Plugs backing out

[Profilact]

I cant figure this out...

 

4 mill long rod dune\play port

cool head 20cc domes

.020over wiseco 795's

+ 4 timing

rad valve

32mm mikuni flatslides

k&n pods

T5's

 

It has happened twice now and its really bothering me. Its not detonating or overheating. One thing though, I have to gap my plugs really close like .022 or it will break up on top end. C'mon guru's, throw some knowledge my way!

 

Thanks,

 

Profilact

[AKheathen]

um, you need to tell us the octane you are running and elevation. i'm sure it's detonating, unless your plug threats are complete toast, which would likely strip when you put the plugs in, lol.......but, if you are sure it's not deto, then put some plug locks on ther untill the next rebuild, which won't be long

[firebanshee]

What octane of fuel are you running? If you are running pump gas at near sea level with 20cc domes and +4 timing you are detonating.

[Profilact]

I am running avgass 100ll motor is not getting hot ar anything it's really weird. I'm at sea level maybe I should back down to 21's?

Edited April 25, 2010 by Profilact

[jbooker82]

It doesnt have to get hot to detonate. I would try some 110 race fuel and see if it still does it.

 

AV gas isnt rated like fuel that is made to be ran on the surface. It is made to be ran in an air plane. You know how just a few 1000 feet affect the compression, and fuel requirements on you banshee. What do you think it does when an air plane climbs a couple 1000 feet?

 

They use fuel mixture (rich) to help fight detonation (wich is the rich octane rateing) at low atlitudes.

[AKheathen]

try backing the timing off to stock......it should run with 100ll strait. what is your squish set at?

[mybikeisaturd]

How long have you been running these domes? Is there a possibility that they are cut for blaster pistons?

[Profilact]

Jeff is on the case via PM. I don't understand how backing down the timing will help if its already detonating. And since everyone is convinced that deto is happening, I will agree. Just thought I would definately hear\know if it was.

[AKheathen]

because detonation is just the fuel burning uneven and where it shouldn't, like on the surface of the sparkplug and chamber/pistons. too much timing can start thr burn too early and it gets to the surfaces and explodes on them, which shocks the plug loose

[Profilact]

Makes sense. Not the the fuel is igniting prematurely, but before it should via timing. What is the best course of action? Reduce timing or increase dome size? Where will i see the most performance losses?

[gooniemon]

ever thought about jbwelding the plugs in, i bet u they wont back out anymore

[Koolguyson]

Makes sense. Not the the fuel is igniting prematurely, but before it should via timing. What is the best course of action? Reduce timing or increase dome size? Where will i see the most performance losses?

 

Back the timing off.

[Koolguyson]

ever thought about jbwelding the plugs in, i bet u they wont back out anymore

 

JB weld might loosen up with the heat and vibration.

 

I would put a little tack on it if it were me.

 

(Kidding...DON'T do this). And never put one of those stupid plug locks on it.

[WINDYCITYJOHN400]

Your fuel isn't the issue. (Unless your not getting enough of it) I run 100AV gas and can jump from VP-110 to AV gas without rejetting. (Tim at Titan Racing talked me out of the whole "AV gas isn't made for 2 strokes" point of view) +4 timing isn't all that agressive either. I'd say you have "Trinity Disorder".....it's when your domes just don't work with your piston shape. (If you know anything about Trinity you know what I'm talking about. LOL.) I think you can solve your problem fairly easy by doing a squish measurement. Contact Tim at Titan Racing or any other major builder regarding getting custom domes cut. (For about $150 you can get domes made specificly for your motor. Why go with off the shelf standard cuts when customs aren't that much more?) Hope that helps your problem.

[Profilact]

Yeah I know about the whole avgas thing - i ran it all last year. Im not switching fuel as it would cost me a fortune to ride all season on c-12. Its either domes or timing, but one of these if not both have to change. I just want to know which one will make me lose the most power, that way I will do the opposite.