Topic: Help! ‘73 CB750 exhaust flange - screws frozen

[Jcop.550]

Trying to remove the exhaust on my cb750. I got the outer headers off no problem. The 2 inner ones have flanges with frozen screws. I used an impact screwdriver, and applied some heat with a torch. They won’t budge. Easy out will not work either.

Any help/tips appreciated. Thanks




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[newday777]

Get the header off the flange 1st to access the screws easier. PB Blaster first followed by a torch around the pipe to expand it, then twist back and forth.

[Don R]

 I've had the best luck with a snap on 3/8" drive x #3 bit in my battery impact. I have broken a couple of those bits though too. Snap on guy fixed them even though I'm not a regular customer.

[BenelliSEI]

Those can be an absolute Bit*&! Are you saving the pipes or are they scrap? If the pipes are scrap I have had some luck extending the top slot with a Dremel disc grinder (small 1” wheel) and the opening them up with a cold chisel….. alternatively, my manual impact driver with about a 3” long JIS impact bit. The flared head of the screw actually rusts solid to flange so if you get the piipe off and they just won’t move, drill the head off the screw. Once the spigot is removed, the remaining threaded bits come out easily with a pair of vise grips.

WARNING: When beating on the head of the screw with a hand held impact driver (definitely what you should try first), make sure you are hitting straight and square. You may need to remove the fender and wheel/tire to get a straight blow. If you hit at any kind of an angle, you risk breaking off the “tower” casting that the screw is threaded into. Don’t ask how I know this…….

[BenelliSEI]

Is that the “orange bike”? Those pipes look totally roached. Cut them off tight to the spigot with a saws-all and pull the motor. Flip the motor upside down and use the manual impact driver on those screws. With direct access, they will come off much more easily……

[Jcop.550]

Those can be an absolute Bit*&! Are you saving the pipes or are they scrap? If the pipes are scrap I have had some luck extending the top slot with a Dremel disc grinder (small 1” wheel) and the opening them up with a cold chisel….. alternatively, my manual impact driver with about a 3” long JIS impact bit. The flared head of the screw actually rusts solid to flange so if you get the piipe off and they just won’t move, drill the head off the screw. Once the spigot is removed, the remaining threaded bits come out easily with a pair of vise grips.

WARNING: When beating on the head of the screw with a hand held impact driver (definitely what you should try first), make sure you are hitting straight and square. You may need to remove the fender and wheel/tire to get a straight blow. If you hit at any kind of an angle, you risk breaking off the “tower” casting that the screw is threaded into. Don’t ask how I know this…….

I thought about the dremel. The metal is so soft I was worried about it stripping again but I’ll give it a try!


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[Jcop.550]

Is that the “orange bike”? Those pipes look totally roached. Cut them off tight to the spigot with a saws-all and pull the motor. Flip the motor upside down and use the manual impact driver on those screws. With direct access, they will come off much more easily……

Yes it is. I’ll do that as a last resort. Also wondering if I could weld something on that’ll be stronger to get it out. Going to try every option I have. Thanks!


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[HondaMan]

If you drill them off, use a 1/4" drill bit thru the crosspoints, and if it won't let the head fall off, step up to 9/32" for a little bit of extra 'flare' to make the beveled screw head come free.

[Jcop.550]

If you drill them off, use a 1/4" drill bit thru the crosspoints, and if it won't let the head fall off, step up to 9/32" for a little bit of extra 'flare' to make the beveled screw head come free.

I like this idea.. might give that a go. How would you recommend I remove the threaded part once the head is off ?


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[seanbarney41]

I was just having the same problem a couple nights ago.  Lots of hammering, penetrating oil, propane torch heat, but #2 just could not get enough twist because of it being between the sidestand and centerstand and hammering at the impact was of little use because no room to swing with the front end in place...finally gave up for the night.  Thought all the next day of way to press the pipe off the spigot without damaging anything...my pipes will be keepers!  Anyway, never came up with a good idea but when I got back to messing with it, somehow the spigot was loose and the screws came out easily.  I guess the heat, oil and hammering just needed time to work?  Hope you have as much success!

[Jcop.550]

Update. Got it out by drilling the head out, prying it off then using an easy out extractor to get the stud of the screw out. I was afraid of doing this but gave it a try and turned out to be quite easy. Thanks for all the help and suggestions!




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[calj737]

Do yourself a favor: prior to reinstalling a screw, run a tap in that hole with a bit of WD-40 on it. Youre only "cleaning" the threads, not re-cutting them. Gently run the tap in and then back out. And when you do reinstall screws, use copper anti-sieze on them. Its the higher heat compound and it will alleviate this in the future somewhat.

[Jcop.550]

Do yourself a favor: prior to reinstalling a screw, run a tap in that hole with a bit of WD-40 on it. Youre only "cleaning" the threads, not re-cutting them. Gently run the tap in and then back out. And when you do reinstall screws, use copper anti-sieze on them. Its the higher heat compound and it will alleviate this in the future somewhat.

Good to know. Thanks for the tip. I will definitely do that when the time comes


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[BenelliSEI]

Also….. Go to a really good hardware source (around here I use “Bolts +”) and take in a sample. They provided me with a matching screw, nicely plated, that takes a metric Allen socket. Clean threads, a good anti-seize product, and much easier to install and remove!!

[BenelliSEI]

If you decide to use an aftermarket pipe that doesn’t use the standard spigots, don’t use the 8 Allen cap screws that most of then come with. Take the time to install the correct studs (as used on K7/8 cb750’s). The alloy in the head is easy to strip with repeated use. A nice fitting, deep stud, with some blue loctite, will last forever and save the wear and tear.

[jjc]

Anytime I am mating two different metals, I use anti-seas. (Yo Ho Blow the man down). If I want it to stay, blue lock tight. Red for studs ( if using Red the only way to brake the bond is a torch / heat.