Spark plugs backing out on their own

[Wmich06]

I have a 2003 banshee with a cool head installed and after only a couple minutes of riding the spark plugs will back out on their own, im using ngk's. Any quick fixes or tips?

[06specialedition]

I've heard detonation does that to your plugs.....Maybe do a search. Don't even start it until you figure it out.

 

Good Luck!

[TexasBansheeMan]

Predet and a lean condition will make them back out. You might need higher oct gas, or a jet change. Either way your doing damage now.

[mailman]

Assuming the plugs were installed correctly, then yes, it is detonation. There are a number of things that can cause this like; old fuel, too high compression, over advanced timing, and poor dome design to name the most common ones.

Tell us a little bit about your bike like compression, the fuel you are using, timing advance if any, stock head, cut stock head, or head with domes.

 

Mailman

[Wmich06]

The compression is 150 in each and im running premium gas with a 32:1 oil mixture. Could that have something to do with it?

[Sandfrk33]

Make sure you find the problem as stated. My buddys bike did that after a rebuild and fried the top end in a couple hours. He had the head milled and the compression was off the charts. What domes are you running?

[mailman]

The compression is 150 in each and im running premium gas with a 32:1 oil mixture. Could that have something to do with it?

 

I think 150 is too high for pump fuel but some will argue. How old is the fuel? Where did you get the domes from?

If you are looking for a quick fix, try to run some av-gas or race fuel in the motor and see if the plugs still back out?

What carbs and jetting are you running? TexasBansheeMan had a good point that it could be lean jetting also.

[AKheathen]

detonation usually causes that. sometimes, it will hapen if you overtighten the plugs, but it takes more than a couple minuets to back out......on a stock motor, 150psi is perfectly fine on 90+ with an accurate reading. first thing you should do is a squish test. make sure your compression tester has a shrade valve in the tip, and that the tip is as long as the sparkplug threads, and you are kicking it over holding wot, untill the needle stops moving. then, pull the head and check the dome size. you will need to know the bore size and if any porting is done. the compression ratio is more a deciding factor than cranking compression. you can deto with as little as 140psi, or be fine closer to 180. oh, and elevation and timing will effect it, too.

[Tedder]

These guy's are absolutly right, Detonation will rattle the plugs loose. Been there done that with both my alcohol bikes. 99.99% of the time it's a lean condition.

Fair warning - Fix it or you'll break it for sure.

[fastquad02blaster]

You'll have church pistons in her before long man. HOLY.

[firebanshee]

If you have trinity domes then that is your problem,i had 185 psi on each cylinder backing out plugs with trinity domes running alky.Switched out domes to some custom cut ones and sill had 185 psi, changed nothing else and problem went away.

[slacker1bob]

I have a 2003 banshee with a cool head installed and after only a couple minutes of riding the spark plugs will back out on their own, im using ngk's. Any quick fixes or tips?

 

I have the same problem. I have a 421 cub with a cool Head. Herr Jugs cut me some 24cc domes and the compression is about 135 each side. I have ran 91 and 91/111 mix and had the same problem. Im also running slightly rich. 158 mains with twin 35mmpwk. Its done this every time. Ive tried different plugs. I just use a plug lock and that cures it. I have no signs of detonation, and no running problems. I guess my point is, it may not be detonation

[Darthwall]

I have had this happen lots of times bike ran good and a plug came out turned out to be jetting and fuel dont run high comp domes and cheep fuel if you think octain booster will help do some research there are a few but not many also always check you squish band the prob could be that easy

Edited July 23, 2010 by Darthwall

[AKheathen]

um, how are you tightening the plugs, slacker? if you over tighten them, they can streatch the threads in the head, and they will flatten the gasket, so there is no spring pressure to keep them seated. you should really read the plugs, too. plug locks should never be used. they do not cure any problem, just mask a warning sign

[jbooker82]

The only thing a plug lock is good for is changing spark plugs.