rt carb main jet ???

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HotRodRob

New Member
Apr 14, 2013
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Western KY
Yep, Theon is right on. Stock NT carbs usually come with a 70 jet which seems a little too rich for most places. The RT carbs can come with a range of jets depending on what application its being sold for. I think both my RT carbs came with 70s though. Although you should probably run it a little rich for break in. After you run the first couple tanks of fuel then do a plug chop(search this forum for how to read plugs) to determine if you need to go leaner or not.

So, Keep what you have stock for the first couple tanks. Its usually recommended to use a little more oil for those first couple tank fulls to make sure all your internal parts are well lubricated. Some kits recommend 16:1 (I believe that value is for regular motor oil). If you use good quality two stroke oil I've found 20-25:1 for the first couple tank works good. Then use what ratio your oil recommends.

After those first couple tanks check the plug color. Dark and oily means your running too rich. Light grey/white means too lean. You want your spark plug to be a nice chocolate brown color.

By following these steps you will expect to have a dark plug because of the extra oil and bigger stock jet. That is ok at first to help your motor break in, but once it has some miles on it its important to tune the carb for your area and use. You will want a smaller jet size(lower number) if you are running rich. If its only slightly rich(darker chocolate brown color) going down from a 70 to a 68 may be what you need. If its really dark you may want to go down more to maybe a 64 or 66. I get a few jets in the 60-68(62,64,66,68 would be a nice set to work with) range and narrow it down for what that carb/motor needs.

There is no standard jet that will work for everyone everywhere. Also, even two different bikes with the same kind of motor in the same location could need different jets from the other. Hope this helps. If you have any questions don't hesitate. We have a ton of people on here with great experience and knowledge.