Striped spark plug threads

Hey all. I have a question about what to do about striped threads on the head..not the spark plug itself. The previous owner muscled the sparkplug in..and i found out after the fact (of buying). Now i'm unsure how to fix. Is there a tap i could get to rethread? What are my options? thanks ahead of time.

 

You can tap the hole, depending on how bad the threads are dorked up but don't be surprised if the threads don't hold against the compression and the engine spits the plug out at you.

The other option is a spark plug helicoil. You can buy them at most auto parts stores. You use the specified drill bit to enlarge the hole, and then use a tool to screw a thread insert into the head. Your spark plug screws into the insert, which is now permenant.

It might sound dodgy, but they work pretty well. I have an aluminum headed outboard engine and this repair worked perfectly for me.

 

Helicoils are great. One question how would you prevent metal flakes going into the cylinder

 

Well my outboard engine was horizontal and not that much metal went into it. I drilled a bit, and then use a computer component vacuum cleaner with a skinny tip to suck metal bits out of the cylinder and drilled some more.

It's a risk to be sure. Otherwise, you'll have to remove the head.

 

I would try a thread chaser first. You can buy "spark plug thread chasers" specifically built for the job, at the auto parts too.

Either way, you'll want to pull off the exhaust pipe, run the motor around so that cylinder has the exhaust valve open and hook up your shop vac in place of the pipe so you're not dribbling metal shavings into the cylinder. (And be careful not to bang into the open valve if you're drilling.)

 

Did mine.

Move the piston up as far as you can without the tap hitting it when you cut the thread.

I filled the gap above the piston with a clean cloth.
No drilling is needed - but ensure that you tap is lined up square with the original thread.
Put plenty of cutting compound on the tap so that any shaving stick to the compound
Clean the tap with new compound a number of times.
After you have cut the thread, fit your helicoil, hook the cloth and then gently pull the cloth out.
Lastly, attach a small tube to a vacuum cleaner and go in and suck up any small bits that might be lying inside.

 

found out i have the same problem. would it be a reasonable assumption that any metal shavings that didn't get sucked out of the cylinder would score the walls and eventually cause bad compression? or is it "safe" to say that the head material is so much softer than the piston, rings, and cylinder walls that a few flakes of metal will cause little to no real damage.

anyone ever turned their bike upside down to do something like this?

 

AutoZone has a Kit that is a New Sleeve --> NOT a HeliCoil.

http://www.oem-tools.com/product_info.p ... ts_id=1607

The Kit comes with everything you need to repair One Spark Plug Hole.

To keep the Taps cuttings from entering the Cylinder do the job SLOW.
Grease the Tap.
Cut half-way down.
Withdraw the Tap and CLEAN it.
(I scrape-off the mess with a small screwdriver ... then, shoot the Tap Clean with Carb Cleaner)
Re-Grease the Tap.
Finish cutting the Hole for the Sleeve.
USE THE RIGHT SLEEVE --> Read the Instructions.

Clean the Tapped Hole
Carb Cleaner or Alcohol

Use the High-heat Ultra-strond Thread Locker that comes with the Kit.
Install the Sleeve
Remove the Installation Tool
Stake with second too provided.

Editors note:

I have used this Kit on a XJ-Bike.
It works Great.
Dont overtighten the Plug after the install.
The sleeve might stay on the Plug when you Pull the Plug.

 

That kit is a helicoil copy. Note the description of "stainless steeel wire with a diamond shaped cross section wound to the shape of a spring thread". Not to say there is anything wrong with it.

I've used the similar kit for other applications. It's priced a bit less than helicoil kits, but comes with fewer inserts. The quality seems every bit as good as helicoil.

I've used Time-serts for spark plug holes, and really like them as the installation tool expands them in place so you don't have to worry about them backing out when you remove a plug. Problem is they're pricey, the tool to install them (and it's size/plug base specific) is north of $100. Still, might be worth a call to the local motorcycle shops to see if anyone can do one for you.

 

do i understand right that these kits make the plug hole larger, and then return the hole to the correct size by installing a sleeve?

looking into my hole, most of the threads are ok and i can screw the plug most of the way in. there's a couple spots that are cross threaded. i shouldn't need a helicoil in this situation should i? i'm thinking i just need to re-tap the existing hole.

 

i'd chase the threads first, if not then use the sleeve. it works great and that's what's on my # 2 plug. but if over tightened it will stay on the plug (found that out the hard way)

 

well that's a relief. still looking for input regarding little bits of metal falling into the cylinder and not being able to get them out.

 

grease on the tap will hold most of the metal shavings. if done slow you'll end up with longer shavings/ fewer pieces. with the addition of a shop vac and the exhaust valve open you should be good. maybe change the oil after if you were concerned about it.

 

This happened to me a month ago when my plug shot out of the cylinder. I went to my local Napa and bought a long shank 14mm helicoil kit and some heavy duty gease. (to catch the metal shaving from going down into the cylinder barrel.)

I did the job right there in the parking lot.

After you are done tapping it, a good idea is to keep the sparkplug out and run the engine for a while, this will expel any loose particles that may have dropped down into the cylinder.

Make sure you put some high temp lock-tite on the helicoil when you install it, and it should be as good as new.

The whole experience only took about 25 minutes.

 

GET A CHASER!

Sears sells them...
http://www.sears.com/shc/s/p_10153_1260 ... d=BVReview

Get the $6.99 craftsman one, worth the $1 over the KDTools brand because it has a lifetime warranty

Chase it, and see where you are at. Always good to have one to keep the threads clean.

As far as bit in the motor, as Fitz said - exhaust valve open and a shop vac

 

do you think i could loop a wire around the end of it so that it rides in the grooves to hold a piece of sponge to the bottom of the chaser? that should catch any metal filings and pull them out when i remove the chaser no?

 

Wouldn't risk it, you can stick a shop vac on the exhaust, with the exhaust valve OPEN turn on the shop vac and let it suck.

Then get to chasing. anything that falls down will go right in the exhaust valve and out the exhaust.

 

WOOT! thread chaser worked like a charm. no more backfire. finally got to take 'er out and wind it up a bit.

(who has 2 thumbs and is very glad he stopped shifting before 6k? this guy!)

 

haha... good job getting over 6k!

Did you get the sears one I told you about?

 

yes - got the sears one. it's hard to get it started straight, but once you're going, it goes good.