XJ 700 Carbs

Now we have eventaully ironed all the bugs out of this machine....Well we haven't actually...

The adjusting screw that covers idle on on the carb that feeds no1 cylinder will not move ......it's stuck....we've tried everything...... no joy.

You can hear the motor dragging on tick over.....We've squirted cold water on the exhaust headers from a washing up bottle.....it evaporates almost instantly on cylinders 2,3,4. No 1 cylinder, it dissapates slowly.

If you open the throttle and get the revs up to 3000 rpm. The engine smooths out and water evaporates on all the exhaust headers instantly.

Doesn't look as though it's running at all on tickover on No 1 cyl.

As we cannot move the idle mixture screw adjusting screw it looks like new carbs........as xj700 are as rare as rocking horse doodah over.....does anyone know if a set of prediversion xj 600 would be any good.....We'd have to change jets needles etc but are the chokes the same size.

 

belay that .....I'm tired so garbage cometh forth......... it's the air adjusting screw thats locked

 

Use PB Blaster or something and soak it upsidedown overnight. Then, using a heat gun, heat up around the screw, screw, carefully, cause there IS a little O ring in there that might melt. Get your screw driver, pres down REALLY hard, and turn.
If that doesnt work use a drill and a small reverse drill bit and drill into the brass a little ways. Make the hole big enough for your smallest stud extractor. Hammer it in, turn it out.
If that doesnt work, drill it all the way out, careful not to hit the threads on either side, or you'll have to re-tap it.
then clean it out really really good
-Chris

 

use Kroil http://www.kanolabs.com/

you DO NOT want to brake those tabs or try to extract it. they are REALLY SOFT BRASS.

Trust me.... I already made this mistake.... you DO NOT want to go there....

 

How did you extract the idle mixture screw once you buggered up the threads? Because i did it too, lol...

 

I also have this problem, although I was lucky enough to stumble across a replacement set of carbs so I just swapped in a new carb.
Bad advice trying to use a screw extractor as that was my first inclination, all it did was shred the brass and dig into the threads of the carb itself. I have heard that letting a little nitric acid will slowly dissolve the brass and not hurt the alum, then you would need to either run a thread cleaning tap down the bore or drill and re-tap and have a new air mix screw custom made for you. The nitric acid thing is on my to-do list once I get several other projects off my plate and want to rebuild a spare set of carbs for sh!ts and grins.

 

yea i tried using an extractor and it did exactly what you said. Luckily for me i messed up the top of the brass when it was at 2.5 turns out (factory settings) so it's kind of ok (it does need a minor tuning) and that's why i still want to replace it. i just have to figure out how to get it out! (Len has the pilot air mixture screw 'fine thread' for $16), so i have half of the equation figured out. Let me know if your nitric acid job works!