TOPIC:

Well, everything was going way too well in getting my 750 engine buttoned up.  During the final head re-torque, I managed to strip the front (timing chain tunnel) head bolt.
After a brief cry (and a few minutes of thought) I came up with a relatively painless idea to fix... which I'd like to run past the wisdom of The Forum.

My plan is to simply notch the cylinder block with an angle grinder, which should allow me to place a nut at the end of the cylinder bolt.

Is there any reason that this wouldn't work?

Thanks!

(photos below depict stripped cylinder block assembled in chassis, and spare block for visualizing dimensions)
 

I'm gonna say NO! That bolt needs to be able to stretch... and I suspect this and time, are the reasons it stripped the hole. Looks like a new helicoil/insert is on your list.

Also, grinding on the head? ...na, don't. You risk weaking what little is still there.

I'm sure others will have more for you, hang tight...

 

For holes like that I use a 1/4" open end wrench on the tap then turn the heli coil in with w small screw driver. I wouldn't try a nut or cut anything.
Steve

Kawasaki would not have used such an expensive bolt there unless the engineers had a dang good reason. A hardware store straight shank bolt with a nut may create a new set of problems. Also, that sharp corner in the notch you propose will concentrate the pulling forces there, crating a weak spot that will be prone to cracking and breaking. Repairing the threads and replacing the bolt with a new, factory correct one will be the best way to reduce future problems.

SWest wrote:

For holes like that I use a 1/4" open end wrench on the tap then turn the heli coil in with w small screw driver. I wouldn't try a nut or cut anything.
Steve

+1 , IMHO if you went the "notch" route to have half a chance of "even pressure" the notch would need to be milled parallel to the gasket face which would cost more than doing the job correctly and still be a "bodge" 

Neither Partzilla nor CMSNL show that style bolt in that position, though the pictures may be incorrect. They show an ordinary, straight shank shoulder bolt. I still vote for correctly fixing the threads.

Well, that idea went over like a lead balloon. 

I appreciate the feedback... and good observations on the bolt type.

That bolt actually came in a bag of hardware that arrived with the GPZ head that I bought off of eBay.  There were two of them included, and via process of elimination I had them assigned as timing chain tunnel head bolts.  My original bolts are relatively ordinary flanged items.

Is it safe to assume that I will need a replacement head gasket (having just finished crushing my new one)?

You will indeed need a new gasket 

Just following up… I went with a Time-Sert thread repair insert.  A bit on the spendy side for sure, but a nice kit.  Installation was easy following included instructions.  

Yes those 6mm repairs are nice, good job

Better than new. Nice.

Nice... looks like you drilled this in place? ...by hand???
Good job, thanks for the writeup.