I am amazed that something every beginning mechanic knows is lost on those who consider themselves smarter. Some people "diss" the Phillips screws found on Hondas, calling them ridiculous and proposing socket head ("Allen") screws as superior replacements and insisting that these screws by design tear up in use. These folks have never learned the correct technique for working with Phillips screws. Properly handled, Phillips screws outlast the engines and carburetors they're fitted to. Consider the following.

1. Part of the beauty of vintage Honda assemblies is their original Phillips screws. They came that way, they look correct that way, they are beautiful. Allen screws by contrast to me look foreign, like an unecessary and inappropriate modification. Just my opinion, naturally. And I'm very aware some manufacturers used them at the factory.

2. The Phillips screws in vintage Honda engine covers are meant to be installed and removed using very light-duty cordless impacts. Special T-handled screwdrivers were specified by Honda, but today this parses out to the nutrunner, i.e. low-powered impact.

3. The most common mistake people make in regard to Phillips screws is they choose the wrong screwdriver. Wrong because its size is inappropriate, wrong because its quality is poor, and wrong because a hand-held screwdriver is the incorrect tool for engine cover screws.

4. Among all the other misinformation found online, some folks are very vocal in insisting that JIS Phillips screwdrivers are mandatory for use on Honda's Phillips screws. This is not completely correct because it overlooks the fact that every career Honda mechanic has known for generations: proper-fitting screwdrivers were available and were used by Honda dealer techs long before JIS became known. Honda never characterized their factory tools as JIS. Snap-On never did either. Nor did SK, Proto, Mac, Husky or any of the others who sold (and in most cases still sell) proper fitting, high quality Phillips screwdrivers. It isn't only the JIS spec that works best on Honda Phillips screws. Any high quality Phillips screwdriver is equal, whether called JIS or not.

5. Something else career Honda techs know is that Honda case screws that have been undisturbed for a long time should be "shocked" before removal. This simply means hitting them square on their heads with a large diameter straight punch and a hamner. A couple smart hits and you'll be surprised at how readily the screw comes out.

6. One of the most harmful pieces of advice found online is that of the use of hand impacts. It might seem a hand impact would double as shocker and impact at the same time. Unfortunately, it's not so. Even in experienced hands, the hand impact is a deadly piece of equipment. The ditrius of its use can be found all over ebay: broken engine covers, broken carburetors, and screws that after unsuccessful attempts at removal now have to be machined out.

7. Allen screws are a liability in most instances. Normal Phillips screw tightening results in about a 10 inch-pound force. The average person tightens an Allen screw to three times that. It is almost impossible to not over-tighten Allen screws, unless you use an Allen screwdriver, not a hex key wrench.

Further reading:
Screwdrivers