06-25-2017, 12:31 PM | #1 |
Join Date: Jun 2017
Posts: 7
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High idle when hot!
Hello. I understand this is a common issue, but I haven't yet quite found the solution for my bike.
I have a Magician 250 that idles fine when cold/warm. But after 30 min or so of riding, it idles very high. There is a small tear in the hose that connects the airbox to the carb - it happened when I was removing the carb for tuning. But I didn't think it would cause this problem. I will get it patched tomorrow, but in the meantime, I would like to get your opinion. My bike: Magician 250 Carb: Stock PZ30 Main jet: 110 Pilot jet: stock |
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06-25-2017, 02:41 PM | #2 |
Join Date: Apr 2017
Location: Omaha, NE
Posts: 8,049
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Three questions.
Can you adjust the idle speed down when it is hot? Idle speed should be set with the bike at operating temp (hot). What is the idle mixture screw set to? Does the idle hang at all if you give it a little rev or if you come to a stop, or does it immediately return to it's idle speed? An air leak before the carburetor, such as in the intake tube, will potentially cause a lean condition if enough air gets in. That won't directly affect the idle speed, but can cause a bike to get hung up or idle at a higher RPM. If plugging that hole doesn't change anything, then that makes my first two questions relevant.
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Hawk Information and Resource guide: http://www.chinariders.net/showthread.php?t=20331 2018 Hawk 250 - Full Mod list here. http://www.chinariders.net/showpost....62&postcount=1 2024 Royal Enfield Shotgun 650 https://chinariders.net/showthread.php?t=34124 |
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06-25-2017, 05:06 PM | #3 |
Join Date: Jun 2017
Posts: 7
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I re-adjusted the idle screw after I took it for a good ride. It idles fine now when it's hot. On the flip side, it's a little harder to get it started when it's cold. It won't start with the choke off (ambient temperature 75-80F). I will start with the choke on, but I have to keep my hand on the throttle and rev it to keep it from dying.
The air /fuel mixture screw is set to 1.5 turns. I also have the needle shimmed with 2 washers. Idle hangs a bit when I rev it. But it's not too bad. |
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06-25-2017, 06:20 PM | #5 |
Join Date: Jun 2017
Posts: 7
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Maybe this is what I need to do! The bike ran fairly ok out of the box so I didn't think of checking/adjusting the valves. I will do that and report back. Thank you!
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06-25-2017, 07:51 PM | #6 |
Join Date: Apr 2017
Location: Omaha, NE
Posts: 8,049
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Carbed bikes will never idle quite right when not up to temp. The cold engine doesnt atomize fuel properly so it needs to be richer, thats what the choke is for. You just never want to run with the choke on for more than a minute or so. Nursing the throttle til it gets hotter is also a normal part of the carbed bike life. Once I can get either of my bikes to hold an idle, even if its a bit low, I start riding it. I am just easy on the throttle until they get warmer.
Hanging idle generally indicates a slighly lean condition in the idle mixture. You may have to do a little more adjusting with the mixture screw.
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Hawk Information and Resource guide: http://www.chinariders.net/showthread.php?t=20331 2018 Hawk 250 - Full Mod list here. http://www.chinariders.net/showpost....62&postcount=1 2024 Royal Enfield Shotgun 650 https://chinariders.net/showthread.php?t=34124 Last edited by Megadan; 06-28-2017 at 07:24 PM. |
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06-28-2017, 06:40 PM | #8 |
Join Date: Jun 2017
Posts: 7
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Valve clearance was indeed the issue. There was no clearance on my Magician. I set the both the intake and exhaust to 0.05 mm.
I previously had to use the choke to get it to start even during warm weather. But now it starts straight up; no choke needed. Thanks to everybody for the help! |
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06-28-2017, 07:12 PM | #9 |
Join Date: Sep 2016
Location: Texas
Posts: 165
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Yuppers. Tight valves can do more harm than loose valves.
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06-28-2017, 10:20 PM | #10 |
Join Date: Sep 2015
Location: East Central Hellinois
Posts: 1,344
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Glad u caught the issue and corrected it prior to a catastrophic failure
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09-18-2017, 08:08 AM | #11 |
Join Date: Apr 2011
Location: Fort Myers, FL
Posts: 39
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Wow! I have the same issue with my Magician 250, i.e. idle at cold start would be very high once engine warmed. If low idle set when engine warm, I would have to throttle the engine w/ choke upon start, and hold throttle.
And thus... this AM will be adjusting the valves!!! Thanks for the diagnosis on the idle issue. Update... I adjusted the valves... from no clearance / tight, to .03mm intake and .05mm exhaust. Amazing difference! I actually hear the valves "ticking" a little now, vs before... no tick. The idle is now stable at both cold and hot engine. No choke needed upon cold start. Previously, there was a slight backfire on deceleration... now no backfire. Unsure, but power and acceleration may be slightly better also? I had no idea a minor valve adjustment would be so noticeable.
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Magician 250 (9/2016 engine label) Kawasaki 650 KLR Honda 1300 VTX Qlink XF200 Last edited by clark; 09-18-2017 at 10:20 AM. |
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09-18-2017, 02:57 PM | #12 | |
Join Date: Apr 2017
Location: Omaha, NE
Posts: 8,049
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Quote:
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Hawk Information and Resource guide: http://www.chinariders.net/showthread.php?t=20331 2018 Hawk 250 - Full Mod list here. http://www.chinariders.net/showpost....62&postcount=1 2024 Royal Enfield Shotgun 650 https://chinariders.net/showthread.php?t=34124 |
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09-18-2017, 04:56 PM | #13 |
Join Date: Nov 2016
Location: robertsdale alabama usa
Posts: 1,007
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An air leak before the carburetor, such as in the intake tube, will potentially cause a lean condition if enough air gets in. That won't directly affect the idle speed, but can cause a bike to get hung up or idle at a higher RPM. If plugging that hole doesn't change anything, then that makes my first two questions relevant.[/QUOTE]
air leak befor carb will only get you unfiltered air not a lean condition. air leak after card in between enginr and carb will cause lean condition.
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1991 harley heritage softail classic 2016 hawk kaw h1 400 tripple 13' long chopper in progress 2009 johnny pag bar hog 2004 hd electra glide ultra classic shriner edition 1997 harley davidson 1200 sportster 1972 harley davidson amf sx250 |
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