stripped cam bearing caps

any way to repair pulled out helicoils? my bike had helicoils in every one of the cam cap bolts, the inserts were the short ones that pulled out, now the only way to fix the the bolts that do not have the dowel to go through is with larger timeserts, what do i do about the locating dowels on the cam caps? you can't use the dowels if you install larger inserts. whoever repaired the head originally should have used longer helicoil inserts to begin with, otherwise i wouldn't be asking these ?'s any ideas for a suitable repair? or should i just scrap the head and look for another? anyone have an extra 81 and up j model head laying around to sell? what about heads off kz 1100s, will they work also?

There are several articles on this subject. Pretty recent too. Roy

one of my friends is a machinist and we came up with a repair that would be a permanent fix, i don't trust the helicoils or the timesert methods because there just isn't enough material being utilized to hold either method of repair, with the timeserts you can't use the dowels on the cam caps, we are doing all 16 cam cap bolts and will have the head back on next week sometime, after looking at all the repair methods out there, this will be a permanent fix and no worries about a helicoil failing on you miles from home. will keep you posted on this and see if it will work.

avidflyguy wrote:

any way to repair pulled out helicoils? my bike had helicoils in every one of the cam cap bolts, the inserts were the short ones that pulled out, now the only way to fix the the bolts that do not have the dowel to go through is with larger timeserts, what do i do about the locating dowels on the cam caps? you can't use the dowels if you install larger inserts. whoever repaired the head originally should have used longer helicoil inserts to begin with, otherwise i wouldn't be asking these ?'s any ideas for a suitable repair? or should i just scrap the head and look for another? anyone have an extra 81 and up j model head laying around to sell? what about heads off kz 1100s, will they work also?

I have a head that is "lying around"
I believe it to be an early gpz head...but am not positive...do you know the valve sizes?
or any other way to tell for sure?

avidflyguy wrote:

one of my friends is a machinist and we came up with a repair that would be a permanent fix, i don't trust the helicoils or the timesert methods because there just isn't enough material being utilized to hold either method of repair, with the timeserts you can't use the dowels on the cam caps, we are doing all 16 cam cap bolts and will have the head back on next week sometime, after looking at all the repair methods out there, this will be a permanent fix and no worries about a helicoil failing on you miles from home. will keep you posted on this and see if it will work.

You have my interest...keep us informed.

By "dowels", I assume you are referring to the knock pins, right?

I've tried two different methods, both with success.

I've drilled and re-tapped for an M8 bolt. But you can't do that where the pins are.

I've also used these thread inserts . The drill bit size needed for these fits inside the existing hole for the knock pin. So after drilling and tapping for the insert, the knock pin still fits snug in its original hole.

that is similar to what we are doing, but the inserts that are commercially available are too short, we wanted to use longer inserts so that there is more threads to lock into the softer aluminum, so we machined much longer inserts, we used inserts .925 long in the holes with out the "knock pins" and .700 long inserts for the holes with knock pins. we used a bridgeport mill to center all the holes and drilled and tapped each of the 16 bolt holes, its the only way to do it with affecting the alighnment of the caps

the head is back on the bike, installed new valve seals while it was apart, valves looked very good. no leaks at all around the valves perimeter, even with out springs. felt good about the condition of the head now. cam bearing cap bolts torqued up good and solid, no more pulled threads. I think the repair we did to the heads would be beneficial to anyone who has this problem. i don't think the commercially availble inserts are quite up to the task and i think you would have problems down the road with the short inserts