Topic: What the heck to do now? Helicoil issue

[Sporkfly]

Hey guys,

On my #1 exhaust the threads stripped out from the cylinder. I helicoiled the hole and threaded the stud back in, no issues. I had the nut for the exhaust flange finger tight, tightened it a quarter turn and the helicoil has pulled out of the cylinders.

Basically: What the *#!$ do I do now? There's clearly an issue with the aluminum at that stud. Any ideas?

[bucky katt]

i've seen the metal around the stud area actually split. the 750f head on my k4 motor did that, i tiged the cracks AND heli-coiled them all

[michrobi]

Sounds like you'll have to try another helicoil, if the one didn't take. I would double-nut the stud and torque it down before putting the header on - to be double sure.

[jeepster]

Before you install the new helicoil add some threadlocker or JB weld to the hole.

[mystic_1]

If the hole is now stripped out too large, go to the next bolt/helicoil size.  You may need to drill out the exhaust flange or collar to fit the new size too.

mystic_1

[Raul CB750K1]

I may be wrong, but I seem to recall that the exhaust studs have different pitch in either ends -having a finer pitch in the end that threads into the head.

[srook]

It sounds like the hole is too big for the helicoil you are using.  Try a keyed or locking insert instead of a helicoil.  They have a larger o.d. and use standard drill and tap sizes.  There are a few diferent styles to choose from: http://www.mcmaster.com/#threaded-inserts/=2v9a0n
Scott

[turboguzzi]

You might want to go the good old "stepped stud" route, i.e. a custom turned stud that has 8mm on one end and 6mm on the other. if you stripped the hole too bad, there's also a 9mm thread, or you could go up to 10mm if there's enough meat around

another tip is to drill the hole deeper than it is. Just check what do you have behind it so you dont drill into the port or something.

TG

Before you install the new helicoil add some threadlocker or JB weld to the hole.

Jeep, the temperatures around that area make any resin based locker pretty useless.

[bryanj]

try Keenserts

[754]

By now you are running low on room.
 I use this method to fix that.(Better have a machinist buddy )

 Tap hole to a new standard or metric thread,(go straight) closest size that works. Use good aluminum bar, 6061 or 7075. Then you machine an insert to fit that snugly, ie no real clearance, DONT part it off the bar. Drill the middle of this, for your tap hole (for stud) and thread You can cut a relief, where you want this insert to end but leave dia about 1/8 over stud size.

 Now you run this into the hole, with red loctite, till it bottoms.. then grab bar with vise grips and tighten more!.. if it does not break on the notch, saw it and file flush.

 Now you have a strong aluminum insert, that is not fighting expansion rates everytime you ride the bike.

 It will be stronger than,
 The original material
 Any welded repair............. because the aluminum has higher strength, and has not been annealed

[Sporkfly]

By now you are running low on room.
 I use this method to fix that.(Better have a machinist buddy )

 Tap hole to a new standard or metric thread,(go straight) closest size that works. Use good aluminum bar, 6061 or 7075. Then you machine an insert to fit that snugly, ie no real clearance, DONT part it off the bar. Drill the middle of this, for your tap hole (for stud) and thread You can cut a relief, where you want this insert to end but leave dia about 1/8 over stud size.

Good idea there. I'll have to go bug the fella that taught my machining class to give me a hand since I don't have the machinery .

[754]

Sounds like you are in luck

 It takes someone willing to acceprt the challenge & do it right, more than someone just in it for the money.

 Probably have to bring the bike to them, Getting a nice fit thread, can take a try or two, pretty well have to fit it.


..............................................................................

 I am surprised the helicoil failed that easy, unless the tap drill used cut oversize.

[Sporkfly]

How about these guys?

http://www.timesert.com/html/bigsert.html

Is that what you had in mind 754?

[754]

It really depends on the present size of the hole, no sense in going any bigger than need be.

[Bryan Boyle]

I may be wrong, but I seem to recall that the exhaust studs have different pitch in either ends -having a finer pitch in the end that threads into the head.

Fine pitch = hard metal (steel, etc)
Coarse pitch = soft alloys

[fmctm1sw]

Sporkfly... Thought about this a week or so ago.  Is that you partaking in an alcoholic beverage with an advertised age of 20?   

[Sporkfly]

I was in the UK at the time, so it was perfectly legal 

Anyway, I'll need to measure the hole the helicoil made and look into the big-serts. The kits run at about $75 per. Yowza!

[VTCBike750]

Did this ever end up getting fixed?