Help needed with pilot mixture tuning

[bsw]

Hi,

I've only had my XJ a few months and trying to get her correctly setup. I've checked/adjusted the valves - there were a few with next to no clearance. I've cleaned the carbs - didn't look too bad.

Now I'm trying to tune the carbs. I've read a bit here and know that I won't get perfect without a dyno and gas meter but still think I can get better that what I have now.

I used the ball bearing method to get the butterflies close. I think a mate has a manometer I can borrow to fine tune these later.

My issue for now if the idle circuit. I read the posts about using the header pipe temperature to check lean/rich so I attached the temperature probe to my multimeter and set to work. I does not stabilize as quickly as an IR thermometer would, but it still gives me some idea.

No. 1 and 2 were about 220C so I left them alone. No. 3 was much lower so I turned the screw in a bit to lean things out and warm it up a bit. I got it up around 200C when I moved on to No.4. I don't know what it was running at because the thermometer is slow to stabilize but it was still climbing quickly at 250C. I tried turning the screw out to make it richer, measure - still way too hot, measure repeat until I was at least 4 turns out and still running hot.

I gave up for a while, let it cool and pulled the No. 4 plug. I was black, sooty and even maybe wet - clearly not running lean.

Can anyone suggest why No.4 could be running so hot when it does not seem to be lean?

This had clearly been an issue with the bike for a while because I recall when pulling the carbs down to clean the No. 4 pilot screw was at least 4 turns out - I suspect the previous owner had been down the same path...

I don't think this is just an issue with my crappy method of measuring temperature - I move the probe to No. 3 and it starts falling quickly, back to No. 4 and it climbs quickly.

Thanks!