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Old Yesterday, 07:38 PM   #1
Nihon Newbie OP
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HELP! Seized screws in Al engine block

Restoring a 1972 Honda CB100, and it has about 30 philips head screws holding on the case covers, and joining the case halves themselves...Poor fastener choice, Honda.

All but 3 of them are seized, can't break them loose with a regular screwdriver, and they're all quite soft. All have been painted over, but I don't care about the paint, they're all getting re-finished after disassembly. All have been hit with PB blaster oil, helped break 3 loose, others too well sealed with paint.

Have tried the basic (non-helical) screw extractor bits from Sears and all that did was bore a divot into the screw head. Don't care about ruining all the screws, obviously. Have access to an impact screwdriver, but am worried about cracking the old aluminum cases, and the fact that most are adjacent steep side of cases, making the angle of attack way tilted, considering the impact driver's girth.

Please advise, thanks!
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Old Yesterday, 08:03 PM   #2
whisperquiet
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Standard equipment for those of us working on Japanese motorcycles from the 70's...........impact screwdriver.

http://www.skygeek.com/ats-650-s.htm...2-EhoCqnTw_wcB

BTW....my first motorcycle was a new 1971 CB100.
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Old Yesterday, 08:04 PM   #3
lesman
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Hand impact. Sears, Harbor Freight or Snapon. Absolute must. Some people have great success with Milwaukee, Hitachi or Hilti electric impact.
If you booger the thread. Use a chisel to make notch. Then use a punch to tap the screw counterclockwise. More extreme measures, left hand drill bits, screw extractors.....sometimes you can get a pair of pointed vise grips on the head of the screw. This is where I tell you that you should use only American Made Visegrips if you only have one shot at the repair.
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Old Yesterday, 08:13 PM   #4
anonny
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Agreed, hand impact. As a side note those Honda screws are JIS (Japenese Industrial Standard or something close to that) and require a JIS screwdriver to be done by hand and not damage the screw heads.
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Old Yesterday, 08:47 PM   #5
hpsVFR
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Quote:
Originally Posted by anonny View Post
Agreed, hand impact. As a side note those Honda screws are JIS (Japenese Industrial Standard or something close to that) and require a JIS screwdriver to be done by hand and not damage the screw heads.
AFAICT, basically everything made in Japan (and lots of stuff made elsewhere in Asia) with a 'philips' screw on it is actually JIS/DIN 5260. Often the JIS screws will have a dimple punched into one quadrant of the screw head to flag it, but not always.

Example from Tecra tools: #1 and #2 JIS drivers. I use the 6" #2 every single day at work, and the improved grip over a US #2 philips is amazing.

If you want a bit driver: http://www.rjrcooltools.com/vessel.cfm The bits are longer than I prefer, but they're nicely made (also by Vessel tools, incidentally).

Wherever you get them, get a JIS screwdriver if you own Japanese bikes. It's a cheap way to avoid a constant hassle and annoyance: those 'soft' screws.
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Old Yesterday, 09:00 PM   #6
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Old Yesterday, 09:12 PM   #7
henrymartin
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Impact. I use a small SEARS electric one, and it does wonders on old bikes and their screws/bolts.

If it fails, try a left handed drill bit. The heat sometimes unscrew them out as you are drilling.

I would not use a screw extractor again (a couple I used broke, both the square tapered kind and the spiral kind). Drilling out the hardened extractor is a PITA (diamond tip on a dremmel). You are better off welding a nut onto the screws you cannot remove by themselves.

Just get some 6mm nuts and weld them on the screws using the threaded hole for the welder. The heat will loosen them up, and the 10mm socket will take them out safely.
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Old Yesterday, 09:26 PM   #8
victor441
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In a pinch the tip can be ground down a bit on a standard Phillips bit and it will fit a JIS screw better, but it would be best to get JIS bits. If the case screw heads are buggered up beyond hope usually there is no need to use extractors, if you drill slowly and carefully (with the right size bit) the head will pop off the screw eventually, the cover can be removed, then the remains of the screw can be removed easily with pliers etc. since there is no longer any tension on the screw (learned this the hard way long ago when like most I was unaware of JIS and stripped case screws using a Phillips)

This page (not mine) has some details and photos on how to do this http://www.dansmc.com/stripbolt.htm

victor441 screwed with this post Yesterday at 09:39 PM
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Old Yesterday, 09:59 PM   #9
Nihon Newbie OP
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Thanks, guys, much appreciated!! Thanks so much for those tool recommendations, too! I'll have to buy some JIS drivers it seems, I own 3 Hondas. Hopefully those would fit in that hand impact driver! Will update whenever I give it a go. Would like to avoid welding if possible, there are 30 of these damn screws that I need to be rid of and eventually replace them all with proper bolts.
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