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ET: Engine (Twin) How to fix crack in ET24 (HRD) Valve Inspection Cap

Texas John

Well Known and Active Website User
Non-VOC Member
One of my Valve Inspection Caps (ET24) has a crack where a DPO took his slip-joint/arc-joint/water-pump pliers to it rather than using the proper tool. Seeking suggestions on how to fix it so it does not leak oil through it. It was previously sealed with white silicone seal (e.g. caulk) which washed when I was cleaning it with gasoline. I do not have a welder. I was thinking of packing JB weld through the crack which the little bit exposed would match the dull gray cap (Stainless?). Other suggestions welcome. Thank you.
 

Robert Watson

Well Known and Active Website User
VOC Member
Just look for a nice used one that matches what you have. Many Owners have a few spares. Post a picture.

Even welded you may need to swap it out for one of the "less accessible" ones where no one can see it!
 

Glenliman

Well Known and Active Website User
VOC Member
I tried Tig welding one and it disintegrated with very little heat applied. I learned afterward that the original caps are made of a non weldable alloy. There might be later jobber versions that are weldable.

Glen
 

Texas John

Well Known and Active Website User
Non-VOC Member
Well - could use 1 HRD cap or two if you would like to help me replace one that has the Vincent Scroll (swap or whatever you would like to arrange). I think these are original as I know they have been on the bike at least since I got it in 1974. The fellow I got it from had more than 1 Vincent so that is probably where the Vincent cap is from. Or maybe he wrecked one so bad he had to replace it long ago.
 

BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
I had four of my HRD logo caps off yesterday to check/adjust the valve clearances. They appear to be original caps and you could see inside that there was some porosity that didn't go all the way through to the outside so the material would be quite thin in places. Welding could be a bit tricky especially as there could be oil ingrained. I would use an epoxy adhesive (Araldite, JB or similar) and maybe swap the caps around to put it in a less prominent position if the epoxy was visible and it bothered you.
If you want a new one the VOC Spares Co have them in stock or alternatively it sounds as if there is a good supply of second-hand caps as a cheaper or maybe even free option.
 

Cyborg

Well Known and Active Website User
VOC Member
If the rocker adjuster comes in contact with the cap, a person could try a thinner gasket so the cap screws down a bit further. Some gaskets I’ve come across are fairly thick. A couple of new caps that I purchased also didn’t have quite the same profile inside and were a little more likely to make contact.

Random tip for the day.... when buying new caps, if they are going on a clean or rebuilt head, always apply some lubricant to the threads.
 

Cyborg

Well Known and Active Website User
VOC Member
150.......pathetic........I've got a 44 gal drum full of those old pesky things............ ;)

Which begs the question..... why do we never toss out old knackered Vincent parts? How many bronze and aluminum large idlers could we collectively come up with? At least I can say I turned one into a hand wheel to replace the broken one on the little Atlas mill.
 

Glenliman

Well Known and Active Website User
VOC Member
I recently saw a photo of a newly rebuilt engine with an alloy big idler in place.
My OZ Rapide had one. John McDougall insisted on checking over the timing case when I had him doing valve seals ( tip of the iceberg)
The teeth on the idler were all intact but severely deformed and just ready to shed aluminium swarf into bearings, oil pump, cams etc...

I've put thicker sealing rings on the valve caps to gain clearance when a skinny ring allowed contact. Not sure how a thinner ring would eliminate contact?
 

Cyborg

Well Known and Active Website User
VOC Member
I've put thicker sealing rings on the valve caps to gain clearance when a skinny ring allowed contact. Not sure how a thinner ring would eliminate contact?

You need to stare at one for a while. It’s counter intuitive, but thinner gasket can help. It brings the fat part down lower giving more room when the valve is wide open.
 

Glenliman

Well Known and Active Website User
VOC Member
I had to raise the rocker caps with thick gaskets on the 1360 , but that is a .440 lift cam. Mk1s are about .315, mk2s .343
 
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