neil
Thrash Merchant
my 125
Posts: 386
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Post by neil on May 29, 2011 19:38:17 GMT 1
hi just wondered if when running in, it would be ok to run a smaller main jet as you wont be in the band. instead of dumping lots of fuel in which wont get burnt properly? which would save fuel and make it abit shaper as their pathetic out of the band.
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neil
Thrash Merchant
my 125
Posts: 386
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Post by neil on May 29, 2011 20:06:34 GMT 1
even out of the band?
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Post by billy on May 29, 2011 20:28:32 GMT 1
Naah don't be a fool now boy. If you stay out of the powerband you're most likely using half throttle at the very most (well maybe you use more throttle on heavy uphills, but then you're not on high rpm's). Now, I'm not sure how, exactly, it looks on half throttle, but I know the main jet will let out a smaller ammount of petrol on half throttle then it does on full throttle, this is because the needle has a smaller diameter at the tip then it has at the other end near the needle clip. So, as the throttle/needle goes up, the main jet lets more fuel pass through. I think I read somewhere that on 350's, the main jets mainly effect 3/4 to full throttle. I could remember wrong though but in theory it is correct. The more you raise the throttle the more the cone shaped needle raise, which makes the main jet hole "bigger".
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neil
Thrash Merchant
my 125
Posts: 386
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Post by neil on May 29, 2011 22:03:07 GMT 1
that makes sense chap. ok say if you were going to jet a freashly rebuilt tuned motor. what size jet would you start at? you obviously couldn,t do a plug chop at full thrash because you,d be running it in.
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Post by billy on May 30, 2011 1:17:23 GMT 1
Look at this thread mate: rdlccrazy.proboards.com/index.cgi?board=80lc125lcchat&action=display&thread=7655If you have a 125 LC with a 10w carb then 210 should be a good starting point. That's gonna be plenty rich enough regardless of what tuning bits you have on the engine. I wouldn't be too scared of revving the engine though. Just take it easy for some 150 miles (or about 100 km's) and make sure not to overheat the engine. Heat cycles is the way to go according to those who knows. Just start by carefully fizzing around with the bike, shut it off, let it cool down, start it again, repeat process. - In time (presumably after at least 100 miles) you should progressivly increase the engine load. You may want to have a look on the head nuts aswell btw, retorque them if neccessary. Remember, TOO low rpm's could actually make the engine run hotter as the coolant may not be circulating properly. I have this "problem" on my 350 LC. If I stay on idle for too long or ride it with very low rpm's, it'll get hot. The 350 LC is best off somewhere around 4-6K rpm's as far as I know. After all, these engines are more like old racing engines, they're meant to be trashed! I don't know if the 125's are like this aswell though but it would be good to check it out so you know for sure.
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neil
Thrash Merchant
my 125
Posts: 386
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Post by neil on May 30, 2011 11:47:55 GMT 1
cheers for that chap and the handy thread
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Post by sooty157 on Jun 10, 2011 21:57:49 GMT 1
i've recently rebuilt my 125, crank and piston mainly and after a 100 miles of steady tootling i started to just show her the power band, that was 50 miles ago and all is still well! please don't take anything i say as gospal but as billy says they are designed to sing just build up gradually
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