Topic: 4 cable carb tips

[Don R]

 The 4 cable carbs on the nugget have a lot of free play in the throttle tube, it's really annoying. I'm wondering if I have a two-cable throttle tube would cause that? I've adjusted the top of the cable as much as possible but can't get the slack out. I'll check the inside of the slides, I've seen the connectors bent. You'd think I'd be an expert having 3 sets of them. But no.
 I recently bought a morgan carbtune and am preparing to do my K0 bikes with it, if I was sure I did it correctly, I could make a photo essay. Any tips from the guys with 4 cable experience?

[Scootch]

I have a Morgan. I like it. Make sure you don't have vacuum leak at the carb ports. Those threaded holes can be stripped. Set the cable free play at the top of the carbs to book. I think it's like 1 mm or so. Get the slides adjusted such that they open and close together and all hit the idle screws simultaneously. Set the mixture screws to 1 turn out from bottom out.

[HondaMan]

Don: by chance, is it a Motion-Pro cable? I had one from them like that, the throttle cable was too long by about 3mm. It felt like 1/4 turn before the engine speed would change! IIRC, I made several tiny "washers" by using a 3/32" drill (it might have been a 1/16" drill - to fit over the cable diameter) into 1/32" thick brass sheet, then hole-punched out those holes to maker a 'washer' of them, and then cut halfway a slot into the hole of each one with scissors. This made a stack of tiny washers that could be slipped over the end of the throttle cable inside the splitter box (that one unscrewed so it could come apart, wasn't crimped nor sealed). It took up almost 3mm of length that way and it felt much better. The washer OD fit up inside the plastic coupler inside the body of the splitter.

Much longer ago: I laid a strip of solder into the groove in the twistgrip, which effectively used up a little bit of the cable length for the larger OD of the groove there. It didn't work out as well as the washer thing did many years later, but I didn't have the tools to make the washers back then, either.

[Don R]

 No idea about the cable, it might be an original. The bike has 25,000 miles and was in pretty good condition except for the poo brown paint. I do have a spare cable, I might try swapping the top section.

 Thanks Scootch, that's what I needed to hear. I'll get the book out too.

[BenelliSEI]

Don…… I had the same issue when I built my first K0. My problem turned out to be the new cable itself (no idea where it came from, probably EBay). At rest, the 4 lengths of inner cable that stuck out at the carb end were just too long. I had an NOS Honda cable, subbed it in, problem gone.
 
I did take the centre barrel apart and build in a “fudge spacer” of some kind, but then the issue was at the opposite end of the operation. Full throttle at the tube only opened the carbs about 85% of the way. So THEN, I threw out the spacer, and drilled a second hole in the throttle tube (and cut out a bit more wire slot) so the single cable was pulling more at rest. MIRACULOUSLY it all worked (and still is to this day). Kept the Honda part for the Sandcast.

Does any of this make any sense??

[BenelliSEI]

I have a Morgan. I like it. Make sure you don't have vacuum leak at the carb ports. Those threaded holes can be stripped. Set the cable free play at the top of the carbs to book. I think it's like 1 mm or so. Get the slides adjusted such that they open and close together and all hit the idle screws simultaneously. Set the mixture screws to 1 turn out from bottom out.

Before all this, it’s important to set the idle manual screws all the same and on the marks (very faint lines on the carb body and knurled idle screws line up like the fuzzy picture in the shop manual). Setting the 1 mm gap is step two. Make sure you look down the carb throats and the slides are all even heights. If one or two carbs are a full turn high or low, you will loose your mind later in the operation.

Every time I do this, it becomes apparent why Honda changed the design very quickly. BUT, getting it all right can be very satisfying too!

[Don R]

 On my blue green bike I dotted the tops of the screws with yellow paint after bench sync'ing them. I'll have to look for the lines.

[BenelliSEI]

On my blue green bike I dotted the tops of the screws with yellow paint after bench sync'ing them. I'll have to look for the lines.

Good idea. I’ll do that next time. Those marks are impossible to see……

[BenelliSEI]

So once the bike is running, here’s what I do.
1. Hook up my old Motion Pro Unit. Make sure all four cables are well down inside the top furls and slack. Fire the bike up and using the manometer, set the idle and carb sync where I want. Using ONLY the 4 x knurled knobs. After this might be a good time for the yellow paint?
2. Using the throttle tube, bring the idle up to 12-1300 rpm (throttle grip not installed yet). I use a small, needle nose vise grip to hold the throttle at this rpm. At low revs, but up off idle, sync the carbs using only the top furls on each carb.

So actually, unlike the later bikes, it’s two different jobs. Last point; I was always a bit frustrated about how easily these carbs seemed to change their setting (as I was watching my gauges!), until I started using the top sealing gasket.

[Don R]

 One of my bikes has teflon tape mostly holding the vacuum plug in, I think one side or the other was thread challenged.

[jakec]

I bought a NOS motion pro cable (packaging was indeed old). The case around the 4into1 cable is black on the motion pro whereas the genuine honda was bare metal. My motion pro cable was on the short side and adding the rubber gaskets at the top of the carbs made it even tighter. I have all 4 carb adjustments bottomed out as well as the two adjustments at the top by the throttle. I barely had enough thread on the curved metal piece to attach the nut. and I barely have any play. But it's working.

[Don R]

 I've been learning the K0 tuning drill today but am not getting much vacuum and occasionally when I do the 2-3 pipes go cold so obviously that's not going to work.
 But I did find the T on the knob shaft and made a white mark above them in case I get lost.

[BenelliSEI]

I've been learning the K0 tuning drill today but am not getting much vacuum and occasionally when I do the 2-3 pipes go cold so obviously that's not going to work.
 But I did find the T on the knob shaft and made a white mark above them in case I get lost.
[/quote

Don… too little vacuum usually means those cylinders are open too much. Try closing them down a turn on the “wheel”. This assumes the cables aren’t holding them open.

[Don R]

 Getting the slides to repeat is an issue, I'm considering swapping to another 4-1 cable I have, my outboard cables are mashed down a bit. The big cam may have a little to do with vacuum too, it's a Kenny Harmon/F cam.

[Don R]

 I did my best, it runs worse. I need to re-check the advancer, it seems to be stuck.

[BenelliSEI]

Leave it for a few days and start again……

[Don R]

 I also removed the K&N air filter, it doesn't fit the early airbox and left me with a cracked painted K0 air box.  I fiberglassed the bottom and put a DSS stock filter in it. I'll put the K&N in the K2 I've been working on it seems to fit better there.