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Hard starting, low/high idle, and preparing for cold weather riding 29 Aug 2021 10:18 #854515

  • Stereordinary
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Having an issue with my bike, and hoping to get some help.

When I’m starting it, I will typically use the choke (or fuel-enrichment circuit as it were). It will quickly start, and jump up to ~4000rpm, but even if I physically hold the choke lever full open, it still drops rpms. So much so that it will dip below 1000, and theoretically die, but I don’t let that happen. I will grab the throttle and slowly raise it while lowering the choke, until it gets back up to about 3000rpm. I’ll hold it there for a minute, and then let off to see where it idles, which has been around 1150 or so. All of this only takes a few minutes, and I can take off, and usually by the time I’m half a mile in, the idle is up to at least the owner’s manual recommended 1250rpm. 

Now lately this process is taking longer, or like today, other things are happening. By that I mean mostly sounds. I’m always listening for sounds consistent and new, and it seems like lately there’s just new sounds every day. Once she gets going it’s like all of a sudden everything just works. I understand this has a lot to do with warm up time, but that leads into the next thing. 

Once I’m on the road and the engine is purring along, things are warmed up, and the bike is behaving exactly like I expect it to, I’ve noticed that my idle sits at about 1500rpm. A few weeks ago I tried lowering it via the idle mix knob, and the bike stalled like crazy. I had numerous embarrassing moments out on the road. It seems like that’s just where it’s happy, and I imagine that has something to do with the air filter. I had swapped the old what looked like a 31-year-old original air filter for a K&N, and that seems to have been a mistake. For one thing the oil leaked all over the damn place. I blew most of it out, so essentially I’m running a K&N with no oil. Maybe that’s my problem right there?

Now I’m sure there are other things that need maintenance. Carb clean, carb balance, and valve adjustment. It’s lat August and I’m in Washington state, so cooler weather is coming soon. I plan to ride year-round, so I don’t want to have cold starting and engine warm up time drag me down. To some degree I feel like I know the answers here, but I need to hear it from somewhere else to get off my butt and take care of it. Any tips/tricks or general advice y’all might have would be greatly appreciated. 
A breeze from the west.
‘90 ZR550 Zephyr aka Zephanie

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Hard starting, low/high idle, and preparing for cold weather riding 29 Aug 2021 13:15 #854523

  • Scirocco
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If you are talking about your 550 Zephyr, your stock carb jet setup is very lean, (idle and main jets).
A friend of me with a 750 Zephyr had the same problem as you, plus a poor power output on acceleration.
His stock main jeting was 88 - 92 - 92 - 88 and 35 idle. After changing to 102 - 106 - 106 - 102 main and 40 idle jets it runs like hell and want´s to rip your arms off.

 
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Hard starting, low/high idle, and preparing for cold weather riding 30 Aug 2021 12:04 #854594

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Interesting, I hadn’t considered that it could be a jetting issue. Is that the general consensus on American market Zephyrs? If so, I’d be really in over my head trying to make any changes to it. I can follow my FSM confidently, keeping everything stock, but I’m no “engine whisperer.” I wouldn’t have any idea where to begin re-jetting the bike. 
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‘90 ZR550 Zephyr aka Zephanie

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Hard starting, low/high idle, and preparing for cold weather riding 30 Aug 2021 15:45 #854609

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Your stock 550 main jetting should be 108 - 110 - 110 - 108 and 35 pilot.
I would go with 115 - 117 - 117 - 115 main and 40 pilot.
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Hard starting, low/high idle, and preparing for cold weather riding 01 Sep 2021 08:32 #854684

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Thanks again. Knowing that I could easily make the swap. Looks like Z1 Ent. sells genuine Keihin jets. 
A breeze from the west.
‘90 ZR550 Zephyr aka Zephanie

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