop, pull plugs take reading then repeat for 3/4 throttle, 1/2 throttle, 1/4 throttle.

If bike is too rich the bike the insulator on the plug will be black and sooty.

If lean it will be clean and white. Tan is all right.

If you have a go pro or other action cam you could mount it to look at the exhaust and see where it is making the most smoke.

Is it smoking at all throttle positions?

zerodaydave · « **Reply #9 on:** July 14, 2016, 05:21:45 PM »

I understand. I'll have to get new plugs before I go chopping up the old.

It smokes a little bit at idle and when I open the throttle. Blipping it a few times gets rid of the smoke.

I also feel like it has less power now but it could be in my head.

Is it worth mentioning there's also a silencer on the muffler?

zerodaydave · « **Reply #10 on:** July 14, 2016, 06:24:27 PM »

So I agree with what you asking me to do. I just pulled the plugs again. I don't even think it's neccesary to do the chop. I'm 100% certain it's running lean. Three of the plugs are almost white. Pics attached. All have good spark btw. And none are oil fouled good news right does that eliminate piston rings?

Question is how do I fix it? I was thinking about resetting the idle mixture screws?

If I understand cal right running lean would cause me to run hot which would ignite fuel in the exhaust which would cause smoke?

chewbacca5000 · « **Reply #11 on:** July 14, 2016, 07:36:47 PM »

Those look pretty dark to me. As far as rings so long as you installed them properly with the letter facing up you should be good to go.

Trying to adjust the idle screw out may help. I think you are a little rich on the idle. It is an easy enough thing to try.

Could also try partially choking it to see if it makes matter worse.

zerodaydave · « **Reply #12 on:** July 14, 2016, 07:45:29 PM »

I just made it worse. See attached. I tried to adjust the idle mixture adjustment.

https://sohc4-forum-attachments.s3.amazonaws.com/F3396345-A2BF-4EFC-99DF-C8186F3C8E7A.MOV

zerodaydave · « **Reply #13 on:** July 15, 2016, 11:01:41 AM »

Riding to get some plugs now. Will chop some #$%* up! I'll post the results.

zerodaydave · « **Reply #14 on:** July 15, 2016, 02:48:54 PM »

So I was about to do the chop and I figured might as well do a compression test why I am at it. Came out to about 122 across all cylinders so it's not the rings or valves. But guess what I did find looking at the plugs again? One plug was seriously out of spec on its gap. Fixed that and drove it around the block. It was like a different bike way more power so my question is is its still smoking. It's not backfiring now. My friend came by and said one of the plugs were carbon fouled. Should I continue with the chop? Should I pour some seafoam in there for the carbon that built up?

Here's the jet kit I'm using. We are currently using 110 main jet and 40 pilot.

http://www.lossaengineering.com/products/jet-kits-for-honda

chewbacca5000 · « **Reply #15 on:** July 16, 2016, 05:54:09 AM »

Carbon foul means too much fuel. Too rich. I can't remember did you say you rebuilt the carbs?

zerodaydave · « **Reply #16 on:** July 16, 2016, 03:17:50 PM »

Just a quick update.

Tore down and cleaned the carbs yesterday and dropped in 105 main jets (previous was 110) and 40 pilots (the kit I linked above). I then synced the carbs again.

Warmed up the bike and took her for a spin on the old plugs. Dropped in some new plugs (bike ran a lot better but still smoking) and took her out on a flat rode got her up to about 7000 rpms in 5th gear and killed it. Coasted to a stop. Swapped out those plugs for the old plugs and road it home. I just need to chop them up but my friend has the dremel lol. Will post again soon.

zerodaydave · « **Reply #17 on:** July 21, 2016, 02:05:45 PM »

There's no visible rings around the plugs I chopped. Here's a shot of two theyre all the same. Running size 105 main jets. 40 pilots. Needles are in stock position.

Thoughts?

flybox1 · « **Reply #18 on:** July 21, 2016, 02:33:50 PM »

How long id you hold it at that throttle position?
RPM and MPH do not matter...throttle position, and length of time at that throttle position does.
What are you using as an indicator to tell you by sight what throttle position you are in??

Those plugs are lean. too lean for any extended riding.
What is the scarring around the crush ring on #4.

zerodaydave · « **Reply #19 on:** July 21, 2016, 02:56:41 PM »

WOT for about 30 seconds at 6-7k rpm. I also rode it to a location where I could actually open it up. Which was stop and go for about 5 minutes.

I imagine the scarring is from the grinder I used to cut the plugs. I'm like a bull in a china shop.

News:

Author Topic: Another smoke thread: 71 Honda CB (Read 2917 times)