Stripped spark plug threads / Running with loose plugs

[Dozer7380]

I think a few of my plug threads in the head may be stripped. I'm unsure if they are but i do know this , after hand tight I go to turn a 1/4 turn with the ratchet the feel i get is that it is tightening a little and then a little loose. I didnt go more than 3/4 of a turn but suspect the last owner may have stripped them. There were non-stock plugs in there and I threw them away after inspecting them.

I rode it around for a few min but didnt want to go too far. checked them again and they seemed to be okay.
So my question is , what is the worst case scenario if i am running with loose plugs.

Any anyone have suggestions on this?
So far i thought about driving it home, helicoil, tap for larger size. Damn... I dont want to take the head off.

[The CyberPoet]

The torque-spec is 8 lb-ft. That's very low. It's definitely lower than the standard car trick of seated + 1/4 turn...

Fixes are:
1. Remove the head, retap for a bigger plug, reinstall;
2. Remove the head, install KeenCerts (not helicoils!); OR
3. Replace the head with an used known-good one.

Cheers,
=-= The CyberPoet

[tzortn]

Use a Helicoil before you use a keyed insert (aka Keen Sert). That way if the Helicoil fails (which they very rarely do) you can go back and put in a keyed insert.

[opelguy]

on plugs?

I've tried a couple times to use a helicoil on a plug, and in both cases they would not seal combustion chamber pressures and had to be removed. I think for spark plugs the best option really is the full sleeve insert.

[Dozer7380]

So the 1/2 turn for new plugs in the Haynes is too much?
Also if the threads are no good then should the bike be running?

Im really hoping that maybe some crud in the threads kept it from turning tighter by hand.

[md86]

Re: on plugs?

I've tried a couple times to use a helicoil on a plug, and in both cases they would not seal combustion chamber pressures and had to be removed. I think for spark plugs the best option really is the full sleeve insert.

I read a while back where some guys put a helicoil in an RF , and it worked just fine . Mmmmmmmmm , Rf

[The CyberPoet]

Use a Helicoil before you use a keyed insert (aka Keen Sert). That way if the Helicoil fails (which they very rarely do) you can go back and put in a keyed insert.

I've seen too many motorcycle engines throw spark plugs using helicoils (usually in short order too -- under 100 miles), and SpecialK has mentioned that he has had the exact same experiences with the Kat engines & helicoils. It simply isn't worth the risk, in IMHO.

So the 1/2 turn for new plugs in the Haynes is too much?
Also if the threads are no good then should the bike be running?

I have no clue what the haynes manual says -- I go strictly by Suzuki's own factory service manual. And Suzuki says 8 lb-ft -- I doubt it's a half-turn to reach 8 lb-ft after the plugs have their crush washers touch.

If the threads are no good, you're risking the spark plug shooting up out of the engine. While mechanically all this is likely to do is strip out any remaining threads, it will scare the bejesus out of you, and you won't have the option of riding the bike home (so have a tow-solution ready).

I forgot one more fix:
Remove head, clean, tig weld and then retap to the original size. If you are a good tig welder (or have a close friend who is), this can be a cheap way out -- but if you have to pay for the welding service, you're better off going with an used head or KeenCerts.

The advantage of KeenCerts is that they are steel, and because of how they mount, you should never have an issue with stripping a spark plug again, even if you go gorilla-force on it. If you do go this route, get all four spark plug holes done at the same time (because a previous owner who damages one set of threads probably damaged others as well, perhaps just not to the point of true failure).

PS - curse the vehicle engineers who keep doing such things (putting softer metals in the receiving threads for spark plugs, oil pans, etc.). The cost-to-impliment a steel thread solution at time of casting the engines (having something like a keencert in the mold before the aluminum gets injected) would be under 50 cents per receiver hole!

Cheers,
=-= The CyberPoet

[md86]

I've seen too many motorcycle engines throw spark plugs using helicoils (usually in short order too -- under 100 miles), and SpecialK has mentioned that he has had the exact same experiences with the Kat engines & helicoils. It simply isn't worth the risk, in IMHO

Wow , i'll have to remember that . That sucks .

[tzortn]

I've seen too many motorcycle engines throw spark plugs using helicoils (usually in short order too -- under 100 miles), and SpecialK has mentioned that he has had the exact same experiences with the Kat engines & helicoils. It simply isn't worth the risk, in IMHO.

I can't argue with you here because I have never tried it on a Kat head. My general experience with Helicoils is that they are reliable.

PS - curse the vehicle engineers who keep doing such things (putting softer metals in the receiving threads for spark plugs, oil pans, etc.). The cost-to-impliment a steel thread solution at time of casting the engines (having something like a keencert in the mold before the aluminum gets injected) would be under 50 cents per receiver hole!

Leave the engineers alone. Decisions like this are usually made by the accountants. Although ultimately driven by the consumer. They want low cost so sacrifices have to be made. Adding inserts would add a lot more than 50 cents to the cost of each hole. Even if is was only 50 cents per hole that is $2 per head x 10000 heads per year. That is $20000 spent on solving a problem that can be fixed by following a simple torque procedure.

[The CyberPoet]

Leave the engineers alone. Decisions like this are usually made by the accountants. Although ultimately driven by the consumer. They want low cost so sacrifices have to be made. Adding inserts would add a lot more than 50 cents to the cost of each hole. Even if is was only 50 cents per hole that is $2 per head x 10000 heads per year. That is $20000 spent on solving a problem that can be fixed by following a simple torque procedure.

I can kind of forgive them on the Kat (it is, after all, a price-targetted vehicle with a low-end price). But I curse the Audi engineers & VAG bean-counters who did the same thing with the oil pan on an Audi that cost just shy of $75k new

Cheers,
=-= The CyberPoet

[Dan Dubeau]

Leave the engineers alone. Decisions like this are usually made by the accountants. Although ultimately driven by the consumer. They want low cost so sacrifices have to be made. Adding inserts would add a lot more than 50 cents to the cost of each hole. Even if is was only 50 cents per hole that is $2 per head x 10000 heads per year. That is $20000 spent on solving a problem that can be fixed by following a simple torque procedure.

I was going to say the same thing. Also the same people who strip out plug threads (in alum heads), would also probably screw up steel inserts (ie cross threading). That said, mistakes DO happen. But adding an insert into a casting is more than meets the eye. A whole stem of other quality related issues CAN arise by adding inserts. Cost aside, the benefits do not outweigh the negatives of adding inserts just to prevent some Hamfisted mechanic from over torquing a spark plug once and a while.

[Dozer7380]

hmm choices , choices. I hope I dont have to deck the head. That seems like a whole new can o worms.

[tzortn]

If you do then you may be better off picking up a used on from ebay or a junk yard.

[md86]

Speaking of ripped out threads ......
After doing my valves , one of the valve cover bolts pulled the threads out of the cam cap . It wasn't even CLOSE to being tight , I guess the threads just had enough . Been searching a few places in town today , and noone's even HEARD of a Keen Cert . But I can find Helicoils all day long . Opinions ? I'm now under the impression the Keen Cert is a better solution , but ......

[Hillsy]

Unlike spark plug threads, Helicoils will be OK for cam caps (I had to get all 8 of them done on my old 1100EF).
They are a fine pitch thread and strip quite easily - especially if the tappet cover starts to weep oil and a novice decides it's a good idea to "tighten up the bolts"......