Exhaust stuck on DOHC

[eric moon]

Hi all,
I have searched for any info on this site with no luck. I have a 1979 CB750F SS which i bought for parts for my 1980 model. The donor bike is in pretty poor condition as it has been stored in a damp location, although it does run ok. I want to get the RH exhaust pair off to put on my 1980 which is holed due to battery leakage but I am having trouble getting the finned exhaust clamps off the studs as they are 'welded' by corrosion. I have tried penetrating fluid for a couple of days and I have also tried heating the alloy clamps but still no luck.
Does anyone have any tips to try to remove these clamps?

I only joined the forum recently but enjoy reading all the info contained. I only wish that we had as many sources for parts here as you have in theUSA. Parts in US are relatively cheap but mailing costs are high, especially to Europe.

Eric

[LukeM]

Welcome again to our little MC playground.

I recommend PB Blaster.  Squirt it on the nuts and as much of the studs as you can.  Every hour or so, lightly rap on the studs and/or bolts with a hammer.  The vibration will help loosen the crud little by little.  Spray more PB Blaster, and repeat the process.  In a day or so, you may be able to work it free.  When they start to go, I recommend loosening until it binds, then tighten about a half turn, and loosen again.

If that doesn't work, you may have to use an impact wrench.  There are some that use a hammer, and some are like the guns the tyre guys use in shops.  I think, for the small nut size, a battery operated impact wrench/gun may be most beneficial.  Some would say that judicious application of heat (from a heat gun, or a small torch) can help, but I'm not keen on that application so close to the engine fins.  As is so well put in the Latin:  Sit Mechanicus Cave.  (Let the mechanic beware.)

I hope this helps.  Let us know how it goes.
Luke M

[sgtslag]

Another option is to use a cut-off wheel, in a moto-tool (Dremel), to carefully cut the nuts in half.  After making a cut on one side, try using a large, flat screwdriver, to pry the nut open, and away from the bolt threads; you may need to cut the nut on both sides, to fully remove/pry it off.

Impact drivers exert tremendous torque, so bear in mind that they can easily sheer bolts in two.  They will also break standard sockets, quite easily!  Only use impact sockets.  Don't ask me how I know this...


Best of luck.  Cheers!

[TOOLS1]

If I understand, he has the nuts off, but cant get the flanges to budge. I have had some stubborn ones before. PB Blaster, a hammer, and a block of wood will usually get them off.
TOOLS

[shinyribs]

Like was said before,PB Blaster,or whatever flavor penetrating oil you like,will loosen the corrosion up.After that you can get a small flat blade or a pick of some sort and start licking away at the rust until it un-welds itself. I have never like banging on things until I exhaust all other efforts.

[eric moon]

Thanks for advice. I sprayed with penetrating oil and left for a couple of days spraying at frequent intervals, smacked with a hammer and generally wrenched about but couldn't budge them.
I then scraped around the stud with a sharp pointed tool and grey stuff flaked out. It was dry so the penetrating oil obviously does not work on alloy 'mould'. I then used 1mm Dremmel bit to clean mould out as best I could and finally got 2flanges off one pair.
The other pair are still stuck but I need to get more drills as I blunted the only one I had.
What a chore! !
Eric

[sgtslag]

Have you tried a brass wheel brush attachment on your drill?  They come in different styles, but they will whisk away oxidized metal quite handily; Dremel makes some small brass brushes for their moto-tools, so if you need delicate, small brushes, they can be had.  I brought back some near-death hand tools, just by brushing away the surface rust, and adding oil to their joints.  If you keep at it, the brass will remove good metal, too -- it acts as a sort of sanding method, with wires, instead of sand grit.  Best of luck.  Cheers!

[robs750]

Maybe some heat would help,like a propane torch.

[eric moon]

Sorry, should have mentioned that i had tried the heat method but without any luck. Havent tried getting them off for a couple days as i needed to tidy the garage to fit in another bike i'm collecting tomorrow (CB750KZ 1980). Hope its in better condition than the last one, with the seized pipes!

[LukeM]

Is there any way to fit a bearing puller tool, so you're pulling on more than one point?
Might be tough to get the center to push against, but it's worth a shot.

Sorry you're having rotten luck, but I'd keep working the PB Blaster in there, brushing away the dislodged crud, and working it with heat and pressure.  I'd hate for you to have to replace the head because those little guys wouldn't cooperate.

Luke M