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Offline blackbike

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Heavy throttle
« on: December 17, 2021, 12:41:23 AM »
The throttle on my '74 cb750 has become rather heavy to operate.
Would ultrasonic cleaning and rebuild solve this?

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Offline Airborne 82nd

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Re: Heavy throttle
« Reply #1 on: December 17, 2021, 02:54:40 AM »
Quote from: blackbike on December 17, 2021, 12:41:23 AM
The throttle on my '74 cb750 "has become" rather heavy to operate.
Would ultrasonic cleaning and rebuild solve this?

What changed? What shape are the cables in? Are they routed correctly? Did you change the springs? They are a little strong even in good shape but you make it sound like something changed.

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Offline blackbike

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Re: Heavy throttle
« Reply #2 on: December 17, 2021, 02:59:49 AM »
They've become heavy to operate over time.
New cables didn't do the trick, routing is perfect, spring hasn't been changed.
With the carbs off the bike they don't move smoothly either...

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Offline newday777

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Re: Heavy throttle
« Reply #3 on: December 17, 2021, 03:12:03 AM »
Quote from: blackbike on December 17, 2021, 02:59:49 AM

With the carbs off the bike they don't move smoothly either...

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That is some dirty gummed up linkage on the carb rack and yes it needs a good cleaning.

Has this bike been setting unused for a long time?
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Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 2 K4, 2 K6, 1 K8
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A

Offline pjlogue

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Re: Heavy throttle
« Reply #4 on: December 17, 2021, 03:15:49 AM »
Make sure your slides are clean and not gummed up.  Also, make sure the  throttle slider rod-to-foot is clean and lightly greased.  This foot and where it sits on the slide is important as it needs to position its self as the slide is opened and closed.  The last thing to do is loosen all four carb tops (the round ring that holds the carb slide top on)  with the ring loose, open the throttle all the way so the slides are fully up and then tighten the rings down.  This seats the slide rod foot properly with relation to the top side of the slide.  This will get you the smoothest operating throttle as possible assuming your slides and the bores they ride in are clean and the four cam like fingers the rod tops engage in are clean along with the rubber gromets at the tops of the carbs.  A little silicone vacuum grease on these gromets helps.  Carb spray on these gromets can swell them and make them tight against the rods.

-P.
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Offline blackbike

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Re: Heavy throttle
« Reply #5 on: December 17, 2021, 03:16:16 AM »
It's been sitting unused for a year or so

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