Stuck Fuel Mixture Screw

Hi All,

I have an interesting problem. The fuel air mixture screw on one of the carbs is stuck and will not move. I know its brass and I've been trying hard not to wrench on it too much for fear of breaking it, but It will not budge. I need Help.

A little background:
The bike is a 1983 XJ750 Maxim, possibly a midnight according to someone reading the engine seriel number. I obtained this bike for a case of beer (cheap beer 8) ) in non working order. It had been disassembled 2 years ago in order to replace valve seals according to the previous owner, and in the process of re-assembly nothing got put back together and parts got lost. I pieced the bike back together with what parts I had for it, and others found at a local bone yard. Without doing any work to the carbs I tested the ignition. It will start and run with a shot of starter fluid but only at high RPMs and will stall out within about 1 minute. It wont start with the choke.

I decided to pull the carbs and with the help of my haynes manual clean and check everything. In the process of doing so I came across the previously mentioned problem of the stuck fuel mixture screw.

Any advice/suggestions would be greatly appreciated.

 

Best deal ever...case of cheap beer for a beautiful and somewhat rare bike

I'd take the carbs apart as much as possible, aside from that screw obviously, fill a small bucket or coffee can with penetrating fluid and submerge the end with the screw....unless its in the middle, then dunk the whole thing.

I'm sure someone will have an easier method but thats the first thing that came to mind.

Finding a replacement and gently drilling it out might work too.

 

I would use a tight fitting (reads: correct sized) screwdriver and, here is the tricky part so proceed carefully, tap the top of the screwdriver once. Test the screw. If it does not turn, repeat with a little more hummph. If no luck then, odds are good the o-rings on the screw is adheared to the seat and screw and the only no-destructive removal I know of is to immerse the carb (sans all other rubber parts) into a solvent to soften the rubber. All I've got I'm afraid. Anyone else got any successful tricks?

 

http://xjbikes.com/Web_Links/l_op=visit/lid=2.html

You might try this mailing list, and check the archives. Someone there just recently had the same problem.
Good bunch of folks there too. Several from this site.

 

Thanks for the tips everyone,

I tried them all, and ended up resorting to the purely destuctive means of removing it. My Next question is, Where do I get a replacement? I've looked all over the internet, and called all the local shops and I can't find one at all. I'm in the process of trying to find someone to sell me a single carb and not the whole set of 4. hoping to get the part I need and having backup parts in case I mess something elses up.

Its all out, and I don't seam to have messed up the threading inside the carb body but would like to chase them with a tap just to make sure. The obvious question is, does anyone happen to know what that thread might be?

 

I've got a set of carbs im watching on ebay, hoping to get it cheap just to use for self-educational purposes.

I'd hit ebay, might have some luck. If I do win those carbs and your still looking for one at the time I wouldn't mind sending you one being as I don't plan on actually installing them in anything.

 

http://cgi.ebay.com/ebaymotors/ws/eBayI ... AMEWA%3AIT

If your want to keep an eye on em and bid

 

proe1717
If I were you I'd strip that carb body and get some of that soak carb cleaner that comes in the gallon can that looks like a paint can with a screen basket in it.
Then I'd soak the part of that carb body in the solvent (being careful not to get the solvent into the seals on the throttle shafts) for about a day or so and then try to get that needle out.
If that doesnt work, someone might have stripped it in!!?? Yopu might have to heat that body with a heat gun, trying not to heat the screw as well so that the body will expand where the screw is a nd release it.
Also try not to heat the body too hot around the throttle shaft seals.
Best of luck on this one
Mike

 

Go buy one of those "pencil-flame" butane lighters that were invented to make smoking crack without blistering your thumb possible.

Fill the little "well" above the pilot mixture screw with a few drops of -- OLIVE OIL -- (a non-petroleum + won't readily flame + will get hot) non-synthetic, all natural lubricant.

Heat the little well with the bright blue flame of the lighter that won't blister your finger. When the oil gets hot enough to cook French Fries ... stick a pair of Q-Tips in there and sop-up the hot oil ... leaving any that the Q-Tips don't soak-up.

Using a screwdriver which you have fabricated to a) fit the well and, b) fit the slot on the pilot screw with such precision that there is ZERO end play ... and will apply force to the screw slot ... such that the force will NOT cause the uppermost portion of the pilot screw to have any area -- what-so-ever -- where it will move without the entire mass of the screw moving with it ...

TURN THE SCREW -- IN / DOWN -- (Yes, in ... NOT out!)

Apply initial torque to the pilot screw ... then, with a sudden increase in torque ... attempt to nudge the screw ... IN, IN, IN ... NOT out!

If it loosens and starts to go in ... turn it in -- gently (watchmaker gently) until the screw "Bottoms-Out"

Hit the pilot well with a spray of carb cleaner -- after it cools down so that the spray of the carb cleaner will not ignite causing the spray can to explode and ruin your day!

Fill well with the lightest lubricant you can buy -- (sewing machine oil).

Exercise -- up / down -- the screw until it can be withdrawn up finding well lubricated threading to follow.

If this doesn't work. Drill!

Drill a hole into the SIDE of the well wall -- 3 mm below the top of the pilot screw. A very small hole -- about the size of the head of a pin ... you may have to go to a hardware store and buy a "Number Drill" to do this.

You drill through the aluminum wall and ever-so-slightly into the threads of the brass of the pilot screw. Wrap the tip of the drill with masking tape so it will not penetrate deeply into the soft brass. Use the top of the well to set the drill depth.

Oil. Lighter.

That should do the trick. If it don't ... we're on to more drastic measures.

Drilling the little motor-scooter out without wrecking the threads on the pilot screw well wall.

Good luck ... the Topside Olive Oil treatment usually works.
Phase two almost always works.
Phase three always works ... but, leaves you short a pilot screw.

 

I have heard that pilot screws are unobtanium and you must salvage them from a donor carb. Rick, I'm intriged with your knowledge! I really must get you to write your memoirs!

 

Rick sure knows his stuff!
I would caution about bottoming ou the needle screw as if it is tight you could damage it, if you bottom it out too hard.

 

I managed to get all the brass parts out but seam to have messed up the threads in the process. So I have to buy the carb that i messed up to replace it.

I actually found a guy online that was willing to sell me the single carb, not just the set of 4. The website is www.vtcycle.com He has 2 XJ's listed that are almost complete that he is willing to sell parts from. an 1982 XJ 650 and an 1981 XJ750. His prices are very reasonable. The single carb is $25 with shipping in the US. I haven't gone through the whole sale process yet so I will keep everyone posted on that. So far it seams like a good place to deal with.

 

I would highly recommend the purchase of the entire bank. Much easier to fix up and you have lots of spare parts which, at this point, seems to be where you are headed. You may find that fixing up another bank will be easier than trying to salvage your own. Best of luck to you amigo. Please post your dealings with this yard on the Shop Review board, it may help a few other members!

 

Sounds like a fair shake!?
Good Luck

 

I just contacted the gent at that link about some parts, what a friendly guy!

He sold his side covers for 25$ !!!


The man was sitting on an ebay goldmine!