1979 Carb Rebuild (Pt 1)

zed_thirteen
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Re: 1979 Carb Rebuild (Pt 1)

5 years 3 months ago

#25137

tackelhappy wrote: Thank-you both for replying. I think back to all the Triumphs I've owned with no throttle return cable and don't ever recall ever hearing about the throttle jamming/staying open . But I can understand why the second cable was added for perceived safety reasons-you never know--it might happen.
This investigation on the throttle cable set-up was prompted by inconsistent idle- so with the tank off and watching the return action of the cables I could see very small variables in where the whole mechanism would stop after opening and closing the throttle many times- there would be a very small amount of extra movement in the link rods #-65- they didn't seem to return to the same place/stop every time - small things but significant nonetheless.
So I'll try what you suggest Kawboy and tighten the decelerate cable to pull the gap closed and go from there.

With regard to why have throttle close cable. My first bike was a Honda SS50. One winter whilst driving to work VERY carefully on icy roads I managed to fall off 3 time while braking - also VERY carefully. At this point I decided to turn around and go home. On the fourth time of going down I happened to notice that my front wheel was not revolving - even after releasing the hand lever. Turned out water had got into the cable and frozen. When the brake was applied the ice kept the cable from returning.

Perhaps a frozen throttle pull cable could have a similar effect - I doubt the friction of ice in the cable could overwhelm the return spring though.

1980 KZ1300 B2 Touring/A2
1990 ZZ-R1100 C1

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scotch
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Re: 1979 Carb Rebuild (Pt 1)

5 years 3 months ago - 5 years 3 months ago

#25138

I could see very small variables in where the whole mechanism would stop after opening and closing the throttle many times- there would be a very small amount of extra movement in the link rods #-65- they didn't seem to return to the same place/stop every time

This symptom is typically associated with the sync adjusters on 1 - 2 or all 3 link-rods being screwed in too far, causing the ball-links to bind. This is the reason the manual states that the screws should be turned in lightly until they stop - then backed out 1.5 turns. This allows for some room-to-play when syncing. It's more important to achieve an accurate sync across the three carbs. without unwittingly bottoming the adjusters in an attempt to achieve a greater vacuum.
My experience with many carb-sets has repeatedly proven (on my bike) that 7.5" to 8"hg is the max. vacuum that can be achieved and still have free movement of the linkage rods.

1980 KZ 1300 sr# KZT30A-009997
Always High - Know Fear !

Last edit: 5 years 3 months ago by scotch.

The following user(s) said Thank You: tackelhappy, PaulD

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tackelhappy
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Re: 1979 Carb Rebuild (Pt 1)

5 years 3 months ago

#25156

That's a good place to start- trying to achieve a greater vacuum than 8hg is probably the culprit.
Thanks

" If you can't say what you think, very soon you won't be able to think !
OKANAGAN FALLS. BC ,Canada

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CWB
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Re: 1979 Carb Rebuild (Pt 1)

5 years 3 weeks ago

#25615

Hi scotch, Im a bit late in asking this question. Is it correct to assume that after removing the secondary cable you still have the gap still there as shown by tacklehappy and that is has not affected carb setting for idle?

In other words are you saying the "gap" is not an issue?.

I see Kawboy has offered up an explanation but I can't seem to work out how to do what is explained on my bike with same "gap" problem.

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scotch
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Re: 1979 Carb Rebuild (Pt 1)

5 years 3 weeks ago - 5 years 3 weeks ago

#25620

Again, I removed the "return" cable, it's bracket and "that" spring 30? years ago ! I disliked the appearance of the double cables at the handle-bars and the farting around required when re & re'ing the carbs. and the adjustments required.....as is apparently the situation noted in this topic. I've been using the single "opening" cable for all of these years with NO issues or concerns.
So without the OEM 2X cable arrangement and the experience lacking of having to deal with the set-up, I can't offer any suggestions other then those that others have indicated. Sorry.
I have to agree with kawboy: "My personal opinion is that it's a bit of overkill".

1980 KZ 1300 sr# KZT30A-009997
Always High - Know Fear !

Last edit: 5 years 3 weeks ago by scotch.

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Bigbadbaz123
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Re: 1979 Carb Rebuild (Pt 1)

4 years 7 months ago

#27060

Hi Scotch, followed this as I've rebuild my carbs, thanks very much a super guide.

Sorry if I just missed this, but do you replace the caps over the idle air screws, or can they be left open. 4 of mine had already been removed and were open.

Is 1 and a half turns out a good starting poor to set them at?

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