Carbs. Specifically needles and shimming

[jt]

Guys,



I want to shim the needles on my CBX and 750F, when I put a shim under the needle and tighten the screw the needle does not move like it does without the shim. Is this ok? Or is there another way? Also I found some washers to use but they are .032 thick, would like to find something about .025, where do guys find them?

Thanks

JT

[Passx]

JT,



I would recommend that you do not do this, these motors run too rich on the main jets anyway and you will only make a bad situation worse, they are lean on the low speed jetting for emmisions but not that bad really. The question that I would ask is that if you are trying to make power or make it less cold blooded why add more fuel to a already too rich condition, I read about (and did the same) guy's adding the Dynojet kits and talking about that they no longer need the choke and they now get 25mpg, could it be that they are just dumping fuel in the same as having the choke on all the time. I would start with a good "blueprinting" of the carbs making them all the same as much as possible and then dyno it with a Lamda Air/Fuel sensor and then go from there. You won't regret it.



Steve P. #5220

[jt]

Hi Steve,

Thanks for the reply. I've had the carbs apart to clean and replace the o rings. The bike pulls well through out the rpms but running in 2nd gear at around 2500 to 4000 rpms the eng burbbles and will smooth out with a little choke and run better. It did this also before I cleaned the carbs, which was one reason to clean them. It has stock jets and I turned the pilots out 2 1/2 turnes. I made sure all the passages were clear also. Just trying to get rid of that rough spot.

Thanks for any ideals.

JT

[Passx]

JT,

Have you checked the float levels and made sure that they are correctly set ? Also when I first got my 80 running I had a real problem with the air jets plugging up which will cause problems like you described as well as the needle settings, you did not say what year it is but you may give some thought to a Dynojet kit while it's apart, they usually set them very rich but you have adjustability. The 80 with a 6-2-1 header, a K+N drop-in air filter, 79 cams & Dyna ignition coils used a 98 main jet and the needle in the D-Jet recommended slot and the A/F ratio was pretty good and the power curve was seamless, drivability was like grandma's Caddy, it got 50-52mpg on a steady cruise and made 92 rear wheel HP, then I screwed with it, oh well. If you have a 79 you might consider the low speed jet or air bleed because the rpm range you described is about where you transition from the low speed to the main, if you have a 79 I believe you also have a primary main jet(mid-range) but you'll have to ask someone more familiar with those carb's as I'm not sure about that. One other thing is your ignition working well as it will also cause driveability issues that appear as carb problems. Good Luck, Steve P.

[jt]

HI Steve,

Yes I have a 79, I completely went through the carbs. Made sure the floats where set all passges clean and clear. I am running a late model paper filter and Suppertrapp pipes. Thanks for your help and Ideals will look into them.

Regards

JT

[Dave Ditner]

I've got an 81 with the needles up .028", Kerkers and a K & N replacement filter. I counterbored the aluminum retaining screws to maintain the clearance that was there, but after a bunch of discussions with others, I don't think it's a necessary thing to do. I believe that the purpose of the clearance is to allow the needle to move during production assembly, and not bind up as it could it the needle were tight and to one side of the hole in the slide. I'm sure that in the production sequence, a fully assembled slide is placed into the carb body then the top mounted. Needle clearance might be an issue in this case. But on the bench with the slide bottomed when the retaining screw is tightened, there can be no bind since the needle can't go any lower than it is when the retaining screw is tightened. Bill Hoctor (Buffalo Bill) did his 82 without counterboring and suffered no ill effects. Take your choice

[jt]

Dave,

Thanks for the info, I've located some fiber washer that fit and will give it a try.

Thanks

JT

[bobcat]

jt, kinda late answer but have you tried the 'drop of Loctite' on the screw/plug threads method ?

Turn the screw in until it binds the needle, then back it out just enough that the needle is free
but doesn't move up and down. Always worked for me.

[CBX-tras]

DO NOT use Loctite on the screw.

Wrap it with teflon tape about 4 layers. With that method the screw can be removed without damage with still allowing the needle to wiggle.
This is VERY important to allow the needle to slide through the needle jet without any resistance between the 2 parts.

(20 year old thread).