Wednesday, 23 March 2016

Some general tune-up and and welding a bung in for the AFR-meter

Recently I was asked on a forum, what my stealthy VM38 setup looks like, which coincided very well with some re-jetting work.

 One of the extremely convenient aspects of VM38 carbs is that you can in fact change the main-jets without removing the floatbowl. Unlike when you want to change the pilot jets as they are countersunk in an orifice.
 VM38s sport a brilliantly unique float arrangement.

Bungs for AFR-meters can be bought via various sources. So called Lambda-probes usually sport an M18x1.5mm thread (there's a smaller M12 based version as well, but these are less common!) Usually these rings are around 25mm in outer diameter with a lip, which is a tad bigger. 

 Mark a suitable spot on your down pipe and remember that the Lambda-probe should be angle downwards, so that potential condensation won't pool up inside the probe.
 Drill an as large as possible hole (my biggest drill was 17mm) and then use a die-grinder. Once you're getting close check all the spots where the bung and the pipe touch, the better the fitment, the nicer the corresponding weld.

 Not exactly the nicest weld in the world. :-)
 Oh and a word of warning: NEVER fit a cold plug into a hot threaded bung. Feel free to guess how I found that one out.
 And installed again on the everyday TR1!

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