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Discussion Starter #1
Since rebuilding my carbs on my cl350, I keep having the same problem too much fuel. I rebuilt them 4 or 5 times, and I am getting really frustrated. I realize that the needle does not set into the jet all the way. I see that the guy I bought the bike from had the wrong size needles in there. does anyone know what the correct size is? I have 115 size jets in, is this correct? and also along with what size needle, where can I find them. I was thinking even the adjustable needles will work too, with the c-clips that lock into the needle to adjust the height, any one know where I can get these? please help, I have been working on this bike for a month now, and finally got the electrical and clutch issue straightned out, now it just runs way too rich and bogs down when I ride it. it also likes to flood, and not starts good.
thanx
Nick

just ride it.
 

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Scrambler,
If you have "rebuilt" them 4 or 5 times, I am not sure you have rebuilt them at all. Lets start at the beginning. I assume that these are the stock 350 CV carbs. If you have the stock air filters and exhaust then I think 115 mains might be rich.I seem to recall that my stock mains were 100 or 105s. If you are having flooding problems then you need to check your float height and your needle and seat. The main jet needle is not adjustable on the 350 and I don't know of any aftermarket adjustable needles. I also don't think that is anywhere near being the problem.

Again, are these the stock carbs? Is it a stock exhaust? Is it a stock, clean intake system?
Ken

AHRMA 412
Vintage racing - old guys on old bikes
 

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Just a thought...the rubber vaccuum diaphragms on those cv carbs are prone to ripping -- causing the engine to stumble. Even a pinhole or small tear will really piss you off.

Compound this with a tear in one carb and not the other and the bike will behave very erratically.

The kooky thing about this is sometimes the bike will start and idle fine, but only bog under load. May not be your problem, but you said the carbs were rebuilt several times...might be worth a double check.




Honda go sideways!

Edited by - krapfever on Jul 19 2006 6:11:42 PM
 

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Discussion Starter #5
ok, so here is the deal. I have 115 jets, and short needles. the diaphragm slide needles do not reach the jet. if you put it all together, and turn the carb upside down, and push the diaphram needle all the way down, there is no way that the needle can even come close to the jet. I guess I can try smaller jets, but if the needle does not stop the jet at all when the diaphram goes up and down, I don't really know what to do. the side of my needle says D20Z I don't know if this is the original size, it is from 2 different rebuild kits, and I doubt it is the right size. the carbs are stock, and the airfilters, and exhaust is stock as well.

and to kennesex, in all of my jet kits, they include adjustable needles, with about 5 differents notches in them to adjust the height. also if everything else is replaced, and the slide needle is not stopping the jet at all, and letting a full stream of fuel into the carb then I guess I figured that is the problem of my flooding. I appreciate your help, but I have replaced everything on the carb in regards to all of the jets, needles, floats, etc. I adjusted the height so I know that isn't the problem, they were set way too low, and the bowls were overflowing before I put them back to stock. thanx, I appreciate all of the help.

just ride it.
 

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uuhhhhh.... the needle is not supposed to go all the way down and plug the mainjet. Fuel won't flow up the main jet into the needle jet unless there is enough of a vacuum for it to do so. And there isn't at low rpms and low throttle, which is why those carbs have a pilot jet circuit.
 

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not to railroad this topic, but i just put a henning piston kit into an other wise stock motor, how should i go about jetting this appropriatly. it has great lower end power, but the stock settings are a bit wimpy at the top end. any help will be appreciated.

-scott

scott from chicago
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Scrambler, Unga is right. The needle is not supposed to be a stopper for the main jet. It is tapered to vary the amount of fuel that will flow out of the jet at various throttle opennings. The fuel is supposed to be drawn through the main jet by the lowered air pressure above it. Bernoulli's Effect states that the more rapidly air flows the lower its pressure. The venturi effect states that the smaller the diameter of the mass of moving air the faster it flows. Those two principals govern how carburetors work. Gravity only provides the flow of fuel into the float bowl. If your carbs are overflowing when the engine is not running there is only one cause. The needle is not sealing against the seat. That can be caused by either foreign material between the needle and seat, float level too high( float level is determined with relation to the carb in its normal operating position, not upside down when you are working on it) or a worn needle or seat, maybe both. Stock Honda CB350 needles are not adjustable. If your aftermarket needles are adjustable, then generally, one should start with the clip in the center position. Raising the clip, lowering the needle, will place a thicker portion of the needle's taper into the main jet and cause a leaner mixture. Needle position only affects the midrange mixture ( aprox. 1/4 to 3/4 throttle).

Scott, The only place to start on jetting after a major engine mod is to actually take a look at the plugs. Jetting should be done in the sequence of main jet, then needle, then pilot circuit. So, put a set of new plugs in it and run it out and do a plug chop at full throttle to see what they look like. White and clean - too lean, go bigger on the main jet. Black/really dark brown and wet - too rich, go smaller on the main. Light brown/tan - just right.

Good luck you guys. Trying to go at this in less than a systematic way will frustrate you to no end, waste your time and if you are at a race weekend, screw up all your races and practice.(don't ask)

Ken

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Vintage racing - old guys on old bikes
 

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ken, thanks for the help, i'll see you at mid-o. i'm splitting garage 25 with big bob.

scott from chicago
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Scott,
Sorry, I won't be at Mid-O this year. It sucks to be a principal, my summer is over I have to be back at school at work next Monday. We are flying back to Alaska on Sunday. My racing season is over till next summer. Good luck at Mid-O and have a great time.
Take as large a selection of main jets with you as you can find. If you are still running the stock CV carbs there may not be a lot of guys there with a selection of other sizes. If you are running Mikuni VMs then all the 2 stroke guys will have lots of jets to borrow. If you need to make jets bigger then get a set of welding torch tip cleaners. The abrasive cleaners will easily take a jet out to the next larger size. Just go one size tip cleaner at a time since they are not very uniform in the steps.

Ken

AHRMA 412
Vintage racing - old guys on old bikes
 

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Discussion Starter #12
Ok, so I feel like an idiot. I didn't know about the carb needle thing. my floats are a little off and that may be my prob. I readjusted them once. I will go back and see if that is my problem. also, since I am running so rich on the 115 jet should I replace the jet to a 100 or 105 possibly? will this make a difference or should I stick with the 115's? let me know I apologize for the mix up of info, I tried. please help.

just ride it.
 
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