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| Need help with tuning and jet selection on 76 cr250m https://vintagedirtbikeforums.alp-sys.com/viewtopic.php?f=21&t=4172 |
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| Author: | sting66cp [ Sun Oct 06, 2013 7:35 pm ] |
| Post subject: | Need help with tuning and jet selection on 76 cr250m |
I have a freshly rebuilt 76 cr250m. It starts on about the third kick with the choke on, and runs out real nice once you get the rpm up a little. It seems really fat to me on the bottom. It loads up pretty easily at lower rpm and will not idle. I'm guessing the main jet is to rich. I don't know what size the factory main and pilot jets were, so I don't know how far from stock I am. This is definitely not an area of expertise for me, appreciate an advise here. My setup: Main Jet MX140 Pilot Jet 55 NGK BR9ES plug Red Line synthetic at 32/1 Premium 92 octane fuel Near sea level Will changing my main and or pilot jet help cure this? What would you recommend. Thanks |
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| Author: | sting66cp [ Mon Oct 07, 2013 5:10 am ] |
| Post subject: | Re: Need help with tuning and jet selection on 76 cr250m |
I have been told that the bike is acting like the pilot jet is clogged, but it is not. |
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| Author: | rayivers [ Mon Oct 07, 2013 8:21 am ] |
| Post subject: | Re: Need help with tuning and jet selection on 76 cr250m |
From what I can tell, your bike came with 148 main and 55 pilot jets, and a 2.5 throttle valve. A 140 main seems pretty lean to me. I'd put the needle clip is in the center (#3) position to start, if it's not there already. Have you set the float level? This can make quite a difference at low to mid throttle settings. My Clymer manual indicates the correct height is 20mm. and the adjustment procedure is in the link below, page 42 (actual page 46): http://honda-elsinore.alp-sys.com/manuals/MR25076/ShopManual76mr250.pdf Does adjusting your air screw have any effect? It should help with your idle and low-throttle operation, possibly a lot (2.5 turns out max). A 52 pilot might help even more. I've only jetted this carb for a 125, so someone with 250 experience should have better info. Ray |
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| Author: | sting66cp [ Wed Oct 09, 2013 7:38 pm ] |
| Post subject: | Re: Need help with tuning and jet selection on 76 cr250m |
rayivers wrote: From what I can tell, your bike came with 148 main and 55 pilot jets, and a 2.5 throttle valve. A 140 main seems pretty lean to me. I'd put the needle clip is in the center (#3) position to start, if it's not there already. Have you set the float level? This can make quite a difference at low to mid throttle settings. My Clymer manual indicates the correct height is 20mm. and the adjustment procedure is in the link below, page 42 (actual page 46): http://honda-elsinore.alp-sys.com/manuals/MR25076/ShopManual76mr250.pdf Does adjusting your air screw have any effect? It should help with your idle and low-throttle operation, possibly a lot (2.5 turns out max). A 52 pilot might help even more. I've only jetted this carb for a 125, so someone with 250 experience should have better info. Ray Thank you for the advise. I adjusted the float level and switched to a 50 pilot and it is running much better now. Ken |
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