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Discussion Starter #1 (Edited)
I had to repair an engine where the thread of the locking screw for the manual timing chain tensioner was demaged.


For this I made a tool with which I can drill out the defective thread and replace it with a glued-in socket.


The RepKit essentially consists of two guide sleeves: One for drilling out the defective thread and pre-drilling to the core diameter for an M10x1.25 thread and one as a guide for the tap.

Here as an example the sleeve for boring to the bead wire diameter for cutting the thread:

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The sleeves are centered through the hole in the rear engine cover and are pressed against the engine by a shortened clutch spring. Shown here on a "sacrificial cover" that was broken out for this purpose:


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For drilling, the cover must be placed on the motor and fixed with 2 M8 screws on the left and right.


For cooling and lubrication when drilling in aluminum, the hole is flooded with ethyl alcohol or petroleum:

:
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Since the drill chuck of the cordless drill or a drill with a size 10 chuck is too big at this point, a smaller chuck is clamped into the machine to make the pilot hole for thread cutting:


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Next, the guide sleeve is exchanged for the one for the tap, the cover is put back on and the M10x1.25 thread is cut. Again, it should be well lubricated with ethyl alcohol or petroleum.


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Discussion Starter #2 (Edited)
Now the preparation of the repair socket follows. To do this, an M6 screw is screwed into the socket and a large washer is pressed as a depth stop with a lock nut against the socket. I only did this with a screw, but the lock nut has the advantage that the screw can be countered with a size 10 wrench to unscrew it and can be easily removed after loosening the lock nut without the risk of the threaded insert turning.


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Then a little bit screw locking agent is applied and the bushing is screwed in until the washer rests against the hole. After the screw has been unscrewed from the socket, the repair is practically complete.


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And with the new thread, the tensioner is ready for use again and sits like new :D


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I hope you never will need it,

...but if you do, then this is a way to a successful and professional repair. ;)
 

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That's a great fix Ralf. That is always the hardest part to try and repair messed up threads, getting the location of the new hole/threads in the correct location. Your method solves that issue but you will need a sacrificial cover to make the drill jig, correct? I'm assuming you had to custom turn the drill bushings for this also?
 

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Discussion Starter #5
... but you will need a sacrificial cover to make the drill jig, correct? I'm assuming you had to custom turn the drill bushings for this also?
Hi Doug,

no, I don't need a sacrificial cover. I only took it the first time to see myself, how it all fits and to show it off, what it looks like inside. :)

The drill jig bushes fit every motor with a manual chain tensioner. You simply put it together with the spring through the hole from behind and put the original cover on the engine.

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Here in Germany I lend the complete kit, as shown in the photo, including the tools, the thread insert and also the Loctite for a fee.


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If you are interested, I can make a drawing of the drill jig bushes and the thread insert some day and make them available here.
 

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Gotcha. Hopefully i won't ever need to do that but you never know, cheers.
 
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