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low idle at cold start and high idle after warm up

Old 09-27-2017, 01:03 AM
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low idle at cold start and high idle after warm up

Hi. I've been having these problem since I got my bike 5 mos ago.

1. No idle at cold start, engine will stall if I let go of the throttle.
2. After the bike warms up (middle of temp guage) the idle will shoot up to 1900 rpm.

Tried solutions to no avail:
1. Adjusted the idle screw. If i adjust the screw to lower the idle on already warm engine, it will idle fine until the next cold start run by then it will have very low idle and will stall if I let go of throttle this is until middle of the temp gauge. Problem is when its cold (before the middle of gauge) there's no idle.

2. Full cleaning of carb. Completely striped off & cleaned.
Previous owner killed the choke. Cable & connectors was taken of covered w/ epoxy. He may have over tighten a nut & cracked it, its covered in steel epoxy. Everything else is fine except for the choke. All the jetting, needles, etc. were cleaned. I think its running standard jets.

3. Installed a new hiflo standard air filter. Previous owner put a DIY foam filter which was burned. It was fixed on carb cleaning.

The bike still has act, pair valves & stock TPS setting.

Will getting a new carb solve this? I reckon its the choke causing the headache. Thanks for all your inputs.

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Old 09-30-2017, 07:29 PM
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The behavior you describe is typical of an internal combustion engine. When cold it will idle at a lower RPM for a given fuel mixture. The choke restricts the air to richen (increase the fuel content) the mixture up while cold. I would fix the choke. If it's not fixable, a set of used carbs is from 200 to 300 bucks on eBay, shipped.

I have a manual 'cruise control' on one of my bikes. It holds the throttle at a set point. I use that sometimes, rather than the choke, to hold the throttle open while the engine warms. You could use something like that on your bike until you get the choke fixed.

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Old 10-01-2017, 08:21 AM
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Your choke linkage and circuitry needs addressed. Fix these then see how she does.
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