Topic: Well #$%*! I think Ive done it this time. Stripped exhaust hole.

[VTCBike750]

So long story short.  #1 exhaust was leaking. I tried to use what I thought were crush exhaust gaskets in some kit that came with the bike (from oldbikebarn). They didn't crush too well and I managed to strip the exhaust holes to #4.

Based on the number of shavings I got out and how far into the hole the stripped threads look to go 3/4), the PO may of done this as well.

Its not totally stripped. I can still get the bolt to thread in some what and it does have retention.  Id say about 3/4 of the way in the bolt sort of hits a stop and doesnt want to go further.  Im thinking that maybe I could retap it

Ive read a few things about helicoils and timeserts, but these almost seem to much for the sort of repair that I need.

Some day Id like to pull the engine for a rebuild, and I can have this sort of thing repaired by a machinist.

Id appreciate any help with this one guys, I sort of feel F*#ked.

[Jon]

Helicoil if you don't want a bodge job.

It's a DIY job for a long lasting repair.



Cheers
jon

[sick_seven_fifty]

DONT DRILL IT OUT YET...if it still threads in part of the way and stops, then that means there should be enough meat there to just get a tap/chase the threads.  Just take the bolt to a hardware store and get them to sell you a tap that matches the size of that screw, then screw the tap in and out of the hole to clean the threads.  This is a VERY easy fix, so don't make it more complicated on yourself by drilling and and retapping or helicoiling.

If you do this, and the screw won't tighten down (i.e., keeps spinning, totally stripped), then at that point you will need to drill the hole and helicoil or tap it it to larger size.

[sick_seven_fifty]

Another note...what you described in your original post sounds more like it is cross-threaded, not stripped.  Stripped means it will not tighten down at all...cross-threaded means the threads have crossed at some point, and the screw won't go in all the way.

[VTCBike750]

Thanks sick_seven_fifty. Im trying to come up with the most conservative approach. What Im thinking of doing is either retapping or trying to rethread it.

I read a post once about taking an appropriate bolt, cutting a groove in it, and using that bolt to rethread/remove debris from the hole.  Trying to preserve as much of the metal on the inside, by not cutting. Thoughts?

Then Im thinking of using loctite when done (is there something better?). Then after the riding season or in a year or 2 when I pull the engine, ill get a machine shop to fix it.

[sick_seven_fifty]

If you've ever seen a hole tap, it actually looks like a bolt with a couple of grooves cut in it, so yes in theory you could make one with a bolt BUT it would be very difficult as these bolts are made of hardened steel, and when you cut the groove, you will also, mangle up the threads a little bit, and the cut won't be perfect.  It would be worth your time and money to get a proper tap.

I wouldn't bother using lock-tite...if the bolt won't tighten well enough after you chase the threads, then something else needs to be done to repair it.

Also, examine the threads on your bolt as well...if any of them look damaged go ahead and get a new bolt as well...it will cost you pennies to get a new one.

[VTCBike750]

Another note...what you described in your original post sounds more like it is cross-threaded, not stripped.  Stripped means it will not tighten down at all...cross-threaded means the threads have crossed at some point, and the screw won't go in all the way.

Basically I was tightening things down, thinking that that crush washer was being crushed, and then felt the threads give. Looking in the hole there are threads missing (but not entirely), but I can still thread the bolt in. I guess its hitting an area where its cross threaded about 3/4 the way in.

[VTCBike750]

I have a tap set, I just dont want to jump into anything and muck it up more.  Also, the threads on the bolt look great!

[sick_seven_fifty]

Just make sure you've got the right tap before you start.  If the tap is marked you can check the bolt with a thread gauge, but since most people don't have a thread gauge handy....:

What I usually do is find the tap that looks closest to my bolt.  Drill a piece of wood and tap it with the one I chose, then thread the bolt into the wood to make DOUBLE SURE I've got the right tap.

After that, just thread the tap into the hole in the head.  Screw it in a couple of turns, then out one turn, then in a couple of turns, then out one turn, etc., etc.  This will allow the debris to fall into the grooves of the tap.

Don't be scared to get in there and do it...just go slowly and think everything through.

Good luck!

[camelman]

I don't know all the tap lexicon, but there are a few different types of taps on the market.  One type will roll the metal back into place while another will cut new threads.  Some have tapered ends while others have flat ends.  I think you should wait to hear what type is best suited for what you are doing.  If you end up cutting new threads, then you might cut through whatever is left.  If you use a tapered tap on a blind hole, then you might only really capture one or two threads before you bottom the tap out, which could make it very easy to tear out those two threads.  I'm sure one of the machinist experts will weigh in shortly.

Camelman

[sick_seven_fifty]

Indeed, camelman, there is more than one type.  The type that more or less moves the threads around is called a thread chaser, rather than a tap.  Good luck finding one though.  It's not something that is commonly found in hardware stores (at least not in my neck of the woods.)  A tap can be used the same way, but greater care needs to be taken in it's use.

Great advice though, and indeed if you can get your hands on a thread chaser, it would be worth it to try first.

[sick_seven_fifty]

If you have a Sears...

http://www.sears.com/shc/s/p_10153_12605_00942275000P?prdNo=1&blockNo=1&blockType=G1


I wouldn't mind having this set myself!

[Bodi]

It should be a 6mm x 1mm pitch. Check to be sure but I'm pretty sure.
The problem with what you describe is that if it was crossthreaded the outer part will be messed up, and the bottom part is probably OK threads... however when you retap the tap will follow thw crossthreading and probably destroy the good threads below.
A helicoil is really easy to use. You drill out the old threads with the kit drill, tap with the kit tap, and insert the helicoil with the inserting tool in the kit, then break off the tang with something. For this application make sure you use a long insert! There are different lengths and the short one is not good for much torque before pulling out. Use copper antiseize (high temperature kind, anyway) since without it the stainless insert reacts with the head aluminum and the steel bolt, corroding the aluminum alloy and then the insert just pulls out after a while.

[VTCBike750]

Sears is like a candy store.

Got the rethreading kit. Im gonna try to save this thing, hopefully not mess it up further. I guess worst case I could helicoil it. Ill keep you guys updated.

Thanks for the help

[VTCBike750]

Hey whats your thoughts on Alumiweld for something like this?

[sick_seven_fifty]

I think you are headed in the right direction with the rethreading kit...good luck!

Not sure what you are suggesting to do with alumiweld, but I can't think of any good use of it in this situation.

[Ernest T]

The problem of with that kit is they don't sell individual taps.  I bought it and used the heck out of the 6 mm X 1.0 and now its worn enough to not work well and I can't find a replacement.  I don't want to spend $40 more just to get another tap that will wear out again.  I've googled them and it seems that the only ones sold individually are for spark plugs.

[sick_seven_fifty]

Don't leave us hangin'!  How did it work out?

[VTCBike750]

Haha, oh dont worry Ill let you guys know. Im waiting on some exhaust gaskets, along with some countershaft oiler screws, that I had to order. Im hoping Saturday is the day that I put it all back together.

I did go through each exhaust hole and measure the depth (range of 26-30 mm, little surprised by the variation) and how far in the bolts would go in until the first resistance, where I had to start screwing the bolt for it to go in. The 2 bolts for the 4th exhaust are totally stripped 9 and 12 mm in, leaving some remaining threads in the hole! The middle threads aren't perfect, but arent totally stripped. So there is some optimism and light at the end of the tunnel.

I havent tried to thread the bolts all the way in, I wanna to run the thread repair in first.

My thoughts on the alumiweld was to "weld" it on to the side of the holes and retap or screw in the bolts and then flow in the alumiweld. Just thinking outside the box. It seems hard to get large objects up the the proper temp for the alumiweld to bond.

 

[Duanob]

Just helicoil it and forget it. If you pulled threads out of the aluminum head the head material is soft and will happen again. I bought a 6mmx1.0 tap/coil kit for $14 that worked perfect. It came with 6 inserts and I know that if it happened to one stud it will happen again. I am ready.

[VTCBike750]

TADA! The bike is back together with the exhaust back on and so far no leaks .

I ended up running the thread repair and a tap as well.  I ran the thread repair in as far as it would go and then used a tap for the remaining length. Definitely make sure that it engaged the left over threads.  Tried to screw in the bolts and came up with a lot of resistance keeping the bolt from screwing all the way down, about 3-4 mm.  So I then ran the tap down the holes a few more times cleaning up some of the deep resistance. I used a torque wrench at 80 inch lbs, and was able to get everything put together nice and flush.

By the way guys, thanks again for all the help. I did buy a Helicoil set but with hopes that I could return it.  So far so good. Also I cant emphasis how awesome the thread repair kit is.  I ran them through everything that I had apart, definitely cleaned up a lot of crap.

[VTCBike750]

Well apparently swapping out the exhaust gaskets, and the droppibg the exhaust again did the hole in.  Time to helicoil!

[754]

 Dont FEAR the Helicoil.. shoulda done it right away.
 Ernest, 6x1 should be commomnly available..get a good quality one should be around 10 bux, and better than the rest of yours..
 However, the ones we are talking about are probably 8 x 1.25mm.
 The cutting of a bolt, its not hard to cut with cutoff disc, run nut on to debur... but, it will be undersize(compared to tap), and have NO radial relief..

 If you wear a tap in only a dozen cuts its probably junk, I often got 600 to 1000 cuts on say a 5/15 tap doing holes  3/4 or 5/8 deep..maybe that aint so good.. its only 4-7 hrs tapping..

[VTCBike750]

Its pretty badass! And unbelievably easy

Anyone know of any long term problems with the corrosion of aluminum and the stainless steel

[754]

 No.. Stihl chainsaws had every thread in their alloy cylinders helicoiled from factory.. probably for reliability..