Jet Kits - Factory, Mikuni vs. Dynojet
by Mtbierio (Cugino Pegaso)
edited by Kristian #562
Please read the Disclaimer before attempting any work in this FAQ.
BMW F650 Classic Jet Kits
The salient part of any jet kit is the needles, these are some dimensions I have taken from the needles from each kit. Refer also DJ's recommendations in the Performance Modifications FAQ
|Tip to Richest Slot||49.75mm||50mm|
Looks similar, but the Dynojet looks richer at full throttle (smaller dia. at tip).
The Dynojet is described as a stage II for mild tuned bikes with snorkel removed and stock or aftermarket exhaust. the Factory kit is described as stage 1 but fits similarly set up bikes.
The Factory kit seems to have a better selection of Mikuni jets, the Dynojet kit uses their own jets. Both come with slide springs. The Factory kit also has idle jets. The main jets they come with are a mix from 130 to 140. Below is a chart I found on the net that describes how to map DJ jets to Mikuni jets. Of course it maps jets above our applicable range.
Flow rates based on size markings of Mikuni and DynoJet jets are not comparable. As a guide the chart indicates equivalent sizes based on the diameter of hole in the jet.
Mikuni jets are chamfered on the inside opening at the threaded end and Dynojet's have a machined flat surface. Keep this in mind when using this chart. These physical differences will never allow an exact comparison.
This chart is intended to be used as a tool to assist you in making a more accurate decision when selecting a jet size range or comparing tuning data where an opposing brand is being used. Actual jet sizes are highlighted.
There are only a few examples where a DynoJet jet exactly matches a Mikuni, (such as the MK150/DJ160 and MK187.5/DJ200). DynoJet jets are marked according to the diameter of the hole in the jet. i.e.: DJ150 = 1.5mm and DJ175 = 1.75mm.
This is not true for Mikuni or most other OEM equivalent jets. This size Mikuni jet, (N102.221 Super BN), is marked according to its' flow rate, i.e.: 150 = a rating of 150 cc of fuel per minute.
Dave #365 measured the Stock Spring & the DJ Spring. Stock is 4 3/4" long (120.6mm) and the Dynojet 4" long (101.6mm).
Mikuni / Dynojet Size Comparison Chart
http://www.thunderproducts.com/dial_a_jet.htm - Not tested on the F650.