Author Topic: Can anyone explain this throttle spring?  (Read 417 times)

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Offline Bigmant

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Can anyone explain this throttle spring?
« on: December 21, 2024, 12:03:05 PM »
Hey gang!

Just curious if anyone has any idea how this may make the throttle on a Cb750K feel as easy as a modern bike? My spring is SO heavy that my forearm is burning after about 20min. Wondering if this guy somehow figured out something clever!
‘73 CB750 K3 Owned by my father and now me

Build post: http://forums.sohc4.net/index.php/topic,190516.msg2216419.html#msg2216419

Offline bryanj

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Re: Can anyone explain this throttle spring?
« Reply #1 on: December 21, 2024, 02:36:18 PM »
No idea but what is going on below?
Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline denward17

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Re: Can anyone explain this throttle spring?
« Reply #2 on: December 21, 2024, 02:56:26 PM »
No idea but what is going on below?

Air pods?

Offline Bigmant

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Re: Can anyone explain this throttle spring?
« Reply #3 on: December 21, 2024, 05:06:29 PM »
No idea but what is going on below?

Yea AirPods
‘73 CB750 K3 Owned by my father and now me

Build post: http://forums.sohc4.net/index.php/topic,190516.msg2216419.html#msg2216419

Offline PeWe

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Re: Can anyone explain this throttle spring?
« Reply #4 on: December 22, 2024, 12:39:28 AM »
Stock spring is very hard on these carbs.
I found a weaker spring at Webike. Not cheap but painless throttling without the throttle grip rubber twist on its tube. Important that cables are routed so return will work by let go off the grip.

My Mikuni TMR32 carbs need very little to lift. Despite that a quick return.
I think my old Mikuni Smoothbore VM29 was easy to handle too.
« Last Edit: December 22, 2024, 11:32:54 PM by PeWe »
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline pjlogue

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Re: Can anyone explain this throttle spring?
« Reply #5 on: December 22, 2024, 01:48:29 AM »
I replaced my throttle spring with a similar length spring with lighter coils.  The throttle is much easier on the wrist now but will still return to a closed position if I let go of the grip.  I found the springs at Lowes.

-P.

Offline rotortiller

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Re: Can anyone explain this throttle spring?
« Reply #6 on: December 22, 2024, 04:10:58 AM »
There are also thicker grips available offering a better leverage however the wrist travel is longer with the larger circumference. And then there are those throttle brake thingies. Not a problem for some, as wankers do have a very strong wrist lol!  :)

Offline Phoenix

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Re: Can anyone explain this throttle spring?
« Reply #7 on: December 22, 2024, 08:46:02 AM »
I just stretched mine and it works fine.
Ed Spengeman
Indy
1971 CB750K1 (Stock)
1973 CB350 Twin  (Gone)

Offline Bigmant

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Re: Can anyone explain this throttle spring?
« Reply #8 on: December 22, 2024, 01:25:37 PM »
I also found a similar length spring with a lighter compression at ACE hardware. Works like a charm. The bike in the picture though looks to have two springs, and the rubber is covering where the two hooks join. I’m amazed it worked so well despite looking somewhat janky.
‘73 CB750 K3 Owned by my father and now me

Build post: http://forums.sohc4.net/index.php/topic,190516.msg2216419.html#msg2216419

Offline Oddjob

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Re: Can anyone explain this throttle spring?
« Reply #9 on: December 22, 2024, 05:05:36 PM »
Fit a small split ring, like a key ring, I fit some around 8mm and that reduces the amount of strength needed to pull it by around 20%.

I fit the ring around the lower peg when I have carbs apart, then just hook the spring onto the ring. If you haven't got carbs apart I suppose you could try and thread it on.

Offline Bigmant

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Re: Can anyone explain this throttle spring?
« Reply #10 on: December 28, 2024, 07:27:17 PM »
I’m wondering why someone would split the throttle springs into two springs and then tie it back with a spring. Why not just use a lighter spring?
‘73 CB750 K3 Owned by my father and now me

Build post: http://forums.sohc4.net/index.php/topic,190516.msg2216419.html#msg2216419

Offline Bigmant

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Re: Can anyone explain this throttle spring?
« Reply #11 on: December 28, 2024, 07:30:18 PM »
Here it is again, I’ve brightened the picture up a bit.
‘73 CB750 K3 Owned by my father and now me

Build post: http://forums.sohc4.net/index.php/topic,190516.msg2216419.html#msg2216419

Offline PeWe

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Re: Can anyone explain this throttle spring?
« Reply #12 on: December 28, 2024, 10:31:07 PM »
Spring is attached too high?
Here a set when I assembled them.
See green arrow where the pin is for spring upper attachment.
And yes, the seen holes in chromed parts have not yet got the bolts when photo was taken ;)
« Last Edit: December 28, 2024, 11:04:51 PM by PeWe »
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967