View Full Version : Gasket or no gasket???
23rd July 2010, 02:58
I'm in the process of rebuilding my 71 xlc top-end due a massive oil leak around the rear base gasket (amongst other issues). After removing the heads, it appears the leak may have come from the joint where the two sides of the crankcase meet. Is there supposed to be a gasket here? The exploded view in my manual doesn't seem to show one, nor can i find one for sale, however, i have seen several pictures online of engines that appear to have this gasket.
Also, does anyone know the exact torque specs for the crankcase bolts and crankcase center stud (all original hardware had been removed)? Is there a particular pattern for tightening?
Thanks for the help!
23rd July 2010, 06:17
No gasket between the crankcase halves. Should be a sealant in there. Usually ThreeBond, HondaBond, YammaBond - all the same product made by 3M company.
Post this question in the IronHead section for more information and alternatives.
23rd July 2010, 07:39
Moved it to Ironhead area.
23rd July 2010, 08:20
What Mick said. No gasket at all. DO NOT use RTV silicone sealant either. Motorcycles and Silicone do not get along very well.
23rd July 2010, 11:19
+1 on no gasket and no RTV silicone (unless you like rebuilding motors).
A few (of many) relevant threads:
23rd July 2010, 12:54
thanks for the help. Gasket or no gasket i still think this could be my issue. I noticed that the crankcase center stud was loose when i got the bike, and i also cant see any sealant whatsoever at the joint where the two halves meet. How big of a deal would it be to split the halves and apply sealant? The only apparent leak is around the rear cylinder but its a big one. also, anyone know the torque specs for the crankcase bolts? thanks again...
23rd July 2010, 16:52
Something to watch out for. The gray HD sealant looks just like cast aluminum. I took mineral spirits and then acetone to clean the case halves. Every time I cleaned them, the old sealant came off. It must have taken half a dozen times before I was sure that I was down to the bare metal. If you use HD sealant, be sure to read the instructions first. Once you start, you only have a few minutes to get all the sealant on and the case halves pressed together. Otherwise, the sealant will skin over and not give the best seal.
23rd July 2010, 20:44
Good to know. I guess it would be hard to see the sealant if it is the same color as the cast aluminium. Still there seems to be like a 1/32" gap between the cases at that rear cylinder (the leaking one) with no visible sealant. Anyone have those torque specs or know the fastener type for those crankcase bolts and center stud? I figured i'd tighten them to the correct torque values first and see if that, combined with a new base gasket, takes care of the issue. Sound reasonable? Would it be a big project to separate the cases and add sealant (I'm still pretty new to all this). Thanks for the advice guys...
23rd July 2010, 22:45
Torque values for standard fasteners is in the front of the factory workshop manual.
24th July 2010, 00:37
The bolts in the case are not original and therefore i can not locate them on the "General Fastener Tightening Specification" chart. thanks though...
24th July 2010, 07:20
Like most topics, this has been discussed before (http://www.google.com/cse?cx=partner-pub-2703004910810092%3Aas0j5qlve3i&ie=UTF-8&q=ironhead+case+bolts+torque&sa=Search) and you are correct, the FSM is silent on torque values or even bolting the cases back together after splitting them.
Post 19 of this thread quotes T&O as 12-14 ft-lbs (http://xlforum.net/vbportal/forums/showthread.php?t=651305).
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