Jet size question

[notjoe]

Are stock jets messured the same compaired to Dynojet? I have a stock 05' 400ex carb. The main jet has 148 on it. With the install of quad works kit (K&N filter, outerware, dynojet kit). Dynojet instructions says install 142 w/ stock exhaust and 146 w/ aftermarket exhaust. If there messured the same why go down in jets. I thought you should go up?

[JOEX]

Originally posted by notjoe
Are stock jets messured the same compaired to Dynojet? I have a stock 05' 400ex carb. The main jet has 148 on it. With the install of quad works kit (K&N filter, outerware, dynojet kit). Dynojet instructions says install 142 w/ stock exhaust and 146 w/ aftermarket exhaust. If there messured the same why go down in jets. I thought you should go up?
Dynojet uses a different numbering system than stock Keihin jets.
Generally the Dynojet numbers are smaller than the Keihin jets. There is a table around here some where that has a rough conversion, may in the How-to setion or FAQ setion....