I have an O.S. .25LA RC engine I got used.  I have a C/L venturi and NVA to go in it, but the screws holding the carb in are stripped. apparently the previous owner used the wrong screwdriver to try and remove the screws, and now they're stripped beyond hope.  What would be the best way to remove the screws without filling the case with metal filings?

Remove  the backplate, and  drill the screw heads with a , just under 3mm  drill bit dead center, or if you have a mill  use it
If you get metal in it you can use air to blow it out, then clean it with  something like  WD40  or  brake clean.  If you like you can fill the crank port and  bottom case with a  paper towel.
The other thing you could try is  to take a dremel  thin cut off wheel, and  cut a  slot across  the  bolt head, heat the  head  with a solder gun, then try to  remove with screw driver.  I would much prefer  the heat and try the screwdriver after slotting

Randy

What Randy said, use a dremel cut off wheel and slot it ,then heat it ,.if it has lock tite a slight tap on it first will help

I have that problem every time I buy an old OS.

Heat.  WD-40.  Cutting a slot in the bolt-head.  Bigger Vise Grips.

When I buy a new OS, I promptly replace all the bolts with metric Allen heads.

    Get real screwdrivers, and they will work better than Allen wrenches.

https://www.amazon.com/Hozan-JIS-4-JIS-Screwdriver-3rd/dp/B00A7WAHTU/ref=sr_1_1?ie=UTF8&qid=1513299538&sr=8-1&keywords=hozan+screwdriver


     Brett

Brett is  correct   you need  JIS  screw drivers,  however  many times this will not help  as  on used ones,  the  heads  are already  mangled,  I get them all  the time in my shop

Randy

Chris, I’ve never had much luck with the needle nose vice grips in the past.  I was trying to avoid that.  I’ll put that in the “possibly’ column.

Rich, I don’t have an easy-out that small, unfortunately…

Randy, Bob, and Paul.  I’ll try a Dremel to cut the slot and a torch to heat it up before trying a flat blade screwdriver.  I’m assuming a heat gun will not give me enough heat for this evolution.

Brett, I have that exact set of JIS screwdrivers.  The previous owner stripped out the screws, not Moi.  But I’m stuck trying to fix his error.

Mark

Mark   I would use a  solder iron before a torch,  let it get hot first then put it on the  head of the screw

Randy

Sometimes using exactly the right screwdriver, and pushing hard into the screw as you try to unscrew it, will work.

If not -- what everyone else said.

Impact driver after heating area and applying penetrating oil. Tap lightly. Support opposite side of Venturi. If you happen to have an impact driver or know someone who digs 70s era Japanese bikes.


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impact of any kind is way over kill. a lite tap with a small peen hammer is all that is needed

My real ' Vice Grip ' vice grips  have a SERRATED tip to the JAW , so weeny screws such as those ( Though youll mark the case as they swing / rotate , unless you mask it ).

These Suckers will GRIP the screw head on the nasty little loctited os 25 cases , whereas a plain end ' copy ' will just screw and skew off .

So , shopping for Vice Grips , check theyve got the serrated jaw ends , for such finery as the carb screws .

Putting the case , supported by a bearer offcut / on a solid bench , and leaning on a correct fit screwdriver , is the first option .

Seem s to be some clear locking compound on the LA 25 ones .

Don't hit the impact driver hard. Give it a tap. After backing up opposite side of Venturi. The small screws are not used when engine is converted to CL. Yes heat and use penetrating oil first. Phillips drivers are useful on stripped Japanese Standard screw heads. Wider points sometimes get a grip on stripped screws. I've used a twist push driver successfully on the screws. Don't know if they're made anymore. Recently I used one like a low impact impact driver on a stubborn screw. Banged on the top of the grip same as an impact driver. It worked. Careful. Be careful. Venturi might crack.


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this is a bleedy impact driver . !





Though theres prettier / dandier ones these days , of course . and probably always was . At a price . Nowadays being made in china . . . .

Cheap & nasty ones have a fair bit of SLACK . Require pre loading in required direction . Or just cuts across the slack . Need bits that fit the screw , too .

A Sort Tap with a Large Clout seems preferable to a hard light thing ?? .
Really needs ' job ' suporting under at impact point .
Which describes the risk of flattening it . 

Vice Grips I used ' end on ' perpendicular . 1/2 ? in. jaw . ( Handle rotated / in line with screw axis ) as qweeney little screw things .
The real vice grips are invaluable for ' one piece stuck '  as our forign freins say .  [/img]

Dennis, are you talking about this type of screwdriver?  I have had one forever, but have never used it since I first got it.

   No, and those are of little utility. What Dennis is referring to is this:

https://www.amazon.com/TEKTON-2905-8-Inch-Manual-7-Piece/dp/B000NPPATS/ref=sr_1_3?ie=UTF8&qid=1514388020&sr=8-3&keywords=hammer+impact+driver

     Which is also of little/no utility in removing screws from model engines. You don't want to use a hammer on any model engine. Get a proper JIS screwdriver like this one:

https://www.centralhobbies.com/prod_detail.php?cat=14&subcat=95&id=1726

    and stop screwing around with "workarounds". And in fact, once you strip the head with a Craftsman or similar, these frequently WILL still remove it, because the Phillips-head will damage the center of the "cross", and a proper screwdriver will engage the entire slot to the edge - where it requires both less force, and has not been stripped off.

    The "impact driver" approach is the crude way to attempt to use improper Phillip's-head drivers on Japanese motorcycles. It's not necessary in that case, either, but if all you have is conventional Phillips, it will sometimes work - and frequently, strip it out in a tiny fraction of the time it took to strip it by hand.  I cannot find any place to get JIS bits for such a driver, so the solution in that case is ALSO to get proper screwdrivers as reviewed here:

https://www.webbikeworld.com/vessel-jis-screwdrivers-review/

  Of course, you can grind a conventional Phillips to get the right shape, if you know what your are doing. The angle needs to he slightly shallower and the point needs to get knocked off, and all the edges should be straight and sharp.

    With proper screwdrivers, JIS cross-head  fasteners are superior in most ways to Allen heads - they certainly have less tendency to strip out because the local forces on the parts that meet are much lower. The only advantage to the Allen screws is you can get them in higher grades, and are almost universally available in the sizes you need. There is no issue removing the screw holding on OS carburetors, I have done it many times, it just comes right out with a "pop" when the Loctite or whatever lets go.

 Additionally, people tend to use a driver that is too small. The biggest one that fits is the right one, and it usually looks absurdly oversize. Too small, and it will strip out anyway.

     JIS drivers tend to work well on regular Phillips because it engages the outer edges of the slots,  but not the other way around. The Phillips drivers tend to bottom out on the JIS screws, leaving it only touching the inner corners of the "cross".

  Note also that JIS screws are identified with a little dimple on the head, telling you not to use a Phillips driver.
   
    Brett

It was common to buy a hex head replacement screw and bolt kit for most jap bikes as we ALL commonly stripped out each and every "Phillips" screw with our USA Phillips #2 or #3 driver...

NONE of us having and internet and KNOWING that Japanese Industrial Standard (JIS) was different...we just cursed the stupid Japs for using soft steel screws and happily slammed a hammer to the fact for the impact driver to get rid of the inferior Jap Junk

   Same here. the Suzuki shop I worked at (and later raced for) use the same "impact driver and a 5-lb sledge" approach.  We knew the things didn't fit properly but not why, and assumed they were just too soft.  Towards the end of my motorcycle tenure I saw some Yamaha factory mechanics popping them on and off with great ease, so I asked them how, so I worked up the courage to go over and ask, and they said "they aren't Phillips, and you can't get these screwdrivers in the US, go grind a Phillips like this (and held it up). Sure enough, after a few tries we got something that worked. BTW, I think we found that the giant Craftsman #4, reground, fit the case screws on the Suzuki GT series very nicely.

    The most interesting point was that they were still using the JIS cross-head screws on the Yamaha factory bikes, at least for the low-stress applications like engine side covers. They could certainly *afford* Allen head screws.

     Brett

   

    The most interesting point was that they were still using the JIS cross-head screws on the Yamaha factory bikes, at least for the low-stress applications like engine side covers. They could certainly *afford* Allen head screws.

     Brett

That's definitely interesting.
I have seen a lot of "philips head with dots" on Japanese electronics from Furuno in the last couple decades at work.
I always thought the dot was indicated that machine threads were under the head, not sheet metal threads, but am happy to know the real meaning. 

Hi depending on the design and size of the head sometimes you can slot them with a dremel or hack saw. If there is not enough room to do this can you get a replacement head as the next measure will probably damage it if you drill out the tops of the screws then remove the remains of the screws if enough protrudes with vice grips. Another way if you are very good with a mig welder with fine wire is to weld a screw driver to the head of the screw. The heat of doing this helps removal. Good luck Regards  Gerald 

I don't mean to flog a dead horse, but very frequently, you can strip the head out with a Phillips driver, and then still get it out with a proper screwdriver, because proper screwdriver engages the ends of the slots the Phillips driver can't reach.

Dead or not, the horse deserves another thwack.  I've done this, too, more than once, with good success.  But only, only, only if you use the proper screwdriver.