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I just checked the needle jets I have and none of them seem to be crossed drilled. I believe them to be stock jets.

Thats interesting , perhaps I won't drill after all. Still have some carb issues but much less now I have blocked the 5mm hole in the inlet rubber!!.

I have a 2.70mm drill bit ordered to use as a no go gauge for checking my existing 265 needle jets. Will beiterestingto see is the older ones are really warn or if it is the needle that gets the most wear.

They dont wear evenly so a well worn one will possibly still measure 265 at some point so even a 265 bit would not feel loose?. I suspect you would have to make up a flow rig to measure any changes.

Well after doing the drill bit test I can tell you that they do wear significantly. I am sure it is not as precise as the method mentioned by Bob, but it at least told me which ones were definitely oversized and I was pleasantly surprised to find one old looking one that seemed to measure fine.

One of my projects is to rig up a sensor in the exhaust and instrumentation to read the emmisions on the move. This should enable me to set up the SSI carb and maybe reduce the richness due to reversion at low rpm, I wil also be able to asses the effect of diferent exhaust systems as I have three options .

Hi Bob,
Have you considered a product like this?
http://thesensorconnection.com/egt-prob ... cktabs_2=2
I used this on go-cart engines to adjust carburators on-the -fly.

Bruce

Let me know what you find out Bob. I have become very fascinated by these little carbs as I have been restoring the spares I have over the winter to keep me busy on bike stuff.