Question about 1986 Honda CB 700 SC Nighthawk

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I have the non-california version and I can't figure out how the fuel lines run from the tank to the carbs.

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A service manual is a valuable tool with an aging bike. I suggest the dealer/mfr. or Clymer books. In the meantime, go to the library reference section...646 stacks should have what you need.

Posted on Oct 14, 2009


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1 Answer

Koehler 27 won't start

Take off the bowl on bottom of carb. look for water/fuel issues. Clean it all out. Drain fuel tank look for fuel issues. refill with non-ethanol 89 octane fuel treated with marine grade stabilizer such as Sea-foam. take out plug(s). Crank it without plugs a few times to dry out cylinders. Try it again use starter fluid to start it. Good luck..

Sep 14, 2015 | Cub Cadet Garden

1 Answer

Filled up my tiller with mix fuel ran it to half tank then it stopped running, when depressed the throdle it bogged out and stalled, restarted did the same thing, now pump bulb won't fill with gas either

One of 2 things has happened. You might not have mixed the 2 cycle oil in the fuel correctly when you added gas and you now have a large amount of 2 cycle oil in the fuel system or.... You have debris in the fuel system that now needs to be removed.

The fact that the primer bulb is not working is telling you that there is not fuel coming from the fuel tank. Most 2 cycle fuel tanks are vented. There is supposed to be a rubber in the top of the fuel cap that allows the fuel tank to breathe. If there is a vapor lock in the fuel tank due to the rubber missing or there is some other non-original form of fuel tank cap gasket, this will cause your current symptom.

Additionally... if your fuel tank line has fuel shut off manifold at the carb attachment point there is a tiny white screen inside that fuel manifold that clogs. You have to remove the manifold BOLT and then slide the plastic screen out of the manifold to clean it.

You have to ensure that with the fuel line to the carb disconnected that you have fuel flow to the carb. I suspect the problem lies in the line from the fuel tank. Some models have an in-line mini filter that can also clog. Just check for fuel flow at the carb connection... no fuel then check the tank for debris and the fuel lines for obstructions.

Thanks for choosing FixYa,

May 03, 2011 | Ardisam Inc Earthquake Mini Cultivator

1 Answer

Have a poulan pro ppb350 31ccweed eater runs short time. put a carb kit in carb engine runs a short time.then dies.not sure if fuel lines are in correct place on carb?

This is an ongoing issue for users, and rightfully so. Small diameter line out of fuel tank (has filter in-tank on end) connects to the side of the carburetor that has the fuel pump....that is the cover without the hole in it. Other larger diameter fuel line out of tank connects to the longer nipple on the external purge/primer bulb. The bulb "pulls" fresh fuel from the fuel tank to the carb and then out of the carb to itself, where it then pushes any air/old fuel back into the fuel tank. The remaining larger diameter fuel line in this setup goes from the metering chamber (has cover with writing on it and a vent-hole) side of the carburetor to the smaller nipple on the purge/primer bulb. Years ago on 2-stroke trimmers, primers were not even used, choked the carb with a slide lever and gravity let fuel enter the carb from above...a few pulls, a "pop"...slide it off of choke and away you went.
If the purge/primer bulb is on top of the carb...small line from carb body to small hole in tank with filter. Larger diameter line goes from the bulb on the fuel pump side of the carb to the larger hole in the fuel tank where the line is held in place with a nylon nipple connector that keeps the line from pulling out of the fuel tank.

Sep 11, 2010 | Poulan Garden

1 Answer

Cannot get fuel to come out of tank to carb for starting. have trx engine 3.3 in a revo model 5309.tks engine will run if you inject fuel directly into carb.

Could be an air leak or seal problem with the fuel tank. One fuel line goes to the carb, the other line that goes from the exhaust pipe to the fuel tank pressurizing the fuel tank so that fuel will be forced to the carb. I would check the fuel lines and tank for leaks. The tank can leak air around the lid or a seam in the tank itself. I would also check any inline fuel filters for blockages or leaks also.

Jan 05, 2010 | Toys

1 Answer

87 kawasaki isn't providing full power!!

Hi again and welcome back to FixYa,

Appreciate much the rating on your first post.

Yes on the carbs. At this point, perhaps your best move would be:
  • inspect the burn marks of each sparkplug. This would be your basis which carb needs closer attention; very light brown - lean (too much air / too little fuel) or very dark - rich (too much fuel / too little air);
  • carb pull down, full dis-assembly. All non-rubber parts must be soaked in carb cleaner;
  • a can of compressed air maybe used on the small holes;
  • for the age of the bike, special attention on hoses ends that may have splits, cracks or just plain loose (fuel & vacuum);
  • carb sync even just to check / make sure all are even.

Incidentally, there is a California version of this year/model. For emission control purposes, performance has been toned down. With so many attachments to the fuel lines and vacuums, it is possible that there is a leak somewhere.


Nov 18, 2009 | 1987 kawasaki ZL 1000 A1 Eliminator

1 Answer

I have a McCulloch 3200 chainsaw on which I installed a new primer bulb and fuel lines. The old fuel lines were broken. I figured out which line runs to the carb from the primer bulb but where does the...

From the fuel tank to the carb, from the carb to the primer, from the primer back to the fuel tank. The bulb sucks fuel through the carb excess fuel is returned to the tank. HTH

Oct 08, 2009 | McCulloch Garden

1 Answer

Cant figure out where fuel lines go on mccullogh chain saw

Fuel lines: one comes from the tank...has a filter in side the tank...runs up to the intake of the carb... you can tell by hooking up the lines to the carb, and put one into a gas supply... press the prime bulb... if it pulls gas, thats the one to hook into the tank...if not it 's the other... there should only be two lines a fuel supply and a return pressure line. Clean the air filter while you've got it apart....

Jul 01, 2009 | McCulloch 26cc Gas Blower Mcb3208

4 Answers

Poulan 2050 chainsaw. Fuel line routing. Replaced all fuel lines. Primer bulb is marked Tank and Carb side. Tank side is for larger line and runs into tank and fuel filter. Carb side is smaller diameter...

Replaced my fuel lines on poulan 2050 today. The large diameter line is a return line from the primer to the tank. The smaller diameter line is the supply line from the tank to the carb. You need to cut this line and run a second piece of small diameter line from the card to the primer. I'm not sure if it makes a difference which of the two stems on the carb is the inlet or outlet line. I used the top stem as the inlet, and connected the bottom stem to the primer. My chainsaw started right up. So I either got lucky or maybe it doesn't matter.

Apr 14, 2009 | Garden

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