Best order of operations for sorting out carbs/idle

Hey all,

Looking for some wisdom here as I delve into the dark arts of carbs/mixture settings/poor idling. It's worth noting I've never played with this stuff before, so I'm learning as I go.

Let's lay it all out there. I have an XJ650 (Engine/frame number 14R-000219, which I believe make it an XJ650RJ Seca from Oceania. I live in New Zealand).

I've recently sorted the valve clearances and given the carbs a clean to the point that i'm confident that the pilot and main jets are clear. (I have not gone to the Church of Clean, yet). I did note that the main jets were stock at 110, but the pilot jets were 43's, so slightly above stock (I think?). The pilot mixture screw looks to have also been tinkered with, as the tab of protection is violated.

The PO has put an aftermarket muffler on it (I don't know if the exhaust itself is stock) and it has the stock airbox.

What I'm finding is that I'm fouling up plugs on cylinder 1 and 2, and it simply won't idle, with them getting wet pretty quick, and cylinders 3 and 4 get black and sooty, which both sound like a rich situation. I suppose I'm just wondering the correct order of things to get everything straightened out? Do I start with a full carb rebuld, replacing the jets back to stock? Or do I leave them be, with the 43's, given the aftermarket muffler? Do I start with checking the coil resistance, or do I mess around with the mixture screws first?

The bike is a learning project, so I'm more than happy to do any work required, I'm just not sure of the most sensible order to get things sorted without wasting time on dead ends etc.

I hope that paints enough of a picture. Thank you in advance if you can help out!

 

You said you did valve clearances---- just verify that you used the correct chart.....
.11-.15mm for intake
.16-.20mm for exhaust

Carbs---a total teardown/clean/rebuild is the way to go. Otherwise you risk going in circles to you finally end up doing that anyway.

That said, if you need to do just basic stuff first.

Put in a new set of plugs

clean the bowl and enricher well sobthat you can spray cleaner through the well jet. If that is clogged, that carb wont fire up very easily. (Do all four)

Reset all 4 mixture screws to 2.5 turns out, and re-colortune and re-sync. You may have gotten things a bit out of whack.

Find out if you have a vacuum leak or not at the throttle shaft seals

If you have to go farther, check your wet float levels

Check those things, then we'll go from there

 

Awesome, thanks so much for that, hogfiddles.

I've started by double checking the valve clearances after my first attempt, and a couple of them do need further tweaking. I've ordered new shims this morning to clear that up and bring them into the specs you've provided.

Once that's done I'll move on to the new plugs and enricher jets - which I believe are the "permanent" jets that stick right down into nearly the base of the bowls? Is that correct?

Colortune plugs are proving impossible to find here in NZ, so I'll need to look at ordering one from overseas (The story of my life, living all the way down here).

Is there a way to test the throttle shaft seals without tearing the carbs down?

Will keep ya'll posted as I dig into this. Really appreciate the help.

 

Jets in bottom of wells-- yes, those must be clear

Seals-- test by spraying propane, ether, carb cleaner, etc near the t-shaft seals. A vacuum leak will be evident by an increase in rpms.

 

http://xjbikes.wikidot.com/carb-specs
you need to look at all the jets and needles
the 650 has a few different jet specs around the world the pilot air jet and main jet needle also changes sizes
jet specs
Years & Models: 1982 XJ650 14R models (UK/Europe)
Carb Manufacturer: Hitachi
Carb Series: HSC32
Carb Model ID: 5N900
Main FUEL Jet Size: #112
Pilot FUEL Jet Size: #43
Main AIR Jet Size: #50
Pilot AIR Jet Size: #225
AIR COMPENSATOR Jet Size: unknown
Starter FUEL Jet Size: #40 (non-replaceable, in float bowl)
Main jet NEEDLE ID: #Y-10
Main needle JET Size: #3.2mm (the main needle JET is also known as the "power valve" or "emulsion tube").
Fuel Level in float bowls: 3mm +/- 1mm (.118" +/- .039")
Idle RPM's: 1,050 rpms