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Unread postPosted: Thu Apr 10, 2008 2:14 pm 
Rookie
Rookie

Joined: Thu Apr 10, 2008 2:06 pm
Posts: 2
Location: Bellingham, WA
I noticed a few of you are in the WA, and I am looking for a "mentor" of sorts to help me learn what I need to maintain a bike properly. Got my endorsement, but it is no good without good maintenance of the bike.

I recently got my hands a 1978 CB400A that has been sitting for years. I got it up and running, changed tires, fixed some wiring issues and changed the battery. Now I am running into an issue. It seemed that the throttle stuck one day when running a 6-8 mile jaunt. The handle itself did not, but when I shifted out or gear, it went into a high idle and started overflowing the fuel through the carburator overflow.

I pulled the carb and cleaned it, check the float arms and then changed the seals and put it all back together. I did some practice runs around the area and messed with the idle knob to make sure it did not die when in first gear at a stop. All seemed to be back in order.

Well, made that trip again and got to the place I was going and found it locking into a high idle again without the actuall throttle sticking. I reached down and adjusted the idle and it died. I noticed I was overflowing fuel again. I shut off the gas valve and parked it, and will have to ride it home tonight, at least it is only 6-7 miles, but last time it ran through 90% of a tank of gas and the reserve.

Any help is appreciated. Anyone hobbists in northwest WA, USA, or southern BC, Canada, feel free to arrange to come by and take a look. I have the Clymer manual, I just need the right direction here.
I recently got my hands a 1978 CB400A that has been sitting for years. I got it up and running, changed tires, fixed some wiring issues and changed the battery. Now I am running into an issue. It seemed that the throttle stuck one day when running a 6-8 mile jaunt. The handle itself did not, but when I shifted out or gear, it went into a high idle and started overflowing the fuel through the carburator overflow.

I pulled the carb and cleaned it, check the float arms and then changed the seals and put it all back together. I did some practice runs around the area and messed with the idle knob to make sure it did not die when in first gear at a stop. All seemed to be back in order.

Well, made that trip again and got to the place I was going and found it locking into a high idle again without the actuall throttle sticking. I reached down and adjusted the idle and it died. I noticed I was overflowing fuel again. I shut off the gas valve and parked it, and will have to ride it home tonight, at least it is only 6-7 miles, but last time it ran through 90% of a tank of gas and the reserve.

Any help is appreciated. Anyone hobbists in northwest WA, USA, or southern BC, Canada, feel free to arrange to come by and take a look. I have the Clymer manual, I just need the right direction here.

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When will they make an "guy in a crash helmet" emoticon?

Proud owner of: 1978 CB400A Honda Hawk (Hondamatic) Orange -Mostly original, a bit road worn, needs a bit of maintenance.


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Unread postPosted: Thu Apr 10, 2008 5:00 pm 
Legendary 2000
Legendary 2000
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Joined: Thu Jul 21, 2005 6:36 pm
Posts: 2422
Location: Phoenix, AZ
Sex: Male
Years Riding: 30
My Motorcycle: '93 Honda Nighthawk 750
I'm not in WA, but I think you're going to have to tear into those carbs again. If fuel is coming out of the overflow tubes, you either have the floats set too high, or there is some gunk obstructing the float needle (not uncommon on a bike that sat for a long time).

Did you clean out the tank and the petcock when you cleaned the carbs? If not, gunk from there could have contaminated your clean carbs. At the very least, you should install an inline filter after the petcock to catch this stuff.

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Bikin' John
'93 Honda CB750 Nighthawk


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Unread postPosted: Sun Apr 20, 2008 10:54 pm 
Veteran
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Joined: Sun Apr 20, 2008 12:20 am
Posts: 67
Location: Vancouver bc
Just as you described. Just as the flynrider wrote. I fitted a $2 in line fuel filter. Tank is still rusty, but problem abated. You'll need to flush the carbs out again though- the crud is still in them.
Justin


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Unread postPosted: Mon Apr 21, 2008 10:47 am 
Rookie
Rookie

Joined: Thu Apr 10, 2008 2:06 pm
Posts: 2
Location: Bellingham, WA
Thank you all for the info.

Pulled the tank again and checked it. Lots of gunk, so a neighbor and I cleaned it out with solvent. Now I just need to pick up a filter and change the seals on the carb.

Someone mentioned bending float arms, in another forum, but did not specify direction, and I don't think I can easily bend the arms for this bike without possibly marring other functionality.

_________________
When will they make an "guy in a crash helmet" emoticon?

Proud owner of: 1978 CB400A Honda Hawk (Hondamatic) Orange -Mostly original, a bit road worn, needs a bit of maintenance.


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Unread postPosted: Mon Apr 21, 2008 11:27 pm 
Veteran
Veteran

Joined: Sun Apr 20, 2008 12:20 am
Posts: 67
Location: Vancouver bc
Older timers will talk about setting ther float height. They are refering to a small brass tab that sits on the same plane as the arm to which the float(s) is/are attached. You and I both know, from having seen the inside of these carbs far too often, that the float, float arm, and little tab are all of plastic, and therefore CANNOT be adjusted. Another problem that does occur, and causes some throttle problems, but not as much as yu describe, is when the float needle valve- the one with the rubber tip and spring in the bottom, pushed up by the float- rubber gets worn and either doesn't seal properly, or the float can't push the needle home far enough, cause the rubber is missing. I hope to hell that makes some sense. Affects performance some, but not as much as you describe. If you're in the States, you are very lucky as you have acces to JC Witney and co. They have a rebuild kit, but not available in Canada!
Good luck.
Justin


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