Help! My head has been (POORLY) tapped and countersunk. What can I do to fix it?

tzimmerm

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Hello all. My name is Thaddeus. You can call me T. I'll jut give you all the whole story, because in my experience, the more you know about anything, the better you are able to offer advice. So, this is my first motorcycle,chopper,and XS650. I have wanted an XS for years, ever since me and my stepson built motorized bicycles together and I quickly caught on to the fact that most of my favorite "bobbers" online or in "The Horse" mag were XS650's, or vertical twins. Fast forward about 5 years to this february, I see an ad on Craigslist while at the gym for two XS's, "make an offer". I offer 450.00 and two days later I have my first Xs- a 79 engine with a PAMCO HIGH OUTPUT ignition kit, including the NGK BPR7EIX plugs, in an '80 frame that has been chopped with a Monstercraftsman brat kit with a Biltwell diamond-stitch seat, rolling on spoke wheels. I was thrilled. I thought I had gotten a deal. Now here is a good point in my story to point out a couple facts that are relevant today. 1. I am married, and the wife has me on a strict budget of 100.00 a month. I don't want to talk about it. 2. When me and my buddy picked up the bike, the P.O. Had it wired with a battery and ignition key, but the battery was dead. My buddy hooked his jumper pack up to the terminals and we kickstarted it and watched it idle for about a minute. I revved the throttle and it was smooth and responsive. I kickstarted it again in my driveway when we got home with the jumper pack to show my wife and kids. So I know it IDLES Good. 3. I have no wiring harness, I bought this as a chopper, and the wiring was a fucking MESS, but it ran with a jumper so I knew it had to be SOMEWHAT correct. The P.O. Claims he replaced the piston rings and lapped the valves. At this point, I have enough budget and believe all I need to finish it is a headlight, taillight, and some cosmetic things like bars and grips. A couple weeks later a friend of mine sees the bike and tells me the welds are total shit and not to ride it. I stress for a week but decide to take the plunge and I order a TC BROS engine stand and the day I get it I tear everything off my bike and with the help of my buddy, manage to get the engine in the basement. I notice the right exhaust port looks wet, so we take out the plugs. They looked weird and had little teeth on them. I realized about a week later that the head had been tapped, and that the thread inserts came out with the plugs. I found some inserts at auto zone, which appear to be exactly the ones that came out. The tapped threads in the head are oval shaped; I can thread the insert in about halfway and can wiggle it left to right about 1/4 inch. I also realized that if I threaded the spark plug all the way in, it was contacting the valve! After looking at some more pictures online, I realized the head for whatever reason has been countersunk about 1/4 inch where the tapped threads are, thereby sinking my spark plug the equal distance TOO DEEP into my piston chamber! So, here I am today. It's April, I want to be riding by my Birthday in June. My brother in law, a professional welder by trade and a hardcore biker/Harley guy, is cleaning up my frame and re welding the shitty welds on the brat kit. When he texts me to let me know it's done, I will start sanding and prepping it for a QUALITY rattle can paint job. (Thats one thing I CAN do GOOD). Once it's painted I will be ready to re-install the engine and hopefully that will be that. I am planning on using a PMA and capacitor with headlight/taillight only to run the SIMPLEST and CLEANEST wiring possible. My plan is to order Hugh's PMA, and a SPARX Cap. I know this probably WON'T be the case, but I am HOPING since the bike kicked over and idled strong before I took it apart, that in theory it should run just as well after putting everything back together. My plan for the threads is to install the inserts with GREEN loctite, as recommended by my machinist gear head friend, and to use washers between the spark plug and head to make up the difference of the countersink in the actual head. I am already WAAAAY deeper than I ever planned to be in this thing. I am basically Building a chopper from the ground up at this point, but I really couldn't get deeper than opening the engine, which I REALLY can't afford to do right now, time-wise or financially. I guess what I am HOPING for is the Approval of everyone on here whose experience and wisdom I trust. Please let me know if my plan seems reasonable enough, or if it's too much to hope for or there's something I am overlooking. Thanks in advance for taking the time to read this and for any advice or wisdom you have to offer!
 

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Looking at the picture, I can't tell for sure if the spark plug area has been machined or not. I suspect not.

What I think is more likely is that you have the wrong plugs and they're too long. They should be NGK B7ES or the equivalent.

If that's not the case and you do indeed have the right plugs, I don't think "stacking washers" is the answer to the problem. That's just asking for a major compression leak.

While the best solution is to replace the head, I understand (believe me, I understand) that the funds are not there. Personally, my next move would be to find a shorter reach plug in the same heat range.
 
Thanks for the reply. I updated my post to include this info, but the plugs are ngk BPR7EIX that arenincluded in the pamco high output kit. I am assuming they are the right length because i cant believe they would include too long of plugs in the kit, but I could be wrong. Has anyone else had clearance issues with these plugs? Does anyone know of any differences in the heads from year to year? I looked at several pictures online of heads and in those pictures there wasnt a recessed area around the plug hole. If I did use the washers, I would be using thread tape on the plug and i would still be using about 3/4 of the threads on the plug anyway.
 
I might have the mechanic friend do his best with the inserts for now. If you need washers then cut one thick one instead of a few thin ones. Use the crusher type washers like on the plug to seal the washer to the head. Ride it this way and hope it holds till you find a new head.
When buying a new head, get the rocker box that goes with it. After casting the head and rocker box they machine the mating surfaces then bolt the two parts together to finish machining the cam bearing supports, valve cover holes and such. After the machining they stamp matching 4 digit numbers on both parts. On the front between the exhaust valves.
A mismatched set might work, but more likely to leak oil.
Swapping the head won't be hard.
Leo
 
......wife has me on a strict budget of 100.00 a month. I don't want to talk about it.

Holy sh*t! You get a hundred!?! :D

I might have the mechanic friend do his best with the inserts for now. If you need washers then cut one thick one instead of a few thin ones. Use the crusher type washers like on the plug to seal the washer to the head. Ride it this way and hope it holds till you find a new head.
When buying a new head, get the rocker box that goes with it. After casting the head and rocker box they machine the mating surfaces then bolt the two parts together to finish machining the cam bearing supports, valve cover holes and such. After the machining they stamp matching 4 digit numbers on both parts. On the front between the exhaust valves.
A mismatched set might work, but more likely to leak oil.
Swapping the head won't be hard.
Leo

:agree:

One thing: BPR7EIX -Projected tip.

BR7EIX -Non-projected.....maybe short enough:shrug:
 
Hi T and welcome,
while Helicoils, Timeserts etc. usually work OK I'd suppose your plug-holes may need a real old-fashioned fix.
Drill & tap them M18 and thread an M14/M18 adapter in there.
Fix it into the head with the strongest & most heat resistant Loctite that's available.
That'll give you a new sparkplug hole that's the right depth.
 
while Helicoils, Timeserts etc. usually work OK I'd suppose your plug-holes may need a real old-fashioned fix.
Drill & tap them M18 and thread an M14/M18 adapter in there.
Fix it into the head with the strongest & most heat resistant Loctite that's available.
That'll give you a new sparkplug hole that's the right depth.

The only adequate way to perform this repair Fred, the head needs to be removed to prevent all those tiny little abrasive iron (combustion chamber) filings from being deposited inside the cylinders.

I am already WAAAAY deeper than I ever planned to be in this thing........which I REALLY can't afford to do right now, time-wise or financially....

Band-aid machining can get you going, I just don't believe it'll get you more than a season or two at best, usually resulting in sudden compression loss.
 
The only adequate way to perform this repair Fred, the head needs to be removed to prevent all those tiny little abrasive iron (combustion chamber) filings from being deposited inside the cylinders.
Band-aid machining can get you going, I just don't believe it'll get you more than a season or two at best, usually resulting in sudden compression loss.

Hi NONclow,
thing is, pulling the head, either to work on it or to replace it, involves pulling the motor and the OP has posted that he's already too far into it.
Yeah, too effin' bad and ain't we all been there, eh?
However, what I'd try before I got involved in an engine removal I didn't want to do is to set up an airflow through an exhaust valve (piston at compression stroke TDC, long threaded screw through rocker arm to force the exhaust valve open) to blow the shavings out past the tooling rather than fall into the combustion chamber.
I'd use my air compressor but perhaps a shop vac in blow mode would work?
 
Hey T what happened with your plug thread issues in the end ? I came here to get an overall picture of your bikes History to help with your current running issues

Its good to try and finish a thread off with the solution so that those that are helping you know if this is still a problem and others with the same problem have an idea what will resolve their issues ;)
 
On my NGK BP7ES the distance from the crush washer to the top of the ground strap on the electrode is 23mm when eyed balled with a metal ruler. This means the head can accommodate 23mm without hitting the piston head.
 
no one said use red lock-tight on the thread inserts ? ok I will ! don't use green you want it permanent not something you can take out again...... so use red lock-tight !
the insert tapped hole probably isn't as oval as the owner suspects.... it was probably the angle he was looking at.
use red lock-tight on the thread insert ( helicoil) and a shorter plug and your good to go.....
use the stock plug for the bike ..... i don't care what they sent in the "KIT" use what the engine calls for !
Bob...
 
no one said use red lock-tight on the thread inserts ? ok I will ! don't use green you want it permanent not something you can take out again...... so use red lock-tight !
the insert tapped hole probably isn't as oval as the owner suspects.... it was probably the angle he was looking at.
use red lock-tight on the thread insert ( helicoil) and a shorter plug and your good to go.....
use the stock plug for the bike ..... i don't care what they sent in the "KIT" use what the engine calls for !
Bob...
Agree with the Red and I’d use anti seize on the plug threads. Better chance of not pulling the insert. Might be a good idea to remove plugs while cold too. That way the Loctite will still have a chance to hang on.
 
T, a shop weinered my plug threads once upon a time. This is not the end of the world. There are kits available. Either Keensert or Helicoil or a couple others. Not too hard on the budget iif I recall correctly. Remove the exhaust head pipe. Rotate the engine via lefthand cover alternator bolt. Both plugs out. Tape a vacuum cleaner hose to the exhaust. Make sure all the air is coming through the plug hole. Follow the directions on the insert while keeping the vacuum running. I did this on a 2-3k mile motor and it was good 47K miles later.
 
I am still scratching the head. After satisfying the head itch, what if the transmission is a no go? All that time and money before even testing.
'TT':umm:
 
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