spark plug loosening up?

[hartwill]

Anybody ever had a problem with their spark plug backing out of the cylinder on them when they ride? I kept hearing detonation in this new motor a few days ago and I noticed oil splattered up around my spark plug come to find out it was almost all the way backed out. Then I tightened it up and checked my timing and everything seems fine now but my plug keeps getting loose. Just wondering If you guys have had this problem before or any ideas to a solution. My next step is brand new gas and then going back to the stock ignition. Oh, my compression is pretty high haven't checked it yet but you can't kick it over unless it's at TDC on the down stroke. Also running 110 octane 32:1 with benol... Thanks guys.

[C-LEIGH RACING]

That is a sure sign the ignition timing set to high, cause it will rattle that plug loose every time.

What coolant temp is the engine running normally.
Neil

[hartwill]

I don't have a thermostat on my coolant line. Just did a compression test with a snap-on tester and pegged it out at 250psi after 4 kicks.

[hartwill]

Maybe I need higher octane fuel?

[HAYESTRX250R]

Had this happen to me once while riding MX. Scared the crap out of me because I thought it had blown up, and the noise it made lol. No problems since.

[bholzgen]

This has happened to me before... The plug flew out, and oil was everywhere. I was sure it had blown up. Then come to find out my buddy hand tightened the plug. Not cool lol

[Grande Huevos]

i had this happen on my 330 once when running pump fuel... made the switch to vp 110 and it hasnt done it since. Also isnt 230 psi kind of high?? I though you wanted to be between 200-220 max?

[hartwill]

Im thinking about trying 118 octane If I can find it. I don't know what's the highest compression you would want to be at but I can't get an accurate reading because my gauge maxes out @ 250psi and I buried the needle after 4 kicks..

[atvmxr]

a) your compression is way too high. you can reach a point where motor performance begins to suffer

b) the compression is causing detonation which is making the head hot and allows the spark plug to back out.

i have had a plug back out a few times over the years (like once every 3-4 years) usually in the summer time when Im hammering a MX track in the second moto.

[beerock]

with that high of comp you need c14 or c16


also with that high of comp you will wear out the main bearings and con rod bearings (piston and crank faster...


what head gasket are you using? or if dome what cc dome?

what ratio are you mixing the gas and oil?

you also need to find a comp tester that will measure your compression.... I remember some where someone or read someone saying 265 psi is close to max, however you could run higher just need the octane for it and if you dont mind rebuilding the motor all the time...


just so you know higher comp is great for low end power but will kill the engines ability to rev out.... the lower the comp the more it will rev out

[latheboy]

I ran my quad with 240lbs compression, but I never ran less than 114 octane. I ran 10 gallons of 118 Rockett brand also. I ran a total of 40 gallons of fuel thru it, tore it down and the piston looked like new.

[hartwill]

Originally posted by beerock
with that high of comp you need c14 or c16


also with that high of comp you will wear out the main bearings and con rod bearings (piston and crank faster...


what head gasket are you using? or if dome what cc dome?

what ratio are you mixing the gas and oil?

you also need to find a comp tester that will measure your compression.... I remember some where someone or read someone saying 265 psi is close to max, however you could run higher just need the octane for it and if you dont mind rebuilding the motor all the time...


just so you know higher comp is great for low end power but will kill the engines ability to rev out.... the lower the comp the more it will rev out
This is a pro cross cylinder, 76mm piston, pro cross head with o rings, and 22cc dome. I got a round about compression number using Carlos' method using just the dome size, no actual dome cc measurement taken and it was right around 15.8:1 compression. I am currently running 110 32:1 with super techniplate.

[beerock]

ok well, you could switch to amsoil dominator and run 50:1 ratio like i do, that will give more gas for each power stroke and less detonation.(more gas cooler cylinder)... and see if that helps with detonation...

if you want that size dome and the pwoer with it you more then likely will have to go higher with fuel octane OR raise the dome size... you will lose a little bottom end but what you lose on bottom youll gain on top as far as rpm's go.

its up to you, to me i would raise the dome because im sure the motor is putting out tons of power if you choose to keep that dome its gonna cost you more money on fuel and shorter time period in between rebuilds due to the stress on the upper and lower con rod bearings and main bearings

[hartwill]

thanks beerock. what size dome would you suggest so I can run 110? I am going to order some of the vp c16 for now but its hard to find and $80 for 5 gallons. thanks again.

[beerock]

I think 28cc however dont go by me I havent played with my motors in a while lol.. cleigh should know...

I also think you should switch your oil to amsoil dominator and run at 50:1 it will give you more gas per gallon and more gas to run cooler since the oil ratio is lower...

dont worry about 50:1 with the amsoil... I ran my 265 WOT for 80 hours(glamis cali for 10 days) with amsoil and vpc12 or torco 110...

also one way to lower detonation is to run the motor a little rich(change your main jet...

not to many peole play with the needles either but it can make a mjor difference in mid throttle response... however you need to get your detonation under control first before trying to get a crisper mid end..