Sticking throttle valve

[mca2]

Today I took my '68 CB77 out for a drive. Yes, for the first time! All seemed to go well, except that it wouldn't idle below 4000rpm.

When i got home, i quickly found out that the throttle valve of the right carburetor didn't want to seat fully. I dismantled the carb and when i pressed it down fully, it got stuck abit. I must say the valve was quite warm, almost hot. The insulator doesn't keep so much of the engine heat away it seems. After it cooled down, the valve move somewhat freely, although it still got abit stuck when fully pressed down.

The valve looks different as i expected. It seems to be steel/chrome (coated)?



The carb body seemed to be clean and round internally.

So what are my options? Just simply sand down the valve? Or is this a wrong throttle valve?

[LOUD MOUSE]

The slide is chrome/brass and if ya will insert the slide and move it in and out of the carb body ya will see the area where the slide is sticking.
I use a fine grit sand paper (cut 1x3 inch and fold with grit out) then use my finger to sand the shinny area in the carb.
I insert the slide several times until I have cleared the bad area.
Don't over tighten the mounting nuts. .......lm

Today I took my '68 CB77 out for a drive. Yes, for the first time! All seemed to go well, except that it wouldn't idle below 4000rpm.

When i got home, i quickly found out that the throttle valve of the right carburetor didn't want to seat fully. I dismantled the carb and when i pressed it down fully, it got stuck abit. I must say the valve was quite warm, almost hot. The insulator doesn't keep so much of the engine heat away it seems. After it cooled down, the valve move somewhat freely, although it still got abit stuck when fully pressed down.

The valve looks different as i expected. It seems to be steel/chrome (coated)?



The carb body seemed to be clean and round internally.

So what are my options? Just simply sand down the valve? Or is this a wrong throttle valve?

[mca2]

The slide is chrome/brass and if ya will insert the slide and move it in and out of the carb body ya will see the area where the slide is sticking.
I use a fine grit sand paper (cut 1x3 inch and fold with grit out) then use my finger to sand the shinny area in the carb.
I insert the slide several times until I have cleared the bad area.
Don't over tighten the mounting nuts. .......lm
[...]

It seems the slide sticks at the bottom of the carb near the main jet, so pretty hard to reach. Is it also possible to sand down the slide itself a bit? Or should i be careful with the chrome coating?

[LOUD MOUSE]

Is the bottom where the shiny spot is?. ........lm

The slide is chrome/brass and if ya will insert the slide and move it in and out of the carb body ya will see the area where the slide is sticking.
I use a fine grit sand paper (cut 1x3 inch and fold with grit out) then use my finger to sand the shinny area in the carb.
I insert the slide several times until I have cleared the bad area.
Don't over tighten the mounting nuts. .......lm
[...]

It seems the slide sticks at the bottom of the carb near the main jet, so pretty hard to reach. Is it also possible to sand down the slide itself a bit? Or should i be careful with the chrome coating?

[mca2]

I polished the carb slides and used wet'n'dry 800 paper on the shiny carbs spots. Now they seem to be moving without any problem, yet still waiting what will happen if the bodies get hot.

In the process i fixed the float height (28 back to 22.5mm) and raised the needle to its standard position. Is the needle number 2423 correct for this type?

And why the explicit tip not to overtighten the mounting nuts (besides the usual prevention of damaging the soft aluminium)?

[brewsky]

Overtightening the mounting nuts will bend the flange out of shape and allow air leakage.
3-4 ft-lbs is plenty.

Put a straight edge across the flange at the mounting holes to see if yours are already out of shape.

[305nutt]

if you overtighten the nuts, it will also warp the body causing your slide to stick. I use lock washers and just snug the nuts. I also put some black silicon on both sides of the insulator to prevent air leaks. nutt