As seen in previous post, the z1 blew out 4 (non-heli’d) cam cap bolt holes randomly, out of no where after a year of being totally fine.
So, I heli-coiled the z1 cam caps fucked threads last night.
Went well. Engine is fixed. Really glad I didn’t have to take head off and take to Mar auto. I loosened and re-tightened all 16 bolts. All tightened down well. Hopefully no holes blow out again. Gotta love old shitty bikes and high-lift cams.
So, now I have about 8 or 9 of 16 holes heli-coiled.
My method of installing heli-coils is below: (all points open for debate)
- buy new pep boys thread repair kit – m6 / 1
- buy some blue loctite
- if not taking engine apart tape shit off real well
- drill out hole on super low speed with motor oil on drill bit
- use thread repair kit to re-tap hole to bigger size. Oil on tap
- while re-tapping hole, turn in 1 full turn. Then back out half turn every full turn
- while re-tapping hole, completely remove tap every 3 full turns to clean debris from tap inner catch area
- once hole is re-tapped and smooth, clean out any debris and oil
- put heli-coil in with a small drop of blue loctite on outer side of heli-coil
- make sure bolt goes into heli-coil smoothly
- I would not recommend using any loctite on the bolts that go in and out the cam-cap holes as they need to be serviceable, regardless of if any of the holes are heli’d or not.
- Larry Cavanaugh, the kz cylinder head guy, recommended keeping the threads on the bolts that go down into the cam caps holes oiled or greased. He said this to me in one of our emails when he ported my head and fixed a couple fucked holes.
- Specifically Larry said: Make sure you oil the cam tower dowel pins and the boss holes they go into in the caps when you install the cams. Oil the cam bolt threads too. Make sure the tapered end of the dowels point up toward the cap. The majority of stripped cam tower bolt holes result from the caps binding on those dowel pins
- Done. Go race people.
5 responses to “Heli-coil heaven”
Published - Feb 15, 2020
Trip to Pittsburgh to Wheel Mill. Washed up for sure. Ilford Delta 3200 film.