Topic: Carb issue. Need help

[Magilla]

I finally got my 76 CB750k back together this weekend.  All electrical is working. Starts up on the first kick. All seems good.  Then gas starts pouring out on the ground just in front of the rear tire.  If I shut the petcock off it stops.  When I open the pet cock  back up the gas starts draining again.  It does this while the bike is running and when it is off.

Also based on the feel of the exhaust (hand held at outlet of each pipe) it seems that cylinder number 2 is not running as strong as the other three cylinders. I feel exhaust coming out but it does not come out as much as the other cylinders.

Any thoughts on this one?

[Dimitri13]

Whack the float bowls with the butt of a screwdriver, that should free any debris stuck in the float needles. This is assuming you just cleaned the carbs. If not, then do so.

[CycleRanger]

Yep, stuck float, or crap in the needle.

[Magilla]

I have never had the carbs off.  I believe this may be beyond my technical ability.  Honestly it scares me a bit.

[lucky]

I have never had the carbs off.  I believe this may be beyond my technical ability.  Honestly it scares me a bit. One step at a time. Just take your time.

Nothing to be scared about.
I would take them off and put in new float needles though.
Drain all of the float bowls into a pan first. by opening the drain bowl drain screw.
There is one on each carb. Just open the screw until it starts to drain No need to remove the screw.

If you do not have a manual you need to get one.

STEPS FOR REMOVAL.
Put one zip tie from the carbs to the frame rails above, to support the carbs.
Remove air cleaner.
Remove the four float bowl drain lines from the bottom of the float bowls.
Undo the choke cable at the carb.
Undo the throttle cable at the carb.
loosen the four clamps that connect the carbs to the rubber boots.
Cut the two zip ties.
Wiggle the entire set of carbs up and downwards.
They will come off.

Let us know when that part is complete.

[CycleRanger]

I have never had the carbs off.  I believe this may be beyond my technical ability.  Honestly it scares me a bit.

You don't have to remove the carbs to check the floats and needles.
You can remove the the bowls to access them.
Remove the drain screws and drain the gas then flip the clip up and the bowls pop right off.

However, if you have never removed the carbs and cleaned them you probably should in the near future.

You can download the shop manual here: http://www.honda4fun.com/materiale-documentazione-tecnica/shop-manual
Get the parts list too.
http://www.honda4fun.com/materiale-documentazione-tecnica/parts-list/parts-list-cb750

Take your time and you can fix it. It's not that complicated.

[Magilla]

Do the carbs have the be synced after they are removed and cleaned? 

[Rgconner]

If you touch the adjusters on top, yes.

[Magilla]

Sounds like I wont be touching the adjusters on the top

[Magilla]

UPDATE:  I pulled the overflow tubes off each carb and found the one that was overflowing.  Lightly hitting it with a small hammer did not work.  So I did as you suggested and drained the bowl and then removed the bowl.  There was a fair amount of debris in there.  I cleaned everything up and tested it with the bowl off.

Float down, gas comes through.  Float up, gas stops.

I put it back together and tested it and bingo, no gas leakage.  I started it up and still no gas leakage.  So then I took it for a ride.  The first ever since I have owned it.  It ran pretty well and was fun to ride the short distance I rode it.

The idle seems a bit low so I will need to find the adjuster for that.  Also I am going to pull the other three bowls and clean them this week.  if there is debris in one there will be debris in the others.

If I summon up the corrage I will try to remove the carbs and clean them.  The guys in this forum make it sound pretty straight forward.

Thanks for the help all.

[CycleRanger]

Excellent!   

[matt mattison]

I would check my tank to make sure rust or sediment was not the original source of your carb debris as well. You would hate to go through carb cleaning over and over.

[trueblue]

I would check my tank to make sure rust or sediment was not the original source of your carb debris as well. You would hate to go through carb cleaning over and over.

+1 if your carbs need cleaning then the crap has to come from somewhere

[Magilla]

I think the sediment may have been there from before I owned the bike.  I just got the bike 6 weeks ago.  Since then I canged the tank.  The new tank was beadblasted and sealed prior to installation.

in the for what its worth catagory. . . the tank I took off was completely rust free too.  I'm not sure where the crap in the fuel bowl came from but I get the feeling it had been there for a while.  I'm going to install an inline fuel filter tonight just to be safe.  Like I said, it had to come from somewhere.