fuel tanks

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panhead55
Posts: 46
Joined: Mon Jul 14, 2008 5:22 am
Location: phoenix

fuel tanks

#1

Post by panhead55 » Thu Aug 14, 2008 3:07 am

does anybody wish to clear the air on fuel tanks? so ive heard two theories on the old panhead pet cock fuel tanks AND the more recent pet cock design from 67 on... the first... was when harley changed from the pan top end to shovel tops the shovel head's stuck out a bit more and hit the left side fuel line and early pet cock so harley panicked and moved it to the other side in 66(which failed) and then moved over to the back left in 67 to remedy the situation. the other theory i heard was... that after a while the (in the tank pet cock) would weaken or grow loose causing fuel to slowly seep into the carburetor and then into the motor and if sat for a period of time, would be hard to kick and eventually catch fire upon firing, so harley changed the design therefore ditching their old technology... so im running 1954 tanks on my pan and a friend told me to add a shut off valve between the pet cock and linkert carb if i stay with the old design. would anyone care to add their own comments. thanks a lot, billy



panz4ever
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Re: fuel tanks

#2

Post by panz4ever » Thu Aug 14, 2008 3:59 am

Billy, been running the same stock tanks on my 65 (since 1970) and other than using a copper washer instead of the brass, I've never had a leak down problem so long as I remember to close the rod when I park it. Think that if the rod is not seated properly you might get leaks, but so far so good. Think adding a shut off valve is overkill.

Cotten
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Re: fuel tanks

#3

Post by Cotten » Thu Aug 14, 2008 4:11 am

Sorry this will be observations and not 'theory', making the 'air' murkier, not clear:

When 5 gal tanks were introduced in '65, the extended metal lacked support, so the already critical alignment from top to bottom was compromised. Metal moves. Just bolting to the frame could skew the valveseat from 'straight', and the un-due force needed to make the brass washers seal easily deformed it farther.
(As Panz4ever pointed out, the copper crushwasher used on the carb bowlnut eases this problem to a great degree. Funny how the Factory ignored it, as it fits exactly!)

So, in '66 the cheaper-to-produce thread-in ('K-model') petcock was used, on the right side. (Both 5 and 3.5 gallon versions exist.)
It took a half a year or so to figure out that it took a gallon or so in the tanks for the motor to start on the kickstand. (duh)
So the thread-in petcock was moved back to the left tank for the later '66 production (or so I'm told).

Please beware that the Factory petcock alignment tool for the earlier tanks has a design fault, in that metal must be moved past 'straight' to spring back to 'straight'. It can come close, but never exact.

But of course, there is a way.

...Cotten

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