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| Need help with Keihin throttle slide needle selection https://vintagedirtbikeforums.alp-sys.com/viewtopic.php?f=21&t=4278 |
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| Author: | sting66cp [ Mon Apr 14, 2014 8:20 pm ] |
| Post subject: | Need help with Keihin throttle slide needle selection |
I have a 78 cr250 that I'm racing, it has a Keihin carburetor. I would like to purchase 2 throttle slide needles for it, one that is one size richer, and one that is 2 sizes richer. The one in it is marked "AJM". Can anyone tell me what needles I will need? and where to possibly by them? Thanks for any advise you can provide. |
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| Author: | rayivers [ Tue Apr 15, 2014 8:01 am ] |
| Post subject: | Re: Need help with Keihin throttle slide needle selection |
That AJM needle is really lean. Here's a chart: http://www.jetsrus.com/a_jets_by_carburetor_type/needle_keihin_N427-48.html The needles listed at the bottom of the page are the ones that are still available. Here's some additional relative info on some of the OEM Honda 66mm needles - only the diameters are precise, sorry: 31A: D .106"/ 2.705mm (leanest) 16201-430-000 '79-'80 CR125/'78-'80 CR250/'81-83 CR480 opt. 31C: D .106"/ 2.705mm (much leaner) 16203-430-000 " " ECA: D .1025" / 2.604mm, medium L1, medium taper (leaner D1, otherwise lean to medium) 271006: D .0983", short L1, shallow (dual?) taper (medium) MR250 34mm 271302: D .0988", long L1, shallow taper (leaner) '76 CR250M 36mm 271309: D .0972", long L1, heavy taper (richest) '73 optional 36mm L1 can have a big effect on throttle response, especially if the straight diameter, pilot jet, and throttle slide cutaway are close to ideal. Jets 'R Us and Sudco should have the needles, and I couldn't really suggest anything without knowing the complete carb setup. Ray |
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| Author: | sting66cp [ Tue Apr 15, 2014 4:09 pm ] |
| Post subject: | Re: Need help with Keihin throttle slide needle selection |
rayivers wrote: That AJM needle is really lean. Here's a chart: http://www.jetsrus.com/a_jets_by_carburetor_type/needle_keihin_N427-48.html The needles listed at the bottom of the page are the ones that are still available. Here's some additional relative info on some of the OEM Honda 66mm needles - only the diameters are precise, sorry: 31A: D .106"/ 2.705mm (leanest) 16201-430-000 '79-'80 CR125/'78-'80 CR250/'81-83 CR480 opt. 31C: D .106"/ 2.705mm (much leaner) 16203-430-000 " " ECA: D .1025" / 2.604mm, medium L1, medium taper (leaner D1, otherwise lean to medium) 271006: D .0983", short L1, shallow (dual?) taper (medium) MR250 34mm 271302: D .0988", long L1, shallow taper (leaner) '76 CR250M 36mm 271309: D .0972", long L1, heavy taper (richest) '73 optional 36mm L1 can have a big effect on throttle response, especially if the straight diameter, pilot jet, and throttle slide cutaway are close to ideal. Jets 'R Us and Sudco should have the needles, and I couldn't really suggest anything without knowing the complete carb setup. Ray Thank you for the response and information. I also found this link which has been very helpful. http://www.duncanracing.com/TechCenter/ ... etting.pdf |
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