Stuck Mixture Screw ... but not like you're thinking

[desert_max]

Some intrepid forum watchers may remember my "resurrection" of a long-sleeping, one-owner '86 VMax this past February. After spending about a month tending carbs, clutch hydraulics, brakes, ignition issues, oil leaks and minor cosmetics, I put down almost 1000 joy-filled VMax miles until the clutch started going out. I hit a snag putting it back together (my own stupidity) and the Arizona Summer heat set in, so the bike has been waiting to come back to life.

A couple of weeks ago, I got the clutch sorted and, of course, after almost 4 months in the garage heat, there were issues on both left side carbs - even after treating the gas! Pulled them out, installed new pilot jets (and new mains while I was at it), re-installed and HAD THE SAME DANG ISSUE! Idle is poor, not hitting solidly on left side, but runs fine on the road after it gets up on the mains.

I went to do a shotgun (thinking there's a booger somewhere in the slow circuit), but one of the mixture screws will screw out, but will not blow out even with ~100psi. The other popped right out - as did all four back in February when I went through them last time.

Does anyone have a trick for getting a screw out that's off the threads, but just won't come out of the tunnel? I have stopped just short of trying some sort of "adhesive on a stick", but I cannot conceive of another way to get the blasted thing out.

Any ideas?

 

[sdt354]

Does any air blow past the needle, when giving an air blast from the top of the carb? Needle backed out of course.

 

[Parminio]

Have you tried taking some WD40, put the straw right up next to it and put a small shot on it, then screw it back in and out a couple times?

 

[Tom Determan]

This is a last resort approach I would use: The reverse helix easy out kits that screw into a drilled hole. Bottom it out and drill in 1/8 " or so, tap gently / install the extractor and screw it out. Before that I would try compressed air as you are, while turning the screw. Could you smear some epoxy with a toothpick along 1 side of the hole right up into the threads a tiny bit, start with a very thin layer and see if the adjuster will grab that epoxy and "thread" itself out ? Might need a couple layers before the screw can grab the glue. This one is easy to recover from with picks and a Dremel bit.

Or maybe just use the Dremel first and clean the hole ?

 

[desert_max]

Yeah, I filled the tunnel with WD-40, blew out the excess, ran the screw in and out a couple times. Still no joy. Couldn't tell how much air was getting through, but it was enough to produce a few micro bubbles from residual WD-40.

I walked away last weekend. But it sits out there. Mocking me.

 

[desert_max]

Hmm. More ideas. I am definitely not interested in drilling it out...yet. Definitely a last resort. Would be a shame to have to do that on a perfectly good mixture screw. Might try fiddling while blowing.

And a dab of epoxy was exactly what my next step was gonna be, I was just fishing for alternatives.

Thanks guys.

 

[MImax]

There has to be something blocking it from coming out, build up of corrosion or something? I just pulled mine out and there was some corrosion in one of them that made it harder to get out. Perhaps screw it in all the way and then feel with a pick or toothpick for any irregular area. May be able to then lightly scrape it off or use a small, hard plastic, bottle brush. Worth a look.

 

[Tom Determan]

Maybe WD 40 or any liquid from the bowl side would pressurize it better. The "feeds" are so tiny and leakage around the threads might allow air to bleed off too fast to build pressure on the screw. Any liquid might build more pressure.

 

[desert_max]

Great feedback! Really appreciate it guys. Will try and get out there tonight, but most likely it'll be Saturday before I could get back at it. Thanks for the chatter.

 

[Screwloose]

I took a hacksaw to the tunnel and removed it (the tunnel), exposing the top of the screw. It gave me enough screw top to grab it with fine pliers and slightly pull back as I turned it backwards (CCW). The screw then jammed which was good, then I put some heat on the casing and continued to draw it back with a screwdriver. At the end up you do not notice the removed tunnel when the carbs are back on. The cause of the whole scenario is that when I put Trigger (gen 1 Canadian ) on the side stand the tunnels on 3&4 carbs get some condensation now and then, this causes enough oxidisation over time to stop the screws from easily coming out. I.E. condensation rolls out 1&2 due to the angle of the bike on the side stand, but does not on 3&4. That’s my theory, but it was clear to me that 3&4 tunnels were more oxidised than 1&2.

 

[Radioguylogs]

I'm with Mlmax.

I'd screw it back in and try to clean the exit hole with a drill bit and a dental pick.

 

[sdt354]

A 1/4" drill bit will clean the tunnel out. I'd grind the point off the bit and make it flat. Seat the A/F screw then twist the drill bit in by hand.

 

[huw s]

I've very rarely had any succes with easy out's - I think the problem is they expand the screw as they grip it, and invariably come out alone....
However, having had this same issue on my 1200, and left well alone for the summer, I recently bought a full set on ebay, with carbs one and two ok, 3 and 4 seized, and partially drilled out screws.
So, I stripped the set with a view to using body 2 instead of 4 - they look identical, with the exception of a different throttle shaft and pressed in steel inlet tube. But before taking things further, I thought I'd have a look at the mixture screw. The PO had indeed drilled it, all the way down to the parallel bit where the spring sits. I managed to push the remains out! Then, thinking "this is easy" tried a new screw. No luck, the old screw head was still in there.
I tried hex heads etc, but nothing would turn it out, and I really didn't want to drill it and risk taking the thread out of the body. So I ground a flat bladed screwdriver so it fitted in the hole in the screw, and pressed and turned, expecting ot worst it would scrape the remains out. Well what do you know, out cane the remains, in one piece!
Success. Now I can swap bodies over. One question though, the colour of this set is different, they've turned a dark grey? Is this some cleaner someones used, or did the metal mix change at some point?
Edit to add - got my carb numbers wrong - of course I meant to say carbs one and four interchangeable..

 

[Tom Determan]

Nice to hear you got the mess cleaned up ! That's always a relief.

I suggested the reverse helix easy out and I agree 100 % with "rare success". A really stubborn thread needs a really good bite which can cause expansion in a thin wall situation and then it just feeds on itself. Those easy outs work OK when there's plenty of wall remaining to prevent this expansion. If you try and "cheat" and use a smaller easy out, they can break off and then the mess is compounded. It's definitely a balancing act that needs the right amount of luck thrown in. I wouldn't expect a pilot screw to need much more than a tiny extra bit of torque to come out.

 

[desert_max]

But that's what's so frustrating about my condition, and what the title alludes to. FIrst of all, I did not get a chance to get into the shop today. I'm extremely aggravated by that, but a man has to do what a man has to do when the wife has needs...Horticultual needs.

But my screw is not stuck IN the threads it's stuck after it comes OUT of threads in the tunnel. I have gotten a number of very good suggestions here and I will report back after I djg into it...literally.

 

[02GF74]

M

There has to be something blocking it from coming out, build up of corrosion or something?

I would guess it is distortion of the screw driver slot, even if it is, doesn't really help getting it out. Only way I can think of is using grease or oil pumped in from the other side.

Does tapping the carb body move the jet any way?

 

[huw s]

Some intrepid forum watchers may remember my "resurrection" of a long-sleeping, one-owner '86 VMax this past February. After spending about a month tending carbs, clutch hydraulics, brakes, ignition issues, oil leaks and minor cosmetics, I put down almost 1000 joy-filled VMax miles until the clutch started going out. I hit a snag putting it back together (my own stupidity) and the Arizona Summer heat set in, so the bike has been waiting to come back to life.

A couple of weeks ago, I got the clutch sorted and, of course, after almost 4 months in the garage heat, there were issues on both left side carbs - even after treating the gas! Pulled them out, installed new pilot jets (and new mains while I was at it), re-installed and HAD THE SAME DANG ISSUE! Idle is poor, not hitting solidly on left side, but runs fine on the road after it gets up on the mains.

I went to do a shotgun (thinking there's a booger somewhere in the slow circuit), but one of the mixture screws will screw out, but will not blow out even with ~100psi. The other popped right out - as did all four back in February when I went through them last time.

Does anyone have a trick for getting a screw out that's off the threads, but just won't come out of the tunnel? I have stopped just short of trying some sort of "adhesive on a stick", but I cannot conceive of another way to get the blasted thing out.

Any ideas?

I just re-read this. You can use .8mm mig wire to carefully push the screw out. I managed to get the remains of both the drilled out screws on my set out this way.
Good thing you haven't drilled it!

 

[[email protected]]

https://www.kleintools.com/catalog/screwdriver-sets/screwdriver-set-slotted-screw-holding-3-piece
I use these at work for holding screws in tight spots. Not sure if they'd grip enough to actually pull out a stuck screw but they do grip well enough to install a screw in some really awkward spots

 

[sdt354]

M
I would guess it is distortion of the screw driver slot, even if it is, doesn't really help getting it out. Only way I can think of is using grease or oil pumped in from the other side.

Does tapping the carb body move the jet any way?

A blast of air down air jet on top of the carb, should send the needle across the garage. It's got to be crud in the tunell.

 

[desert_max]

Well guys, I feel compelled to at least provide an excuse for the delay in getting back to this thing. The deal is, my wife has at least as many gardening projects simultaneously underway as I do motorcycles in the shop. No joke. I had horticultural obligations.

Anyway, got back after this thing today. Turns out the mixture screw was not really stuck in the tunnel. The problem is (yes still is) that there’s an obstruction behind the screw that won’t allow air to push it out. I have plenty of flow between pilot air jets one and two, but neither of them pass air through the idle mixture screw port. I ended up pushing the screw out from inside the carb barrel. It actually easily pushed right out with a stiff piece of wire.

I no longer have an ultrasonic cleaner. But, I’m not even sure that’ll clear this obstruction. I have forced copious amounts of carburetor cleaner both ways through that darn thing followed by 100 psi pushing carb cleaner in my face, clothing and everywhere else...except where it will break down whatever is eating my lunch. And so the obstruction is still there.

Is my only recourse a serious ultrasonic treatment? Does anybody have a roadmap of these passageways and/or know whether I can pass that same wire in just the right direction? I’m probably going to try it anyway, but the last thing I need is to break the darn thing off inside the carb body somewhere.