Failed helicoil repair

[Griffin]

Yesterday was a rough day. I reassembled my dohc cb750 with a Wiseco 823 big bore kit last week. After getting it together I dropped a small vinyl thing down a spark plug hole. After a lot of trying to fish it out I dropped a metal hook in there as well. Hours later I decided to remove the head, again, to get the junk out. In the process of relieving pressure on the intake cam chain I stripped the hole for the front cam tensioner bolt. After pulling the bolt out I found it had a helicoil on it so apparently this happened before.

I found something called a Time-Cert but the M8 kit is $72. Might be cheaper to take it to a machine shop.

Any other options you guys have come up with? JB weld on a new helicoil maybe? Or drill and tap out to 10mm and use a 10m bolt?

Have to say I'm pretty disappointed with this turn of events I was so close to the first fire on the new piston kit. Already had the engine back in and wired all up. Had plans to button up carbs and exhaust yesterday before it all went sideways. I'm terribly frustrated and tring to figure out what to do next. Can't believe I've wasted so much time by screwing stuff up.

[TOOLS1]

You could probably get a machine shop to install a timesert for around $35.00.
TOOLS

[Griffin]

That's what I'm thinking is the best plan.

[Griffin]

I'm not so sure it was a failed helicoil after all. But I had trouble tapping it I don't seem to have the right size drill bit and I rounded the tap. Definitely going to a machine shop now.

I pulled the can chain b tensioner and found the tube covering the spring is cracked. Anyone ever replace that with something at a hardware store? Or have a good one I can buy. There's not much on eBay in the US.

[TOOLS1]

That plastic tube? Throw it away, it is not needed.
TOOLS

[Griffin]

Perfect thanks!

On Jul 16, 2017 8:26 PM, "TOOLS1 [via Vintage and Classic Honda's]" <[hidden email]> wrote:

That plastic tube? Throw it away, it is not needed.
TOOLS

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[shinyribs]

Griffin wrote

I'm not so sure it was a failed helicoil after all. But I had trouble tapping it I don't seem to have the right size drill bit and I rounded the tap. Definitely going to a machine shop now.

I pulled the can chain b tensioner and found the tube covering the spring is cracked. Anyone ever replace that with something at a hardware store? Or have a good one I can buy. There's not much on eBay in the US.

I know I'm late to the party, but your tap rounded off going in to aluminium? Not to be rude, but that must not be much of a tap.

These particular holes are well known for stripping. Heli-coils only work worth the taps they come with, and they come with good taps. Heli-coils are stronger than Time-serts. Helis have deeper, coarser threads that grab the surrounding metal much, much better.

[Griffin]

I ended up figuring it out. The tap worked out ok I may have jumped to conclusions too soon.  After getting the 21/64 drill bit it wasn't too bad. It's not perfectly straight which bugs me but it holds the tensioner fine. I put a new O-ring on the bolt too. Seems like it will be fine now.

On Jul 23, 2017 9:39 PM, "shinyribs [via Vintage and Classic Honda's]" <[hidden email]> wrote:

Griffin wrote

I'm not so sure it was a failed helicoil after all. But I had trouble tapping it I don't seem to have the right size drill bit and I rounded the tap. Definitely going to a machine shop now.

I pulled the can chain b tensioner and found the tube covering the spring is cracked. Anyone ever replace that with something at a hardware store? Or have a good one I can buy. There's not much on eBay in the US.

I know I'm late to the party, but your tap rounded off going in to aluminium? Not to be rude, but that must not be much of a tap.

These particular holes are well known for stripping. Heli-coils only work worth the taps they come with, and they come with good taps. Heli-coils are stronger than Time-serts. Helis have deeper, coarser threads that grab the surrounding metal much, much better.

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[sandy]

sounds very cool