To helicoil or not to helicoil...(cam caps)

Thought you all might like to hear of my experience with checking valve clearances the other day. Opened up the cover, and started checking torque on cam caps, and found 3 stripped, enough to turn by hand, (bought the bike back from a friend after 15 yrs). Anyhow, went to the forum and got a lot of great info on helicoil process, etc. So, I called the local KZ shop here in Chicago, Redline, and they said don't helicoil right away.
What I found was that the actual depth of the tapped hole for the cam cap bolts is actually abot 6mm deeper than the actual bolt. I simply purchased 5mm longer shoulder bolts, and popped them in. Worked perfect. No hassle at all. They did say that the proper torque for these bolts is 90 inch#/ 7.5 Ft#, not the 9ft# as stated in the shop manual. Did that on all the caps, felt right instead of the 9#, which always felt right on the edge.

I'll check tourques again next weekend to be sure all goes well...

Thanks for sharing that tip, I'll remember it for sure!

So you are saying that the threads were stripped out the depth of the stock bolts, so you put in a 5mm longer bolt?

The bolts are 6mm with a 1mm thread pitch, so that means with your new bolts you only have 5 threads of engagement.

Jay

APE Jay is dead on. In the tooling industry we wont settle for anything less than 1 1/2 times major diameter for dept engagement. That would mean you need to have 9 mm of thread engagement or more if you desire though not required.
Les Holt

All my cam caps are helicoiled. Have taken cams out munerous times with zero issues. Now have shim under buckets so will be doing more often.

Even tightening them to 5 ft/lb, all the exhaust cam caps will stip over time. Don't know if the aluminum gets soft from heat or they used less threads in the head or what, but on a 650 it will be the exhausts that stip. Helicoil works great on these.

This is all great info, I kinda thought that there might be some issues/formula out there with thread depth. On 2 of the three holes the threads were stripped at the top. I could drop the bolt in about 6mm or so with no thread contact. With the longer bolts, it seemed that I definitely had a long way to go in once I contacted the threads. The other one had the bolt stripped. Go figure. That one contacted threads at the top all the way down.
I think I might open it up again and see what amount of thread depth I actually have and compare it to these formulas.
If they do work out, it might be a great way to go if you are in a pinch, or have one bolt stripped.
I agree that shim under should probably helicoil if they come in and out a lot, but my 900 just never seemed to need much in the way of vale adjustment.
K

When someone races, they will typically not helicoil the cam cap bolts but will drill all of them and retap to 8mm w/1.25 pitch and use stouter bolts. Use the generic 8mm torque recommendation listed in the front of a Kaw service manual. If you do decide to use inserts, I use Recoil inserts available through Maryland Metrics in "kit" form. The kit includes the tap and install tool. Problem with Helicoil is that they are just wound pieces of steel and come un coiled and come out fairly easily (use RED Loctite when installing). The Recoils don't come apart but still require red Loctite to keep them in. A better (and MORE EXPENSIVE) alternative is the Timesert which has a mechanical lock so they don't come out. Maryland Metric sells those as well. If using inserts, get the longest you can in 6mm w/1.0 pitch.

Thanks for the tips wiredgeorge. I'm thinking we should put a few recoils in our parts box in case we have trouble at the track.

Post edited by: Jackman, at: 2006/08/21 11:20

Thanks wiredgeorge,
I like the recoils, the idea of how they compress on insertion seems simple and easy.
I'll keep an eye on the bolts, and if the head needs to come aprt again, I think that either inserts or redrill will be on the menu.

RomSpaceKnight wrote:

All my cam caps are helicoiled. Have taken cams out munerous times with zero issues. Now have shim under buckets so will be doing more often.

All mine too. no problems.

wiredgeorge wrote:

When someone races, they will typically not helicoil the cam cap bolts but will drill all of them and retap to 8mm w/1.25 pitch and use stouter bolts. Use the generic 8mm torque recommendation listed in the front of a Kaw service manual.

Working on my CSR, I removed the head to replace the head gaskets, o-rings, etc. When mounting the cams back on, one of the cam cap bolts was stripping. I was going to helicoil it, and was debating whether I should buy a kit and do it myself, or take it to a machine shop.

I called a local shop, and the guy suggested that if possible, I should just drill it out to the next size re-tap, and use a bigger bolt. Hadn't thought of that, but it seemed reasonable. Plus, I already have all the tools for this.

So I thought I would check here on KZR, and sure enough, WG suggests the same thing.

Is there any downside to this, or precautions I should be aware of?

Thanks.