first big mistake

so i was drilling out a sheared off exhaust head stud, but failed to notice that it was sheared so the remaining surface was angled.

when i tried to drill it the bit walked and i fouled the threads, and i still cant get the remaining piece of stud out.

I was thinking i could continue drilling, then tap out a new, larger stud hole.

Is this possible/advisable? there is ABSOLUTELY NO WAY that I can get the remnants of the existing stud out, and even if i could the threads are shot so i couldn't get a new stud in.

the frame is in the way so it will be really hard to tap out with my drill... any advice for this (besides a different drill or pulling the motor?)

the PO ignored the problem and worked around by attaching that side of the plate (for lack of a better term) to the frame with a piece of sheet metal, but methinks this would pull on the pipe, possibly creating a leak.

ideas?

 

if you continue drilling a larger hole, you can tap it for a Heli-Coil and you'll be all set. If you're unfamiliar with them, check out THIS video on youtube showing how it works.

 

sounds good. how much is a helicoil syustem?

what size are the exhaust studs?

 

But there is one issue with the helicoil in your case.
Since you said the drill walked to the side and now you aren't close to the middle if you put a helicoil in the new hole, it will most likely not line up with the hole in the exhaust collar.
You will most likely have to enlarge the hole in the collar also.
If at all possible, you should try to get the enlarged hole close to the center of the stud and straight somehow.

It's possible you could make a homemade "drill bushing" and use that to help control the drill bit. IF you want to try, I'd grab a chunk of steel...maybe 3/8" thick, and use the collar as a template to drill two holes in the plate the correct distance apart. Then bolt the one side to the head with the good stud, and then use the other hole as a guide to drill the oversized hole. It should help you keep the drill straight and close to the center.

I know not everyone has access to the stuff you would need to do it, but you get the idea of what I would try to do.

 

That sounds like a very hard thing to do with the head still on the engine. I'm going to give you some advise here. If it were me. I would pull the head off and take it to a machine shop to get repaired properly. If you keep drilling you run the risk of making that head non repairable. A good machinist could put that head in his head bench and clamp it tight and machine that broken stud out. We simply can not do that with a hand drill. I have been down that road before. If you get the helicoil in there crooked the exhaust flange won't fit anymore either. Which causes even more issues. Hope it all works out for you.

 

good idea mike. the hole in the collar (so that's what it's called) is actually already enlarged from the PO's shoddy repair job. I'll do what i can and post an update when im done.

thx

 

Great vid on YouTube, Bluepotpie. Makes the Helicoil process clear.

Is there any of the bolt showing? There was an interesting thread a while back about using wax. If not, or if it doesn't work, I second the machine shop route.

 

Bite the bullet, yank the head, and take it to a machine shop. Anything else is wasting your time and jeopardizing the prospect of ever fixing it correctly. Yes, it sucks. But you will only make matters worse trying to do it by hand, the laws of physics are TOO stacked against you.

 

wow. wish i had waited for those last few responses, because i just did what y'all said not to, and, guess what, now it's pretty much unfixable.

awesome.

so... what exactly is the "exhaust flange?" is that the plate/collar dealio we were talking about before?

and... my next bright idea. Please shoot me down if it's ridiculous.

I mangled the threads, heli coil wont work. there's nothing left to machine out... so what i'm thinking is i could use a small steel bar to connect the collar on the broken one to the stud on the next pipe over.

better put, could i bolt a piece of steel to the adjacent good stud and collar, then bolt the collar where the bad stud was to the steel bar? would this provide enough force to hold the pipe in place?

can i still take it to a machine shop and have them work out something a little more professional for me?

how much would it cost, approximately, to have a machine shop create a new, larger threaded hole in the head and widen the hole in the collar so i can get an extra large stud in there?

 

A machine shop can fix it for you. It may now take some WELDING but it's not unfixable. Just don't make it any worse.
I really wouldn't try to jury-rig something off the other pipe; remember halfway measures got you where you are.

 

that's good to know. and yeah, you're right as usual fitz. i probably shouldn't half-a$$ it. i actually have a neighbor who welds and does a LOT of serious mechanic/machine work. he's a log truck driver and does all his own repairs. I'll have to ask him if he can fix it for me...

what would this fixing entail? welding the stud into the gaping hole i created, or something more subtle?

 

plus if you make the one stud do the work of two, it will probably snap off too.

 

The head will have to be cleaned so there is no oil in and or around the area where you were drilling. Hot tank and bead blast. The old stud will need to come out and the whole thing will need to be welded up solid. This is the part where the machine shop comes in. They will need to machine that area so the hole for the stud can be drilled and tapped. Not sure how the gasket mating surface made it through what happened but that may need attention also. Don't know what the shop rates out there are but you'll have some $$$$ into it. Maybe you could pick up another head with no broken studs and spend the money on a nice valve job instead.

 

Good thought. I picked up a spare 550 head, COMPLETE with cams and cover, for $10 on Ebay.

 

mn maxims, that sounds way more up my alley.

how easy/difficult is it to replace the head/cams? do i have to take all the valves and stuff apart too?

i might just bite the bullet and shell out the cash for the machinist.

 

i would try to buy a new head first and which ever one cost less thats the one your go with. a new head might have better vavles, shims and cams then the ones in your bike right now. who says once you get this fixed that you dont have to spend more money on the shims or vavles? my idea would to try to find another complete head and then have spares off your old one. youll have two sets of cams, shims, valves, sprokets. might just cost you as much as you need to pay out for the machining.

is there a wrekcers near by? ask them how much it would cost for them to take it off, then ask how much it would save you for you to take it off, i dont know about where you are but somethigns are half as cheap if you do it yourself.

good luck. remember to look at all your options before you do anything else. speed kills and costs lol

 

haven't found a head for a good price... the only one i can find is on ebay for $100

the machinist is only $76/hr... and he said it'll only take about 30mins.

question: I'll be able to get at the valve adjustment shims once i take the cams off, correct?
I'll also be able to see what my extremely loose exhaust valve on cyl 1 is caused by if i take off the head, right?

 

While you have it off you can examine the whole valve. I would be tempted to examine and replace parts and lap them while I had it off....