Topic: 1978 THROTTLE RETURN SPRING

[rickibrown]

My 78 has the hardest throttle twist tried a lighter extension spring and then the throttle hangs up on deceleration.
So hooked back up the OEM torsion spring all is good.
Has anyone resolved this issue.
I'm 72 yrs and cannot ride far without cramping.
thanks Ricki

[Stev-o]

Hey Rick...

How old are the cables?  Has the routing changed recently? 

[bustech51]

Hey Rick,
I'm  going with Steve-o on the faulty cables.  If you haven't  lubricated them they will get hard to either push or pull.  That will give the feel of sticky carb mechanism.

Sent from my SM-T350 using Tapatalk

[TwoTired]

 I Find bigger diameter grips help.  Did that after making sure the cables were smooth in operation.  Also gentle wide bends in the cable make operation easier.

Cheers,

[scottly]

Hey Ricki, have you heard of "cramp busters"?
https://www.crampbuster.com/

[rickibrown]

Thanks all, When cables are disconnected from carbs, throttle cables are loose as a goose. oiled etc.
they are original however, very clean bike low miles.
It has to do with the 78 spring being overly engineered, I have heard the 77 was not as bad
looking for one to try. Will put the cramp buster on have used them in the past.
This is all original bike so would like to use OEM spring, maybe new cables as a matter of elimination.
Source for these please.

[Ichiban 4]

Thanks all, When cables are disconnected from carbs, throttle cables are loose as a goose. oiled etc.
they are original however, very clean bike low miles.
It has to do with the 78 spring being overly engineered, I have heard the 77 was not as bad
looking for one to try. Will put the cramp buster on have used them in the past.
This is all original bike so would like to use OEM spring, maybe new cables as a matter of elimination.
Source for these please.

Hi rick..

I have a '77 that has a similar problem with being hard to twist w/OEM spring.  And I've checked all of the things mentioned here..and it still "did it" (I'm in my 70's also..but have dealt with this since I've had the bike..which goes back to the early 2000's BTW).

I tried two things: 1.) stretched out the OEM spring so that it didn't have as much tension 2.) got a replacement spring from the local hardware store..with less tension..and used that (like you BTW).  And..like you..I have to manually shut-down the throttle now when decelerating..but mainly to get to idle.

I figure that manually tweaking the throttle is preferable to hassling with the throttle when riding..getting tired wrist..etc.

I've also thought that probably if one wanted..they could experiment with various return springs of various tensions and perhaps different lengths to come-up with a better solution..but personally figured that I can live with it the way it is now (having to tweak the throttle to get it to idle..basically).

I know this is probably not the ideal solution to this issue..but just wanted to relate that it seems a lot of us with '77 and '78 550's (from what I've read on these forums) have had to deal with the same situation.

Hope this was reassuring to some extent..

Cheers..Al/Ichi

[TwoTired]

Thanks all, When cables are disconnected from carbs, throttle cables are loose as a goose. oiled etc.

Of course they are, as there is no tension on them to cause friction on the cable sheath.  Stiff cables are from internal friction between sheath and the cable twist wires.  These occur with bends in the cable forcing contact with the sheath and core.  Can make grooves.   I thought the original cables were plastic lined to prevent metal to metal contact and actually deteriorated when petroleum oils were applied.  I understood graphite dry lubes were to be used with an evaporative carrier for penetration.  I've been using a product called Dri-slide.  If the lining is worn, it will move fine without tension and very course when under tension as it is forced into the wear points, with more tension causing more friction.

Your spring is not over engineered.  The engineers expected poor maintenance, and made the spring strong enough to operate with inevitably worn, draggy, and non-ideal cables, as a hanging throttle at the wrong time can be quite harmful to rider.

Good luck!

[Deltarider]

Best tip so far I've read at the UK site: http://www.sohc.co.uk/index.php?topic=26115.msg239571#msg239571 Simple and effective.

[thep1pe]

Hi there deltarider
I tried the link you posted and it sends me to the correct site, but it has not got any info somehow. Is there something l have missed?

[Deltarider]

OK. Let me quote Maax1200 then...

Dont know if anyone allredy came up with this idea so i though i would share it.
Found the throttle return spring to be way to stiff on my CB500 -74 and came up with this easy fix (yes, i have new cables and all that).
It reduced the force needed with at least 50% and there are plenty of spring left to close on its own and now it feels like every other bike iv ever owned.
And the best part, it was free.

[BenelliSEI]

My K8 was a bear to pull too. From memory, I think I inserted a stainless cotter pin and then hung the spring from the loop. Tossed a spare one in the tool kit about 5 years ago. Must remember to have a look at the original, next Spring!

[Steve_K]

Back in the 70's I put a VW carb spring on my 550.  I had superbike handle bars , so I spent time positioning cables so the spring worked.  Cable routing and some lube on the throttle tube can help. Check that the twist grip is not dragging on the bar end.
Steve

[HondaMan]

My 78 has the hardest throttle twist tried a lighter extension spring and then the throttle hangs up on deceleration.
So hooked back up the OEM torsion spring all is good.
Has anyone resolved this issue.
I'm 72 yrs and cannot ride far without cramping.
thanks Ricki

Doesn't your spring wrap around the throttle shaft (about 5 times) and then press against the idle stop plate for the return action?
If so, it is really tough to reduce that one's pull. What I have done in the past to those is: made a short, stiff wire to hook into the anchor-end of the spring (where it wraps around the carb body) and played with the length of it until it was strong enough to return to (colse to) idle. Then it was much less tension up to about 1/3 throttle, which helped a lot.