Author Topic: Idle speed went ballistic (Read 3942 times)

70CB750 · « **on:** January 31, 2012, 04:35:20 PM »

This morning we had 34F or so, she started nicely, rode to work 10 miles or so. During lunch break took her and Ruger GP to the range, she was flawless.

On the way home, at a stop sign she decided to idle at 2500 instead the typical 1000.
Got home, dinner, checked for cable problems and such (she is 4-1) but all slides were in the right position and snapped back in place fast and nice.

This time she started to idle at 1000 but in 20 seconds or so went to 2500. Took her for a spin, she runs well, just the idle.

Next steps - yank the carbs and clean? Maybe pull slides first to see what I can see? I am not sure at this point but it must be some fuel air mix delivery problem.

Opinions?

tlbranth · « **Reply #1 on:** January 31, 2012, 04:50:34 PM »

well I suppose it could be a stuck float or some such, but I'm betting on a cable problem. Although the gradual speedup doesn't fit. Did you move the handlebars or something like that?

TwoTired · « **Reply #2 on:** January 31, 2012, 04:54:06 PM »

What's the fuel level in the gas tank?
Are you using the reserve setting? Does it change the idle speed?

70CB750 · « **Reply #3 on:** January 31, 2012, 04:55:21 PM »

There is one more thing. She was hard to start - I am running warmer plugs now (7) and it was 70 in Virginia. I dont think it has anything to do with it, just thinking aloud:)

70CB750 · « **Reply #4 on:** January 31, 2012, 04:57:03 PM »

The tank was full this morning, less than 30 miles ago and I had it On, not Reserve.

BobbyR · « **Reply #5 on:** January 31, 2012, 04:57:44 PM »

One thing that happens is that people adjust the idle speed screw before the bike is really warmed up. I was chasing the same type of problem. Run the bike on the highway get her nice a warmed up, set the idle than and see if it stays put. Even now if I do a nice highway run the idle speed tends to rise a bit. They like to be run fairly hard.

TwoTired · « **Reply #6 on:** January 31, 2012, 05:08:56 PM »

How much free play is in your twist grip? How old are the cables?

brooze72 · « **Reply #7 on:** January 31, 2012, 05:17:30 PM »

Subscribed. I experience this too, occasionally, & am wondering WTF. Usually happens when fully warmed, carb rail seems fully returned. Done some reading & maybe a sync is needed? (it was just eyeballed) Full disclosure, I am not using the push cable.

TwoTired · « **Reply #8 on:** January 31, 2012, 05:31:52 PM »

Carbs out of sync can cause idle to race when warm. Especially, if the stock air filter is eliminated and the stock exhaust back pressure is reduced.

Spanner 1 · « **Reply #9 on:** January 31, 2012, 06:07:20 PM »

+1 on the carb sync. and no play in the push cable too.... if the slides are out of balance, one cyl. will 'dominate' and cause increased idle and 'racing'. Taking-out any push cable slack will stop or reduce that occuring IMO

brooze72 · « **Reply #10 on:** January 31, 2012, 06:24:49 PM »

Thanks TwoTired & Spanner1. I'm running stock air filter but I think 4 into 1 aftermarket (repaired) muffler isn't supplying a lot of back pressure. Good points guys, I will address these issuse in the spring.

70CB750 · « **Reply #11 on:** February 01, 2012, 02:55:08 AM »

There is about 1/4" play in the grip an the cable is fairly new - aftermarket replacement of 4-1, no loose wires on it or kinks by the handle.

I went ahead yesterday and checked the synch and it is back to that weird vacuum where #4 registers almost nothing on the gauge no matter what. You have to understand it is a K0, the synchronization is done (after setting cable play in the carb lid) using the throttle stop screws.

Tonight I will go over the cable with the tank out of the way and check slides and carb boots and such.

The warmer plugs have nothing to do with it, right?

Thanks for the help, gentlemen.

the technological J · « **Reply #12 on:** February 01, 2012, 08:23:24 AM »

has an airleak been ruled out? that mixed with outta synch carbs.... maybe order new o ring for infront of the intake spigots

70CB750 · « **Reply #13 on:** February 01, 2012, 08:38:17 AM »

Gotta say I didnt know there are o rings in front of intake spigots. Never had them out.

Duke McDukiedook · « **Reply #14 on:** February 01, 2012, 09:29:46 AM »

Whevever there are big temperature changes I have to usually adjust my idle speed, when it got warm here I noticed my idle was a little low but I know it will be cold again soon so I didn't mess with it. I'll have to fiddle with it when it gets warmer in the spring.

754 · « **Reply #15 on:** February 01, 2012, 09:34:57 AM »

NO orings to change in there..

Check your advance, make sure it moves FREELY.......if that does not work look for an intake leak..

Duke McDukiedook · « **Reply #16 on:** February 01, 2012, 10:05:34 AM »

Yeah, no orings in intake spigot, look for an intake leak, crusty manifold rubbers.

70CB750 · « **Reply #17 on:** February 01, 2012, 10:34:59 AM »

Quote from: 754 on February 01, 2012, 09:34:57 AM

NO orings to change in there..

Check your advance, make sure it moves FREELY.......if that does not work look for an intake leak..

Would not advance stuck higher cause pinging? Using car experience here.

754 · « **Reply #18 on:** February 01, 2012, 10:48:32 AM »

Just chedck it, wont hurt..

70CB750 · « **Reply #19 on:** February 01, 2012, 10:58:33 AM »

I will. Just thinking about it at work.

the technological J · « **Reply #20 on:** February 01, 2012, 12:09:05 PM »

ooops is there o rings on the 550? i swear i replaced some

70CB750 · « **Reply #21 on:** February 01, 2012, 05:17:05 PM »

Well I checked what I could - slides, needles, advance on Pamco - run quick synchro and took her for a spin.

Rode for 15 minutes on the reckless driving level - 20 above speed limit in VA:) - and stopped and sure enough, she idled high again. Dropped the idle speed down by ear right there and from that point she behaved like a good girl.

I am inclined to believe it was the weather change that threw her off like that.

BobbyR · « **Reply #22 on:** February 01, 2012, 06:21:54 PM »

As I said they normalize when hot. I suspect now it will idle about where you like when she is at operating temp. These are pretty cold blooded.

70CB750 · « **Reply #23 on:** February 01, 2012, 07:31:31 PM »

Yes, Bobby, I think your first reply was spot on.

lucky · « **Reply #24 on:** February 01, 2012, 08:51:53 PM »

Quote from: Brooze72 on January 31, 2012, 05:17:30 PM

Subscribed. I experience this too, occasionally, & am wondering WTF. Usually happens when fully warmed, carb rail seems fully returned. Done some reading & maybe a sync is needed? (it was just eyeballed) Full disclosure, I am not using the push cable.

you need to add another return spring if you are only using the pull cable.
Ask me how I know.
Also check and make sure your carb intake boots are still in position.

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Author Topic: Idle speed went ballistic (Read 3942 times)