Topic: i messed up.......cross threaded spark plug

[999]

so after overhauling everything i could think of on my K3,i went and cross threaded the 4th spark plug.......i have 120 compression in cylinder 1-2-3 and have a huge 0 in cylinder 4.so what are my options,is it possible to take the top end off while keeping the engine on the bike??if so i could just tap cylinder 4 and be good i think but if i have to take the engine out i might as well freshen up the top end i guess,im not in a position to do the work myself so if anyone knows a good mechanic for an engine rebuild in the Montreal QC area give me a heads up,thanks for your help

                                jason

[Gordon]

Whether or not you can remove the valve cover and head with the engine in the frame depends on what bike you have.

[999]

1973 cb750k.thanks!

[andy750]

No you cant remove the head with engine in frame. What I have seen done successfully in the past when this happened was to re-tap using a vacumn cleaner to catch any debris...tricky...but it can work if done properly.

[vames]

I once cross threaded a spark plug on an old XS650 I had one time. I bought something called a "thread chaser" which is not quite as sharp and bite-ey as a tap, and it worked like a dream.

[Slams77]

I used an internal thread chaser that I picked up from my local automotive store which re-threads from the bottom up, and I didn’t have to remove anything either.  Just use plenty of grease to avoid the shavings from falling back in to the hole.

[999]

awesome advice,thanks a lot.... i feel a little better about it now.cheers!

[malcolmgb]

re-threads from the bottom up

how does that work  do you have any pictures of it.

[Slams77]

This is what I used.  First start by inserting the chaser with grease all the way through, turning the knurled knob just until it catches the bottom portion of the threads.  Then rotate it as if you were unscrewing it.  Make a few passes adding grease to the chaser each time until it is fully expanded and the threads are repaired.

[ARANUC]

i had the same thing happen to my bike. But after taking the head off and looking at the price of the tap it was easier just to take it to the Honda shop they charged me 35bucks to drill it and put a heli-coil in. Better then  me trying and messing it up

[IainC]

I had this happen on my old 350f and I ended up ordering some expensive heli-coil kits and used one of them. Worked fine but I think I may have been better off taking it to a shop to have it fixed, but I didn't want to tear into the motor.

If you don't take the head off, be careful of metal shavings getting into the cylinder, I used grease to catch most of it.

[dave500]

a chaser is good,but if its really stripped its stripped,hope yours can be repaired easy

[City Boy]

Hi gang.Another trick if thread is not real bad is as follows;using a hack saw,cut a couple of slots at 90 degrees to the threads on a spark plug,apply some grease to plug threads,and thread into hole.As plug cuts into damaged part of threads the filings will accumulate in the slots you cut.    Rock On

[Motoguy23]

If you dont want to buy a thread chaser you can get a regular bolt that threads into the spark plug hole and cut notches in the side with like a hack saw or if you have a cut off wheel and air compressor that would work best.

[Gorms]

No you cant remove the head with engine in frame. What I have seen done successfully in the past when this happened was to re-tap using a vacumn cleaner to catch any debris...tricky...but it can work if done properly.

This is what I did when I mildy f-ed mine up. I also duct taped a small tube to the end of the shop vac and stuck it into the combustion chamber to get any pieces that might have made it through.

[MCRider]

No you cant remove the head with engine in frame. What I have seen done successfully in the past when this happened was to re-tap using a vacumn cleaner to catch any debris...tricky...but it can work if done properly.

This is what I did when I mildy f-ed mine up. I also duct taped a small tube to the end of the shop vac and stuck it into the combustion chamber to get any pieces that might have made it through.

Yeah, small tube is good. And I'd suck it first before doing anything else. This will pull any moisture, oil, water, out so any bits not caught in the grease will fall on something dry and allow you to suck it out at the end of the process.

It can and has been done.

[999]

can anyone confirm that i need a 12mm thread chaser?im actually having a hard time locating a 12mm one, locally  only 14mm and 18mm.thanks

[City Boy]

Hi.Yes,you need a 12x1.25 pitch.   Rock On

[tgtint]

Put vasoline on the chaser it helps keep the metal from falling into the engine.

[tino montreal]

I know multiple mechanics in montreal.... send me an email

[flybox1]

Hey Tino, what's with digging up 3+ year old threads ?

[tino montreal]

Sorry, new to site. Everything old to you, is new to me 
Having trouble finding easy out tool in my area, Montreal.

[lrutt]

And a recommendation for the future, get your self about a 6" length of 5/16" (I think) fuel line. Make the PERFECT tool for starting plugs. Simply insert the ceramic in the rubber hose then drop it down into the hole and spin it in. If you can't spin it in with that hose extension then something is wrong and needs to be corrected, plain and simple.

A real life saver. And......ALWAYS make sure there is a little dab of antisieze on the plug threads, add to new or confirm it's still sufficiently coated on a used plug. Just good practice. I've used this method for 40 years on all the current bikes I own plus the dozens I've had in the past and NEVER had a problem. I might have had to chase some threads on an old bike as the plug would not spin in with the hose extension, that would have been on a newly acquired bike, but once baselined, never ever had a problem.

[Vinhead1957]

+1on Irutt   Simple things work the best!

[Maurice]

It's all nice and well as long as you don't have to deal with the dreaded PO. Who knows WTF he's done.

BTW, if anyone needs I've got this tool and 1 insert. Seems to work great, see here.