xj600 ,engine overheating

hi , all,
so i finally got my xj600 bobber project finished, and i am really pleased how it turned out, here it is..


i went off on a road trip with some mates to tour around "Middle England" mainly minor roads and twisties.
and all was fine did about 800 miles, bike starts, idles and runs just fine, but on the way back home, we decided to go on the motorway (highway) ,and travelled for about 1 hour at 70mph, i glanced down at the oil temp gauge i had fitted, and it was reading 104 degrees c. so i rolled off the throttle a bit ,dropped the speed to 60 mph and the temp dropped a little to 98 degrees c,
engine is air cooled with an oil cooler fitted, though its not the standard oil cooler, just a cheapish Chinese one
when i got home i inspected the plugs, and they are white on the tips, with a little blistering on nos 1 and 2

so i am thinking the engine is running quite a bit lean, and as it is happening a high throttle, i am assuming its not the mixture screws, i rebuilt the carbs on the project, but never checked the main needle groove setting, could it be the needles need lifting a notch?
bike has standard airbox and filter.
but exhaust is a 4 into one, with a custom made adapter , and a simple single muffler (with not a lot of baffeling)

anybody any ideas what would be the best way to diagnose/ cure this?
thanks for any help
ps colourtune is white /blue but plug starts smoking after a few secconds

 

Yep, defo lift the needle, two notches. Then you know what happens - more plug cuts. But, you'll need to do it whilst at load - ie, spot layby, switch off, coast to a halt, pull plugs.
Good luck

 

yep , thanks for replying, gonna give it a try this week hopefully

 

104C is nothing to worry about anyway. However, any mixture discrepancy should be addressed asap.

 

really, this is oil temperature i am measuring , its above boiling point of water, and theres blue smoke comming out of the engine breather, (i fitted a pod type breather on top of the clutch housing) ?

 

104C = 220F. For automobiles, I looked it up, 230F - 260F is the regular range for non synthetic oil. Is a motorcycle any different?

 

For Beetles and T2s they reckoned 120C was an upper limit. Oil temp generally lower in water cooled motors though.

 

wow, thats an eye-opener for me, never thought, motors would run ok at that temp. so maybe ,if i sort the mixture issue it will be ok?

 

Lubricating oils have a very high boiling point (somewhere around 300 degrees Celsius or 572 degrees Fahrenheit).

 

wow, so maybe i'm worrying over nothing, i dont have a oil temp gauge on my other 600 so i dont know what that runs at.
thanks

 

I would still check the needles mabe it is running a bit lean when you were on the motorway.

 

I agree that she’s just running a tad lean. Somewhere on YouTube there is video evidence that an XJ can be run without oil, while stationary, and at full throttle for half an hour before catching fire and finally seizing. It’s posted here somewhere too.

 

Yeah on theVW type2 bus forum - they often advise against fitting temp gauges as they cause so many panics.

 

yeh , my nephew is a VW fan, he says they call them "Worry Meters"

anyway today i removed the diaphragms and checked the needle positions, --they were all in grove 3
so i lifted them all up to grove 5, and went for a short run, around 20 miles ,at 70 to 80 mph on motorway.
and now thats more like it , temp didnt get above 100c, took outer 2 plugs out (1 and4) and they look a lot better (browner)

i came home through some heavy traffic, so not a proper plug chop, so i will get a few more miles on it and see how it goes.
the Haynes manual has some contradicting gobbledygook, about the needle positions.
take a look at the page, what do you make of it, it gives 2 different positions for no3


look at the line (needle clip position) for xj600??