Topic: Question re: stuck throttle from new(ish) bike owner...

[deKA]

Hi:

I've owned my first motorcycle, a '74 CB550K, for almost two years. For various reasons, the bike has not been ridden for about four months. When I went out to try starting it for the first time the other day, I discovered that the throttle was completely stuck.

Now, for all this time, I've been taking the bike to a shop for maintenance, because living in San Francisco on a steep hill with no garage, there really was no place for me to even attempt working on it. But I just moved, and I now have a garage, so I'm determined to start learning how to do my own repairs. I even have visions of doing a restoration. Fixing the throttle seemed like a fine place to start. Except...I'm already stumped before picking up my first wrench.

It seems that I only have one throttle cable! Specifically, there doesn't seem to be a push cable, only a pull cable. Is this possible? My first thought was that someone stole it, and that's why the throttle was jammed. (Hey, people here steal your sparks plugs because the ceramic insulator apparently makes a good improvised crack pipe, so it didn't seem completely preposterous.) But when I look at an earlier photo of my bike, I can see that it *always* only had one throttle cable.

So my question is -- could there be a valid reason that I only have a pull cable? Should I just try unsticking or replacing it? Or should I go ahead and replace the missing push cable? I've gone out and bought both a Clymer and Haynes manual, plus downloaded the service and parts manuals from honda4fun.com. There's no mention of anything like this.

I remember that after the engine used to get good and hot, there would always be a pronounced delay between closing the throttle and the engine revving down. I imagine this might be the reason. And I just thought that's the way these old bikes ran.

Thanks for any advice,
David

[kghost]

You don't "really" need two cables. Normally a spring closes the carbs back up.

But, they were there for a reason (smoother operation, safety, etc) and I would go back with both.

[Gordon]

Kghost is right, but installing a push cable won't solve your sticking throttle problem.  You need to find out where exactly the problem is.  Could be the throttle grip, or the pull cable, or the throttle assembly on the carbs.  Also, the delay between closing the throttle and the engine revving down is probably either a carb problem or a sticky advance mechanism. 

[MetalHead550]

Start with the simple things first man.  My 75 was in a collection for about 20 years and saw heated garage maintenace but was rarely ridden.  My throttle cables and throttle linkage were kinda sticky from disuse.  My revs would come down slow as you describe becase after cracking the throttle, the sticky cables resisted returning to closed position.  Go ahead and take the top cover off the right hand controls where your throttle cable goes and shoot some wd40 or equivalent down between the cable and its casing then work the throttle a bunch.  While youre in there check to see if there was evidence of a push cable and replace it if so.  Then hit all the moving parts of the throttle linkage between the carbs with wd40 and again work the crap out of the throttle.  Hopefully thatll take car of it!  Let us know!

[Gordon]

MetalHead550,

I was approaching the slow rev-down issue as a separate problem from the sticky throttle, since that was happening when the bike was in regular use, before the stuck throttle came into the picture.  But I definitely agree with you that the sticking throttle needs to be addressed first. 

[deKA]

Thanks for the advice. I'll work out the throttle cable issues first (sticky pull and missing push), then ride it around for awhile to see if the delayed rev down thing is still going on. If so, then I'll know where to start looking to fix that. I'll let you know how it turns out.

On a somewhat related issue -- the bike *has* been sitting for four months, with a partially filled tank and no added stabilizer. (What can I say, I'm just learning about this stuff.) Should I do anything special when I first start her up? Drain the carbs first, run some kind of carn cleaner solution though, etc.? Or is four months not long eneough to really cause any problems?

BTW, as you can see by my number of posts, I'm brand new to this board. What an amazing resource! I will do my best not to abuse it by pestering you all with too many questions! (Even though it's very tempting.)

--David

[MetalHead550]

Yes, four months is long enough to cause problems.  If you store the bike and dont start it periodically while stored, its good practice to drain your float bowls.  Gas that sits for long periods without stabilizer not only goes bad but will eventually gum your carbs up.  For bikes that ran great and then have sat for a long time and wont start with a new battery, dirty carbs are almost always the cause.  You should be ok though.   The gas is bad so drain the tank and the float bowls and put fresh gas in.  You dont want to start the bike with bad gas cuz itll just run like crap and make your spark plugs nasty.  You may want to remove the mixture screws from each carb, taking note of the number of turns out from bottom they are, and filling the float bowls with carb cleaner after you shut off the gas and empty the bowls.  Let it set overnight then drain and turn your gas back on and see how she runs.

[phylo101]

Hi!

Ok, here we go - pull the old cable. You COULD revive it - form a plasticene/playdoh/modelling clay funnell around one end and hang it up on a string overnight, with the funnel filled with WD40. Itll eventually slip all the way thru. Next morning, tweak the inner back and forth, and inspect both ends next to the nipple - are there any tight spots as it moves? If so, replace theres a faint kink somewhere inside, and itll be somewhere for dirty lube to cake up again, as well as putting unnecessary drag into the loop.

Now, does your throttle grip turn freely without the cable in the switchgear? If it doesnt or its sticky at all, remove the switchgear and clean the two semicircular troughs where the throttle tube sits. Clean the insode of the tube. Reassemble with frsh lube; WD40 is great but thin.....but you dont want anything heavier cos itll drag enuf to be noticeable.

Now, the carb end; remove the tank if you havent already, and wet the carb mechanism THOROUGHLY with easing oil of some sort or WD40 - REALLY wet it down to wash off the old dirt and crud. Lube where the long shint steel pins run thru the top of each carb. and youll se a strange mechanism hanging below where the cable fits, that seems to open at half-speed when you pull on the cable - thats the carb"ramp" and thats EXACTLY what it does - turns your jerk of the wrist into a bob-weight-controlled smooth action. Flush every bit of crap you can out of that.

Reassemble everything , go for a ride, and remember JUST how fast your throttle will open now! New brake pads might be a good idea lol lol

As for the return cable - forget it. Its only on there cos the DOT and EPA mandated it to be sure that ALL parts of the combustion chain are under positive control...which is crap. Adding the second cable back in just gives you a SECOND cable to worry about, lube regularly etc. Dont bother.

Phylo