Mikuni jetting advice

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10 inch Terror
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Sat Feb 12, 2011 10:30 pm

Silly question i know! But if an engine is running rich how do i get it to run leaner? do i up the jet size or do i go lower? And advice suggestions very welcome. Cheers Pete

shocky
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Sat Feb 12, 2011 11:28 pm

10 inch Terror wrote:Silly question i know! But if an engine is running rich how do i get it to run leaner? do i up the jet size or do i go lower? And advice suggestions very welcome. Cheers Pete
it depends were it is running rich if in the mid range then it could be the slide needle or atomizer if its on full throttle it is generally the jet and this would need to be made smaller to weaken it however tread very carefully and note what you do every time in a book and keep checking the plug color at various throttle positions ,if you dont know what you are doing then id leave well alone BTW what size is the carb
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monkey boy
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Sat Feb 12, 2011 11:50 pm

Hi mate.
Not a silly question at all.
There are several things you can do to lean up your carburation.
Going smaller on the pilot and main jets will lean it off,going bigger will richen it.
You can also fit a different diameter needle(higher number making it leaner,lower number richer)
You can also move the clip position on the needle,moving the clip up will lean it off,moving it down will richen it up
All of these adjustments affect different parts of throttle opening,so you need to assertain which part of your throttle opening is rich by doing some plug chops.
Adjust one thing at a time then do some more chops,dont try and change too many things in one go.
Check this out,It may help http://scooterotica.org/forum/viewtopic.php?f=5&t=475
Hope this helps
CHEERS AL

10 inch Terror
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Main scooter: Lambretta LI Imola 185
Location: Farnborough Hampshire
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Sun Feb 13, 2011 9:44 am

BTW what size is the carb[/quote]
Thanks for your reply mate, it's a TM 28, Imola kit with Franspeed JL 3 pipe. Fuel and oil pour out of the pipe and i've been told it's running very rich. Pete

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