Topic: replacement fuel feed lines that connect carbs to each other (k8) carb

[mustangcar]

i am referring to the small lines that connect the four carbs to each other on a 77-78 750k carb,about 1 -1/2 inch  long each,are replacements hard to find? I am in the process of tearing down the carbs,shimmed the needles with #4 brass washer,i spinned the washers abit on a grinder to make the  round diameter smaller for a better fit,,,well back to the lines what alternative hard rubber lines are out there?,maybe from a lawnmower store? or the honda stealership?

[tinyrobot]

I believe I was able to get these from service honda.  Although they come in one piece and you cut to length.  Let get back to you on this.

[mustangcar]

thanks Tinyrobot,when i opened them up ,each one had two brass fittings inside i guess so they won't kink/bend,, lines are most likely are metric sized

[tinyrobot]

there are two lines that connect the carbs together in black rubber.  Which ones are you describing? #8s or the #16-18 set

[mustangcar]

there are two lines that connect the carbs together in black rubber.  Which ones are you describing? #8s or the #16-18 set

,, looks like #8,they are the accelerator diaphram pump feed lines,,,just came back from  the Honda dealer,they are discontinued

[tinyrobot]

Yup, I thought as much.  I had to ebay a set of ok condition carbs to get those.  I had 2 cracked lines on mine.  Search around I got my carbs for $15 or something.

[mustangcar]

thanks for the ideas,forgot to mention the parts guy at honda gave me a piece of FREE,(yeah free thats wierd) 1/8 inner diameter green colored see through fuel line,said it was for a scooter,,fits nice and snug ,i inserted the brass tube inserts in each hose,, FYI there is two brass tube inserts about 3/8 inch long in each stock black hose,,the stock hoses looked a bit dry rotted thats why i am replacing them,,i tried painting the hoses silver with rim paint and the paint covered them well,having  see through hoses is also neat I just didn't like the green color,the whole carbs are getiing painted with "Duplicolor brand" silver metalic rim paint,this paint covers well with a nice metalic flake in it

[SteveD CB500F]

Post some pictures of the completed carbs.

Anyone else painted theirs?

[KB02]

Okay, couple of things. In the diagram, I think it's 16-18 that you are asking about. The #8's are the upper vent tubes.

I'm glad this post came up. I just finished the rebuild of my K8 carbs and had no idea those little brass inserts were even in there. My tubes were old a cracked as well and so I replaced them with some clear tubing. After reading this post I went back to the trash at my work bench (which doesn't get thrown out often) and dug one of those tubes out to look at it a bit closer. This is the big one of the three (#18) and it has two little brass tubes. I took a picture:


What is the purpose of these little tubes? Should I put them into the new rubber? Do I need them?

[eurban]

Assuming that those brass tubes were not how the rubber tubing was attached (you obviously were able to attach your new tubing to the carb bodies right?) then they could either be some sort of restrictor or something to keep the tubing from colapsing.  These lines are the supplies for the accelerator pump nozzles.  The pump is on the #2 float bowl assembly and pushes the fuel from there to the other 3 carbs.  Perhaps it is somehow beneficial to the fuel squirting process to restrict the connecting hose ID?  Or perhaps there was a tendency for the fuel line to colapse due to the heat of the engine and maybe even a bit of a vacuum effect once the pump has done its squirting?  Don't know for sure but you can see how well your new tubing is working by observing the pump nozzles (fuel on, air filter off, these are the brass nozzles located next to the choke plates on the bottom of the carb bore) and wacking open the throttle quickly.  Fuel should squirt down the carbs throat.  However, you still might not be able to tell whether those brass pieces would have made a difference in function, particularly if it is an anti colapse device and requires a hot and perhaps somewhat aged fuel line before its services are  required.  Hope this helps.

[KB02]

I just check measurements:
Two brass inserts per tube.
Center tube inserts measure 12mm each.
Outer two tube inserts  measure 9.5mm each.

Yes, the tube attach to the carbs via nipples on the carbs. I would assume that you have it right about them being either anti collapse or restriction devises of some kind.

[mustangcar]

i guess you really don't need those little inserts but for some extra safety so they won't kink with the heat and pop off I say put them in the replacement line,don't really think its a restriction thing,just support,,,,those accelerator super small squirt spray nozzles are enough restriction,,,was thinking of oversizing the squirters with a micro drill bit