Carb synch- cables [Archive]

RickyT

09-28-2008, 12:03 PM

All the various carb synch articles say to ensure 4mm of slack in the throttle cables prior to adjusting the carbs. My right side throttle cable adjuster is screwed all the way in (max slack) but there is still no slack in the cable. I've checked both ends of the cable and can find no way to increase the slack. Anyone run into this before? How can I fix this? New cable?
Thanks for any help. 85 R80 no ST, RT, GS, S or anything else...

20774

09-28-2008, 12:35 PM

Sounds like there's something wrong with the cable. I forget the models...do you have the splitter under the tank or do the throttle cables run independently from each carb all the way to the throttle grip housing? If your cables run from the carbs to a under-tank splitter, you might have a problem there. I'm not that familiar with that setup...I have the two cables all the way to the grip.

As long as both ends are not hanging up or not fully seated into their slots, etc., then you might have the wrong cable.

RickyT

09-28-2008, 01:10 PM

Thanks Kurt. I have the model where the two cables both run to the throttle grip. I've opened that and the cam aligns with the index on the grip, both cables are seated in the connector at the end of the chain that attaches to the throttle cam. While scanning some other posts I noticed a reference to the choke cables being adjusted correctly. I'm away from the bike right now or I'd check that. Could there be a problem with a choke cable holding the throttle open on one side?

20774

09-28-2008, 02:27 PM

Could there be a problem with a choke cable holding the throttle open on one side?

Ricky -

On my /7, the choke mechanism is completely separate from the throttle. I would think the same on yours. Sounds like you've been all over every inch of the cables. Make sure the routing doesn't have any major kinks. What if you were to swap one side with the other? The distances are a little bit different because one carb is slightly ahead of the other. It might give you the adjustment you need.

RickyT

09-28-2008, 04:28 PM

AnnapolisAirhead

09-28-2008, 08:23 PM

That's a good idea. I have indeed been all over the cables and there are no kinks nor twists. I can't think of anything on the carbs that would explain it. I'll try swapping the cables and see what happens- it would explain whether it is a cable or a carb problem. Thanks Kurt.

If you have a single throttle cable going into the throttle (handle bar), there is a splitter barrel with another barrel adjuster (like on the carb ends) and both right and left carb cables should seat into the splitter barrel properly too. You probably have to remove the gas tank (two thumber screws and two fuel lines, easy) to see the splitter.

Boxerkuh

09-28-2008, 08:36 PM

I believe there is some confusion wheater it is the throttle cables or the choke cable. The throttle cables are totally independent, one cable for each carb, both feeding into the throttle hand. The choke cable is a single cable on the top and under the tank it splits off into 2 cables. Having read your post I believe the problem is at the carburator adjustment. I would totally disconnect the cable at the carb and make sure that the inside of the cable runs freely (this will also ensure that it is okay on the top). Then I would reattach it to the carb. Without a picture it is difficult to assess if indeed it is totally slack. (I am thinking that the bike was running okay before hand and you are only making adjustments and have gone totally the opposite way). There are two points of adjustment at the carburator, one with the screw itself and one with the nut. Make sure that the top is okay first. BTW, is it only one cable that is giving you fits or is it both?
My food for thought anyway...:eat :drink

AnnapolisAirhead

09-28-2008, 08:40 PM

I believe there is some confusion wheater it is the throttle cables or the choke cable. The throttle cables are totally independent, one cable for each carb, both feeding into the throttle hand.

Actually, that's only on some bikes. My throttle cables, for example have a splitter under the tank and a single feed to the actual throttle on the handlebar. The splitter is identical to the choke/enricher cable splitter (a 2-into-1 barrel with an adjustable, threaded barrel on the end furthest from the carbs). I think they may have made this change on the later airheads (post /7) and I'm not sure what bike Ricky has. I think that if he ahs a bike with the choke lever on the airbox and not the handle bar, then he probably has each carb cable feeding ito the throttle handle, otherwise, he probably has a splitter--but I could be wrong.

Hope this helps. Got a pic of your bike?

Boxerkuh

09-28-2008, 09:06 PM

Actually, that's only on some bikes. My throttle cables, for example have a splitter under the tank and a single feed to the actual throttle on the handlebar. The splitter is identical to the choke/enricher cable splitter (a 2-into-1 barrel with an adjustable, threaded barrel on the end furthest from the carbs). I think they may have made this change on the later airheads (post /7) and I'm not sure what bike Ricky has. I think that if he ahs a bike with the choke lever on the airbox and not the handle bar, then he probably has each carb cable feeding ito the throttle handle, otherwise, he probably has a splitter--but I could be wrong.

Hope this helps. Got a pic of your bike?

Yeah, I know, but this is a 85, monoshock if I understand it correctly,

sumran

09-29-2008, 07:19 AM

A couple of things that you have probably checked already:

1) Be sure the cable housing is fully seated in the cup on top of the adjustment bolt. A burr or trash in the bottom of the cup could effectively reduce your cable length.

2) Be sure the ferrule on the cable end is properly seated in the arm on the carb and that the arm is not bent.

You can get a little more adjustment room by moving the locknut on the adjusment bolt below the flange on the carburator. If you do this, you will need locktite on the nut. Otherwise it will vibrate loose.

I did this on mine and it gave me enough slack. I only needed a turn or two more adjustment. After a few thousand miles, I readjusted the carbs and there was just enough slack to move the nut back on top. Not an ideal solution, but it kept me on the road rather than waiting for a cable.

RickyT

09-29-2008, 04:37 PM

It is a monoshock. I will try the 'locknut on the bottom' approach and reinspect the cable ends to make sure they are seated all the way. I thought they were, but honestly did not think about junk in the bottom of the ferrule. The housing is a bit frayed at the end of the cable so it is just the metal inside housing that is seating in the ferrule end. Good tips all- Thanks. If that doesn't reveal anything I will let Ted Porter check it out in two weeks- I have a 'post purchase' inspection scheduled then (i.e. how much grief am I in for Ted??).

Polarbear

09-29-2008, 05:43 PM

My old Airhead knowledge and my personal bikes, show me the twin throltte cables are 70's BMW tech only and the newer mono shock bikes came with the split cable under tank thing! Did BMW switch back and forth with these through the years??? My R100/7 has the cables you descibe as stock units and mono shocks were not here 'till '81 and the new GS800, which I also had. Some confusion as to what bike you have and cables, make one think this bike has been changed somewhat. The twin throttle cables are very straightforward and properly routed, will have no issues. Something is out of whack and a quick looksee should resolve it. Best Wishes. Randy:thumb :usa

sumran

09-29-2008, 08:48 PM

Could you describe your cable end? It should have a metal cap on the end of the housing if it is an OEM cable. Your last post said the housing was frayed at the end. That might prevent it from sliding in properly. More importantly, it may mean you don't have the right cable for your bike.

AnnapolisAirhead

09-29-2008, 08:52 PM

Ricky, if at all possible, a picture would be worth a thousand words...or two.

If you can, maybe take a picture of the cable end that Randy just posted about (e.g. the frayed end, etc.) and another of the actual throttle. That might help describe the bike, cable, etc.

RickyT

10-01-2008, 11:35 AM

It very well could be a mongrel bike. It's 23 years old and who know how many owners have done what. It does have the throttle grip with both cables coming out and one each routed directly to the carbs. I manage to spend some quality eyeball time with it last night and noticed th inner cable winding thingy has more space between the wires at the nd of the short cable than it does the other. I confirmed this by switching the cables and then the other carb had no slack. Eventually I cut off the lock nut on the tight cable such that the cable adjuster could be screwed deeper into the carb boss. This gave me enough slack that I could then synchonize the carbs. Time for a new set of cables.

Whoever it was that said the best tool in the box is the eyeballs was right.

Thanks all.

sumran

10-01-2008, 01:14 PM

I cut off the lock nut on the tight cable such that the cable adjuster could be screwed deeper into the carb boss.

I hope you ordered another locknut along with your cables. That perfect sync won't last long without it. Glad you found the source of your problem.

AnnapolisAirhead

10-01-2008, 02:01 PM

...Eventually I cut off the lock nut on the tight cable such that the cable adjuster could be screwed deeper into the carb boss. This gave me enough slack that I could then synchonize the carbs. Time for a new set of cables.

I'm curious, why wouldn't you just use a wrench and loosen the lock nut? :scratch

Cutting it was surely much more difficult and you will definitely need it to keep the carbs in sync as Randy mentioned. :banghead

Or did you cut the (top of the) barrel screw that is used to adjust the cable?

RickyT

10-01-2008, 09:54 PM

The barrel was screwed in all the way and the cable was still slack. The only way to screw it in further was to remove the lock nut. Since the locknut won't slide over the lead doober at the end of the cable that goes into the lever on the carb, I had to cut it off. Yes, I'll be replacing both cables next week. Curious about that 70's reference to the single throttle cable coming out of the throtte grip though.

RickyT

10-01-2008, 09:56 PM

Oh yeah, and the fray I referred to is the metal spiral wound liner in the cable that keeps it from compressing. It wasn't so much frayed as it was stretched such that the cable housing is longer than it should be. Make sense? Sorry for the lack of pic- it's been a bear of a week and I just didn't find the time to get them uploaded.

PGlaves

10-01-2008, 10:02 PM