News:

Main Menu

Screw head fouled, Carb of course

Started by RBFD415, September 23, 2016, 01:00:38 AM

Previous topic - Next topic

RBFD415

In disassembling the front carb (1982 Vision), the Phillips machine screw that holds the retaining clip on the needle valve seat is FUBAR (that's slag for MESSED up!). I looked at a couple of options- a screw extractor, the obvious choice or perhaps another- Super gluing a driver bit into the remains of the screw head. My thoughts are that this machine screw is going to be a major hassle to find a replacement if I damage it further. Anybody else experience this? Any thoughts on the best route? I'm thinking that replacing that seat (especially since I have a brand new one in the rebuild kit), is a no brainer. I've devoted a great deal of time into the cleaning of these 2 carbs and really want to have the best running bike I can with the time and money expended so far. The seat in there now is the original from 1982.

fret not

Brass or steel screws put into the "alloy" that makes the carb body can become a bit corroded and lock in place.  I'm not sure what the molecular process is but it can be a problem.  I have tried banging the screw with a hammer or punch to shock the threads, then applying WD40 or some thin penetrating lube like ATF, and twisting the screw out.  Sometimes drilling the center of the head so the head pops off, then gripping the remains of the screw shank with ViseGrip pliers.  If the worse comes to the worst the screw can be drilled out and the hole re tapped.  Fortunately that is not much of a precision or load bearing application, so a tiny bit off from center should not make a critical difference in function.  At least you have visible access to that screw.
Retired, on the downhill slide. . . . . . . . still feels like going uphill!

pinholenz

Nearly every time that I have messed up a small screw in the carb I have headed for a screw extractor only to find that the counterclockwise drill bit provided with the extractor actually removed the screw by itself.

My guess is that the heat from the drilling actually shakes corrosion loose.
Only one '82.5  eXtreme Zen 550

The Prophet of Doom

Are you using a JIS driver? Phillips drivers are incompatible with the screws on the vision and are a recipe for disaster.
If my normal JIS driver fails,  I use a Vessel Megadora 980 Impacta.  That's a 12 degree impact driver with a JIS tip.  There's just about nothing it won't remove, and I'll always go for that next, then vice grips, drilling and screw extractor as a last resort.


On very rare occasions (narrow shaft & good access) I will cut a slot with a dremmel and use a flat bladed screwdriver


If you won't (or can't) get a JIS driver, grind about 1mm off a Phillips so the driver fits better into the screw. It's not as good, but better than using Phillips drivers.    Also a little valve grinding paste on the tip can help stop it camming out of the screw and destroying it.








RBFD415

I'll have to pled guilty as charged, I most likely didn't use proper tip driver in the fastener! At the time I did it (last rebuild), none of the fasteners were stuck, none were stuck this time either, except of course this one. Since the head of this screw is pretty messed up, I'm thinking we're beyond just a case of trying the right screwdriver tip- but then again, who knows?

After many years of working on a varity of things, I've managed NOT to ever have a screw exactor set. I was looking for everybody's input before I picked up one. Do we know what that screw is, size and thread? I really don't even want to think about taping that screw hole out to different size!

That carb is done otherwise, I'm working on the other one now. I buttoned it up, but didn't do the final tightening of the carb top.

Rikugun

I think I'd try what pinholenz eluded to
QuoteMy guess is that the heat from the drilling actually shakes corrosion loose.
Why not try a little heat?
It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan

QBS

#6
My plan A in such cases(If the problem area provides enough access) is to very tightly grab the screw head 90 degrees from the screws' central axis with the smallest vise grip tool I've got and attempt  to break it loose.  All you need to hear is the initial "snap"  of the screw letting go.  After that you're home free.  The head will in all likelihood not break off of the screw shaft.  Even if it does you still take the carb top off and then use the same technique to remove the remaining exposed screw shaft.  If you don't have a very small vise grip buy one.  It is a wonderful option that will serve you well and often down the road.  It also takes up very little room in a road going tool kit. Upon reassembly do not tighten carb screws killer tight.  Just a little snug is all they need.  The next removal will be less problematic.

The above plan is my approach to removing any round head screw I'm not familiar with.  Break them loose with the vise grips and then finish removal with a screw driver..

If you don't have an impact driver study up on what it is and buy one.   It is my  desired approach to removing  the many round head screws found in the engines of bikes I have known.

Ron_McCoy

Whatever tool you use, put the carb body in a pan of boiling water before your removal attempt. The body will expand much more than the screw. On reassembly use a small dab of anti seize on the screw and don't over tighten it. Good luck!

QBS


pinholenz

Also, have a hunt around in your Yamaha supplied tool kit if you still have it. That flat head screwdriver shaft should pull out and have a JIS driver on the other end.

I got my #0 screw extractor and reverse drill as a set from an engineering tool supply specialist. A model engineering shop should have the same thing but may be a bit pricier.  Good luck. Let us know what works for you.
Only one '82.5  eXtreme Zen 550

RBFD415

I got the screw out and saved it intact! Will not waste space with the failed attempts. I ended up cutting a slice across the top of the screw with a Dermal type tool for a traditional blade style screwdriver. Added a few drops of Liquid Wrench. I made a quick jig out of wood to hold down the carb top body, I didn't feel that clamping it in a vice would be beneficial to the integrity of the body! I fasten the body to the jig with three- 3 inch long deck screws I had through the machine screw holes in the top. I chucked a blade tip in a little Makita impact wrench and it amazingly back right out with zero fuss! The prior attempt with heat didn't cut it, not that I discount the effect of using heat- it didn't seem to help with this.

I'm not selling Makita tools, but I have to confess that I picked up a package pair of a Makita cordless drill and impact driver a couple of years ago. I never would have picked up the impact driver alone, now that I've used it for so many projects, its just really an amazing product! Kudos to Makita, great stuff, quality tools!

I'm thinking a small dab of anti-seize would be in order on reassembly for this screw? Would you guys agree?

The Prophet of Doom

Quote from: RBFD415 on September 27, 2016, 11:25:58 PM
I ended up cutting a slice across the top of the screw with a Dermal type tool for a traditional blade style screwdriver.
Another score for advice from the Prophet


Quote from: RBFD415 on September 27, 2016, 11:25:58 PM
I'm thinking a small dab of anti-seize would be in order on reassembly for this screw? Would you guys agree?
I don't bother except for stainless bolts.  Can't hurt though unless you use the wrong sort.  Get one that specifies OK for Ally




Rikugun

QuoteAnother score for advice from the Prophet
Not to diminish your score card (Are we keeping score now BTW?) but the impact used might have been the key.  :)  Those impact drivers are very useful at times. Once I got one I found all kinds of uses for it.

Prophet, not knowing how to fix a flat in a tubeless tyre is worth -3 points so with the point earned here you're still down 2. Just sayin'.  ;D
It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan

RBFD415

The Makita made it feel like it was never stuck?! I think part of the key was preventing the carb top from twisting and resisting the force.

Rikugun

Quote from: RBFD415 on September 28, 2016, 09:46:42 AM
..... I think part of the key was preventing the carb top from twisting and resisting the force.
I agree, the energy has to be put into the fastener properly. I used one to remove panels on a plane during an inspection. The lightweight structure holding the panels would flex allowing the driver bit to lose contact with the screw head with each "hammer blow". It took stripping a couple of screw heads before I realized what was going on.
It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan