Question about 1993 Honda CB 750 Nighthawk

1 Answer

Some gray smoke when starting, worse with choke on

When starting bike with choke engaged, dark grey smoke comes out of pipes. With no choke, only smokes some times, mostly none. Clears up after a couple of minutes. Oil level fine. Hardly ever have to add.

Posted by Anonymous on


1 Answer

  • Level 2:

    An expert who has achieved level 2 by getting 100 points


    An expert that got 10 achievements.


    An expert that got 5 achievements.


    An expert whose answer got voted for 20 times.

  • Expert
  • 156 Answers

That sounds normal. Dark smoke is excess fuel due to the choke. Could be that the carbs need cleaned.

Posted on May 04, 2015


6 Suggested Answers

  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

A 6ya expert can help you resolve that issue over the phone in a minute or two.
Best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
The service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.
Good luck!

Posted on Jan 02, 2017

  • 948 Answers

SOURCE: white smoke both pipes when started minute later gone away

White smoke indicates water in the combustion chamber. If the bike is still running okay I would keep an eye on the coolant level, make sure you're not losing any. Best guess is a blown headgasket. You can do a leakdown test or a compression test to check. If your headgasket is blown, two adjacent cylinders should show lower compression since pressure will be leaking from one to the other.

That's the kind of thing that probably won't run for long. Be sure and keep an eye on your oil level too, if you happen to be leaking coolant into the oil you can dilute the oil to the point it no longer lubricates very well.

Posted on Jan 05, 2009

  • 3 Answers

SOURCE: 05 honda vtx 1800 runs rough

Your carb idle pins/needle valves are either fouled or worn/damaged. Or floats that control your equilibrium for gas distribution throughout the carb array are not working together with valves/pins. Has this bike set a spell, at least once for too long of an interval? I'd pull the whole darn carb setup and inspect/clean, then reinstall exactly to specs. Ask for the very best teardown/rebuild cleaner for carbs at the parts store! Betcha a little elbow grease and a perfect dismantle and clean, then rebuild is all you need! Been there----Did dat!

Posted on Jan 13, 2009

  • 3567 Answers

SOURCE: cbr 125 choke problem

It sounds like the choke line may not have been routed correctly when the new one was installed. Remove the gas tank and check to see that the line is not being stretched anywhere along the way AND that the gas tank when re-installed is not stretching the line. The line may have been kinked when installed. Look at the mechanical movement of the choke at the carb. Does it operate freely? Remove the air filter and look inside the center of the carb, (you may need to use a small mirror for this), does it look like the choke is opening and closing properly when the choke is moved on and off?

Posted on Mar 14, 2009

  • 3433 Answers

SOURCE: theres alot of smoke coming out the exhaust pipe

Sounds like the crank case engine oil level is too high. Ovefilled, Two or 4 stroke?

Posted on Jun 05, 2009

  • 3567 Answers

SOURCE: Engine problem

The bike has bad piston rings. The piston may need to be replaced and the cylinder may need to be honed or re-bored. If you continue to ride just don't let the oil get low.

Please rate this solution. Thanks!

Posted on Jun 20, 2009

Add Your Answer

Uploading: 0%


Complete. Click "Add" to insert your video. Add



Related Questions:

1 Answer

I have a Brute Force 750, starts OK but runs rough after a few minutes, will start smoking a smelly black/gray smoke, and most recently some blue smoke.

When the head gasket fails on a liquid (water) cooled engine the typical smoke colour is white (steam) and that becomes rather underlined by the steady drop of the coolant level and often clear evidence combustion gas is leaking into the cooling system.

Smelly black/grey smoke tends to be produced by an over-fuelling condition such as a stuck choke or strangler or other cold starting aid or perhaps carburettor flooding.

Blue or blue/grey smoke is invariably engine oil burning but I suggest you ignore that until the black smoke problem is rectified and after a short time the blue smoke might also disappear. If it doesn't it could be related to the overheating but the black smoke probably wasn't caused by that...

Mar 18, 2017 | Cars & Trucks

1 Answer

How can I tell if the solenoid in the carb is bad? Started getting gray smoke and it's hard to start. Won't idle cold at all.

the idle solenoid at the base of the carby is used to shut off the fuel idle circuit when the ignition is turned off
If it is bad then the engine will not idle but will run if the throttle is kept partially open
IF the starting problem is made easier by holding the accelerator open a bit then it could well be that solenoid
the "grey" smoke could be condensation from cold weather when starting
If the carby has an automatic choke then check that adjustment as it may not be coming on correctly when cold

Dec 21, 2015 | Cars & Trucks

2 Answers

Everytime i start the engine, there's always a black smoke, if there's a problem in my bike?"

If is you bike and not a diesel, yes. Black smoke is not a good sign. Take for service and don't pre empt mechanic, see what he recommends. Someone who knows your model

Feb 25, 2015 | Motorcycles

1 Answer

Gray smoke coming out of tail pipe 2006 bmw 750li

It sounds like you may have overheated your engine or the cylinder head gasket is leaking. The grey smoke is normally due to coolant getting into the combustion chamber and being turned to what looks like grey smoke but is actually steam. Check your coolant level and if it is dlow this will be your problem. The only way to correct the problem would be to have the head gasket replaced.

Jan 18, 2013 | Jaguar Cars & Trucks

1 Answer

Vstar 650 was leaking gas. Research led me to believe it was stuck carb float. Bounced bike and added some Marvel Mystery Oil (2 oz.). Bike is no longer leaking gas (sweet!) but now there is a...

Might be your miracle in a can fix burning causing the smoke. If its coming out of a joint where it clamps, try to tighten the clamp. Sometimes there is also an exhaust gasket where the one pipe slips into the other pipe that could be broke or missing.

Sep 08, 2011 | 2001 Yamaha V Star 1100 Classic

1 Answer

2005 Cub Cadet RZT 50 dark grey exhaust smoke upon start-up, plus some smoke when blades are engaged. Muffler gets very hot, and the engine seems to choke somewhat. The remote choke lever is opening and...

It sounds like it is very likely you have gas in the oil. This happens when the needle valve in the carburetor is leaking gas thru and into the crankcase. That will have to be repaired and the oil needs to be completely drained and refilled before running. Another thing can be done as a temp fix and that is to place a fuel (gas) shutoff in the line and turn off when not running but the oil has to be changed. Hope this helps you.

May 01, 2017 | Cub Cadet Garden

1 Answer

Upon starting the 1995 Camry the engine dies. There is also grey smoke coming from the tail pipe. Checked the oil and there is no water in it.

Is it gray, bluish gray, or white? White smoke, during warm weather, indicates that you have a head gasket out and it's vaporizing water, it will look much like it does when you first start it on a cold day. Bluish gray indicates burning oil, which could be bad valve seating, severe engine wear on your piston rings and oil is blowing past them into the combustion chamber. Grey smoke is probably water as well, though it could be contaminated with oil, or the vehicle could be running too rich, getting too much gasoline. But typically this is more of a black smoke than gray.

Nov 10, 2009 | 1995 Toyota Camry

1 Answer

Smoke from exhaust... toyota rav4 1996

Welcome to FIXYA

There in only 1 thing i can think of where the white smoke is from it could be anitfreeze if so it would mean a cracked head or a bad head gasket if it gets worse then you have a big problem but if you check the water level and it looks fine then you should be ok for a while

if it was black smoke or a real dark gray then it would be oil

i hope this helps you out have a good day

Jun 28, 2008 | 1996 Toyota RAV4

Not finding what you are looking for?
1993 Honda CB 750 Nighthawk Logo

Related Topics:

157 people viewed this question

Ask a Question

Usually answered in minutes!

Top Honda Experts

Arnie Burke
Arnie Burke

Level 3 Expert

4727 Answers


Level 3 Expert

78257 Answers


Level 2 Expert

342 Answers

Are you a Honda Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides