Yam 70 broken head bolt/replace w/ stud.

[yam 70]

I suspected a stuck or broken ring on my 1989 Yam 70 and decided to look inside the cylinders to see what's going on. Number 6 head bolt decided it wasn't coming out and broke. Par for the course.

No way to get it out,so I drilled down the center of the broken bolt with a small bit and then a larger cobalt drill bit. Amazing how soft these bolts really are, and it appears the bolt that broke was faulty.Tried using easy- outs but even after I had drlled all the way down the broken bolt I had to use all my strength to get the sucker out even after soaking it with WD 40 etc. which was easy, as the case was broken by the easy - out on the inside near the cylinder wall, which exposed the other half the bolt hole.

I intend to build up the bolt hole with JB Weld which should be easy as there is plenty of room to use lot's of the stuff. First I will drill and tap it, then instead of using another bolt, I will insert a stud and use a nut- which I wish Yamaha used instead of bolts, as it's a hell of a lot easier to get a stuck nut off than a stuck bolt. It's easy to soak with penetrating oil and you can always cut a nut off.

Anyone ever used this method as I would think this is the only possible way to fix the damn thing?

 

[yamamarinetech40]

Re: Yam 70 broken head bolt/replace w/ stud.

Well, hopefully you know WD-40 is worthless as penetrating oil, PB Blaster is only one I would use, two I've never seen or heard of a defective bolt in a Yamaha, so you just won lottery on that one...before I had done half of all that i would have used a torch to expand the head(after penetrating oil had soaked in) and then extracted the bolt...this is a daily thing for mechanics in salt water areas...on all makes and models and types.
You can try the jb weld but I really really doubt it'll work, the stud and nut will, but the weld won't.

 

[drewmitch44]

Re: Yam 70 broken head bolt/replace w/ stud.

eather way id like to hear it goes!

 

[yam 70]

Re: Yam 70 broken head bolt/replace w/ stud.

Thanks guys-wondering should I use a helicoil for the stud as a half of one side the hole is missing?

 

[mthieme]

Re: Yam 70 broken head bolt/replace w/ stud.

two I've never seen or heard of a defective bolt in a Yamaha, so you just won lottery on that one..

He said it stuck not defective.
This is hardly uncommon.
I had 4 out of 6 (or was it 6 out of 8) power head bolts do the same thing on an 87' Merc 35 earlier this year. What fun!