Hitchcocks Forum

Doesn't seem to be coming from the rocker covers, new gaskets on them last time I had them off but I have quit a lot of black oil around decompressor AND spark plug, any thoughts on the source? thanks in advance!

what model/year of bike?

Apologies 97 350 iron barrel

Probably porous head, not unusual though more common on 500. Does not usually cause any problems unless cosmetic appearance is important. Am told 'metal weld' will solve though not tried it myself. Mine has leaked in both places for years. REgards Mick

This may be worth a look:-



http://www.ultraseal-slough.co.uk/pressure-testing/

I had this on my 500 and it turned out to be a very fine mist coming out of the slightly loose oil feed banj bolts. It only happened when I was cruising at 50mph plus so wasn't obvious and took ages to work out. Worth checking they are fully tight.

Should read 'banjo' bolt. The thin film of oil travelled all around the head so it really wasn't obvious where it was coming from.

Think you answer your own question, Check the decompressor. A porous casting is most unlikely it would have been apparent for years and years. Often the simplest answer is the right one.

I go with the banjo's on the oil feeds. I've had mystery oil on the head several time and it has always proven to come from there. If you have been using our host rubber sealed washers check that the seals haven't torn. That was the cause of a particularly annoying leak that took me a while to find as it was as described earlier only apparent at speed and when the oil was hot. I recommend new sealed washers from our hosts or soft aluminium ones which can be brought from hydraulic hose suppliers although they are not cheap.

Those crushable washers on plugs don't last forever and can leak. You can get spares on Fleabay. If I remember, the same sort seals the decomp.