Topic: 1978 750K Petcock Rebuild and Tank Questions

[theofam]

I began looking into what's required of using Paddy's tank today.  Of course, the petcock leaks!  Others have exhaustively searched rebuild kits with little luck, and the petcocks are unobtanium (one on ebay that looks worse than mine)!

I drilled out the "rivets," which aren't rivets at all.  Turns out they're bosses in the petcock's main body that, once the res/off/on plate is seated are then mushroomed to secure the plate.  If I had it to do over again, I would have filed off the mushrooms and just popped off the plate.  Thinking they were rivets, I also continued to increase the bit size wondering why the rivet heads wouldn't pop off.  So, I may have drilled too wide in the petcock's body to allow me to tap it (hope not).  At this point, I don't know if I should try to tap the bosses or file them flat and tap the petcock's body.  Here's what I ended up with:


When I popped off the top plate, parts flew!  Is this the correct order of assembly?  I'm not sure if the fiber washer or the spring ring goes on immediately after the lever:


I think I'll reuse the four-hole gasket by flipping it over (in hopes of saving time before IT gets here).  I understand this gasket can be ordered if it still leaks.  Here's a pic TwoTired posted:
http://forums.sohc4.net/index.php?topic=34758.msg413245#msg413245

Online parts diagrams show a washer (looks like fiber/nylon) between the tank's fuel screen and the rubber washer inside the petcock.  The former was missing on my tank, and the latter is trashed:


I can't locate the petcock's rubber washer online, so I'm going to see if I can make/buy one.

On to the tank.  Here are some shots.  If it were yours, would you rinse it with Phosporic Prep and Etch?  I've never done this before, so I don't know if this is too much rust or not.  It is most prevalent in the final pic.  I had to use my shrink ray and parachute in to get these pics!






Your ideas/opinions would be great!

[mrrch]

The tank looks just fine inside, I would not worry about trying to remove that tiny bit of rust.
The rubber washer comes with the intank filter only(I haven't installed mine yet so I will try to remember to measure the washer)
16 x 10 x2 mm approx
I drilled and tapped my 77 750K petcock and used 3mm screws.
The way you have all the parts arranged appears correct.

[theofam]

mrrch, your bike looks awesome - just read your build thread.  Thanks for all the info.

I'm confused.  The parts diagram shows a washer with the in-tank filter, and I've seen other forum members refer to it as a "fiber" washer.  Based on that, I assumed there was a fiber/nylon washer that came with the in-tank filter and the rubber washer was in the petcock at the base of its tube.  So, two washers.

If I read your response correctly, the rubber washer comes with the in-tank filter, so it is the only washer.  Is that correct?

[chickenman_26]

I began looking into what's required of using Paddy's tank today.  Of course, the petcock leaks!  Others have exhaustively searched rebuild kits with little luck, and the petcocks are unobtanium (one on ebay that looks worse than mine)! Your ideas/opinions would be great!

Here ya go. You might contact them to make sure they actually have one in stock. This is the whole deal, including the filter and washer.

http://www.cycle-parts.com/Product.aspx?ProductID=1297413&SKU=16950-405-831

Stu

[theofam]

Stu/chickenman, thanks for tracking that down!  I tapped the petcock this evening (6/32 thread) and will reassemble and run gas through it tomorrow.  If it leaks, I'm trying that link!

[chickenman_26]

Stu/chickenman, thanks for tracking that down!  I tapped the petcock this evening (6/32 thread) and will reassemble and run gas through it tomorrow.  If it leaks, I'm trying that link!

Did you tap the bosses, or did you file them flat? BTW, I suggest replacing that 4-hole washer. Part #16955 268 020

Stu

[theofam]

Stu, I tapped the bosses.  I like the idea of the top plate having the bosses as originally designed.  I may end up getting the four-hole gasket.  I've read a couple places flipping that gasket can be a quick remedy.  So, in the interest of having Paddy on the road by May 3rd, with much to do, I'm trying the quick fix.  I'll know in a few hours if it works or not.

[mrrch]

The rubber washer came with the new filter and should be the only one in there.

[theofam]

Thanks, mrrch.  I put it together that way and NO LEAKS!  Here it is with its new 6/32, allen head screws:


I had to make my own washer.  The old washer is close to 5/16" I.D., so I used one of those and cut it down to fit - seems to seal well enough:



Hopefully, that's all on the petcock.  I'm off to get fuel line and an in-line fuel filter.  I may be able to fire up Paddy for the first time in who knows how long today!  He was parked two POs ago around 1999.  Fingers crossed!

[chickenman_26]

Your in-tank filter looks to be in good shape, and the tank is remarkably clean. Why install an in-line filter?
Anyhow, you lucked out. Hopefully, it'll last a long time.

Stu