1971 ct.70 - throttle assembly too tight - best modification to fix "no spring back"

Discussion in 'Modifications' started by Larry Word, Jan 11, 2012.

  1. Larry Word

    Larry Word New Member

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    I am new to this site so forgive me if I'm not using the search functioncorrectly (send me a link so I can end my ignorance) or something.

    Under the "general ct70 area of the bulletin boards", a user has adiagram of how to my a non-spring back throttle unit spring back on its own? I donot understand the image which I've attached which involves a simple hardware-type spring; perhaps one whose understands ct70 throttle (I've yet to see inside of one...) could enlighten me here which is what I'm hoping/asking for in this inquiry!

    Thanks in advance....

    Larry
    Ga
     

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  3. racerx

    racerx Administrator
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    Break out the heat gun, set it on low, to gently warm/soften the RH vinyl grip enough to remove it. Once that's been done, removal of the single screw in the slot of the outer throttle pipe allows removal of the pipe from the RH handlebar. From there, you'll be able to see what the stock throttle setup looks like and where those extra, custom, parts would go. I could go into a longwinded explanation, but this is an application where firsthand viewing should provide most of the explanation you need...and in few words.
     
  4. jeepin79

    jeepin79 Member

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    This mod is on my list of things to do, I feel like the bike is somewhat dangerous with the "sticky" throttle. Does anyone have a parts list for this or is it just a matter of a trip to Home Depot to find the parts that will work?
     
  5. theraymondguy

    theraymondguy Well-Known Member

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    After disassembling the 40 year old throttle (it's intimidating, but like racerx said it's straightforward once you've made the effort to try it yourself), you should also remove the throttle cable from the throttle linkage and the carburetor. Make up a funnel and attach it to the throttle grip side of the cable jacket. Hang up the cable and fill the funnel with your favourite penetrating oil (3 in 1, Krown T32, or a 50/50 mix of ATF and WD40) and let it drip out the bottom into a pan. Makes a big difference, especially if you work the cable back and forth in the jacket while the lube is in the funnel. Or toss the cable and install a new one (jacket will be black on new cable instead of the factory grey).

    Clean all the components in the throttle linkage. The tube itself (where the throttle grip mounts) will show the most wear. When reassembling be sure to use a light grease (white lithium grease or similar) liberally on all components.
     
    #4 theraymondguy, Jan 12, 2012
    Last edited: Jan 12, 2012
  6. racerx

    racerx Administrator
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    Return spring action was never very positive, hence the term "CT70 cruise control" :40:. They usually work better while the engine is running, still not truly up-to-snuff. A heavier throttle return spring, at the carb end, does help but there's only so much that can be done with a small diameter spring. A helper spring, at the handlebar end is a sound idea.

    That said, throttle cables do become arthritic, for various reasons. Some are non-correctable. I lean toward replacement, nothing like a free-sliding, minty-new, throttle cable. On the other hand, the internal twist grip assembly mostly improves with use, only accumulating dirt/grease paste will gum-up the works. The slide/internal helix (inside the throttle pipe) were manufactured better, decades ago; they also break-in.

    Lastly, the vinyl outer grip cover, at least new OEM replacements, tend to bind at both ends. If you replace yours, make sure you don't press it too far inboard. And, it will probably be necessary to trim the inner lip at the LH end.
     
  7. johnsgm

    johnsgm Member

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    Larry . . . PM sent. Check your inbox.
     
  8. Larry Word

    Larry Word New Member

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    size of 1971 Honda ct. 70 handlebar (inside diameter for spring back set-up)

    My bike is not at my house and to save a trip to storage, can anyone tell me the size of the spring (inside diameter of a stock 1971 ct. Honda handlebar so I can buy the 3 inch. spring and stoppers mentioned in this "handlebar snapback video"....

    Thank you

    Larry

    video: http://lilhonda.com/webboard/private.php?do=showpm&pmid=47264
     
    #7 Larry Word, Jan 12, 2012
    Last edited: Jan 12, 2012
  9. Lucan

    Lucan Member

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    Larry, I just did this conversion when restoring my 1970 CT70. I cannot tell you the spring dimension w/o taking mine apart, but what I did was take a few trips to the hardware store with the throttle parts. It took a few return trips, but it is working well for me.

    ---------- Post added at 09:17 PM ---------- Previous post was at 09:10 PM ----------

    I just re-read your post and realized that you dont have access to the parts. The dimension of the inside diameter of the throttle tube is 3/4 inch on the smaller end, and the length of the tube itself is 3/ 3/4 inches. The stoppers just have to fit in the springs ends. Hope this helps.
     
  10. RMHRC

    RMHRC Member

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    Hi guys first post. I have a 71 ct70 with a Honda nice 110 motor. Normal throttle after market twist throttle.

    I gradually restoring bike back to more stock like parts - and throttle is one.

    Does anyone have a source of the spring that is required to make the part above?

    if no what size spring should I get from the hardware store.

    And what are the plugs either end made of?
     
  11. RMHRC

    RMHRC Member

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    Any help on this? what size spring is needed?
     
  12. kirrbby

    kirrbby Well-Known Member

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    This thread is from 2012. I don't think those folks drop in anymore. But you can take your dimensions right from your own handlebar...

    Measure the I.D.
    Retract the throttle hinge and measure, from the hinge, to the end of the bar. Write it down. Then, spin the throttle to move the hinge toward the end of the bar...measure and write.

    Make a thicker plug to go against the hinge...thicker, because it needs to stay square inside of the bar, AND slide back and forth with the hinge.
    Then make a thin plug for the end of the bar... just to back up the spring.
    Then buy a spring the right diameter, AND capable of springing, long and short, inbetween the plugs...AND, find one with the stiffness that you need to do the job.

    As a alternative. Get your throttle parts all spiffy new and clean and lubed. Same with the cable. Then, take the slide and spring from inside of your carb to the hardware store. Look for a stiffer spring that will fit and work.
     
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  13. RMHRC

    RMHRC Member

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    so would a spring 93mm long x 18mm diameter do the trick?

    I have a genuine throttle rebuild kit to restore the throttle back to original oem inner throttle system.

    I’m not entirely clear on the size of the end caps you refer too

    I found this you tube link

     
  14. kirrbby

    kirrbby Well-Known Member

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    I've heard/read about that fix. Ive heard/read that it works. But I've never tried it myself. If I feel froggy one day I might have to look into it.

    But, maybe someone... in the know, will chime in. Otherwise, I'm thinking that if you start assembling your throttle, measuring, looking, and thinking, you'll be able to figure it out. My one question is, how to keep the thin plug in place, in the end of the bar. It needs to be a tight...pressed in fit...or glued...or something..?

    I would use a washer for the thin plug. And maybe a ⅝" thick piece of wood or steel or something for the thick plug. Guessing at the id of the bar...I'm guessing it's about ⅝" also.
    Just my thoughts.
     
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  15. kirrbby

    kirrbby Well-Known Member

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    Just tinkering.

    A ⅞" hole saw makes a plug about 11/16" od.
    A penny is a really nice pressed fit if you sand a very slight bevel on the id of the bar.
    The wood plug could be made shorter...cut off.

    My setup here is too long for sure, and I don't have the throttle parts here to work with. But this is a good start. Drive the penny in a little and add a few dabs of jb or superglue to keep it there...temporarily permanent.

    I think a VERY good option would be to use a ½" copper pipe end cap for the big plug. They should be a pretty good fit to slide inside of the bar, and would capture the spring end.

    IMG_20200814_093404005.jpg IMG_20200814_095314002.jpg IMG_20200814_095335939.jpg IMG_20200814_095441775.jpg IMG_20200814_095554041.jpg IMG_20200814_095628007.jpg IMG_20200814_100106070.jpg IMG_20200814_100124066.jpg
     
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  16. kirrbby

    kirrbby Well-Known Member

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    Oh ya...the penny is vintage, 1981 :)
     
  17. Gary

    Gary Well-Known Member

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    Wrong penny for that year bike :LOL:
     
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  18. RMHRC

    RMHRC Member

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    Just installing the new oem throttle so this question related to the oem internal throttle assembly.

    Does the ‘threaded stopper’ seat the cable then the cable screws in or is the cable threaded straight into the stopper ?
     
  19. kirrbby

    kirrbby Well-Known Member

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    http://hondaminitrail.com/ct70.html
    Screenshot_20200814-225151.png

    You have to put the ring(throttle stopper) on the bar first. Then install this cable holder as pictured above. Then you can install the throttle hinge.
     
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  20. RMHRC

    RMHRC Member

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    Thanks Kirby

    that video I linked to did it wrong hence my question

    it didn’t seem right not having some seat time

    got my ct70 Honda nice 110 running albeit not continuously as the carb was filthy.

    so I need to remove and thoroughly clean it.

    the oem internal throttle is great - I just need to clean the carb and the engine will fire properly
     
  21. RMHRC

    RMHRC Member

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    upload_2020-8-15_16-17-44.jpeg 11435183-620A-4986-93C3-8379812415D2.jpeg 874BA69D-4C68-43CC-80C7-C434FFA202D3.jpeg EC9E9F5A-92A3-46E9-8DC0-85DECD3C29C1.jpeg 13B6A903-C0C0-4344-A11E-96ED04D95ADC.jpeg C00E4438-99C5-44F9-92FA-8E9FEE8FE575.jpeg


    old v new showing wear and smoothness of original 49 year old throttle tube v the sharp edges of the new part today.

    Rebuilt throttle using old and new parts for best feel.

    Ended up getting the engine to run despite the filth in the carb

    You guys will note the 72 model forks - i prefer them to the original 71 model sticks. Basic bike is 71 model withe the asian concepts Nice110. Running a genuine keihin PE24mm with a genuine Unifilter (44mm bell end if you guys ever need to know)

    Now I need input/help on the following:

    1. New footpegs with springs. Prefer offroad type pegs but not too aggressive. Can I make CRF or XR pegs work?
    2. A gear lever that will work with the Nice 110 motor. I dont want a heel shifter either. Happy to buy Takegawa or G Craft but need advice if they will work.
    3. Ditto for Kickstarter.
    4 New rear shocks
    5. Ovehauling the forks - can I get stiffer 'adult' springs?

    Any of you who have bought Thai motors and parts will note the absolute shiteful metalurgy compared with us in the west. Hence a desire to remove as much of that as possible. And for obvious reasons I will not buy/avoid at all costs Chinesium products.
     
    #20 RMHRC, Aug 15, 2020
    Last edited: Aug 15, 2020
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