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

not the same model, but in a water cooled 660 that would blow gaskets for the same reason i was able to solve it with "x2" helicoils, i.e. inserts that are double the lenght of the std ones ("x1").

Back in the old days when i was doing up british bikes and helcoils where rare/exotic, we solved many problems with a custom "stepped" stud. i.e. nut side was M8 the other going into the aluminum M10 for example.


Check also the head casting, there might be potential to drill deeper for more threads and maybe use a longer stud,

What is the insert. If it's a helicoil, you can peel them back out and if you're lucky you may be able to then restore the thread with the correct STI tap and refit another insert.

If it's got an M6 helicoil then the hole will probably be near to 8mm anyway. And it would have been cut with an STI Tap (Standard thread insert).

You could also have the holes welded closed and then redrilled. You'd need a good TIG welder to do it.

This also has me thinking about the possibility of pouring molten silver solder into the holes then re-drill.

It might be easier to get a second hand head.

__________________
Did some trips.
Rode some bikes.
Fix them for a living.
Can't say anymore.

Same problem on my 87 XR600. Head bolts pulled out, threads repaired (professionally by SEP) and pulled out again. It's sitting there at the moment while I work out what to do.

I do a lot of these kind of repairs (I restore modern classic adventure bikes)

Post a pic up..

__________________
Did some trips.
Rode some bikes.
Fix them for a living.
Can't say anymore.

We do lots of thread repairs at my workplace, almost daily somebody brings in a buggered piece... 90% of the time we use a stake it insert and try to avoid the wire coil type threads if at all possible..https://www.grainger.com/category/fa...ocking-inserts

are you applying also to motorcycle parts?



an M6 = M10 external, an M8=M12....


most times there is not enough meat around....


only application i know for kinserts is BMW cyl studs that pull off the crankcase, there there's plenty of meat around...

Posting photos of cylinder.

You can see with the photos where piece of insert is broken in well, timing chain side.

My head gasket though is blowing out at right exhaust side.

One picture shows an old bad jug i have that shows how the insert is pulled out.

Best way to take out insert?

Thanks

Attached Thumbnails

 

 

 

 

 

I can't see how you can drill any bigger. The cylinder liner is too close for comfort for me. But it might be worth a try.


I would be searching for a replacement barrel.

__________________
Did some trips.
Rode some bikes.
Fix them for a living.
Can't say anymore.

Problem is getting a new one with good threads
Also I would need to rebore as well as my new piston is over sized.


Might be better off getting cylinder with pistonhttps://www.ebay.com/itm/Yamaha-XT60...AAAOSwMNxXX0RQ

Hone the new/used cylinder, new rings and try again.

Any ideas?

Thanks

not sure of what i see there in the various pics... for helicoils you simply grind a steel scribe/picker to a fine point and use it to bend a bit the helicoil wire inwards, once you are able to grab it with nose pliers, just slowly pull it out. dont be afraid to carve a bit into the alu behind the wire to lift it up a bit.



if it's a solid insert, the only safe way is to take it to a die/tool maker and let him "drill it" with his electrical-discharge (EDM) machine. had very little luck with left hand threaded removers.

Update

Always more issues that pop up

On the jug 1 of the timing chain tensioner cover inserts was bad (another thread). Fixed that with help from here-thanks.

Then took jug and head to machine shop to see what could be done. Told me basic helicoil length would not work but that longer one would work. 20mm length. He didn't have but Ebay did.
He put 2 in on right side for $50. Put all back together there to test. Held at 22 ft lbs. I didn't have service manual and he assured me 22 was right.
Took home and reassembled. Now 1 of the head bolts on the other side I can't get tighter then 16 ft lb.

Feel like throwing this in the woods and never look back.

Anyhow just in case i sleep on it and feel somewhat ambitious again....

Can I reuse head gasket at this point? Never started just bolted down. I know the right way would be scrap it but this is 1 of 3 bikes and parts add up.
Do you think 22 ft lbs stripped that other insert?
Feel if I do this again the other old one will strip out but its holding now.

I have several other 20mm m8 Helicoil inserts I just need to get the install tool. 1st time putting in Helicoil, didn't get a chance to watch machinist put other 2 in.

Any advise would be great. Thanks

22 ft lbs is correct torque. Yep I would have redone all threads while I was there! You know you want to! If youre using the genuine yam head gasket it may have peeled the thin rubber layer off when you pulled it apart again? if not then youre lucky and I would reuse as you havnt actually compressed it fully yet anyway due to head stud issue.

Sometimes the wisest thing is to know when to stop throwing good money after bad.

You need a new barrel. Stop rolling your terd in glitter...

__________________
Did some trips.
Rode some bikes.
Fix them for a living.
Can't say anymore.

piston is over sized, so more expense if i get a new jug

this xt has been turdish for a while