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Post by marinervella on Sept 27, 2014 20:46:10 GMT -5
Greetings dawgs,
I'm working on a 2008 Jackel 150 with less than 1000 miles -- engine has the emissions control canister and fuel tank vent/check valve, but not the PAIR system. When the engine is cold, it starts right up and the idle speed goes up to 2000+ RPM and stays there for half a minute. Then it suddenly drops to 1k or less, and might even die if I don't give it a little throttle. Over the next couple minutes, it eventually comes up to 1500 - 2000 RPM then idles smoothly ever after. Carb is clean, diaphragm looks good, enricher seems to be working fine (on the bench, the plunger operates as expected when voltage applied), vacuum lines/intake manifold/air filter etc. seem OK. I just adjusted the valves and the engine generally runs very well.
Can you big dawgs make a diagnosis of what's causing the abrupt change in cold idle speed, based on the above information? Thanks in advance!
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Post by phssthpok on Sept 27, 2014 22:55:52 GMT -5
When the engine is cold, it starts right up and the idle speed goes up to 2000+ RPM and stays there for half a minute. Then it suddenly drops to 1k or less, and might even die if I don't give it a little throttle. Over the next couple minutes, it eventually comes up to 1500 - 2000 RPM then idles smoothly ever after. My gut instinct is that the enricher is warming up too fast (too much voltage being applied?) causing the 'choke' (enriched) fuel mixture to lean out to normal operating parameter before the engine is fully warmed up, which would seem to be supported by the engine idling normally after a few minutes (fully warmed). I seem to recall seeing some speculation/discussion on enricher voltages/operation while researching information on the 11pole stator upgrade.Try testing the voltage being fed to the enricher while installed. IIRC there was some consensus that a lower voltage (5-6 volts vs. 12-14 normal operating volts) would still heat the enricher, but take longer to do so allowing the engine to reach full operating temperature before 'leaning out'. |
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Post by alleyoop on Sept 27, 2014 23:10:49 GMT -5
The fuel mixture is a little on the rich side that is why it jumps up and then drops on you and wants to die unless you open the throttle a little and let more air in. Also after it warms up it should be around 1500-1800 So lean the Fuel Mixture on it 1/4 at a time and test after each 1/4 turn clockwise. 1/4 turn to much in either direction makes a big difference when starting thest motors when cold.
Alleyoop
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Post by marinervella on Sept 28, 2014 10:15:01 GMT -5
Thanks guys -- I will try both those suggestions. phssthpok, I had a low-voltage issue on my 250cc scooter just like you describe -- thought the enricher was bad, but it turned out to be a bad regulator that was delivering low voltage to the enricher, which caused it to warm up more slowly. Here in Texas, that usually means too rich for too long...
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Post by retrobrian on Sept 28, 2014 11:26:01 GMT -5
My BMS was doing the same thing. Started and idled high to start warming up. Then about 30-45 seconds later the idle dropped as the en richer activated... and or deactivated and the scoot stalled. I thought mine wasn't working right. Then I did the air/fuel mixture screw access and tuned the bike to instructions found here. Now it starts the same... and starts to drop, but doesnt stall. After about 60 seconds it levels out to the 1700-1800 idle.
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Post by marinervella on Sept 28, 2014 15:42:30 GMT -5
I'm getting about 11 volts AC to the enricher -- I think that's OK, since as I mentioned, it's usually pretty warm here in Texas, so we want the enricher to close relatively quickly (the wax motor that pushes the enricher needle still takes several minutes to extend completely.)
I am slowly closing the idle mixture screw, and it does seem to be improving. But of course I have to wait a long time for the engine to completely cool down before the next tweak, so it may take a few days to find the optimum setting.
So far, no one has suspected the vapor recovery system -- that's good, because I would prefer to keep that intact unless it's a prime candidate for problems...
Thanks again!
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..BAD TO THE BONE..
