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Post by alibev on Aug 18, 2023 18:59:32 GMT
When cold my Cb250n is very difficult to start. Often flattens the battery so can take a couple of hours to get it going. Choke on or off makes no difference. When it does start it only just ticks over and often splutters with the rev counter showing 0 rpm. Turning the throttle does nothing. Eventually it runs and when warmed up rides just fine. Occasionally when hot if I let the throttle off the revs take a while to return to idle. I rebuilt the carbs with a kit from Dave Silver but that made no difference. The fuel is fresh and the filters are clean with no deposits in the tank. Air filter is clean. In my mind it comes down to the carbs but other than using the default settings I am not sure what else to do. Willing to try anything. Words of wisdom appreciated.
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Post by comstar on Aug 19, 2023 3:36:05 GMT
I'm sure there will be other responses but I fear your problem may indeed be carb related. The carbs on these beautiful machines can be a b*gger to get right. They seem to need to be 100% happy otherwise they will not play ball. Have the carbs on this example stood for some time in the past do you know?
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Post by johnjones on Aug 19, 2023 6:42:36 GMT
Is it fuel is it ignition merry-go-round until your dizzy !
Half the onion, get those red neon plug caps, a quick easy real world visual ignition strength and HT disappearance aid. They can even be used whilst riding the bike, but more easily seen at night, or, take off the carbs for the 23rd time.
Rule ignition in or hopefully out.
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Post by alibev on Aug 19, 2023 6:56:28 GMT
I'm sure there will be other responses but I fear your problem may indeed be carb related. The carbs on these beautiful machines can be a b*gger to get right. They seem to need to be 100% happy otherwise they will not play ball. Have the carbs on this example stood for some time in the past do you know? Yes I think they have. However, I have stripped them and they look good inside. I suspect you are right about getting them right. |
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Post by alibev on Aug 19, 2023 6:58:06 GMT
Is it fuel is it ignition merry-go-round until your dizzy ! Half the onion, get those red neon plug caps, a quick easy real world visual ignition strength and HT disappearance aid. They can even be used whilst riding the bike, but more easily seen at night, or, take off the carbs for the 23rd time. Rule ignition in or hopefully out. I like the idea of eliminating another possible area. Not sure what you mean by neon plug caps. Are these something I would need to buy to test with? |
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Post by buster on Aug 19, 2023 10:32:03 GMT
with the carbs off, I'd go in this order, have a good look at the throttle butterflies they should be working in synchronisation when you move the arm that the cable pulls on. next check the choke butterflies are operating (that rather preposterous linkage can easily be put back together wrong). if alls well with those two you could try my (I really shouldnt be recommending this) dodgy blow into the air intakes for the slides, it gives a really good indication of how well they are operating  next is the notorious bit, the dreaded bl**dy pilot circuit, the pilot jets are pressed in and cant realistically be removed, you'll find them under the push in rubber plugs, some people recommend ultrasonic cleaning, I'd say lots of carb cleaner and an airline, it could take days... did your rebuild kit come with new mixture/pilot screws? did you carefully fish out the old o rings? they assemble in a very specific order, I hold the screw then drop the spring on, then the little washer and then the new o ring. let us know how you get on |
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Post by johnjones on Aug 20, 2023 6:58:43 GMT
Amazon UK, HT tester
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Post by alibev on Aug 20, 2023 12:11:34 GMT
Thank you so much, very helpful. My kit did come with pilot screws and I found the o rings. Will report back once I have given it a try. |
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