Gsx1100 Won't idle lower than 1500rpm

[gorbys]

Assuming my tacho is correct , My gsx1100 engine won't idle below 1500rpm. If I try to set it lower it'll just run for a few seconds before it leans out and die. (observed with a wideband o2 sensor) 

There's no issues with the idle as long as I set it a bit higher, will happily idle at around 1500 all day long. But not at 1000-1100 as I would like it to be. 

Engine is a stock 82 gsx1100 with a hindle exhaust, K&N airfilters and dynojet stage 3 kit. I have gone up one size on the pilot jets but I'm still at 3.5 almost 4 turns out on the pilot jet screws so I have ordered the two next sizes up and I'm waiting for those. 

Any input on what to try or should I not bother anymore with it? 

Carbs are clean, synced, and no air leaks that I can find. 

[gorbys]

Here's a video of it idling after warmed up

https://youtube.com/shorts/w5wMf7T1AMA?feature=share

[Blower1]

Float height set correctly?

[gorbys]

15 minutes ago, Blower1 said:

Float height set correctly?

It's set to the factory spec 

[Gixer1460]

Usual cause is an intake air leak - the larger / richer idle jets would support this theory

[Jonny]

I would guess this is a mixture issue. You may actually be too rich on the screws, which cause the engine to behave like it's on choke and rev high. So when you back the the idle screw out more it kills the engine. I'd stick the bigger pilots in, and go back to 2 / 2.5 turns screws next and see what that it does .

[johnr]

but also check that the auto advance/retard isnt sticking.

[coombehouse]

According to your gauge, it appears to be slightly lean. Mine seems to idle best at 13-13.2 afr though I do ignore it & just tune for fastest, smoothest idle, but these seem to be the numbers it likes.

Have you tried spraying wd40 or similar around the intake boots to see if it affects the idle. This will indicate an air leak

[Gixer1460]

31 minutes ago, coombehouse said:

According to your gauge, it appears to be slightly lean. Mine seems to idle best at 13-13.2 afr though I do ignore it & just tune for fastest, smoothest idle, but these seem to be the numbers it likes.

Have you tried spraying wd40 or similar around the intake boots to see if it affects the idle. This will indicate an air leak

To be honest I never looked at vid till this comment and that set up isn't really the best for accurate measurement as A) its too far from the exhaust ports and B) mounting the sensor like that always a large amount of 'uncontaminated fresh air' into the pipe and around the sensor. This is why they are usually buried after the manifold or collectors, high up in the system. A Lambda of 0.90 - 0.91 isn't too bad and translates to between 13.23 - 13.38 but if its being skewed by fresh air it could be somewhat richer! The above point is always an issue with turbo's that use dump pipes and not a full system!

[gorbys]

Video was just to show it idling stable and not chasing around. I didn't have any other video than this. 

The pipe extends pretty far into the exhaust system so there shouldn't be a whole lot of fresh air contaminating the results, perhaps when idling but with more exhaust flow it shouldn't be a huge issue. It's a setup many use on the dyno. So long as your aware of the pros and cons of it...

I think what's important is that the gauge shows me approximately what's going on as I run through the rev range instead of me trying to guess how this engine "should" behave when I've never even ridden a proper running gsx1100...

Anyways I digress, this was supposed to be about the idle 

I have indeed sprayed around with brake cleaner to try and locate air leaks but have come up empty. Last season I did have issues with that which was down to using the wrong hose clamps, that's sorted now. 

Ignition was something I looked into but it's hard to set the idle when the manual calls for the idle to be lower than 1500rpm. I know the advance mechanism works as I see the timing marks moving with revs. Can I hold the revs at +2300 and set timing based on the full advance marks? 

Sidenote: I never got the ignition system for this engine either, so it's running the 8 valve ignition albeit with a Dyna pickup instead of the points. Don't know if this impacts anything.