1985 XT 600 Kick Start USA

Blew head gasket again [2x]

Intake boot has ripped not sure if added air might of been too much pressure at head but regardless head gasket is blown.

Head is straight, was checked for warping

Insert in head has a broken threads in 2 out of the 4 inserts.

Most probably why the head gasket has blown these 2 x.

Questions

in 2019 is it advised to double up a Helicoil or another type of insert?

I Have another stock jug that would have to be bored to fit current piston (oversized). Not sure of condition of inserts in this one as well. But it doesn't look well maintained. And 1 fin is chipped.

Or look for another jug on ebay

Old Post 2002

From: david lambeth


Hi.
This is one of the most common early xt problems.
Helicoiling the standard threads NEVER NEVER NEVER works.
I wont bore you with the reasons why.
The only way round this problem is to use two double length inserts ( of the helicoil or recoil type ) and longer head bolts. Unfortunately as you have already had inserts pull out and damage the ( now larger diameter ) thread, you would have to go up a size to M9 orM10 inserts and for these there is not enough room.
Yamaha realised this as a problem and for a while the 34k 03 type cylinder was available as a kit with longer bolts and longer threads to take them. Guess what! two years ago this part was deleted.
There are some other rather dubious ways of sorting this problem but really you need a modified 34k,34k01,34k02 cylinder or a good 34k03 standard one OR I can supply a later type cylinder modified to fit the early type top end.
Let me know if you need further help.
D L

Any help would be greatly appreciated.

Thanks
Greg