CB360 Hanging Throttle and other issues.

I've started a new project, and unfortunately need to sell my CB360 to fund it. More details about the other project at:

http://www.dotheton.com/forum/index.php?topic=64772.0

I've been fiddling with the 360 for awhile, and in my frustration, listed it for sale without getting it running 100%. Turns out the majority of interested buyers are even more mechanically inept than myself and don't want to touch something unless it's running flawlessly. I can either slash the price and try to get it out the door, or try to get it running well enough and make some more money.

Here she is:



So, the issues I have are as follows.

- Throttle hangs when I blip it, check out this video (I know the cables aren't routed through the guide properly, it's since been fixed):

https://www.youtube.com/watch?v=ULhTOhXTyKs

This issue started happening when I put lower bars on the bike, but I also adjusted the float height to 21mm before putting the bike back together (I thought this might help with the running rich, I noticed the inside of my carb boots and air filter boots were wet with gas). Could it be an issue with the mechanical advancer?

- It's running rich, plugs are dark and sooty but not wet. It'll start on choke, and after running for a bit it dies if I apply any choke. The exhaust is your basic aftermarket emgo unit, jets are stock, and it has new stock airfilters.

- I went to sync the carbs, but couldn't adjust anything because the sync screw is backed so far out that the motion pro tool can't even crack the lock nut open. Looks like I'll be taking apart the carbs again this weekend. The sync didn't seem terribly off according to my vacuum gauge, but this needs to be addressed.

- Seems like it occasionally misses on the left cylinder (weak spark?). I haven't replaced the battery, but after a charge on my battery tender it reads right around 13.2 V or so.

This weekend is dedicated to getting this thing running right. Any help you guys can provide is greatly appreciated. I sometimes feel like I'm going in circles.

Thanks!

Looking at your video, twisting the throttle forward brings the rpms back down. If that's the case, it's in your throttle housing or cable routing.
If the throttle snaps back like it should and you still get the hanging idle, I would look into a vacuum leak.

Tried re-routing the cables again, still having the same issue. With the bike not running I can definitely hear and feel it snap closed, but when the bike is running I have to keep twisting the throttle forward after I rev it to bring the RPMs back down. I ordered new throttle cables to eliminate that as a variable (I've cleaned them and relubed them already). I'm hoping that fixes it.

I also recharged the battery and the bike ran much better. I think my battery is a bit weak and also needs replaced. After charging overnight and letting the battery settle, the voltage read 12.9. I already installed a new regulator and rectifier, so I'm hoping it's just the battery being weak, and not my stator.

Loosen the throttle cable tensioners found at the handlebar throttle side. they are the nuts that attach the plastic cable cover to the bent metal tubes routing them into the throttle housing on the handle bars. One jam nut / long nut at plastic cable. If you got to twist the throttle back to return they are probably too tight.

Lube the cables.

alzcbz +1 may be a vacuum leak at carbs or A/F needles improperly adjusted. If they are adjusted too lean it can cause it to hang some.

trek97 said:

Loosen the throttle cable tensioners found at the handlebar throttle side. they are the nuts that attach the plastic cable cover to the bent metal tubes routing them into the throttle housing on the handle bars. One jam nut / long nut at plastic cable. If you got to twist the throttle back to return they are probably too tight.

Lube the cables.

alzcbz +1 may be a vacuum leak at carbs or A/F needles improperly adjusted. If they are adjusted too lean it can cause it to hang some.

Click to expand...

I've played with the adjustment some and it seemed to make the issue worse. Right where the plastic cable housing meets the metal tubing is completely mangled on my throttle cable, I'm thinking that's where it might be snagging.

yep PO probably had it all F-ed up and overtightened it.

Just do your best to loosen it. its got pretty long threads on there. I can see it in the vid. but not well enough. Does it have any threads showing at all? If not Its probably way too tight.

hold on a sec...its possible im thinking about this thing backwards. been a long time since I messed w mine. hold on and let me screw w mine a minute.

Yep I was backwards sorry dude. If you see no threads thats as loose as it will go. The more threads you see the tighter. If you see no threads and its still too tight you need to move to the other end (carb end) there is some adjustment there also.

Swapped the cables today. The issue is still there. It feels a bit snappier returning to idle, but there were a couple of times where I would rev it to around 4 or 5K and it would just hang there until I brought the idle back down with the idle adjustment screw. Any ideas what's going on here?

What's next, a carb sync or checking the mechanical advance? Maybe those springs are shot?

Thanks guys.

Both jobs can be equally a mild pain in the butt. Im assuming you dont have carb gauges, to check them easily? Still, I would sync them first.

did you lube the new cables? they are dry off the shelf.

trek97 said:

Both jobs can be equally a mild pain in the butt. Im assuming you dont have carb gauges, to check them easily? Still, I would sync them first.

did you lube the new cables? they are dry off the shelf.

Click to expand...

I used some silicone lube when I installed them. The throttle feels pretty damn smooth, I and rolling the throttle forward no longer affects the idle like it did with the old cables. I have a vacuum gauge and a gang valve to check the sync. I don't have a dampener so the needle jumps like crazy, but I pinched the tubing a bit with a small c clamp and the readings look pretty close. The exhaust pressure feels similar as well (to my uninformed feel). One thing that's kind of weird is when I went to go adjust the sync screw, it was backed out really far. So far that I couldn't use the motion pro tool, the socket portion wasn't deep enough. I figured I couldn't do anything about this until I take off the carbs.

Considering swapping out the whole damn points system with a pamco unit while I'm at it.

JPanichella said:

Considering swapping out the whole damn points system with a pamco unit while I'm at it.

Click to expand...

If you still intend to sell this bike. I wouldnt invest that kind of cake, just to loose it.

Pull the carbs off and check sync w a couple needles or wires the same diameter. open the tops and ensure the slide vents are towards the filter side. lube the linkage. make sure butterflies are centered and not hanging up or dragging on the walls. causing them to hang open.

It sure sounds like its getting air from somewhere. Are the insulators and gaskets good and tight on the head? dont overtighten them. they can warp and loose their seal on the head. I used a little hondabond between the insulator and gasket to seal mine.

checking all that shouldnt take more than an hour or so. Then you can check out, clean up and lube the advancer. That shouldnt take much time at all. If you got a strobe.

trek97 said:

If you still intend to sell this bike. I wouldnt invest that kind of cake, just to loose it.

Pull the carbs off and check sync w a couple needles or wires the same diameter. open the tops and ensure the slide vents are towards the filter side. lube the linkage. make sure butterflies are centered and not hanging up or dragging on the walls. causing them to hang open.

It sure sounds like its getting air from somewhere. Are the insulators and gaskets good and tight on the head? dont overtighten them. they can warp and loose their seal on the head. I used a little hondabond between the insulator and gasket to seal mine.

checking all that shouldnt take more than an hour or so. Then you can check out, clean up and lube the advancer. That shouldnt take much time at all. If you got a strobe.

Click to expand...

Yeah, the pamco comment was out of sheer frustration.

I know for a fact the slide vents are facing the right way, I checked that last time I had the carbs off. I'll take a really close look at the butterflies and see what's going on with that sync screw. Does anybody have a good reference image so I know my carb linkage is set up properly?

If I were getting air in somewhere, wouldn't it be running lean? The plugs are pretty sooty. I'll check and make sure everything is leak free.

I'll borrow a friend's stroke and reset the timing. Hopefully I'm getting close. Thanks for your help, man. I'm glad I helped you get over the 3000 post mark.

maybe, less than ideal. i might be pulling my carbs this weekend. I cant get a good pic til then. but i can get one if i do.

JPanichella said:

If I were getting air in somewhere, wouldn't it be running lean? The plugs are pretty sooty. I'll check and make sure everything is leak free.

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Yes, while vacuum draw is high enough to suck in air through the leaking point. It will be a little leaner. Thats why it can cause the rpms to hang. Without, the extra air, it will return to idle pretty quickly.

see whats happening? the addition of the extra air through a small leak can act similar to holding the butterflies open w the throttle.

Thats why a good sync is important, if one butterfly is open more than the other. Its trying to run one piston faster/slower than the other.

Also, go through A/F mix needle tune in procedure. She may be too rich at idle. causing extra sooty plugs.

Well now that we've talked about how carbs and cause hanging high idles how about the stock timing system? Timing set tooo advanced or or a hanging sticking advance unit can cause hanging Idles. Will also cause rough starting, poor running until you hit above 3200-4000 rpm and if it is way advanced at idle it can cause an incomplete burn of the fuel in the engine because of the late spark which can soot up plugs. Plugs being sooty can be just from you running it too long at an idle with the choke on or can mean you have more issues than just carbs. Air filters can get clogged or be to restrictive. If you have low compression and leaky oil rings the soot can be burnt oil.

And finally if you havn't at least bench synced the carbs then you will end up with a bike that won't idle or will hang idle for a while and then slowly creep back down and possibly die. Dynamic sync on a 360 is bar none the most important adjustment to get right and its probably the hardest adjustment to do. Probably why most people just say the hell with it and why most 360s got parked in the first place.

How much were you asking for the bike as it sits now?

frogman said:

Well now that we've talked about how carbs and cause hanging high idles how about the stock timing system? Timing set tooo advanced or or a hanging sticking advance unit can cause hanging Idles. Will also cause rough starting, poor running until you hit above 3200-4000 rpm and if it is way advanced at idle it can cause an incomplete burn of the fuel in the engine because of the late spark which can soot up plugs. Plugs being sooty can be just from you running it too long at an idle with the choke on or can mean you have more issues than just carbs. Air filters can get clogged or be to restrictive. If you have low compression and leaky oil rings the soot can be burnt oil.

And finally if you havn't at least bench synced the carbs then you will end up with a bike that won't idle or will hang idle for a while and then slowly creep back down and possibly die. Dynamic sync on a 360 is bar none the most important adjustment to get right and its probably the hardest adjustment to do. Probably why most people just say the hell with it and why most 360s got parked in the first place.

How much were you asking for the bike as it sits now?

Click to expand...

Air filters are new and very clean. The compression is 160 cold in both cylinders. I did bench sync the carbs last time I had them off, but will take another look and do a dynamic sync as well. I have a feeling I'm having an issue with the throttle plates binding, perhaps they aren't properly centered.

Sticky throttle can be fixed by getting nice new cables. If that doesn't solve it take the throttle tube off and use some 80 grit Sand paper and hone out the inside making it bigger. Finish with some 400 grit. Then use some wd40 and put the tube back oN. You should have less friction and smother action now.

JPanichella said:

....I have a feeling I'm having an issue with the throttle plates binding, perhaps they aren't properly centered.

Click to expand...

If it does idle back down when you twist the throttle closed that is a very big possibility, I had that issue with mine when i first got it running.

To eliminate the throttle cables being the issue (or more aptly, to NAME them as the issue) Why don't you disconnect them or pull the carbs out and open the throttle/butterflies on the carb with your finger. Does it have a decent resistance when opening and when you let it go, does it snap shut so both butterflies are closed properly. Yes? Well then we know it's not the carburetor, it's the cables. If not, then you know it's carburetor related. Crack the 8mm synchronizing lock nut while the carbs are off, otherwise it's a pain to do on the bike (as it will also be a pain to tighten when you DO sync them properly with gauges.)

As pointed out before, TONS of things can cause sooty plugs. Buy 2 new plugs, install. You can run the bike for 10 minutes or 20 minutes and they'll start turning black if you've got things horribly wrong in the float height, or mixture screws depending upon if you were just letting it sit and idle, or were riding it around. Mixture screws should be around 1.5 to 2 turns out. From what I read, you have stock air filters (new) and stock headers with emgo mufflers which should run almost similar to stock. MAX I would think 2.5 turns out for the AF mixture screws.

Lastly, take pictures to show what you have done, and what you are doing. This helps if we see something that is out of place more easily. Some may notice you routed your cable like "this" and it should be like "that" or similar things. From the video looks like the cables are hanging it up to me. But it should have been sorted quickly by routing them another way so.... :-X