Yet another idle problem, look here.

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mgdavis · #1 Unread post by **mgdavis** » Mon Apr 16, 2007 10:36 am

Went for the first ride after getting my bike back from the shop. It started fine, seemed to idle correctly when cold. After riding a mile or two the bike started to idle at 3000 rpm. Choke had apparently no effect on this. I tried to rev it, but it didn't drop back past 3000. Throttle was not stuck.
Is the general consensus an air leak around the carbs? The bike has factory jets, but this is not a normal condition.
It sounds like the other possibility is that the tech set the mixture wrong at the shop.
Who says what?

revcbl · #2 Unread post by **revcbl** » Mon Apr 16, 2007 1:41 pm

Heh heh.
Sounds like we have the same problem, and almost the same bike (I'm not sure about differences between the 76 and 79).
Unfortunately, I'm not going to get to do anything to mine until at least tomorrow. When you say it's not a normal condition, have you had the bike awhile and it didn't always do this? Reason I ask is, mine always has, and I've never been quite sure. Come to think of it, my cb360 does it to, but the idle is easier to adjust-- just reach down and twist it-- and I never really thought twice about it, just figured it needed a fast idle to warm up.
Let me know what you figure out. I'll do the same.
Cheers.

mgdavis · #3 Unread post by **mgdavis** » Mon Apr 16, 2007 2:51 pm

Yeah, I saw your posting before I put mine up, decided I was special enough to have a thread of my own.
In '79 they went to a DOHC engine, yours should be SOHC. Check my blog for the details, but basically I had the bike last season and it didn't do this. It started running crappy so I took it into the shop to get the carbs balanced. First ride afterward (today), it decided to do this 3000rpm idle business. Tomorrow I'll try to get it into the shop in the morning I think.

revcbl · #4 Unread post by **revcbl** » Mon Apr 16, 2007 3:12 pm

The air leak thing is pretty easy to test (and no trip to the shop required). Just spray WD-40 around the rubber boots while it's running and see if the sound changes.
I suppose they may have forgotten or not tightened the clamps enough if they took the carbs off, but if they were balancing them, maybe the mixture screws are the more likely culprit.
If you do end up at the shop, do me a favor--take notes and let me know what they do. Maybe it'll work for me, too.

#5 Unread post by **Sev** » Mon Apr 16, 2007 3:14 pm

WD40 can cause the rubber boots to dry out and crack. Make sure you wipe any excess off right away if you attempt this method.

mgdavis · #6 Unread post by **mgdavis** » Mon Apr 16, 2007 3:52 pm

I installed fresh boots when I rebuilt the carbs so I really don't think it is that. I'm sitting at work so I can't try the WD anyways. I'm fairly sure it is the mixture screws, I think I'll be there bright and early when the shop opens and make a stink until they fix it. At least it's rideable like this, it would really suck if it wasn't.

mgdavis · #7 Unread post by **mgdavis** » Tue Apr 17, 2007 5:43 am

I got the issue taken care of this morning. The tech took my bike around back to hook it up to the shop tach, so I didn't get to see what they did. He was gone for under ten minutes, when he came back he told me they had "adjusted the idle" to 1100 rpm. I'm assuming there is a knob somewhere for this purpose, I doubt there was enough time to fiddle with every carb.
Hope that helps Revcbl.

revcbl · #8 Unread post by **revcbl** » Tue Apr 17, 2007 11:03 am

Really? If that's all they did (and assuming we have the same problem to begin with), I wonder if you'll find yourself in the same place I am-- trouble idling from a cold start. Adjusting the idle down was basically my workaround solution to the problem (and a way to avoid those embarrassingly high idles at stop lights: "No, I don't want to race. It just does that, officer").
Anyways, I hope that solves the problem for you. I might go take a look at mine.

flynrider · Tue Apr 17, 2007 11:30 am

mgdavis wrote:I got the issue taken care of this morning. The tech took my bike around back to hook it up to the shop tach, so I didn't get to see what they did. He was gone for under ten minutes, when he came back he told me they had "adjusted the idle" to 1100 rpm. I'm assuming there is a knob somewhere for this purpose, I doubt there was enough time to fiddle with every carb.
Hope that helps Revcbl.

Yes. Most bikes have a single knob that will adjust idle speed for all of the carbs together. This is different from the idle mixture screws. Generally speaking, you set and syncronize the idle mixture on the carbs first, then adjust the overall idle speed with the single knob.

mgdavis · #10 Unread post by **mgdavis** » Tue Apr 17, 2007 12:08 pm

I'm assuming that it's going to be more cold-blooded tonight then it was this morning. It was horrible before, so it can't be worse. It's something I'm willing to live with. In the morning I'll let you know if it's giving me trouble.