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Main Area => General GS500 Discussion => Topic started by: dinkydonuts on November 10, 2013, 08:00:35 PM

Title: HOW TO: A fix for when the vacuum tube breaks off the white carburetor cap
Post by: dinkydonuts on November 10, 2013, 08:00:35 PM
Yeah... if someone can give me a more intelligent way to describe the part, I'll gladly replace the wording.

I did this today, and here is the write up. Hope this helps you guys out.

https://sites.google.com/site/gs500maintenanceportal/home/brokenwhitecapfix
Title: Re: HOW TO: A fix for when the vacuum tube breaks off the white carburetor cap
Post by: GS500F2004 on November 10, 2013, 10:20:02 PM
Wasn't aware motorcycles had vacuum tubes in them  :icon_twisted:

(http://www.vacuumtubes.net/images/tworks_fig3%5B1%5D.jpg)
Title: Re: HOW TO: A fix for when the vacuum tube breaks off the white carburetor cap
Post by: the mole on November 10, 2013, 11:43:55 PM
Quote from: dinkydonuts on November 10, 2013, 08:00:35 PM
Yeah... if someone can give me a more intelligent way to describe the part, I'll gladly replace the wording.

I did this today, and here is the write up. Hope this helps you guys out.

Thanks for that, good solution and probably stronger than before.
The only comment I would make is that you should tap the hole with just the M5 0.8 tap, not start with the M4 0.7. The 0.7 means the threads are 0.7 mm apart, so if you start with that one, then the 0.8 threads won't line up wth them. The result will be a kind of chewed up thread which is weaker than it could be. If the original pilot hole is the right size for the thread, then tapping plastic should be quite easy if done carefully.
Title: Re: HOW TO: A fix for when the vacuum tube breaks off the white carburetor cap
Post by: dinkydonuts on November 11, 2013, 12:40:02 AM
Quote from: the mole on November 10, 2013, 11:43:55 PM
Quote from: dinkydonuts on November 10, 2013, 08:00:35 PM
Yeah... if someone can give me a more intelligent way to describe the part, I'll gladly replace the wording.

I did this today, and here is the write up. Hope this helps you guys out.

Thanks for that, good solution and probably stronger than before.
The only comment I would make is that you should tap the hole with just the M5 0.8 tap, not start with the M4 0.7. The 0.7 means the threads are 0.7 mm apart, so if you start with that one, then the 0.8 threads won't line up wth them. The result will be a kind of chewed up thread which is weaker than it could be. If the original pilot hole is the right size for the thread, then tapping plastic should be quite easy if done carefully.

Thanks for the feedback. I'm curious if my tap/die set was mislabeled because the M5 tap was considerably thicker than the M4. For this reason I felt it OK to start with the M4, but the best thing would have been to drill a pilot hole just slightly smaller than the M5 tap and then to put in a clean set of threads.
Title: Re: HOW TO: A fix for when the vacuum tube breaks off the white carburetor cap
Post by: the mole on November 11, 2013, 03:55:15 AM
The M4 tap is a 4 millimetre diameter thread, the M5 is 5 millimetre. Your theory would work if they both had the same pitch, ie. distance between each thread, trouble is these ones don't.
The right size tapping hole for a 5mm tap is 4.2mm.

http://www.newmantools.com/tapdrill.htm#metlink (http://www.newmantools.com/tapdrill.htm#metlink) :thumb:
Title: Re: HOW TO: A fix for when the vacuum tube breaks off the white carburetor cap
Post by: robfriedenberger on November 11, 2013, 08:49:53 AM
Thank you for the post, I think i'm going to go with the easy way first...so if i screw up I have two shots at the hard way lol.