Topic: High Idle and smoking! Help!

[ti4u]

I just bought a CB750 four with 12,000 mles and prepped it before starting.  I change the oil, cleaned the gas tank and put new fuel in it, and I put a little mystery oil down each cylinder before turning over.  It had sat for quite some time.  I started it and it started right up, but it idled really high ( just above 3000 rpm ) and was smoking.  The choke was off and I thought after it ran a while it would settle down.  That didn't happen.  Can anyone help me trouble shoot this.  Thanks!

[Klark Kent]

I just got a cb550 that wouldn't idle below 3000 until i set the tappet gap disassembled the carbs and set timing, after which i was able to start without choke and idle at 1050... these things are good to do either way so i feel good advising you now before the more competent members of the forum REALLY help you.  as for the smoking i know seafoam smokes and i would expect mystery oil to as well.  what color smoke? also i have read of smoking going away just by running the bike.  do the other things and see if running it doesn't get rid of the smoking. 
good luck and welcome
-KK

[ti4u]

Thanks Klark,  I'll give that a try.  The smoke is white and I was just afraid of doing damage to the engine.

[smashme33]

 If it helps any, I run a little bit of Lucas Upper Cylinder Lube in my CB650, and it gives a little bit of a white smoke.

[scondon]

What year is your 750? Have you tried turning the idle adjustment screw on your carbs to bring the idle down?

    Putting oil in the cylinders will blow white smoke out the exhaust until the oil is burned away. Some oil can get blown into the exhaust and may take longer to burn off.

      Since the bike has been sitting so long it is a good idea to go through all the maintenance steps (Valve gaps, timing,check plugs, carb clean, change oil, etc....) before trying to diagnose any problems that may, or may not, exist.

[ti4u]

It's an '82 4 cylinder.  I'm not real mechanical so I will probably have to take it to a mechanic.  I just thought there may be a quick adjustment.  Thanks for your reply.

[Klark Kent]

DO IT YOURSELF!!!!

Nothing on the tune up list is beyond you- it only seems intimidating in theory.  The 550 is my first bike too, and i thought about just taking it to a mechanic and getting it right and then learning how to maintain it from there- but the more i researched these bikes the more confident i got that i could at least do these initial things carefully enough to not create more damage. (and that if i just passed it on to someone else I wouldn't be learning how to maintain it later).   i figured if i took it apart and had to pay someone to put it back together at least i would save on the disassembly labor charges   I spent a week reading posts before i worked up the nerve to disassemble carbs, but it wasn't so bad.  (getting them back in was a total PITA but nothing technical, just a #$%* of a heave ho.)  I didn't separate them, only took them apart enough to get the jets out and cleaner into all the passageways.  You will be happy you did it.  You will know your bike better and won't have to pay someone for the regular maintenance.  I didn't just save money- i got to know my bike and have a clearer idea in my head of what is happening when I ride it.  This will undoubtedly save my ass one day when there is nobody around to even pay to do the work, and once you start learning it is addictive.  At least try and then take it to a mechanic when you fail, at least then you have learned that you are not up to it.  Hell i think the mechanic would respect you more and maybe offer to le tyou watch as he does the work so that you might be able to next time. 

-KK

[Klark Kent]

valve adjustment- feeler gauges, flathead screwdriver,  2 boxend wrenches for the valve cover nuts and the locknut on the tappet 17mm? and 10mm (this one with an offset if possible)

carb disassembly and cleaning- 6mm? wrench for the airbox and such,  screwdriver for the intake and exhaust collars and the float bowls/tops.  needlenose pliers to get the floatpins, parts cleaner and a container to dunk the carbs in (I just soaked the jets in the floatbowls and used spray for the rest of the carb body) and a drill bit 1/16th? to bench sync

timing- feeler gauges for the point gap and one of your rear indicators for the static timing light. (hold the stalk to the frame for ground (they are internally grounded) and put the lead on the point wire) 

I am pretty sure the shop manual for the 750 can be found for free in PDF form (big file if you don't have highspeed connex) and will tell you everything (and more) you need to know.  this forum will tell you the rest.

DO IT
-KK

[ti4u]

Thanks KK, now you got me all pumped up.  I think I'll give it a try.  I need to go get the proper tools.  But your right, at least I'll save the disassembly labor.  Thanks again!

[Klark Kent]

that's great... i can stop using caps then. and i won't have to resort to saying "do it... c'mon... do it," a la benstillershow era ben stiller . (anyone else remember that )

i left out a screwdriver for the points (and probably a couple other things,) but the point is that it is all within your capabilities.  Using the exploded diagrams in the shop manual:
http://www.honda4fun.com/man_officina/man_officina.html    K0 and addendums ('69 - )
http://www.steelo.freeservers.com/  K7
you should be able to make lists of tools like i  did off the top of my head for each individual task and in so doing mentally prepare and see the job for what it is.  Print it out if possible and take it to the bike- it's like having x-ray vision. 
not sure what year your bike is (or if it is an F model?), if these manuals don't give you everything you need search the forum and ye shall probably find.  Or shell out for a clymer manual- avoid haynes. (dog #$%*)

and don't mention it, I'm glad to be able to give advice at all, as my usual contributions to the board are questions and bad jokes.  thanks for the karma.  (and my first "first to welcome" if you like to brag about that sort of thing )

c'mon...  do it.
-KK

[scondon]

The only tool needed to lower your idle is your hand and it is an easy and quick adjustment   Should be a large knurled screw on your carbs that is meant for easy, on the fly adjusting.Back it out with your fingers. Sorry I'm not familliar with the '82 carbs but it should be up front between either 1&2 or 3&4 carbs, I would think

[Klark Kent]

  got ahead of myself.  assumed he meant WON'T idle below 3000
counterclockwise will bring down the idle, try to get it down to about a grand.
-KK