cross threaded spark plug

[kbart1]

well today was a great day AND a really bad day at the same time. got out on my bike FINALLY and did about 20 miles. everything was working great and seemed to be getting better and better with every mile. once i got back i thought i would pull the plugs to check the color as i haven't yet adjusted the pilot screws, they're all at 2 turns out right now. plugs looked good, nice tan color. installed them back one at a time after i checked them and cross threaded #3 plug. any advice on how to fix this? i don't want to make it any worse and am hoping the local honda shop has a trick to fix this? I REALLY DON'T WANT TO HAVE TO PULL THE HEAD as my project was JUST getting completed. AM I HOOPED HERE?????

thanks!
kent

[Samelak]

If it is fully threaded down, the thread could be beyond repair without a heli-coil. Only way to know for sure is to remove the plug. If the thread looks like its still there, you can pick up the thread with a spark plug tap. Coat the tap with heavy grease and tap it. Clean the chips from the grease every full turn to prevent falling into the cylinder. Once the threads are corrected, torque the plug to spec. If it holds without stripping, then you are good. If not, it will need a heli-coil.

[daves79x]

Excellent advice Samelak. I need to say something here about the pilot screw settings. Several newbies here have seemed to agonize over getting these set properly (once the engine is running). The shop manual is to blame for that, I think. They describe a complex procedure using a precise tachometer. Forget all that! Just bench set them to 2 or 2 1/2 turns out and forget them. Minor adjusting will do little or nothing for your carbs. If you still have low-speed problems, it's not the fault of the pilot screws. Get the internals clean and bench sync'd properly and 99% of these carbs will run just fine. Just thought I'd throw that out there since there's been some discussion about it recently.

Not that you wouldn't have cross-threaded the plug at some point anyway, but for this purpose, you didn't need to check the plugs. Your fuel mileage will tell you if all's well. A stock late model will get well into the upper 30's if not 40 mpg with stock carbs.

Dave

[kbart1]

thanks guys

no it wasn't threaded all the way down. probably not even half way down but now i can't get it to bite and go in straight. the plug tap sounds like it MAY be the way to go. i also saw something on the web called a "backout tap" which goes into the plug hole and then it basically expands and then you back it out of the hole starting on the comb chamber side where the good threads are hopefully, anybody tried one of these? either way it looks like i have to drop those damn pipes and tilt the motor again!!!!

good advise on the pilot screws dave. stupid thing is the bike was running / idling great. just wanted to check plugs for lean condition and even STUPIDER YET checked the plug while the motor was hot

kent

[Larry Zimmer]

Unfortunately, while it won't help you, Kent, this picture of what i use to install plugs might help someone else from cross-threading.

It's a rubber vacuum fitting cap. Find one that is a bit of a snug fit over the top of the plug. Then, screw the plug in until it seats. If it won't go in to virtual seat with finger torque, something isn't right. DON'T put a wrench to it until you can fit-tight seat it. This little cap gives enough grip to be able to seat it if it's not cross-threaded.

I've read of the 'back-wards' tap. Can't remember where -- might have been Paul Dean in Cycle World. Sounds worth a try. Don't remember the source. Try 'googling' it.

[kbart1]

thanks guys

that "backwards tap" is actually called a "back tap" i believe and i have ordered one on ebay, along with a spark plug thread chaser. my plan is to try to use the back tap to restore the threads from the combustion chamber out then if need be "chase" them and then HOPEFULLY torque the plug down to see if it holds AND i really hope to do this without having to tilt the engine!!!!! getting the prolink exhaust on and off is a real pain in the arse, not to mention it scratches everything up while doing it! I REALLY HOPE I DON'T NEED TO REMOVE THIS HEAD as i was pretty much finished and ready to go. further to your advise larry about the rubber vacuum plug.

DO NOT MESS AROUND WITH YOUR SPARK PLUGS WHILE EVERYTHING IS STILL HOT!!!!!

i will report back on how the back tap worked after i try it.

thanks
kent

[Larry Zimmer]

I just happened to be going through things for a different reason when I saw this thread. One bit of advice for people who might be new to engine work wanting to do some things themselves. First off --- GREAT!!!! With respect to spark plugs -- in any engine -- screw the plug all the way to the head with finger torque. (If not all the way to the head, AT LEAST 3 full turns.) If you can't do that, something is not right!! You can use the socket on the plug; or, something such as I showed above. Just don't put a handle onto it!!!! If it won't go by finger/hand torque, either you have gotten the plug started with threads crossed; or, the threads in the head need a bit of cleaning. Whichever, sort it out. You will typically never be able to run a plug down past about half a thread by hand if you have started it cross-threaded. And, that can typically be corrected without a big tear-up -- often just by carefully re-starting the plug squarely. (Yes, I studied this at U of HK -- plug change 101.)