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Post by prodigit on Aug 16, 2013 23:38:28 GMT -5
So I've noticed that my motorcycle's idle is very low when the engine is cold, but as soon as it warms up the idle goes up a lot.
I wonder if there's anything that can be done about this.
If I lower the idle too low, the bike won't start. If I set the idle so the bike will start (~800-1000rpm), on a hot engine the idle will surpass 1500RPM (where the clutch starts gripping).
When I set the idle just under where the clutch grips on a hot engine, it's hard to start.
The only thing I can still do is play around with the AF screw.
Is there any advise you would give to play with the AF screw, that could possibly solve my high idle difference (between cold and hot engine)?
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Post by wilds on Aug 17, 2013 0:56:05 GMT -5
Just so you will be able to go back to your original position!
Check how many turns out from bottom position the AF screw is now before you try the below.
After the engine is properly warmed up, put the bike on the center stand and keep it on idle.
Turn the AF screw slowly in small steps either way until you reach the maximum rpm.
Default would be about 2-2½ turns out from bottom position.
After you have the maximum rpm, set the idle with the idle screw.
Let the engine cool down and try starting it and see if it helped.
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Post by JR on Aug 17, 2013 12:34:28 GMT -5
You have symptoms of either a auto choke not working and/or the valves need adjusting. Which scooter what engine?
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Post by prodigit on Aug 17, 2013 20:44:45 GMT -5
It's actually because the idle jet is running too lean. The main jet is running lean, but I'm not going to rejet the bike.
I thought of putting perhaps 10W40 in it, instead of 15W40, as 15W40 gives too hard starts. I'm playing around with a slipping clutch demanding thicker oil (15W40+), a hard starting engine, demanding thinner oil (5W30), a high idling engine at hot temperatures demanding W40 or W50 oil), a vibrating engine demanding 10W40 for least vibration, and from all of these I can only choose one oil to put in there.
The bike needs to run richer, much richer in idle, and only a tiny bit richer at WOT.
I did not know I needed to set the AF screw at max RPM? I thought I had to set it around 2-3k RPM, was I incorrect here?
I should fix the clutch, but no way I can do that right now. Not enough knowledge yet.
The valves are ok, and the bike has a manual choke.
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Post by larrball on Aug 17, 2013 20:57:54 GMT -5
I have my Idle screw set at 1500 RPM at idle after a 30min drive. 3 1/2 turns out on the A/F mix (18mm carb (  Main jet as i was told)) at 758 ft Elevation. But then i have a stock carb and my scooters just a junk china one Prodigit, not like yours.  Oh come on i was just kiddin.. My scoot is way better.  |
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Post by wilds on Aug 18, 2013 4:46:45 GMT -5
Sorry, I might of been unclear there.
English is not my native tounge. I'll try to explain again.
And it's never good to run lean, the engine will reach higher temps running lean... You can also move the clip on the throttle needle down a step, that would make it run a bit more richer.
Keep the warmed up engine runing on idle (whatever idle you have).
Then slowly in small steps turn the AF screw to a point where you reach the highest idle.
When that is done, adjust to a proper idle with the idle screw.
After that try twisting the throttle to see if the engine response is right.
Take it out for a test drive and see if it still is ok.
Let it cool down and try starting it and see if the problem is fixed.
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Post by prodigit on Aug 18, 2013 11:51:45 GMT -5
The above would be in a situation where the carb is jetted correctly.
Would the same still hold true if the jets are too lean?
I set my idle at ~2k RPM. Perhaps I should reset it on a hot engine at ~1200RPM.
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Post by wilds on Aug 18, 2013 23:19:48 GMT -5
The above would be in a situation where the carb is jetted correctly. Would the same still hold true if the jets are too lean? I set my idle at ~2k RPM. Perhaps I should reset it on a hot engine at ~1200RPM. It should be correct even with a lean carb. I would set the idle around 1500RPM |
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Main jet as i was told)) at 758 ft Elevation.