recent purchase '82 RJ SECA idling high rpm when warm

UPDATE

 

If you can get a nice deep blue at 3 turns out and an 1100 rpm idle with everything sync'ed up at that setting, leave it. "Read" the plugs after a couple hundred miles.

Here's something that might help in any further troubleshooting: http://www.xj4ever.com/inside%20your%20carbs.pdf

 

Is it carb pilot air jet, OR cam chain loose??!!

Just bought, and installed new, used, #4 carb body from Len.
Re set the float level on #4 also....

Can get equal sync, across all four dials on vac syncroniser, but still cant get below 1400, at temp, idle....unless I 'lean' the #4 pilot fuel system, OR, set vacuum dials on 3 & 4, slightly lower that 1 & 2. - namely 1 and 2 at '10', and 3 and 4, at '7' - Get nice 1050-1100 idle then.

THERE ARE NO VACUUM LEAKS ANYWHERE!
.
Turn #4 pilot down to 'very lean', and nice 1050 idle again...

This is indicating that too much air is still being metered in to the mixture, on #4, at any given pilot fuel screw setting....?....cos when I turn the pilot screw 'out', to richen the mixture, it will only richen to a mid-light blue, (on the colortune), and the idle rises to 1400 (when perfect sync across all 4 dials), and will not richen any more, (and the rpm doesnt rise any more either) to the yellow (which is supposed to do when over-rich?), even advancing to all the way out.
There should be no issue with pilot fuel supply now because of new, clean, used carb body, and pilot fuel jet.

I looked at pilot air jet, and a micro sized bit of wear, - COULD THIS TINY ABBERATION CHANGE THE METERING OF AIR LARGE ENOUGH TO BE CAUSE OF INABLILITY TO PROPER TUNE #4 cylinder, and send idle +200-300rpm, unless I 'lean' it out???!!, or have less pressure on 3 and 4 carbs, than 1 and 2, at vac sync.

Set vac sync to #s 1 and 2, at #10 on dials, and #s 3 and 4, at #7.5, on the dials, and nice 1050 idle again, with 'mid blue', color on #4 colourtune plug (all others adjusted nice also)

Ive noticed its just the #4 valve/carb again, obviously....

I CAN HEAR SOME CAMCHAIN RATTLE, WHEN ENGINE IS IDLING

Says in Haynes, that mine (RJ), is manually adjusted cam-chain tensioner, and this should be tightened every 10,000 miles, if necessary, and 'noise is heard' - "the valve timing accuracy will be lost", and "the engine cannot run properly, if there is excessive play in the camshaft drive"......

I have no idea when the camchain, was last adjusted/tightened, (this is +30,000 miles old) and it is slighty (?) loose, and that is why I am having problems adjusting to a proper colour/pressure, whatever on the #4 cylinder/carb....?

Perhaps because of 'fluctuating' pressure..from #4 valve (it does 'surge', VERY slightly, every few seconds), and its at the loose (or tighter) end of the chain, when running, is 'upping' the pressure, firing at a slightly higher rate, and also raising the rpms, on that valve....?

I think I should tighten the cam chain, as described in Haynes...and re-sync ...and if that does not cure it, change the pilot air jet....?

:?: Anyone agree with my hypothesis.....?....PLEASE! SOMEONE??!!

Regs. :?:

 

RESEND

 

*************LATEST***********************

Just carried out procedure to tighten the camchain, and sounds quieter when idling - or is that just psychological.....? :?

Idling nice anyway, at temperature, but not checked color on #4 yet.....

:roll: Also, read in a thread, that use 25% less fuel if upgrade to 'bladed' fuse box, from the stock tubular glass one....any truth in that......??

 

fuel consumption due to JUST the fusebox upgrade, highly doubtful.