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Motorcycle Forum / General / Yamaha / December 2006How to deal when there's no gasket?
I am currently restoring a Yamaha XT550. The first thing needed was the shift shaft. Broke the engine down to find there is no gasket for the 2 crankcase halves. It looks like it was sealed with something liquid that later hardened. I have scoured the manual and parts diagrams and I can find no gasket for this application. I have what is supposed to be a complete gasket set as well and there is no gasket for this. My question is this, what do I use to seal the 2 half's? I was planning on using Permatex Black as it gets semi-hard. Any other ideas??? MD >I am currently restoring a Yamaha XT550. > The first thing needed was the shift shaft. Broke the engine down to [quoted text clipped - 8 lines] > >MD thumperstuff.com should have your gasket. Probably some form of liquid gasket in a tube see example link below http://www.hylomar.co.uk/siliconesealants.htm There are quite a few on the market, I only used this example as the hylomar blue has always been good for me to get a stubborn gasket leak to seal. Bob > I am currently restoring a Yamaha XT550. > The first thing needed was the shift shaft. Broke the engine down to [quoted text clipped - 8 lines] > > MD yamaha never put a gasket there. Use a good quality gasket sealant for motors. One that states it can handle high temps and oil. Y our local auto parts store will have it. Dennis >I am currently restoring a Yamaha XT550. > The first thing needed was the shift shaft. Broke the engine down to [quoted text clipped - 8 lines] > >MD > yamaha never put a gasket there. Use a good quality gasket sealant for > motors. One that states it can handle high temps and oil. Y [quoted text clipped - 16 lines] >> >>MD Would the thickness of this material not affect the preload on the bearings in each case half? Too thin and there will be compression, to thick and there could be lateral movement? No, The sealant is of a paste like consistency. Use a small running bead on all machined surfaces, do not just run the outside surfaces. Be consistent. Then, tighten down your bolts as is recommended in your manual, Of course, clean all the old material off first. Did you check to see if there was any slack on any of your shafts, prior to opening the cases? Both vertically and horizontally. That motor puts out tons of horsepower so change all seals and really scrutinize the bearings, You don't what to have to crack those cases to often. Dennis >Would the thickness of this material not affect the preload on the bearings >in each case half? Too thin and there will be compression, to thick and >there could be lateral movement? Dennis is correct but I would add the following. When you have the cases apart and have cleaned them, check to make sure the mating surfaces are perfect. I lightly surface them on a machinists plate (you can use float glass also) with a very fine wet/dry paper. Use it wet. Check for low spots then clean again. Use your manual, on some motors you need to heat one side or the other to get the bearings to slide. You need to tighten using the correct bolt pattern to prevent damage to the bearings and cases. Use the sealer recommended by your Yamaha dealer. Don't use a cheap silicone auto sealer unless you enjoyed doing the job so much that you don't mind doing it again. Only apply the sealer to one half as per the directions and assemble in the allotted time. Other tips: I have a bunch of 2x4's that I made into various size boxes to hold the lower case for assembly. You almost never have the right case holder so these work great in a pinch. Don't forget to inspect your tranny parts and all thrust washers. I always dry assemble the cases with the crank out to measure end play on the various shafts. |
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