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New to me 73 RD 350 Carbs question.

Started by lowandslow, August 12, 2023, 08:19:03 PM

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lowandslow

Hello All,

My first post :help: , need some carb help. I am posting a few pics, are these high-top carbs.
Do the slides look ok, is there that much gap when the throttle is closed or I have something wrong?

I see that there is a wealth of information, thanks to all who provide their time and effort to help a fellow RD enthusiast!!

SoCal250

Welcome  :cheers:

Those are low-top carbs.
The slides should be lower in the bores with throttle closed. The gap at the bottom of the slide should be about 1/3 of what you have. Are the slides resting on the throttle screws or is the something holding them from dropping down more? If on the screws try turning them out a little to close up the gap at the bottom of the slide.
Check the throttle junction under the tank to make sure all the cable housings are seated correctly and not hanging up on something.
Is the throttle cable assembly one that came with the bike or a replacement?
75 Yamaha RD125B   75 Yamaha RD125B (project)
75 Yamaha RD250B   75 Yamaha RD200B (project)
73 Yamaha RD350     77 Yamaha RD400D   79 Yamaha RD400F  
91 Yamaha TZR250R  89 Yamaha FZR400   05 Yamaha FZ6   
05 Yamaha XT225TC  82 Honda MB5  02 Aprilia RS250 Cup (sold)

747drvr

could the slides be in the wrong carb ??    :umm:  :umm:

m in sc

doubtful. more of a not enough cable slack issue id bet.

lowandslow

Quote from: 747drvr on August 12, 2023, 11:05:41 PMcould the slides be in the wrong carb ??    :umm:  :umm:

I had it switched before and it would close more but read that the cutaway should be towards the airbox. Is the cutaway at the bottom of the slide or towards the top?

m in sc

#5
bottom. it creates a higher  vacuum area as the slide rises to draw fuel up thru the circuit.  if you can get them all the way down, adjust the cable in at the throttle all the way and set the adjusters all the way down. set the slide screws on the side of the carb all the way out where they don't touch the slide. then, touching the slide, adjust the side screws in till you just feel them contact the slide,  then turn in 1 full turn from there.  snap the throttle open and closed, when the slide comes down, put your finger on the slide screw, you should feel the slide hitting it when it shuts. then sync carbs  after than, set free play at bar and finally, set oil pump throw and you should eb at a good baseline. .02

lowandslow

Quote from: m in sc on August 14, 2023, 08:35:19 AMbottom. it creates a higher  vacuum area as the slide rises to draw fuel up thru the circuit.  if you can get them all the way down, adjust the cable in at the throttle all the way and set the adjusters all the way down. set the slide screws on the side of the carb all the way out where they don't touch the slide. then, touching the slide, adjust the side screws in till you just feel them contact the slide,  then turn in 1 full turn from there.  snap the throttle open and closed, when the slide comes down, put your finger on the slide screw, you should feel the slide hitting it when it shuts. then sync carbs  after than, set free play at bar and finally, set oil pump throw and you should eb at a good baseline. .02
Just to be sure the adjusters are the screws on top of the carbs that we can screw in more?
from my questions, you must have figured out, Yes I am new to fixing bikes

m in sc

yes the adjusters are on the tops of the carbs. the slide screws,or idle adjustment screws are the big ones on the sides. i thinkt he stock adjusters are 7mm locknut, 8mm barrel. go easy w these, easy to round off.   

lowandslow

Quote from: m in sc on August 14, 2023, 11:49:54 AMyes the adjusters are on the tops of the carbs. the slide screws,or idle adjustment screws are the big ones on the sides. i thinkt he stock adjusters are 7mm locknut, 8mm barrel. go easy w these, easy to round off. 
I adjusted them all the way down. This is what I Could get, pic attached of right slide. I also have this metal wire near the throttle twist?? Is that necessary, I assume I can take it out and get more play to let the slides down more?

m in sc

is the wire necessary? not if its adjusted correctly but it won't hurt anything. that gap you are seeing at the bellmouth is normal as there is a cutout on the back of the slide. are the slides physically hitting the bottom of the carb? you can hear it snap when you open the throttle and release it. if so, you are getting full closure.

this might help, a cutaway of an RDvm28. the slide is at about 1/8 throttle just fyi

start adjusting!


lowandslow

Yes I can now hear it snap when the slides hit the bottom