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Carberator, new parts a must?

Field

CB750 Enthusiast
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So I gave my bike an oil change and it turns over much better now without the water in it! (I used some seafoam, but couldn't get it running, just turned it over a bunch).

It gives a few thumps but won't start. The thumps are fairly rough. I'm worried the points are filthy. The spark plugs are new expensive ones recommended.

I can't get the f'n points cap off! Any suggestions?

Also any ideas as towards the rougher thumping?

I wanted to test spark but the sitaution is that, as you know, the spark plug wire contacts are recessed a little too much. ATM I'm afraid to pull the spark plug out because of debris around it. (I'm not interested in pulling the head). I clearned the contact on the postive side of the battery as it was corroded some, but not bad.
 
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Update...

The crank case hoses that feed back up into the air box had white goo in them. I clearend it out with gas because water wouldn't do it. The Y piece was pretty bad. This must be from the water it had in the crankcase.

I drained the bowels on all four carberaturos and a lot of red rust came out... I think I found my problem. It doesn't seem to be the ignition (which now I realize mine doesn't have points does it?).

Advice on rust in carberuators? Do I take them all apart? Do I need to buy new seals or can I get away with just cleaning them?
 
Nope no points in the DOHC. Sounds like you need to rebuild the carbs. More than likely the the air cut valves will be ruptured and the accel pump diaphram and check balls will be bad. You may want to consider finding a good used set. Only way you will know how bad the inside is is to take them apart and take a look.
 
Well unfortunately I don't have enough money ($200 for a kit now). I guess my bike is going to be sitting for a long time.

My bike only has 28k on it but it is from 1981.

Do you think the air cut valves are bad because of rust getting in?

I'm going to add a fuel filter... I can't believe they have nothing at all!

Draining the tank and hitting it with some sorta rust cleaner would probably be good too.
 
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The air cut valve diaphrams are always bad lol. There should be a screen in the tank that acts as the filter. You could take the carbs apart and see if they are cleanable, you may be able to get by with just cleaning them out. No way of knowing what you will need for parts till you get in there. If the tank is rusty then yes you should clean the tank out, lot of different methods that people use. Many times people think there tank is rusty inside but it is really just very old gas that has turned to a hard crusty varnishy coating. I have cleaned several that had this by filling the tank with turpentine and letting is sit and soak for a couple of day. Just a thought.
 
There was rust in the carberators that I drained out. It sank to the bottom. It was however very fine. I suspect it was just surface rust inside the tank from the many years of existance. I suspect it has caused clogs in the carbs. Perhaps the stabalize is what made it come loose; maybe just it getting ridden more did it.

I guess I'll take the carbs apart and hope for the best. I can afford carb cleaner...

I can't believe how much the carb kits cost. Carb kits for cars are like $30; and they got all sorts of stuff in them.
 
try doing a basic clean of only the jets don't touch anything outside of the float bowl. you can do that for free
 
So just open up the bottom and clean the jets then? The top is where the rubber is at, I assume.
 
Found the kits minus the air cut off thing (which I don't give a hoot about). I might be able to manage under $80 for this whole endevour. That puts me closer anyhow.
 
The air cut valve diaphrams are always bad lol. There should be a screen in the tank that acts as the filter. You could take the carbs apart and see if they are cleanable, you may be able to get by with just cleaning them out. No way of knowing what you will need for parts till you get in there. If the tank is rusty then yes you should clean the tank out, lot of different methods that people use. Many times people think there tank is rusty inside but it is really just very old gas that has turned to a hard crusty varnishy coating. I have cleaned several that had this by filling the tank with turpentine and letting is sit and soak for a couple of day. Just a thought.

Do you mean filled to the top with turp, or just it off gasing was enough to work it?
 
I drained some more gas, no rust. Put in fresh gas and it runs great now.

I think the ignition on these old bikes is too weak for old gas, or gas with stabalize in it.
 
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