Yamaha TRX850 Enthusiasts Forum

Found this online. Not sure of the suitability for the BDST38 but was interesting for me anyway if only to confirm what others have said already. Basically the original has sliding sections that you adjust to match the specified main jet. Cheapskate me printed off the jpg then cut out the slider and setup for the 142.5 main jet. You can then read off the temperature adjuster above the line to get a new jet recommendation. Note it is a difference in temperature not the actual temperature. I looked at it as a typical worst case cold winter European or Japanese riding temp would be about 5 degrees. No one would go out in the snow! So the bike has to be jetted to run at that temp. The temperature adjustment was in Fahrenheit so I added Celsius in red. So the Zero here actually relates to the coldest expected temp i.e. 5 degrees. Typical summer temp in Europe might be mid to low 20s. That's an addition of 15+ degrees so the adjuster predicts 140 main jet. Similarly typical Brisbane summer temperatures could be in the mid to low 30s. That's an addition of +30 degrees so again the adjuster would predict 137.5. This bears out with real life experiences people have reported on. My take on this for me is that I should be trying 137.5 in summer and swap over to 140 in winter if I could be arsed or more likely just go 140. Not really adding anything but still there you go.

https://onedrive.live.com/redir?resid=6 ... hoto%2cJPG

That is pretty cool and seems to be on the money, thanks for sharing

I haven't seen one of these for yonks - more suitable for racing 2 strokes where they run so close to seizing that altitude and temperature conditions can be win or seize!

On my first visit to Dundrod road circuit in N Ireland I ran the same jetting as I'd normally use and seized up the drag to Wheelers. A couple of sizes bigger for safe measures and it wouldn't rev out. The following year I went just one size up and that seemed to do it

I very much doubt it would make any difference on out TRXs