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I fretted for a month regarding a thread repair on the Number 1 vacuum port. Had properly synced my newly cleaned and O-ringed carbs and upon replacing the hex head bolt, the 5 MM threads on the cylinder head, which were suspect after previous carb sync, were stripped enough that bolt could not be lightly tightened. I wrapped the bolt with teflon tape, installed, and then checked out various thread repair options..... I purchased a "Helicoil - style" kit through Amazon...…20 Coils, a Drill bit, Tap, Install Tool with adjustable stopper ring, and Punch to knock off the "Tang."
I did not want to re and re carbs again (but was prepared to do so)...… nor did I did want to risk losing metal...especially the steel Tang....in the intake port.
This morning, I got organized and in 5 minutes, had successfully completed the job.
I purchased an aerosol can of CRC Cutting Oil / Thread Cutting Lubricant. The stuff comes out quite thick and sticky. I attached a "straw - like" attachment to one of my vacuum cleaners......and set to work. The CRC product, sprayed on the drill bit easily took care of nearly all the aluminum bits. The Vacuum cleaner attachment got the rest (filtered through a coffee filter.....couple of weeee soft bits). Next the Tap. Again, the CRC helped to hang on to the very tiny bits. And Taps are designed so that debris can be moved upward along the flutes. Vacuum cleaner got the rest. Then I positioned and screwed in the 'Helicoil'.....Perfect...… Oh, the Tang......well, I used the supplied punch and a heavy hammer...a quick smack....Tang separated. The secret and the thing that made it un necessary to remove the carbs are the strong magnets that 'attached' themselves to the Punch.....and when I withdrew the magnetized Punch from the coil, secure on the end of the Punch was...the Tang. HELICOIL...jpg
I had 4 or 5 practice 'runs' drilling and tapping and coiling and punching into some scrap cast aluminum...…..easy to access potential for FOD (none) and make sure the magnet trick would work. All is well...….
An aside: To ensure hole drilled properly, I made a drill guide from a (approximately) 1/2 inch round steel bar. Ends squared to the 13/64 hole drilled on center. Guide fit perfectly onto machined pad on cylinder head.
I did not want to re and re carbs again (but was prepared to do so)...… nor did I did want to risk losing metal...especially the steel Tang....in the intake port.
This morning, I got organized and in 5 minutes, had successfully completed the job.
I purchased an aerosol can of CRC Cutting Oil / Thread Cutting Lubricant. The stuff comes out quite thick and sticky. I attached a "straw - like" attachment to one of my vacuum cleaners......and set to work. The CRC product, sprayed on the drill bit easily took care of nearly all the aluminum bits. The Vacuum cleaner attachment got the rest (filtered through a coffee filter.....couple of weeee soft bits). Next the Tap. Again, the CRC helped to hang on to the very tiny bits. And Taps are designed so that debris can be moved upward along the flutes. Vacuum cleaner got the rest. Then I positioned and screwed in the 'Helicoil'.....Perfect...… Oh, the Tang......well, I used the supplied punch and a heavy hammer...a quick smack....Tang separated. The secret and the thing that made it un necessary to remove the carbs are the strong magnets that 'attached' themselves to the Punch.....and when I withdrew the magnetized Punch from the coil, secure on the end of the Punch was...the Tang. HELICOIL...jpg
I had 4 or 5 practice 'runs' drilling and tapping and coiling and punching into some scrap cast aluminum...…..easy to access potential for FOD (none) and make sure the magnet trick would work. All is well...….
An aside: To ensure hole drilled properly, I made a drill guide from a (approximately) 1/2 inch round steel bar. Ends squared to the 13/64 hole drilled on center. Guide fit perfectly onto machined pad on cylinder head.
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