One lean cylinder

[Rick65Cat]

Well....I think I found WHY I have one hot cylinder. But, in discovering the problem, another has cropped up. Namely a broken intake boot screw. Fortunately (if theres such a thing) it broke on the outer cyl and its the outside screw.
Now, short of removing the head and getting it machined out..what are my options before I touch anything. I have shot it with "Gunk" penetrating oil to start soaking it.
I do have new O-rings and stainless capscrews on order. Also, I think I will order new boots. These ones are not very squishy

[chef1366]

Tape off the intake port and drill it out with a lefty bit. Alternate with heat and I bet it comes right out.

[Nessism]

I'd try lots of oil spray and heating the screw nub with a propane torch - get it good and hot. Let cool, more spray, maybe two heat cycles, and then try to cut a slot in the screw with a dremmel or similar and then use the impact again using a flat bit. You can also try to weld a nut onto the nub if you have a welder handy (this is the best choice). Last resort: drill it out. Start with a small bit in the center and expand up in size. LH drill bits are reputed to work well for this purpose.

Good luck, take your time, and you will get it.

[Rick65Cat]

The only problem trying to drill it out is the upper frame tube curls down almost in line the the intake port and my drill isn't tiny by any stretch. And the drill bit would be going in on an angle.

I've seen the "weld a nut on" trick done on car stuff but those parts were steel. I'm worried about the heat transfer temps from the welder on the aluminum.

I guess I'll just soak it a few days, tap a mallet on the aluminum around the screw and the screw itself every day. Then cut the slot and impact it with my driver and hope for the best.

[hampshirehog]

I've seen the "weld a nut on" trick done on car stuff but those parts were steel. I'm worried about the heat transfer temps from the welder on the aluminum.

No need to worry - you'll be fine. This works a treat as the heat generated by the welding very often helps with loosening the stuck thread as well.

[chef1366]

Pull the motor. It's only a few bolts.

[Herzie]

What about drilling a small hole and sarificing a torx bit or something? If you get it in real tight you might be able to remove it. And if not you can still drill it out.

[chuck hahn]

I wrote about how i took the bolt out of the exhaust side that had snapped off flush. In that spot ( intake side) i would use a 90 degree angle drill to make the pilot hole. Then use a LEFT HANDED thread tap and tap the hole. Use a LEFT HANDED bolt and put in the bolt...you will be turning counter clockwise to tighten a left handed bolt. As the bolt comes tight you are now turning the RIGHT HANDED bolt out.. shoot it with some pb blaster and it wil be out in two minutes. Just picture it in your mind and you will see what i mean.. screw all that ez out , welding a nut, torque bit bull. keep the tap and bolt for future use. any questions call me...248 219 4122

[Rick65Cat]

Thanks for the replies guys.

Heres whats happened so far in this saga. There was about a 1/8 inch of the shaft left sticking out of the hole. I took a scotch bright pad on a wheel and ran it over the nub to clean off the rust. (rags inside the ports)
Then, I took my dremel and cut a slot across the nub and tried using a flat blade in my impact driver. Broke off one of the tangs on the end of the nub.
So, I dremeled the other tang off to flatten the shaft flush with the aluminum head. Then I took a starter punch and drifted a start point for a drill bit.
Drilled a 3/32 hole into the shaft and luckily it went in straight enough that I doubt it hit the threads. Also drilled right through the length of the shaft (about 3/4")
Then I used a reverse spiral "EZ out screw extractor and attempted to get it to turn. Its stuck fast and I was afraid of snapping the thin extractor. So I drilled a larger hole (5/16) and went to the larger reverse spiral. Still no luck.
I sprayed WD-40 into the drilled hole in hopes that it might seep into the threads from the reverse end of the screw and loosen up the crud that way.

Chuck, I think the hole I've drilled now is too large to get a left handed tap in without buggering up the original threads. I wish I'd thought of that trick a little sooner.

[chuck hahn]

yeah i used a 1/8 hardened bolt.. now plan B..

Since it is drilled out thus far..just keep slowly increaseing the drill bit sizes but stop short of being too big and hitting the original threads in the head. at this point take a very small flat head screw driver and easily tap it in along siide the bolt and the head. the idea here is to remove as much of the bolt as possible so it can collapse into itself with the screw driver. Once it starts to fold in you can usually grip the edges with some needle nose pliers and wiggle it back and forth till it will screw the rest of the bolt out.. again use a propane torch to heat it up and some oil in there and it will come out. run a screw back in the hole once the old stud is out and you should be ok. let me know what happens. oh and anything with a little point like a scratch awl will work to get the bolt to collapse inward too EDIT 125..LOL.. replace the screws with stainless allen head bolts

[Rick65Cat]

yeah i used a 1/8 hardened bolt.. now plan B..

Since it is drilled out thus far..just keep slowly increaseing the drill bit sizes but stop short of being too big and hitting the original threads in the head. at this point take a very small flat head screw driver and easily tap it in along siide the bolt and the head. the idea here is to remove as much of the bolt as possible so it can collapse into itself with the screw driver. Once it starts to fold in you can usually grip the edges with some needle nose pliers and wiggle it back and forth till it will screw the rest of the bolt out.. again use a propane torch to heat it up and some oil in there and it will come out. run a screw back in the hole once the old stud is out and you should be ok. let me know what happens. oh and anything with a little point like a scratch awl will work to get the bolt to collapse inward too EDIT 125..LOL.. replace the screws with stainless allen head bolts

I'm thinking i'm at the point where any more drilling will put me in the orignal threads or darn close to it. I'l try the scratch all....who knows I may get lucky.

[chuck hahn]

only go in at one spot..slowly tap it in and it should start folding in to itself.. Get ahold of that folded in part with the needle nose and turn it back and froth to work the oil in and just be patient and persistant with it..Heat the crap out of it with your propane torch too that will expand the aluminum a bit and help oil get in to the threads

[chef1366]

only go in at one spot..slowly tap it in and it should start folding in to itself.. Get ahold of that folded in part with the needle nose and turn it back and froth to work the oil in and just be patient and persistant with it..Heat the crap out of it with your propane torch too that will expand the aluminum a bit and help oil get in to the threads

Heat is your friend here.

[Nessism]

If you are not centered in the hole work the bit sideways until you are. I removed a broken cam bolt yesterday and had to do this because the pilot hole was off center. In the end I got it centered up and by the time the hole was just shy of hitting threads the screw came out. Of course I was using LH drill bits so that helped in the end, but not while making the smaller holes.

[Rick65Cat]

Well....I've gone as far as I can with the tools I have. I don't feel I got all the screw out.
As best as I can tell, the threads in the hole are ok along one side the length of the hole. I can't see the "other" side of the hole as I'd have to get my head in where the carbs would sit. I'm going to buy an appropriate sized tap and gently run it in.
Now, what would the tap size be? Digital calipers say the dia. of the screw reads almost 6mm. And how many threads per inch?