Author Topic: Riddle Me This Batman(Carb Question) (Read 2168 times)

1974CB750rider · « **on:** September 12, 2009, 01:23:38 pm »

I guess I shouldn't complain much about this issue but I'm just curious because it cost me an oil change every time it happens. My #2 carb on my 74 750K4 about once a year starts dripping gas out the over flow tube. It did it today. I took all my bowls off and every one of them are spotless except the #2. Well I cleaned it up and put it back on and problem solved. However some gas got into the crank case so I need to change the oil on it again, I just done the oil change less than 300miles ago. Anyone got any ideas?

Johnie · « **Reply #1 on:** September 12, 2009, 01:48:53 pm »

If the bowl gets crud inside then you should check the tank for rust/dirt. No other place it could be coming from unless you have really dirty fuel lines. You could put on a couple inline filters to help you out until you get the crap out of the tank. Do you shut the fuel valve off after you ride?

1974CB750rider · « **Reply #2 on:** September 12, 2009, 04:27:38 pm »

Ok thanks for the info but I'm still curious that its only the #2 carb and none of the rest. I looked in my tank a few mins. ago and it looks really clean. I'm going to install some inline filters since thats alot easier than cleaning the carb everytime and doing an oil change. The inside of the tank does look really good though.

Slayer · « **Reply #3 on:** September 12, 2009, 05:41:24 pm »

If your carb is overflowing it is most likely the float valve. I had a leaker also. I readjusted the float height, cleaned up the float valve and stuck a Q-Tip down the float valve seat and cleaned that out. If crap gets stuck between the float valve and the seat it will allow fuel to bypass the valve and overflow. That is how the inline fuel filter can be a preventative measure. Clog that instead of your carbs.

1974CB750rider · « **Reply #4 on:** September 12, 2009, 06:13:24 pm »

Thanks for the input everybody I'll be picking up some inline filters tomorrow. Do I need to put them on both fuel lines?

Johnny5 · « **Reply #5 on:** September 12, 2009, 07:00:52 pm »

Quote from: 1974CB750rider on September 12, 2009, 06:13:24 pm

Thanks for the input everybody I'll be picking up some inline filters tomorrow. Do I need to put them on both fuel lines?

Depends if you want to keep all four carbs clean? But yea, both fuel lines will need one if you put them on.

Johnie · « **Reply #6 on:** September 12, 2009, 07:26:34 pm »

I hear you...I thought I had a clean tank when I bought my K4 in July. But just to be safe I dumped the gas out and the pic below is what came out with it. I did this for over an hour just to clean it out good. Click the pic for a sick sight...

Johnny5 · « **Reply #7 on:** September 12, 2009, 07:33:14 pm »

Quote from: Johnie on September 12, 2009, 07:26:34 pm

I hear you...I thought I had a clean tank when I bought my K4 in July. But just to be safe I dumped the gas out and the pic below is what came out with it. I did this for over an hour just to clean it out good. Click the pic for a sick sight...

Dang, I hope your carbs have teeth to chew their food!

myhondas · « **Reply #8 on:** September 12, 2009, 07:40:07 pm »

Sheeze.....that looks like the SLIME in ghost busters..yew....

Johnie · « **Reply #9 on:** September 12, 2009, 07:48:50 pm »

Yah, I put on a couple inline filters which will stay there for a while. Just goes to show, you can look into the tank and can not see everything. It was half empty and the metal inside was all nice and bright. I was pretty surprised at this junk that came out.

Gorms · « **Reply #10 on:** September 12, 2009, 08:02:09 pm »

Im confused as to how gas got into your crankcase.

1974CB750rider · « **Reply #11 on:** September 12, 2009, 08:32:47 pm »

Well all I can say is my oil tank smells like gas and on these older gravity type gas feed bikes, if you leave your gas turned on lets say over night, without the motor running some gas can leak into the crank case. I figured if my carb got crap in it and the gas was coming out the overflow some could have leaked into the crankcase. Like I said I took the lid off the oil tank and smelled of the dipstick and the oil tank and it smells like gas. Thats why I always turn it off even if I'm just stopping for a few mins. to fill up the tank or whatever. I still can't figure out why this just showed up on that one carb though and not the rest of them.

Gorms · « **Reply #12 on:** September 12, 2009, 08:53:24 pm »

So what does the gas go through the intakes and leak past the rings?

Spanner 1 · « **Reply #13 on:** September 12, 2009, 08:56:55 pm »

Even tho' the needlevalve and its seat ( removable on your K4 carbs, woohoo! ) is tapered, when you look at the needle the contact point between it and the seat is a narrow 'ring' clearly visible on the needle as a wear point. I ' polished ' the needle in the seat with a piece of rubber tube in the jaws of a cordless drill contacting the bottom of the needle to spin it and used toothpaste (!) as polish.......read it here somewhere, worked for me great...... In taking leaking carbs apart many, many times, I have never actually seen a speck of rust/crud actually on the taper of the valve or seat, not a spot it would tend to sit , needle to seat contact more suspect....IMO.

1974CB750rider · « **Reply #14 on:** September 12, 2009, 09:08:33 pm »

Talk to Hondaman about the gas leaken into the crankcase, he can probably explain this better than me. If you want to try it and see if it happens on your bike, next time you plan on changeing your oil go get your new oil and filter and then park your bike for the night and leave your gas on. Check your ol the next morning and see if it smells like gas. I got my info from a retired Honda mechanic that worked on these machines when they were new. He handles alot of my motorcycle work that I can't do and so far hes never told me anything that was incorrect or done me wrong.

Spanner 1 · « **Reply #15 on:** September 12, 2009, 09:21:37 pm »

I agree with 750rider, on the side-stand the float bowl at an angle could allow fuel on the left edge of the bowl to get above the level of the carb throat ( and flow into motor ) before fuel would reach the top of the overflow tube....but on the mainstand??

Also, just a thought, is the tip broken off your side-stand maybe?, allowing the bike to lean a few extra degrees to the side....

Gorms · « **Reply #16 on:** September 12, 2009, 09:34:05 pm »

Not to hijack your thread, but it has me thinking. My tank isnt ready to go on my newly built bike so I fill the carbs with an inverted bottle. My #1 (rider's left) carb now overflows everytime I hook up gas to the carbs. The kickstand is stock but my rear shocks are amost 3/4" taller. Could this cause the overflow?

1974CB750rider · « **Reply #17 on:** September 12, 2009, 09:39:42 pm »

Nope my kickstand is stock and in perfect shape. I got my new oil and filter today and going to change it tomorrow. I'm also going to install inline filters as well and after I ride it for a couple of 100 miles I'm going to check those filters and see what they look like. I may buy 4 filters tomorrow just to have 2 extra on hand, since their cheap.

Johnie · « **Reply #18 on:** September 13, 2009, 05:16:29 am »

Quote from: 1974CB750rider on September 12, 2009, 09:39:42 pm

Nope my kickstand is stock and in perfect shape. I got my new oil and filter today and going to change it tomorrow. I'm also going to install inline filters as well and after I ride it for a couple of 100 miles I'm going to check those filters and see what they look like. I may buy 4 filters tomorrow just to have 2 extra on hand, since their cheap.

Are you going to dump that gas out of the tank to see if there is anything in there?

1974CB750rider · « **Reply #19 on:** September 13, 2009, 05:25:57 am »

That might not be a bad idea, just got up so not quiet awake yet.

1974CB750rider · « **Reply #20 on:** September 13, 2009, 01:43:56 pm »

Problem fixed, inline filters installed and oil changed.

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Author Topic: Riddle Me This Batman(Carb Question) (Read 2168 times)