Topic: Throttle return spring

[junruh]

Hey I’m new here. Thanks for letting me join! Just bought a 1975 Honda cb550f. I’ve done a little bit of mechanic work but never owned a bike till now. I’m missing the throttle return spring that hooks down in between carb 2 and 3. At least I believe there is supposed to be one there? The throttle isn’t snapping back and I just put on new cables. Where do I buy a new spring? Can I use one from another model or model year? I have no idea how tight this spring needs to be and I have a feeling I might have a hard time just picking one up from a hardware store. Maybe someone has a link or part number for any of the above options? Thanks for any input

[CycleRanger]

Hello!
I believe this is the part.
https://www.cmsnl.com/honda-cb550-four-1975-cb550k0-usa_model465/tube-set_16036323004/

[MauiK3]

Welcome
I lost track of the link but others here will help out. A senior member here, Mark Paris, has written a great manual about the CB500/550 F bikes, he goes by the handle Hondaman. Very knowledgeable.
I have his book on the CB750.
These books are the most important tool in your tool collection. Get the book for your bike as soon as possible, it will save you many hours and $$.

[bryanj]

Thats the spring but the pin it attaches to between carb bodies may be missing, trouble is there is no part number for it on cmsnl

[junruh]

Thanks guys! Do you have a pic or where can I find a pic or parts breakdown of where the springs mount on the carbs?

[bryanj]

Go to cmsnl and look up the bike to see parts page, the pin fits inbetween the two centre carbs located in the castings, you have to split the carbs from the bracket to fit itwhich is why people loose it when stripping carbs to clean, it just falls out and gets lost

[Jerry Rxman Griffin aka MuthaF'er]

believe I saw one on EBay with the rubber sleeve

[CycleRanger]

Thanks guys! Do you have a pic or where can I find a pic or parts breakdown of where the springs mount on the carbs?

You can download a PDF of the parts list for your bike here:
https://www.honda4fun.com/materiale/documentazione-tecnica

[junruh]

Does anyone have a pic of exactly where it hooks to? I can’t find a good example in pics or diagrams anywhere online.

[bryanj]

There are no pics as the part was never available, its a rod with a groove around the middle that fits inbetween the two centre carbs just above float bowl gasket lever located by a raised circulat rib on each carb, i could go and strip a set of carbs but dont want to till i need them

[HondaMan]

If the short rod in between carbs 2 & 3 (that holds the bottom end of the spring) is missing, I can make one for you on my lathe for cheap.
I've used a spring from Ace Hardware on both the 750's PD41 carbs and the 550's carbs before, but I don't have that part number. It is 1/2" shorter than the distance between the end of the spring and the pull-closed lever on the carbs, if that helps? Measure from the rod (that should be in between carbs 2&3) to the hole in the throttle lever and subtract 1/2", that will get you sorta close. I also have a whole bunch of springs, donated to me recently by someone experimenting widely with the CB750 springs (on roundtop carbs). If you can come up with a measurement, I could probably find a spring in this collection that would work?

[junruh]

Thanks for the input guys. I purchased a used spring off eBay and freshened it up a little. It works ok but doesn’t snap back super great. I modified a bolt to make my own rod with a groove. May end up getting a spring from a hardware store yet so thanks for the 1/2” short reference!

[bryanj]

Mark now has the sizes for the pin as i stripped some 400 carbs for parts and measure one, no i dont have one available, only 1 between the 2 racks i had!

[HondaMan]

I am currently digging around to find some aluminum rod I can use to make some of these spring retainers: I don't think I'll use steel, as it will just rust and make a mess.

Thanks for bringing it up, Junruh: others will eventually benefit from your posts. That's how it often works around here,

[Little_Phil]

Thanks for the input guys. I purchased a used spring off eBay and freshened it up a little. It works ok but doesn’t snap back super great. I modified a bolt to make my own rod with a groove. May end up getting a spring from a hardware store yet so thanks for the 1/2” short reference!

That's odd. Most complain that the spring is too strong.

[Don R]

 The carb linkage may be crudded up or the slides may have varnish from dried fuel, just a couple things to check.