CB1100 Idle speed instability problem

[pdedse]

[quote="pdedse_imp" pid="85292" dateline="1505138160"]
Well, I think I've done all I can without taking the bike to the dealer.

First it was high idle at 1500rpm.
1. Sea foam
2. "spirited riding" and WOT
3. Throttle reset

One or a combo of the above brought the rpm back to 1050. No issues for a few weeks. Then low idle of 600-700.

1. 300 mile ride
2. more throttle reset

Back to normal latter half of long ride.

Next time, 750 seemed to be the new minimum.

Disconnected battery, no change. Over a week, normal, low, high, normal, high; most recent, no low, only high and normal...you get the idea.

Today: unplugged EOT while bike was cold and then for 20 miles, normal. Stopped for gas, back to high idle. Unplugged EOT with warm engine, no effect. 30 miles of high idle (1250)...but, last 15 miles normal idle, perfect.

Now? I think I'm going to quit trying "fixes" and just ride the bike for a good month.

I'll draw up summaries for service manager, show him the Excel sheet. I suspect that any action likely will involve $100 for a diagnosis which may indicate IACV replacement at $1000 plus, or complete throttle assembly at $3000 plus if I remember what others have said they would have been charged, but bikes were under warranty.

I'd never pay $3000 for a throttle body replacement. But the IACV...maybe. My bike with 9500 miles has not been checked for valves. Seems everybody who has had theirs checked at 8k miles for 12k or even more has received a "valves checked within specs". I was planning to wait till 12-13k for the valves.

So, question for members before I speak with service manager. If a diagnostic showed a bad IACV, would replacing that allow them to inspect valves at the same time? Could I theoretically suggest that "while they're at it--with the IACV--do valve inspection at the same time"? and this way I get two proverbial birds with one expensive stone?

Or does the one (IACV replacement) not give access to valves?

Anyway, I'm thinking today I love riding this bike, it looks great. If I do nothing and just live with high and low idle (mine low idles at 700-750 mostly and doesn't stall), I'd probably just ride it doing minimum, necessary maintenance over time. Don't know if I'd even bother with valve check because what if the idle issues worsen to where throttle body replacement is the only solution?

I don't like having to think about it, but in the meantime I'm going to do my best to enjoy what this bike does and stop worrying about that it won't run as it should.



[quote="Dave_imp" pid="85290" dateline="1504625520"]
Hi all, it's been a while since I've posted to this thread, but here's my latest update: Right now it's a guessing game whenever I ride my bike - will it idle high (1,500 RPM), will it idle low, and possibly stall (500 - 600 RPM), or will it run perfectly? Honestly, it's been alternating between all three conditions. My low idle has been acting exactly the way others have described theirs; dropping to about 500 RPM and then slowly returning to 1,000 RPM, if it doesn't stall. For those who are experiencing the low RPM idle: When this condition occurs, can you please see if you can sense any difference in the way the engine responds when blipping the throttle lightly, from idle speed, like when you are down shifting? I sense that my bike does not respond "normally" when blipping the throttle when it goes into the low RPM mode, and If I was to guess, I would say that the mixture is too lean. Could this be an indication that the IACV is leaning the mixture out too much? I don't know, but I really think that the IACV is a big part of our problem, I am just not convinced that it is the root cause because one of the guys posted that he replaced his IACV and the problem was not cured. Also, I don't understand how unplugging my EOT gauge eliminates the high idle problem (I never unplugged the EOT sensor when I had a low RPM condition). Hopefully one of us will get to the root cause of this. I understand Honda changed the part number of the IACV. Is anyone brave enough to try the new, 2017 American part number IACV in their older model?

Doing the above worked once. Then it didn't seem to have any effect.


Thanks for "listening".
[/quote]
$1000 for IACV replacement? Holy cow. I did it myself and it probably took me 4 hours but I'm not a motorcycle mechanic and I work slowly and carefully. Is the book time really that high? The part is $100 or so.

Also, the IACV does not allow any easier access to the valves. You take the bike apart from the tail up to the throttle body to get to the IACV. The valves you take the bike apart from the top down.
[/quote]
I think it was Johnf514 who had the IACV replaced but under warranty. I asked him how much it would have been and I can't remember the exact amount, but it was $1000 something.

Good to know about the access to IACV and valves. I really had no idea but thought it was worth finding out. Thanks.

Dave, you get to that point and let me know. I'm fly down to SD from Portland. Maybe you could put me up for a couple of nights (or tent space in the back yard). Let me observe your valve inspection / IACV replacement if that's what you opt for. I'll video and take photos along the way, and we'll make a heck of a maintenance "how to" for these forums.

Hi Pdedse - that sounds interesting. I guess that this job would take me about 8 to 14 hours, depending on if the valves needed adjustment or not (including time to drive to the dealer to buy any new shims, if needed), and I would definitely not finish it in a single day. I am slow and careful, and double-check everything I do twice, and clean every area that opening up the bike allows me increased access to. To be honest, I'm not real keen on being videoed, but I will give your offer consideration and let you know. Right now I am drowning in other "chores" I am tackling, and won't be getting to my valves for a while.
[quote='Magnus' pid='182949' dateline='1505153405']
Update: About Six months ago in an attempt to remedy my constant high 1500rpm idle I replaced the EOT (Engine Operating Temperature) sensor and the IACV (Idle Air Control Valve) and did the throttle reset. It made no difference.

Hi Magnus. Can you describe how the IACV works? I'm wondering if it's possible that the valve is sticking in the throttle body. Does it work by rotating a valve that opens and closes an air passageway? My high / low RPK idle comes and goes. Yesterday I used the bike to run errands and it ran the best its ever run - including when new! The idle speed was perfect, and I swear it felt like the motor was making more power also.

Yeah, after I wrote I was thinking that valve check and IAVC access could take awhile, and yep, some down time if shims are needed...but I would be up for it. If you don't like the idea of video, we could do pictures only--easier to upload.

But maybe you don't want someone looking over your shoulder, I get that, absolutely no worries. Think it over, and if it sounds like something you'd be willing to do just let me know.