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| '74 MT250: Plug type and gas mixture? https://vintagedirtbikeforums.alp-sys.com/viewtopic.php?f=21&t=2790 |
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| Author: | reddrt [ Thu Sep 02, 2010 3:42 pm ] |
| Post subject: | '74 MT250: Plug type and gas mixture? |
I need to know the plug type and gas/oil ratio for my '74 MT250. The oil injection has been removed, so I have to pre-mix the gas. Thanks! |
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| Author: | rayivers [ Fri Sep 03, 2010 5:52 am ] |
| Post subject: | Re: '74 MT250: Plug type and gas mixture? |
The stock plug is an NGK B7ES, but I'd strongly recommend a BP7EVX, Yamaha P/N NGK-BP7EV-X0-00: http://www.boats.net/parts/detail/yamah ... 00-00.html In my opinion it's worth the $10 just to see the difference a plug can make, and you may never have to change it again. I run 36:1 Bel-Ray H1R, which would also work well in your bike. Ray |
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| Author: | b-joe [ Fri Sep 03, 2010 3:29 pm ] |
| Post subject: | Re: '74 MT250: Plug type and gas mixture? |
sorry but stock plug is a B8ES. |
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| Author: | nola_fiddy [ Mon Sep 06, 2010 9:28 pm ] |
| Post subject: | Re: '74 MT250: Plug type and gas mixture? |
rayivers wrote: The stock plug is an NGK B7ES, but I'd strongly recommend a BP7EVX, Yamaha P/N NGK-BP7EV-X0-00: http://www.boats.net/parts/detail/yamah ... 00-00.html In my opinion it's worth the $10 just to see the difference a plug can make, and you may never have to change it again. I run 36:1 Bel-Ray H1R, which would also work well in your bike. Ray Hi rayiver, I have a 1979 cr125r, stock plug NGK B9EV. Is there a better plug that I could be running? thanks, nola_fiddy |
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| Author: | b-joe [ Tue Sep 07, 2010 4:57 pm ] |
| Post subject: | Re: '74 MT250: Plug type and gas mixture? |
nola_fiddy wrote: Hi rayiver, I have a 1979 cr125r, stock plug NGK B9EV. Is there a better plug that I could be running? thanks, nola_fiddy you can use NGK B9ES B9EV B9EG B9EIX or what i prefer Denso IW27 but there´s no need to change, B9EV is a good plug. |
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| Author: | rayivers [ Tue Sep 07, 2010 8:49 pm ] |
| Post subject: | Re: '74 MT250: Plug type and gas mixture? |
NF, If you can find it, you might want to try an NGK BP8EVX or BP9EVX plug. Failing that, BPR8EIX or BPR9EIX are pretty much the same plugs in resistor format, and easily available. There's also the BP8ES and BP9ES non-Iridium plugs, which are really inexpensive and would make great try-out plugs. I never have plug-overheating or detonation problems so I'd probably end up using 7-series plugs, but that's just me. I used the B9EV in my CR125M for years. In fact, I have a well-used one from over 30 years ago that's still working fine. But, to answer your question... in my experience, the projected-nose plugs (BPxxx, BPRxxx, etc.) give slightly better low end and throttle response than conventional ones, and even start a little easier too. Although I knew different heat-range plugs made a difference in resistance to detonation and fouling, I never thought they made all that much difference in actual motor performance until I tried projected-nose plugs; now I won't use anything else. You really have to try them one-after-the-other to notice the difference, but it's there. I also feel that Honda tended to supply the Elsinores with pretty cold plugs. Back in the day I was scared to try anything hotter than a 9, but these days I'm much more fearless and went down to a BP6ES for testing in the MR at one point (there was really no difference from the 7, so I went back). I also prefer precious-metal plugs, as it seems they just last forever. Other than repeated fouling from way-too-rich jetting, the only thing I've found that kills them is ultra-leaded Sunoco MO2X race gas; they develop a high-rpm/high-load misfire and must be replaced. I switched to unleaded race fuel, problem solved. Lastly, I don't think vintage ignitions really appreciate 5,000 ohm resistors in the spark plug circuit, although local TV/radio reception probably benefits a bit - so I don't use resistor plugs in my vintage motors. EVO and modern ignitions seem to handle them just fine, though. Ray |
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| Author: | nola_fiddy [ Wed Sep 08, 2010 10:12 pm ] |
| Post subject: | Re: '74 MT250: Plug type and gas mixture? |
Ray and b-joe, thanks for all the great information. I checked my plug and it is an NGK-B9EG that I got from a local honda dealer. I haven't had any problems fouling plugs. I replaced the carb with a vm 32mm mikuni and painfully rejetted the bike till it was right. Just looking for that something extra. I will definitly experiment with your sudgestions. definitly printing this page and putting it in my elsinore manual. thanks, nola_fiddy |
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| Author: | shinysideup [ Sat Oct 23, 2010 10:59 pm ] |
| Post subject: | Re: '74 MT250: Plug type and gas mixture? |
have a b9ev in my 73' cr250, b8es in my 74' mt125. the b9ev is a hotter plug i believe. whatever you end up getting, get the platinum or higher end plug. you wont regret it. better life and power. you wont be sorry. |
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