Karcoma fuel tap leaking

[eastbay]

My fuel tap won't turn completely off. The last time I tried to rebuild one, I couldn't get the cap threaded on without leaving the spring out, and without the spring it leaked. I've got the rubber seal ring on order. Is there a trick to getting the cap on?
https://shop.maxbmw.com/fiche/DiagramsMid/B0000398.png?v=09082020

 

[88bmwjeff]

This video might help

 

[eastbay]

Thanks. Yea, I previously got to the last step and could not get that @#$% cap back on. I have arthritis in my thumbs and after a painful 5 minutes I gave up. I'll try again before I bite the bullet and just buy a replacement. It is a real bitch to compress that spring while trying to thread the cap on and not cross thread it. But the video shows it's possible, but not easy!

 

[eastbay]

For those who like closure, I was able to replace the gasket and get it back together. I steadied the petcock in a vice and used a clothespin to compress the top by pushing down on it. . That allowed me to get the top level and the wood allowed me to still spin the top.

 

[20774]

Great! Nice use of your third hand!!

 

[stevenrankin]

Lesson

Ah, a successful project and a tip or lesson for all the rest of us! Can't ask for much better than that, thanks for the information and it will be filed away in my list of tips in case I ever need to do the same thing.

This is how things in a forum should work, it is so wonderful to have people actually have questions, answers and closure with and issue. Too many time, posts go dead without a result. St.

 

[88bmwjeff]

Thanks for the tip. My petcocks are apart and waiting for a few parts for the rebuild.

 

[kbasa]

Thanks for the tip. My petcocks are apart and waiting for a few parts for the rebuild.

There's a ring that has some little dents in it that serve as the detents when you're rotating the lever. Protip: If you're clearing crud off of them, it doesn't take much sanding to make the detent less obvious when you're operating it later.

 

[88bmwjeff]

There's a ring that has some little dents in it that serve as the detents when you're rotating the lever. Protip: If you're clearing crud off of them, it doesn't take much sanding to make the detent less obvious when you're operating it later.

I used a wire brush that seemed to work well, but did not impact the those rings. Of the 11 parts (or 12 if you count each straw separately), you can purchase all the parts separately except four. The main body, the lever, and those two small rings. These rings are a PITA to clean, wear down, and can be quite crusty. Mine were very crusty and soaking them in carb cleaner did no good. I'm curious why you can't buy replacement rings. Oh well--C'est La Vie

 

[kbasa]

I used a wire brush that seemed to work well, but did not impact the those rings. Of the 11 parts (or 12 if you count each straw separately), you can purchase all the parts separately except four. The main body, the lever, and those two small rings. These rings are a PITA to clean, wear down, and can be quite crusty. Mine were very crusty and soaking them in carb cleaner did not good. I'm curious why you can't buy replacement rings. Oh well--C'est La Vie

It's annoying and I periodically envision taking them apart and using a nail punch to dent the detent out a little further.

And then I think about it a little more and get to "nah".

 

[eastbay]

Great! Nice use of your third hand!!

A clothespin spring does not provide enough force to compress the spring, I used the clothespin to straddle the top, just applying force to one side will not level the top enough to get the threads started. So downward pressure [one hand]with clothespin, turning cap with other. I hope that is clearer. If I did have a third hand I could have photographed the procedure.

 

[stevenrankin]

Remember

LOL, we all need to remember that at one point all this "stuff" was put together on an assembly line with proper tools jigs and robots. Easy peasy there not so when we two armed people need three or four arms, and six eyes to make repairs. St.

 

[88bmwjeff]

I was waiting for one last bit of parts (springs-one was rusty) to be delivered and they came last night. Like an eager beaver, I headed out to the garage to put them back together. That ended up in failure and I was thinking I should have just purchased new ones. I rewatched Airhead Barn's video and headed out this morning and success. They're back together.

I thought I'd add some tips that helped me. This will make more sense if you watch the video. For me, the hardest part was getting the screw cover back on the angle selector with the spring in place. The guy on Airhead Barn video gave some good tips on using a screwdriver to compress the spring. But, it made a big difference how the spring was placed. The place to compress the spring is under (or as close as possible) to under the angle portion. Rotate the spring so the portion going from top to bottom is where you're going to compress with a screwdriver. It's kind of trial and error to get it to a good spot. If it was rotated too much either way, I had trouble compressing the spring enough to get the screw cover on. FYI, once on the screw cover stays in place. Also, I had some extra casting rib at the top of the angle selector where the screw top had the tightest fit; as such, I I filed those areas smooth.

I would also wait to put the O-ring on the angle selector until after you get the screw top on. I didn't on the first one, and I was constantly worried I'd bugger up the O-ring.

As far as screwing it back together, for me it was relatively easy to just assemble it in my hands without gloves. Gloves gave me less dexterity. Granted those with hand issues (e.g. arthritis) may not be successful this way. It was a little fidgety getting the top to start. It is noted that my thumb and index finger are still a little sensitive from getting the covers on. Once started, I used pliers to screw it tight.

Now all I need is my gas tank (it's off getting cleaned and resealed) to put them back.

 

[nrpetersen]

A good application for some special aviation grease called Fuel Lube, which does not dissolve in gasoline. Available from Aircraft Spruce - and I'm sure other places.