Re: Any idea what would cause this?

Posted by seestheday on
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/Any-idea-what-would-cause-this-tp4039735p4039762.html

If it is for sure oil then I agree with cdaiscool.  I bet your valve seals are leaky.  The stock ones are notorious for failing badly.  There are only two paths for oil to get into the combustion chamber that I can think of (someone please correct me if I'm wrong).  Through a failing valve stem seal or through a badly failing ring.  I think that if you had a badly failing ring you would have other issues as well.

When I replaced mine my old ones all tore or broke apart.  I also had visible signs of leakage on pretty much every one.  Jebbysan (who just joined this site) sells upgraded ones that are apparently much better beefier viton ones that won't leak.

Unfortunately you have to pull the engine and head to replace them.  I believe it is possible to replace the valve stems seals in the 1100's and possibly the 900's without removing the head, but I don't think it can be done on our 750's.

While you're there you might as well lap the valves, clean up any carbon build up etc...

I just went through all of this.