Spark plug change :( ICK!

[casey_lamm]

Well I figured I would turn to the more experienced riders on here.


It apprears that changing the spark plug isn't that easy on this bike..to say the least. I pulled it out last night to check the color. But it was an old plug. Didn't have one with me, so I put it back in the best I could. I used the wrench...and I thought I go it down, but I fear it might have been loose. So If I ran with a loose plug for 1 day, would it damage the piston. If it was loose to the point damage would occur, wouldn't you notice it in performance? I didn't really see any drop at all.

Anyway, today I gap the new plug and put it in and have a heck of a time getting it in. I finally did, then reads the part of the manual tigheten 2x. Once at 3/4 turn past seated...Well define seated...not the easiest thing to tell on this bike...at least by me. Then losen then tighten 1/8 turn past seated.

Well after tinkering with it for awhile I got it where I think it seated. Went 1/4 turn past that and left it. Im sure its going to be fine.

I thought I would bring this up because this simple task...wasn't so simple and I worry about the damage to the piston or to the threads...

What do you guys do?

Also, do you think I did any damage from the 1st paragraph? It was only like that 1 day max and even then was less then 2 hrs riding time..

If you read the manual its scary! I don't want to damage my new bike.


Please tell me these bikes are mechanically stronger then the manual would leave you to believe, Im scared to touch the darn thing.

[my88r]

yea they are hard to get in and out. make sure the plug is tight as for ruining your piston im not to sure about that. the Manuel is always scary LOL. good investment is to buy the honda service manuel it will help you out alot rather than the stock one.

[casey_lamm]

I ordered the svc manual, just hasn't come in. :(


Originally posted by my88r
yea they are hard to get in and out. make sure the plug is tight as for ruining your piston im not to sure about that. the Manuel is always scary LOL. good investment is to buy the honda service manuel it will help you out alot rather than the stock one.

seated is when you have it as finger tight as you can get it...then with the wrench, go another 3/4 turn and loosen. snug it up again and then go /8 with the wrench.

it really is simple, that is the procedure you should use on anything when you put in a plug.

i doubt you did any damage with it loose because it would not have been as far in if you had tightened it. if it don't hit the piston with it all the way in, it won't hit the piston if it is not all the way in. it is not like it is bouncing around in there...

[flauge]

Originally posted by my88r
yea they are hard to get in and out. make sure the plug is tight as for ruining your piston im not to sure about that. the Manuel is always scary LOL. good investment is to buy the honda service manuel it will help you out alot rather than the stock one. You oughta try to change the plug with a set of scoops on it. Itd make a preacher cuss:cuss:

[my88r]

Originally posted by flauge
You oughta try to change the plug with a set of scoops on it. Itd make a preacher cuss:cuss: :rolleyes:

[casey_lamm]

I think I got the hang of it... its more of the angle you have to get used to...

Im checking it tomorrow to see how the jetting is doing.


Its pretty powerful. Seems slightly rich..


On a decel w/o throttle...i get one or two minor backfires. If in fact it is rich, it not major at all and I will probably leave it like that just b/c I would rather run that way then lean.

But man...what ever happen to having the plug in the side :) I know there is probably some really good reason...but cripes!


Originally posted by flauge
You oughta try to change the plug with a set of scoops on it. Itd make a preacher cuss:cuss:

[07250ex]

i duno i figure a plug in the top would need to have either your gas tank taken of or the engine taken out?

[Sparky_20]

nah, you can get to it pretty easy from the side. I use a motion pro 18mm deep spark plug socket that is made for a 400ex and a xr400. I also use a wobble head long 3/8 ratchet, no problems. As far as tightening, just use a torque wrench

Leaving the plug loose will more likely damage the threads in the spark plug hole rather than the piston.

[GPracer2500]

There is a way that a loose plug can cause a catastrophic engine failure. I wouldn't call it common though.

If a plug gets just loose enough that it can no longer conduct its heat into the head like it should, but not so loose that the cylinder looses compression around the plug--->the result can be an overheated/melted spark plug. A plug that's melting can cause pre-ignition and pre-ignition can destroy a piston in a few seconds.

I once saw a 250r that had it's plug loosen to the point where you could remove it with just your fingers. Yet it was still holding the compression in. It ran like that until the plug overheated and melted the tip. Luckily the plug stopped igniting properly and the engine quit before pre-ignition could set-in.

This isn't something I'd really worry about too much. But such things can happen if you're unlucky enough to stumble into just the right circumstances.

[CarGuy7a]

the reason for snugging the plug then loosening it then snugging it again is because on a new plug you have to snug it to smash the crush ring. if you just tighten it down in one go you could strip out the threads. that's why the book says to snug-loosen-and snug again.

as for taking the plug out and puttng one in i just use the socket thing that's in the tool kit that came with the quad and stick the allen wrench through the holes at the top to turn it.

[tar]

Originally posted by CarGuy7a
as for taking the plug out and puttng one in i just use the socket thing that's in the tool kit that came with the quad and stick the allen wrench through the holes at the top to turn it.

That's exactly what i do and it works llike a charm.

[REPOMAN]

if you dont have the tool kit that came with the quad you can buy a socket specially for the 400ex. they are not cheap though i think i paid 15 or 20 bux for mine and i would spend that much again in a heart beat.

the stock kit is a pain in the ......
it is so much easier when you can use a ratchet.
it is also easier from the throttle side and scoops don't bother me at all.

[casey_lamm]

I will be buying the tool.

I have the one that comes with the kit but I dont like it. WHen turning it in by hand it feels like the socket wants to work its way off the plug.


Originally posted by REPOMAN
if you dont have the tool kit that came with the quad you can buy a socket specially for the 400ex. they are not cheap though i think i paid 15 or 20 bux for mine and i would spend that much again in a heart beat.

[Barrymaxx]

Are there no auto mechanics here? Doing a plug on a 400ex is peice of cake compared to plugs in the back of a minivan motor.

I never found this a problem. I just pull the cap off, put the wrench on it, and unscrew it?

With the honda tool its easy.

i agree it is easy, i just hate than stupid honda way of sticking the allen through the hole and turning...then back through the hole again...if you happen to be doing this on a hot engine, with a hot plug that you can't use your fingers to get out after it is loose, then the socket is a real nice commodity to have...

i hated that way on the very easy to get to 300ex when i had it...hated it on the 400ex and i hate it on the 450r...if i ever remember to see what size wrench the honda socket for the r takes, i will buy a ratcheting wrench for it...

[400exrider707]

Originally posted by casey_lamm
I think I got the hang of it... its more of the angle you have to get used to...

Im checking it tomorrow to see how the jetting is doing.


Its pretty powerful. Seems slightly rich..


On a decel w/o throttle...i get one or two minor backfires. If in fact it is rich, it not major at all and I will probably leave it like that just b/c I would rather run that way then lean.

But man...what ever happen to having the plug in the side :) I know there is probably some really good reason...but cripes!


backfiring on decel is lean on the fuel screw. If its running rich it should be puffing black smoke and bogging.

[casey_lamm]

yea, i realized my mistype. Im giong to adjust it next time I get to ride. Currently im 3.5 turns out as the dynojet instructions say.


Originally posted by 400exrider707
backfiring on decel is lean on the fuel screw. If its running rich it should be puffing black smoke and bogging.