38 mm TMX flat slide calibration

[Kherrin]

anyone have good jetting specs for a stock interceptor with 38 TMX flatside carbs for near sea level operation?

[Interceptor398]

Welcome to the site!!  I have not played with that set up but maybe someone here has.

[Checkmarks]

You would be the first with flatsides.  You need an independent wideband o2 sensor.  You can get somewhere close with 600 rmk Polaris carbs.  First, find the main jet when wide open throttle (WOT) that puts you in the 13:1 air fuel (AF) ratio.  Starting rich saves your pistons and cylinders.  At idle AF ratios really don't matter, too lean and the motor just wont run and too rich is just costing extra go juice fine tuning here gets you out of the hole with power.  Mid range is the difficult bugger.  Needle jets, Jet needles Throttle valve cut or pillow....  Always stay rich > 14.7:1 always.  Motors put out more horsepower in around 13-12.5:1 AF

You can save some disassembly putting in jets with a tempaflow manipulating the altitude screw to give a margin that covers multiple jet and step in the correct direction to approximate how far you can change the jetting.  This lets you skip thru lets say 50 points worth of jetting.

Near sea level, best to start with 500 mains at least.

[Lloyd (ljm)]

Checkmarks

 Do you mean a set of rack carbs off a Polaris?
Will they fit without seperating them?

[Checkmarks]

I have yet to look to see if they align without modification.  It is possible to narrow the rack carbs to a degree.  I cannot remember how much but not enough to fit a 670 rotax motor.  I am sure they will make the Kawasaki motors.

Yes, I do mean a set of rack carbs off a Polaris.  On the 600s they used 38mm and on 7/8s they used 40mm.  The 40s are way too large and would destroy the low end.  Those 38s on the other hand put on the 550 motor would work well.  Very light go paddle compared to the 38 round slides; even with aluminum throttle valves.

[Checkmarks]

I personally never tried but then I didn't know they put 38s on 600 sleds until recently.  They are probally too much for 440 but 550 are another monster.

[Kherrin]

Got info on jetting TMX 38 non rack carbs. Got info from Bob at image from old notes for what it’s worth and my be a good starting point as usual.  389-Q0 needle jet.  6fm46 needle  310 main jet 35pilot.  I’m restoring # 304 interceptor and might be a bit on conformation of jetting.