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Old 03-27-2012, 05:20 PM   #1
OhioAirhead OP
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Removing the Cylinders on an R90S

I am attempting to remove the cylinders on my '76 R90S in order to have them bored. The problem is, they are stuck on with Yamabond or some equivalent and won't budge. Does anyone know any tricks to getting them off?
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Old 03-27-2012, 05:38 PM   #2
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Originally Posted by OhioAirhead View Post
I am attempting to remove the cylinders on my '76 R90S in order to have them bored. The problem is, they are stuck on with Yamabond or some equivalent and won't budge. Does anyone know any tricks to getting them off?
Crowbar. Slowly, pry all around the cylinder. Work it SLOWLY.

Sometimes it's necessary to re-bore ... but if you don't absolutely have to I wouldn't. Hone, new rings and go. Prices and maintenance go up for one over's. Just my opinion of course.

Good luck.
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Old 03-27-2012, 05:44 PM   #3
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A couple years ago when I was working on the pistons for my R90/6 all I could find was second over size. Nobody had 1st over size. Of course the S bike uses a different piston I think but I did think this was strange.

There is a 3M product that is sprayed on sealing compounds and frees them. the only place I've every seen it is in boat stores, West Marine. Maybe check on line or something. It's a spray on. Boats use heavy sealing compounds for sea-cocks that go through the hull.
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Old 03-27-2012, 06:18 PM   #4
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Make a cylinder and head puller tool. 1/4 or 3/8" x2" steel, M8 nut on the valve cover stud, M10 nuts behind the tool on the studs. Use it to pull the heads and/or cylinders off. If you are just pulling the heads, take off the cyl head nuts @ 12 and 6. If you need to pull the cylinders, leave the two head nuts on.

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Old 03-27-2012, 06:34 PM   #5
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^Those center valve cover studs seem to pull out on their own, much less under this torture. I wouldn't do that. I have made some wooden wedges to go between the engine case and the first set of cooling fins. I really like the way wedges can exert a great deal of force, and not chowder things up. Also the spray product mentioned above is called "De-Bond", and it works great, but I don't think you'll need it.
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Old 03-28-2012, 10:22 AM   #6
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use a rubber mallet.
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Old 03-28-2012, 10:49 AM   #7
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Modeled after BMW tool No. 209 thrust bridge, it rarely strips the center bolt. If the center bolt goes, it needed to be repaired anyway.

Wedges, crowbars and mallets on the fins are not good on fins.
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Old 03-28-2012, 11:33 AM   #8
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use a rubber mallet.
+1
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Old 03-28-2012, 11:53 AM   #9
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use a rubber mallet.
+2. Hitting the barrels will induce enough wiggle to break the seal free. If you aren't comfortable hitting the fins hit the exhaust or intake.
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Old 03-28-2012, 04:55 PM   #10
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I finally got them off. I was being a bit too timid with them the first round. Thanks for the replies.
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Old 03-28-2012, 05:25 PM   #11
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