xj750 Mixture Port Cleaning

The 'Sacristy' in the Church of Clean....Mixture Ports( engine side):
Multi Screwdriver
1/32" dremel bit
1/8" bit
pic tool 6-8" long
Carb spray
Compressed air, small nozzle
New O-Rings from XJ here
Head mounted flashlight
Lamp
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A 1/32" dremel drill bit is Exactly the right diameter tool to clean these 4 ports, with room to spare.
Remove the brass or rubber plugs if present. 3 of my brass plugs were gone, per prior service, so I carefully drilled #4 out. A 1/8" bit works, somewhere around 3/16" depth you will stop, keep cking so you dont blow thru the screwhead below. Plug comes out easy by reversing the drill. Vacuum your shavings, they go everywhere. Backout and remove the 4 screws. Using a pick tool,pull spring, washer, and o-ring, wear rubber gloves to help catch stuff. These tiny parts tend to want to fling far far away. I also found my original springs were better quality( firmer) than the lame new ones, so I re-used. Now look down those ports, the lamp light from inside the carbs will be visible( or not). Go outside, blast each with carb cleaner, check again. Actually outside daylight is best place see if you cleard the debris. If you see 4 clear 1/32 round holes, and seat is clear of all old debris, nearly done. Go back to bench and softly ream or drop the 1/32" dremel bit into the port, using 2 hands( one finger in carb(catch)), and other to gently move bit up and down thru hole to clear any deposits. Blast again outside with cleaner. Blast carb too. Allow cleaner to evap. A drop of Marv mystry on the screw, dab of silicone on o-ring, and put it back together(o-ring, washer,spring, screw). Soft seat, then back out 2.5-2.75 turns. Done.

 

you can also spray down through the air jet hole in the topside of the carbs(under diaphragm) and up through where the pilot jets screws into body. they are all connected.

you can block off the many holes to increase flow through each hole.

look at this link to see how the holes connect for each circuit in the carbs
http://www.xj4ever.com/inside your carbs.pdf


the mikuni photos show a good photo of the mixture screw and how it works

 

Putting a steel cutting tool (even the dull part) into an aluminum port is bad practice, but is ok to do if one takes great care.
Often it's completely unnecessary though. A good soak in Berryman's and all the ports will be clean (even the enrichment jet in the float bowl).

 

I agree...that's why I highlight NO reaming, (dont put the bit on a drill), but use to gently push out the debris... 3 of mine were clogged to some degree.

 

Yes, this I did first when I removed the cover and air jets. You see, I was considering 'not' removing the mixture screws.....tsk tsk. Glad I did. I also had trouble breaking the carbs apart, the rack scews were frozen. This time put a fresh drill batt in, and got the rack off and broke everything down. Can I leave the confessional now...?

 

No, tell us more!

 

The rack screws were originally assembled with thread-locker. If re-assembling, either skip using it or use the low-strength (purple) locking fluid.

 

was ckg operation, and noticed the choke switch on the handle bar seemed to spring back to open, instead of staying closed?? I did lube the cable, mistake? hmmm

 

The cable should be lubed.
Is the screw for the choke handle tight? Is the spring washer there?
Is the cable adjusted for proper throw at the carb bracket?

 

your open and close are mixed up, they all tend to close by themself, they cant open themself

 

Engaging the thumb switch moves the plungers up, but its like they spring back.

 

The plungers have springs on them that push them closed. The thumb lever has a spring washer that resists the pull of the plunger springs. If the screw is loose, or the spring washer is weak/missing, then the plungers will close.

 

Good call, I will ck em.