Topic: Carburetor CB350F

[rrecroc]

Greetings,

Does anyone know what model/designation the Keihin carburetors are that are used on a 1974 CB350F. I can find no markings on the carburetors. One of the throttle valves has a loose needle. To get to the needle, you have to remove something called a valve plate (inside the throttle valve), whose two screws will not move ....... and have thin phillips heads on them. They are screwed through metal and plastic and there is not enough protruding on the other side (besides being surrounded by a "depression" created by the bottom circular "lip" on the throttle valve) to even try to grab with something else in improvising. If I didn't know better, I would say threy were screwed into the plastic while red hot. The only thing left to do is remove the heads with a drill and the space to manage ever even a small bit is almost nil. I would not trust any adhesive I am aware of to hold the needle from an external point.  Does anybody know if this part is available from anyone ?
Thanks ......


Thanks .....

[Deltarider]

1974 CB350F

Year means nothing. To be safe, always identify your bike by comparing frame- and enginenumbers in the first few pages of the various parts lists. In your case either Page -IV- of the Parts List CB350F  http://www.honda4fun.com/pdf_parts_list/pdf_spac350/CB350_73/CB350_73_01.pdf or
Page -V- http://www.honda4fun.com/pdf_parts_list/pdf_spac350/CB350_74/CB350_74_1.pdf will tell you what the carbnumber is supposed to be and where to find it on the carbs. I don't know what you intend to do, but I have not yet encountered a single CB350F that had to change it's needle or position. My suggestion would be: leave them alone.

[Flyin900]

Post some pictures as I have had those carbs totally stripped down with no issues in taking them apart. If you don't have a shop manual then that is part of your problem, as it details all the correct procedures to dismantle and reassemble the carbs.

Possibly not the right carbs for the bike yet unlikely, as they are pretty small and model specific on the CB350/400F models.

The throttle valve needles are not totally ridged either and do need to have movement within their assy.

[harisuluv]

1.  The carbs for the CB350F model are:  656C.  The markings are on the bodies above the engine side intake.
2.  The needle jets aren't supposed to be fixed.  You should be able to spin them, and they will have slight side to side movement.  This is normal.
3.  The two screws probably don't move cause they are rusted stuck.  There shouldn't be any plastic in the assy you're talking about.  Either someone for some very odd reason put it there, or you are mistaken. 
4.  The most common predicament people encounter here is that they themselves use a non JIS screwdriver on those little screws and strip the heads to where they are useless.  If you don't have a JIS screwdriver, get one, and stop messing with it until you ruin it beyond repair.
5.  Drilling off the heads won't get you very far cause then you will still need to extract the rest of them and will have almost nothing to grap onto in a very cramped space.
6.  As stated, it might be best to leave it as is, unless you absolutely need to get in there.  Why do you need to get in there again?
7.  I have any part you could need for those carbs.  If you find yourself needing something you can PM me and I can sell it to you.

[rrecroc]

Managed to get one out after using numerous chemicals, freezer/heat (different coefficients of expansion/contraction), etc ....... the slide is made of some strange material that looks like the old bakelite used in the 50's and 60's in electronic devices. The screws hold the so-called "valve plate" ....... the extension of the "valve plate" (vertically) is what the "arm" is attached to that raises and lowers the slide. I have 2 shop manuals ...... a reprint of the Honda manual and a Clymer's manual. After removing the one screw, I could see what the problem is ........ 2 materials that have some type of chemical reaction where in contact and simple time passed.
The screw I removed has some strange corrosion on it ...... actually remnants of the bakelite I believe, which fuses the two together. If I have to drill the other out, so be it ...... in the manuals they easily remove the plates but hey the manuals were printed in the 70's  LOL.
I have learned much in this adventure ........ including finding spacers/washers not easily found. One carburetor I disassembled was missing a washer and a spacer/"axle" support in the top of the carburetor which I concluded was teflon. Managed to finally use 2 of some I found in China (half the original thickness).
Also, I would like to recommend two books published by Haynes in 2000 ....... one on fuel systems and one on electrical systems for motorcycles.
I very rarely give-up and I hope to have it all reassembled by tomorrow evening ........ I broke the carburetors completely down as I've always liked to know what makes things "tick".
I drove my mother crazy as a young lad ......... taking things apart ......... and sometimes not remembering how to put them back together.
Once, the end of a Benjamin air rifle, propelled by an unseen internal spring, put a deep gouge in the ceiling ......... could easily have hit me in the face. After that I became more careful when disassembling things.
I always come to you guys first when I have a problem ....... experience often beats a manual due to erros in printing.
Thanks all ........

[rrecroc]

You're right ......... not plastic ....... material is odd .... reminds me of the old "bakelite" used in electronic circuits of the 50's and 60's ...... see mu last post ...... thanks much

[rrecroc]

Yes, when I compare it with the other slides, there is more movement with this needle but being in the needle jet, they would have to be capable of movement to prevent binding ............ I HAVE DECIDED I WAS WRONG ON THIS CALL AND AM PUTTING THE ONE SCREW I TOOK OUT BACK IN ........ that is why these forums are so useful ...... people who do these things regularly know what's "normal" ....... if anybody ever has to remove those screws you will have problems due to the corrosion/shemical reaction between the two materials

[rrecroc]

Thanks for all the help ......... now I know where I can get parts ..... which could have saved me much time and aggravation as one carburetor was missing a washer and a spacer/support for the shaft that moves the slide up and down in the top of the carb.
You are right about the needles needing to be able to move ...... makes sense now .......
Also correct about there being no room to access the screws at the bottom of the slide.
At least a weekend that has been crappy and rainy is ending on a better note.
Thanks .......

[rrecroc]

PS : Still no luck on finding any numbers on the carb body ..... just      KEI     HIN  (with symbol between the two syllables) and JAPAN underneath the 2 syllables ..... no other numbers/letters anywhere ....
Thanks

[rrecroc]

Thanks much for the links sir ....

[harisuluv]

Right above the engine side intake..