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Kacoma straight (No. 2) petcock disassembly

G

guyatou

New member
Attempting to rebuild my petcocks, but I can’t get the threaded washer off.

I tried beating it in a circle with a screw driver and mallet and that worked for a while. I also tried with a spanner that I use for photography lens repair, but it just slips.

Clymer doesn’t say anything about a special tool. Is there one? What am I doing wrong?

Thanks in advance!

F0DB68DE-4239-478F-B247-F07D35854384.jpg
 
Karcoma

No, its a goofy situation. Make sure the lip around the circumference of the tap plate is more or less vertical, not leaning inward, then take a screwdriver and pry up on the flat plate with the handle on it. Don't chicken out and the plate will move up and out possibly slowly because of the cork gasket. It is primitive technology but actually very doable with a little persistence.
 
Thanks. I'll try some PB Blaster in the morning and see how it goes. It seems like there would be a special tool for this application, knowing BMW.
 
It seems like there would be a special tool for this application, knowing BMW.
Click to expand...

And therein lies the krux of the biscuit.. . . they weren't made by BMW.

Check the upper portion of the threads, you may have buggered them up while "beating it in a circle" ... if the threads a distorted the retainer won't come clear.

I rebuilt mine, they still leaked, so I ended up replacing them... ..
 
Thanks for the advice and encouragement, all. I'll double check my threads, and I'll try needle nose pliers after a generous soak in PB. Can't hurt! I'm trying to avoid replacing the petcocks -- since there are two of them, the cost will really add up.
 
New petcocks are $40 each, or less than the price of a cheap tire for the bike. Try rebuilding if you like, but keeping the bike's fuel supply contained and directed, and being used twice every time you turn the bike on and off, the value of reliable petcocks is pretty high, IMHO. The marginal additional cost of replacing the units, rather than buying the rebuilding kits for 30-ish year-old petcocks, is modest.
 
Petcock

khittner said:
New petcocks are $40 each, or less than the price of a cheap tire for the bike. Try rebuilding if you like, but keeping the bike's fuel supply contained and directed, and being used twice every time you turn the bike on and off, the value of reliable petcocks is pretty high, IMHO. The marginal additional cost of replacing the units, rather than buying the rebuilding kits for 30-ish year-old petcocks, is modest.
Click to expand...

Agree with above my 1978 R100/7 had straight petcocks, in one of them the detent balls were stuck so petcock would work if you got lever in right place which did not always happen , so next step shut petcock pull off fuel line to make sure gas is shut off ( assume you have one good petcock ). Finally decided to not be a cheapskate and buy 2 new petcocks and I find the straight ones cost much more than curved ones, cheapskate back, got new right and left curved ones, bike did not care with new fuel lines they work has they should and look right
 
Here was my problem! There was so much varnish in the selector that it wouldn't even turn. The original cork gasket is down in there somewhere. I was able to get the washer unscrewed using lots of PB Blaster and a pair of needle nose pliers with the petcock in a vise.

I got them both rebuilt and all of the passages cleaned out, but the reserve straw on one of them broke off, so I'll probably have to replace that one at minimum (there doesn't appear to be a way to replace the straws). Unfortunately, the straight petcocks are a little pricey, but the last thing I want is to get a bunch of sediment in my carbs if I have to switch to reserve.

This was a good learning experience though. I feel pretty confident that my rebuild is solid, and only cost a few bucks each.

IMG_8213.jpg
 
Here's my final update:

I ended up not being able to repair one of the petcocks (coincidentally and fortunately the one that had the broken straw). One I rebuilt worked great -- the other leaked. I took it back apart, and there was a divot in the pot metal of the back of the selector knob. It was allowing fluid (alcohol in my test) to seep around the rubber gasket and drip.

Thanks to all who gave me awesome input on this. I'm learning every step of the way, and am excited to get this bike on the road -- maybe as soon as December!
 
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