Fuel cox Lapping

[tater1]

Hello,

As a proud new owner of a 67 ace 90 and new member I'd like to pose my first query.

What is the best way to lap in the fuel cox? I got it to stop leaking outside but still leaks between holes, and out carb.

Thanks Don

[Bert44]

I started with Autosol, a polishing compound for aliminium sidecovers then went to a paint cutting and polishing compound. Finer and finer does it.

[taber hodaka]

Don how did you get that name, are you a spud farmer? In the beginning of first grade. my nick name became spud. --------------- welcome to the hodaka world, post a picture. --------------Clarence

[MTrat]

I posted an item in the last Resonator which should solve your problem. I've had good luck restoring numerous brass fuel cocks.

[go_hercules]

I have tried and tried to lap in the brass valves. Can always get them to seal about 98 percent. They won't drip for about two days and you think you've got it, then there comes the drip. Seems that with other types of petcock one mating surface is softer than the other so any grit will embed in the softer surface and not wear into the harder surface. This goes for rubber disks, old cork inserts, and to an extent even the nylon cone type. When I lap in the brass on brass type, the surfaces look smooth and flawless, not a scratch to be found. Then turn them on with gas and oil mixture going through so they aren't dry, and just a few operations create tiny scratches. I have done this on the bench so I am sure the gas is perfectly clean with no contaminants from the tank. So if anyone has a really fool proof way to do this, PLEASE lay it on us !!!!!

[Bill2001]

I have a pair of non-leaking brass petcocks for show but use modern potmetal repros for reliable day-to-day use.

[BrianZ]

Try running thicker gas?

[Bullfrog]

It appears there are two types of people in Hodaka-land. Those who have successfully lapped/restored a brass fuel petcock, and those who haven't. I'm in the latter group.
Ed

[Al Harpster]

I had success lapping the original aftermarket brass petcocks from Strictly Hodaka. The new ones from Strictly have O rings in them.

This may or may not work with OEM petcocks.

Hand lapping did not work, even after several attempts.

I added power to the job with a variable speed drill, low RPM.

Mine required so much lapping the brass nut and washer would not tighten up the fit of the male and female surfaces.

The hole was lapped so much bigger and the taper so much smaller that the male taper section went in too far to get a fit to tighten.

This is where the washer and lock nut come in.

This is how I was able to get the taper snugged up.

Then I screwed the handle back in place.

I used various grades of the wax buffing compound sticks that I use with buffing wheels. Shave some off, mix with solvent, slather it on.

If you have lots of time on your hands, this process or perhaps some steps of this process may help.

Yes, I've got a lot of time on my hands. And I hate to loose.

[Al Harpster]

sorry about the pictures, they loaded in reverse order.

[DG29]

I have also had success lapping the stock brass ones. Maybe I just got lucky and I should try my luck with another set that I have?

[MTrat]

The method I described in the recent Resonator involves creating a kinda 'pseudo 0-ring' effect and has worked for me.

[go_hercules]

Otilladillon, when you say hand lapping did not work, can you explain what you mean. Did it just not look as smooth as drill polishing? Did it look as good but just still leaked? Or something else? I am just wondering because I have not tried the drill, just hand. But even by hand I was able to get a beautiful finish - but it still leaked...

[Al Harpster]

Hand lapping did not stop the leaks.

I thought surface finish was important, and it probably is.

But with these aftermarket units the fit male taper to female taper was rather poor.

I sensed there was not only poor fit, but out of round condition.

As I turned these by hand I felt them bind up at say, three o'clock position, then free up at nine o'clock position


I could not remove enough material with hand rotation to get the leak to stop. Or stop the variations in binding up.

I think you can see the finish I achieved on the male part in the photo.

Not great by any means, but it does seal.

The drill set up allowed me to lap til the cows came home. No finger or wrist wear on me. All cutting on the mating parts.

It took a bit of time, but I wasn't willing to give up. I just got tired of trying to remove enough material by hand driven lapping.

[go_hercules]

I see what you mean. Did you take off so much material that the hole in the plug part didn't line up anymore??

[go_hercules]

I see what you mean. Did you take off so much material that the hole in the plug part didn't line up anymore??

[Al Harpster]

The holes were somewhat misaligned after the power lapping.

This reduced the area for flow.

I ran a drill bit through from the outlet side to "open it back up" once it was reassembled.

Drill size might have been in the range of 3/32 to 1/8.

Only a little material needed to be removed from the hole in the plug part.

Might have worked ok with out this drill process. Was not sure how much flow was really needed.