Post by alyn on Oct 25, 2016 0:58:15 GMT -5
Hi all,
I just picked up a 7900 miles 2008 Linhai Aeolus Classic 260 YP250 clone with its normal 257cc engine. Had a Znen 250, SSR Rowdy and an Xciting 500 so am not new to scoots. Was getting slight stumbling when returning to idle so decided to pull the carb and give it a clean and also wanted to check the jets as my other chinese scoots all came jetted too lean from the factory. Then the nightmare began....
The good news was my carb is a genuine Keihin 30MM CVK and came with a #128 main (the same size specced by Yamaha for the 2000 and above YP250) but it only had a #38 pilot (yamaha spec for the YP250 is a #43 or 44 with same engine). I proceeded to disassemble and clean everything with air, carb spray and a needle cleaning kit (I've cleaned these kind of carbs many times without issue). The membrane still looked good, needle was clean, found no obvious clogged jets. Disassembled accelerator pump, etc. all looked great. No varnishing, no debris. Cleaned every hole, tube, orifice, etc. and reassembled. When I got it all back together it started perfect. Idled great. The auto choke did its thing immaculately and when it was warm I adjusted the air/fuel mixture with a tach and could blip it hard without it stumbling and if I revved it fast it would wind up to 7k (I only did this briefly) without stumbling BUT --
If I slowly rolled on the throttle from idle when I would slowly get to 1/4 throttle or so, the scoot would stumble and die (on the center stand). Vacuum hoses were fine, fuel hoses were fine and like I said if I revved it fast it was a monster, the slow rev up is what killed it.
Decided to break it down again and while I was at it, I wanted to see what a bigger pilot would do. I cleaned the whole carb again but popped in a #42 and a #130 main to test. It fired right back up, idled great, I adjusted the mixture after it warmed up, it blipped fine (but I could hear it was too rich) but it revved up to 7k without issues and idled back down fine. Yet again, when applying slow throttle, at about 1/4 it died. Took it off reassembled again, popped in a #40 pilot, keeping the stock #128 main, reinstalled and it did the same thing. Took it off, cleaned it again and put both jets back to stock, reinstalled and it is still doing the SAME THING. It idles perfect, blips perfect, fast full throttle works great it JUST dies at 1/4 throttle if I rev it slow.
I am baffled. I did Alleyoop's test - when I slowly revved it I would get to the point where it was about to die and I would back off slightly a 1/4" or so and the bike would stumble but it would settle back down to perfect idle (it would not speed up) - apparently this suggests a rich condition but I don't understand why all of a sudden it would do this with the stock jets unless I screwed something up consistently in the 4 reassembles?? FWIW, have adjusted the valves and rechecked them. They are perfect.
Scoots down and I'm out of ideas. Solutions anyone??
Thanks in advance!
EDIT - FINALLY SOLVED! Cleaned my garage and found the NEEDLE COLLAR on the floor. Put it back in the carb where it belonged and life is good again :-)
I just picked up a 7900 miles 2008 Linhai Aeolus Classic 260 YP250 clone with its normal 257cc engine. Had a Znen 250, SSR Rowdy and an Xciting 500 so am not new to scoots. Was getting slight stumbling when returning to idle so decided to pull the carb and give it a clean and also wanted to check the jets as my other chinese scoots all came jetted too lean from the factory. Then the nightmare began....
The good news was my carb is a genuine Keihin 30MM CVK and came with a #128 main (the same size specced by Yamaha for the 2000 and above YP250) but it only had a #38 pilot (yamaha spec for the YP250 is a #43 or 44 with same engine). I proceeded to disassemble and clean everything with air, carb spray and a needle cleaning kit (I've cleaned these kind of carbs many times without issue). The membrane still looked good, needle was clean, found no obvious clogged jets. Disassembled accelerator pump, etc. all looked great. No varnishing, no debris. Cleaned every hole, tube, orifice, etc. and reassembled. When I got it all back together it started perfect. Idled great. The auto choke did its thing immaculately and when it was warm I adjusted the air/fuel mixture with a tach and could blip it hard without it stumbling and if I revved it fast it would wind up to 7k (I only did this briefly) without stumbling BUT --
If I slowly rolled on the throttle from idle when I would slowly get to 1/4 throttle or so, the scoot would stumble and die (on the center stand). Vacuum hoses were fine, fuel hoses were fine and like I said if I revved it fast it was a monster, the slow rev up is what killed it.
Decided to break it down again and while I was at it, I wanted to see what a bigger pilot would do. I cleaned the whole carb again but popped in a #42 and a #130 main to test. It fired right back up, idled great, I adjusted the mixture after it warmed up, it blipped fine (but I could hear it was too rich) but it revved up to 7k without issues and idled back down fine. Yet again, when applying slow throttle, at about 1/4 it died. Took it off reassembled again, popped in a #40 pilot, keeping the stock #128 main, reinstalled and it did the same thing. Took it off, cleaned it again and put both jets back to stock, reinstalled and it is still doing the SAME THING. It idles perfect, blips perfect, fast full throttle works great it JUST dies at 1/4 throttle if I rev it slow.
I am baffled. I did Alleyoop's test - when I slowly revved it I would get to the point where it was about to die and I would back off slightly a 1/4" or so and the bike would stumble but it would settle back down to perfect idle (it would not speed up) - apparently this suggests a rich condition but I don't understand why all of a sudden it would do this with the stock jets unless I screwed something up consistently in the 4 reassembles?? FWIW, have adjusted the valves and rechecked them. They are perfect.
Scoots down and I'm out of ideas. Solutions anyone??
Thanks in advance!
EDIT - FINALLY SOLVED! Cleaned my garage and found the NEEDLE COLLAR on the floor. Put it back in the carb where it belonged and life is good again :-)
